INTRODUCTION — The acute immune-mediated polyneuropathies are classified under the eponym Guillain-Barré syndrome (GBS) after some of the authors of early descriptions of the disease. GBS is one of the most common causes of acute, acquired weakness and is often provoked by a preceding infection. GBS may be complicated in some cases by respiratory failure or autonomic dysfunction.
The pathogenesis, clinical features, and diagnosis of GBS will be discussed here. Other aspects of GBS are presented separately.
●(See "Guillain-Barré syndrome in adults: Treatment and prognosis".)
●(See "Guillain-Barré syndrome in children: Epidemiology, clinical features, and diagnosis".)
●(See "Guillain-Barré syndrome in children: Treatment and prognosis".)
PATHOGENESIS — The acute polyneuropathy of GBS is often triggered when an immune response to an antecedent infection or other event cross-reacts with shared epitopes on peripheral nerve (molecular mimicry) [1,2]. All myelinated nerves (motor, sensory, cranial, sympathetic) can be affected.
●Pathology – The range and extent of pathologic changes depend on the clinical forms of GBS. Patients with the common acute inflammatory demyelinating polyneuropathy (AIDP) form have prominent demyelination on electrodiagnostic studies and lymphocytic infiltration on sural nerve biopsies, while those with other forms such as acute motor axonal neuropathy (AMAN) form have prominent axonal loss without lymphocytic infiltration or complement activation and few degenerating nerve fibers [3]. (See 'Variant forms of Guillain-Barré syndrome' below.)
•Demyelination – In AIDP and the Miller Fisher syndrome (MFS) variant form, a focal inflammatory response develops against myelin-producing Schwann cells or peripheral myelin [4-6]. Demyelination is thought to start at the level of the nerve roots where the blood-nerve barrier is deficient. The breakdown of the blood-nerve barrier at the dural attachment allows transudation of plasma proteins into the cerebrospinal fluid. Infiltration of the epineurial and endoneurial small vessels (mostly veins) by activated T cells is followed by macrophage-mediated demyelination with evidence of complement and immunoglobulin deposition on myelin and Schwann cells [5,7,8].
Demyelination blocks electrical saltatory conduction along the nerve. This causes conduction slowing and leads to muscle weakness. More widespread but patchy peripheral nerve demyelination follows, with added electrical conduction block causing further weakness and electrophysiologic evidence of nonuniform conduction slowing within and across different nerves. Axonal degeneration occurs as a secondary bystander response; the extent relates to the intensity of the inflammatory response.
Peripheral nerve remyelination occurs in recovery over several weeks to months. However, in a small percentage of patients, there is superimposed severe axonal degeneration with markedly delayed and incomplete recovery.
•Axonal loss – Immune reactions against epitopes in the axonal membrane cause the acute axonal forms of GBS: AMAN and acute motor and sensory axonal neuropathy (AMSAN) [4]. These forms are relatively uncommon in the United States but more frequent presentations of GBS in Asia. (See 'Acute axonal neuropathies' below.)
In the axonal variants of GBS, antibody and complement-mediated humoral immune response leads to direct axolemma injury [9,10]. There is a paucity of inflammatory infiltration. The primary immune process is directed at the nodes of Ranvier (short intervals between successive segments of the myelin sheath along a nerve), leading to axonal involvement with conduction block caused by paranodal myelin detachment, node lengthening, sodium channel dysfunction, and altered ion and water homeostasis [11]. This process can rapidly reverse in some cases but may progress to axonal degeneration in others. The motor nerves are involved at the ventral roots, peripheral nerve, and the preterminal intramuscular motor twigs [12]. In the motor-sensory variant, sensory nerves also are affected.
●Autoantibodies and molecular mimicry – GBS is triggered by a cross-reaction of an immune response to an antecedent infection or other event with shared epitopes on peripheral nerve (molecular mimicry). Autoantibodies that react with epitopes on peripheral nerve appear to be the immune trigger after an acute infection in many cases of GBS [1,2,13-15].
A case report from Japan in 1990 linking AMAN to a preceding infection with Campylobacter jejuni and antibodies to the GM1 monosialoganglioside prompted interest in the role of Campylobacter and antiganglioside antibodies in GBS [16-18]. Subsequent reports on C. jejuni have provided further insight into the mechanistic role of autoantibodies in the development of GBS through molecular mimicry [19].
Infection with C. jejuni is the most common antecedent in GBS and a leading cause of acute gastroenteritis [20]. (See 'Infection' below.)
C. jejuni can generate antibodies to specific gangliosides, including GM1, GD1a, GalNac-GD1a, and GD1b, which are strongly associated with AMAN and AMSAN [21]. A strain of C. jejuni isolated from an AMAN patient carrying immunoglobulin (Ig)G anti-GM1 antibody expressed an oligosaccharide structure identical to that of the terminal tetrasaccharide of the GM1 ganglioside [22]. Autopsy studies show that, in AMAN, IgG is deposited on the axolemma of the spinal anterior root [21], indicating that IgG is an important factor in the development of AMAN [9]. (See 'Acute axonal neuropathies' below.)
Similarly, C. jejuni infection can generate antibodies to the GQ1b ganglioside, a component of oculomotor nerve myelin [23]. GQ1b antibodies are frequently found in variants characterized by ophthalmoplegia, such as MFS and Bickerstaff brainstem encephalitis (BBE) [23,24]. Antibodies to GT1a, which cross-react with GQ1b, have also been associated with bulbar forms of GBS [25,26]. (See 'GQ1b syndromes' below and 'Rare variants' below.)
Patients with C. jejuni enteritis not complicated by GBS do not produce the specific antiganglioside antibodies [17]. Genetic polymorphisms in lipooligosaccharide biosynthesis genes in C. jejuni that modify ganglioside expression as well as immunogenetic factors in the host are thought to play a role in the development of GBS [27].
There is also an association between GBS and infection with Haemophilus influenzae, Mycoplasma pneumoniae, and cytomegalovirus. Cytomegalovirus infections were associated with antibodies to the ganglioside GM2 and with severe motor and sensory deficits. Other infections were not related to specific antiganglioside antibodies and neurologic patterns in GBS, but these relationships are not well documented [12,22].
These antiganglioside antibodies are considered to be the pathogenic components that trigger GBS because of their association with the acute illness in GBS and because immune-mediated therapies such as plasma exchange are effective treatments for GBS [28]. (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Immunomodulatory therapy'.)
ANTECEDENT EVENTS — In some studies, up to two-thirds of patients give a history of an antecedent respiratory tract or gastrointestinal infection [10,29,30]. In the International Guillain Barré Syndrome Outcome Study (IGOS), 76 percent of patients reported a triggering event in the four weeks prior to GBS [31]. This included an upper respiratory tract infection in 35 percent and gastroenteritis in 27 percent.
Infection
●Campylobacter jejuni infection – C. jejuni gastroenteritis is the most common precipitant of GBS, identified in approximately 25 percent of cases [20,32]. Of note, only 70 percent of those infected with C. jejuni reported a diarrheal illness within 12 weeks before GBS onset. In an analysis of available biosamples from 768 patients in the IGOS cohort, laboratory evidence of recent C. jejuni infection was found in 30 percent [30].
A study from Sweden estimated that the risk for developing GBS during the two months following a symptomatic episode of C. jejuni infection was approximately 100-fold higher than the risk in the general population, with GBS developing in an estimated 0.03 percent of patients with C. jejuni enteritis [33].
There are significant geographical differences in C. jejuni infection. Certain strains of C. jejuni have been associated with GBS in Japan (strain O-19) and South Africa (strain O-41) but not in Europe [34,35]. Likewise, the rate of preceding C. jejuni infection varies by the form of GBS, being found in about 60 to 70 percent of acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN) cases and up to 30 percent of acute inflammatory demyelinating polyneuropathy (AIDP) cases [36,37].
Furthermore, Campylobacter-associated GBS appears to have a worse prognosis than patients with other triggers, manifested by slower recovery and greater residual neurologic disability [20].
●Other infections – Multiple reports have found an increased risk of GBS following other influenza-like illnesses [29,38-41]. In one study from the United Kingdom, the relative risk of GBS within 90 days after an influenza-like illness was 7.4 (95% CI 4.4-12.4) [38].
•Cytomegalovirus – Antecedent cytomegalovirus infections have also been associated with GBS [42-44]. As an example, a case-control study from the Netherlands that evaluated 308 patients found that serologic evidence of recent infections, including cytomegalovirus, was significantly more common among patients who developed GBS than matched-control patients who had other neurologic diseases [45]. Patients with human immunodeficiency virus (HIV) infection were excluded from this series. Laboratory evidence of recent cytomegalovirus infection was found in 30 of 768 patients (4 percent) in the IGOS cohort [30].
•Influenza A and B – In a study of 150 patients with GBS from China, influenza A and B were the most common antecedent infections after C. jejuni, accounting for 17 and 16 percent, respectively. Influenza B has been associated with a pure motor form of GBS that more frequently requires mechanical ventilation compared with influenza A, which is usually less severe [32,46].
•HIV – GBS also occurs in association with HIV infection, predominantly in those who are not immunocompromised. However, GBS can occur in any stage of HIV infection [47]. GBS has been reported after acute HIV seroconversion and following immune reconstitution from highly active antiretroviral therapy [48]. The clinical course and prognosis of GBS in patients with HIV infection appears similar to GBS in those without HIV infection.
•COVID-19 virus – Several cases of para- and post-infectious GBS associated with coronavirus disease 2019 (COVID-19) have been reported, though a direct causal relationship has not been established [49-51]. In a case-control study of 76 patients with GBS occurring over an 18-month period during 2021 and 2022, COVID-19 infection occurred in 11.8 percent of patients within six weeks prior to GBS compared with 2.4 percent of matched controls without GBS [52]. GBS associated with COVID-19 infection appears similar to classic GBS in clinical presentation, electrodiagnostic evaluation, and response to treatment [53,54]. (See "COVID-19: Neurologic complications and management of neurologic conditions", section on 'Guillain-Barré syndrome'.)
The risk of GBS appears higher with COVID-19 infection than with COVID-19 vaccination [52]. The association between GBS and vaccinations against COVID-19 are presented separately. (See 'Vaccinations' below and "COVID-19: Vaccines", section on 'Guillain-Barré syndrome'.)
•Zika virus – An association between Zika virus infection and GBS has been reported, but a direct causal relationship has not been firmly established. This issue is discussed in greater detail elsewhere. (See "Zika virus infection: An overview", section on 'Guillain-Barré syndrome'.)
•Others – GBS has been reported following infection with the varicella-zoster virus, Epstein-Barr virus, herpes simplex virus, hepatitis E, chikungunya virus, Japanese encephalitis virus, and the bacteria H. influenzae, Escherichia coli, and M. pneumoniae [30,45,55-60]. Approximately 6 percent of patients from the IGOS cohort were found to have laboratory evidence of multiple recent antecedent infections [30]. The importance of these infectious agents as triggers of GBS is uncertain.
Vaccinations — Some instances of GBS have followed vaccination, but the associated risks appear small or negligible. Some studies have failed to find an association between vaccination and subsequent GBS risk. As an example, individuals who received either the 1992-1993 or 1993-1994 influenza vaccinations were not at significantly increased risk for GBS, but combining the two seasons suggested that influenza vaccination resulted in approximately one additional case of GBS per million patients inoculated [61]. By contrast, a retrospective study that analyzed a northern California health care database from 1994 through 2006 found no increased risk of incident GBS following any vaccination and all vaccinations combined, whether using a 6-week or 10-week risk interval [62].
There appears to be little or no risk of GBS associated with routine immunization schedules. In a study that analyzed a large database of 253 general practices in the United Kingdom with a mean of 1.8 million registered patients from 1992 to 2000, there were 228 incident cases of GBS [63]. Onset of GBS within 42 days of any immunization occurred in seven patients (3.1 percent), with an adjusted relative risk of 1.03 (95% CI 0.48-2.18).
The risk of GBS after vaccination appears substantially lower than the risk of GBS triggered by acute infection [64,65]. In addition, preventing acute illness through vaccination can reduce infection-triggered GBS. Vaccination has not been associated with GBS recurrence [66,67].
●Influenza vaccination – In the United States, an increased risk of GBS was associated with the swine influenza vaccine in 1976, although the severity of the risk has been controversial [29,41]. Subsequent meta-analyses and cohort studies have found that influenza vaccination is associated with low or negligible risks of GBS and has supported the safety of vaccinations [38,68-73]. As examples, a meta-analysis of data from six adverse event monitoring systems, the 2009 H1N1 influenza A vaccine used in the United States was associated with a small increased risk of GBS (relative risk [RR] 2.35, 95% CI 1.42-4.01) [68]. The number of excess GBS cases was estimated to be 1.6 per 1 million people vaccinated. In a population-based cohort study from Quebec evaluating the H1N1 vaccination during the fall of 2009, a small but significantly increased risk of GBS was reported for the eight-week postvaccination period (adjusted RR 1.80, 95% CI 1.12-2.87) and during the four-week postvaccination period (RR 2.75, 95% CI 1.63-4.62) [69]. The number of excess GBS cases attributable to the vaccine was approximately 2 per 1 million doses [38,39].
Other studies have failed to identify a risk of GBS associated with influenza vaccination [38,70-72]. In a multinational self-controlled case series in Europe, there was an elevated risk of GBS following influenza infection but not following influenza vaccination [71]. Moreover, when adjusted for confounding by influenza-like illnesses, there was no association of GBS with the pandemic H1N1 vaccine [70-72].
A history of GBS should not be considered a strict contraindication for influenza vaccination, except for patients who had GBS over the preceding three months or had vaccination-related GBS [67,74,75]. The management of patients with GBS is discussed separately. (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Subsequent immunizations'.)
The risk of GBS associated with influenza vaccination, approximately one to two excess cases of GBS per million people vaccinated, is substantially less than the overall health risk posed by naturally occurring influenza [41]. Influenza vaccination for the prevention of seasonal influenza is reviewed in detail separately. (See "Seasonal influenza vaccination in adults".)
●Meningococcal vaccination – Cases of GBS have been reported following administration of the quadrivalent meningococcal conjugate vaccine MCV4 (Menactra). This issue, along with meningococcal vaccine recommendations, is discussed separately. (See "Meningococcal vaccination in children and adults".)
●Recombinant zoster vaccination – Cases of GBS have been observed in a postmarketing observational study during the 42 days following vaccination [76]. These cases represent an increased risk of 3 cases per 1 million doses of vaccine administered to adults age 65 and older. (See "Vaccination for the prevention of shingles (herpes zoster)", section on 'Adverse events'.)
●COVID-19 vaccination – Cases of GBS have been observed with the adenovirus vector-based Janssen/Johnson & Johnson (Ad26.COV2.S) and AstraZeneca (ChAdOx1 nCoV-19/AZD1222) COVID-19 vaccines in the United States and Europe [77-81]. In the United States, 123 cases occurring within six weeks of immunization in 2021 were reported among 13.2 million administered doses [81]. Adenovirus vector vaccines for COVID-19 are no longer available in the United States. (See "COVID-19: Vaccines".)
Rare cases of GBS have been reported with messenger ribonucleic acid (mRNA)-based COVID-19 vaccines, however data from multiple population-based studies suggest this finding may reflect the baseline risk of GBS [82-85]. In one cohort of 76 patients with GBS occurring during an 18-month period of 2021 and 2022, receipt of an mRNA COVID-19 vaccine dose in the preceding six weeks was associated with a reduced risk of subsequent GBS (odds ratio 0.41, 95% CI 0.17-0.96) [52].
The US Food and Drug Administration (FDA) and United States Centers for Disease Control and Prevention (CDC) request that practitioners report possible cases of GBS occurring after vaccination to the Vaccine Adverse Events Reporting System (VAERS) online at https://vaers.hhs.gov/ or by telephone at 800-822-7967.
Other triggers — A small percentage of patients develop GBS after other triggering events such as surgery, trauma, or bone-marrow transplantation [86,87]. GBS has also been linked to systemic processes, including Hodgkin lymphoma, systemic lupus erythematosus, and sarcoidosis [88]. GBS does not appear to occur with increased frequency during pregnancy, but the incidence may be increased in the postpartum period [89]. Several medications have been reported to trigger GBS, including:
●Tumor necrosis factor-alpha antagonist therapy [90]
●Tacrolimus and suramin [91]
●Isotretinoin [92]
●Immune checkpoint inhibitors [93-96]
EPIDEMIOLOGY — GBS occurs worldwide with an overall incidence of 1 to 2 cases per 100,000 per year [1,2,97,98]. While all age groups are affected, the incidence increases by approximately 20 percent with every 10-year increase in age beyond the first decade of life. In addition, the incidence is slightly higher in males than in females.
There is regional variation among the variant forms of GBS with axonal forms being more common in Asia than North America or Europe, where demyelinating forms predominate. (See 'Variant forms of Guillain-Barré syndrome' below.)
CLINICAL FEATURES — The typical clinical features of GBS include a progressive and symmetric muscle weakness and absent or depressed deep tendon reflexes. Patients may also have sensory symptoms and dysautonomia. (See 'Examination findings' below and 'Variant forms of Guillain-Barré syndrome' below.)
Time course of symptoms — Initial symptoms may become apparent and patients typically present within a few days to a week after onset of symptoms. GBS symptoms typically progress over a period of two weeks. By four weeks after onset, more than 90 percent of patients have reached the nadir of the disease [99].
Progression over four to eight weeks is sometimes called subacute inflammatory demyelinating polyradiculoneuropathy (SIDP). The management of patients with GBS symptoms within eight weeks is discussed separately. (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Approach to patients who relapse or worsen'.)
Disease progression for more than eight weeks is consistent with the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Prognosis' and 'Chronic inflammatory demyelinating polyneuropathy' below.)
If the nadir is reached within 24 hours or after four weeks of symptom onset, alternative diagnoses must be considered [100]. (See 'Differential diagnosis' below.)
Examination findings — Studies of patients with GBS from the United States and Europe primarily describe patients with acute inflammatory demyelinating polyneuropathy (AIDP), the most common form of GBS [88,99]. Such symptoms may include the following.
Weakness — The weakness in GBS can vary from mild difficulty with walking to near complete paralysis of all limb, facial, respiratory, and bulbar muscles, depending on disease severity and clinical subtype.
●Limb weakness – Classically, there is flaccid proximal and distal arm and leg weakness. The weakness is usually symmetric and starts in the legs, but begins in the arms or facial muscles in about 10 percent of patients. Most patients progress to weakness in both arms and legs by the nadir [99].
●Cranial nerve and bulbar symptoms – Facial nerve palsies occur in more than 50 percent with AIDP, and oropharyngeal weakness eventually occurs in 50 percent [99]. Oculomotor weakness occurs in about 15 percent of patients.
Cranial nerve symptoms including ophthalmoplegia are also diagnostic features of some variant forms of GBS. (See 'GQ1b syndromes' below.)
Severe respiratory muscle weakness necessitating ventilatory support develops in 10 to 30 percent with GBS [31,99,101].
Deep tendon reflexes — Decreased or absent deep tendon reflexes in the arms or legs are found in approximately 90 percent of patients at presentation [99]. Most patients will develop hyporeflexia as symptoms progress to the nadir.
However, normal or even increased deep tendon reflexes may be found in some patients with GBS [102]. These include patients with the acute axonal neuropathies and Bickerstaff brainstem variant forms. Normal reflexes in GBS have also been associated with patients who report an antecedent diarrheal rather than respiratory illness [102,103]. (See 'Variant forms of Guillain-Barré syndrome' below.)
Hyperreflexia is also geographically variable, reported more frequently in cases from Japan associated with axonal forms [102,103].
Other findings — Other neurologic symptoms and autonomic dysfunction may also develop in some patients with AIDP and may be prominent features in some variant forms of GBS. (See 'Variant forms of Guillain-Barré syndrome' below.)
●Sensory involvement – Paresthesias in the hands and feet are reported by more than 80 percent of patients, but sensory abnormalities on examination are frequently mild.
Pain due to nerve root inflammation, typically located in the back and extremities, can also be a presenting feature and is reported during the acute phase by two-thirds of patients with all forms of GBS [104,105].
●Dysautonomia – The prevalence of autonomic dysfunction ranges from 38 to 70 percent of patients with GBS [106,107]. In a 2020 retrospective review of 187 GBS patients, the most frequent autonomic symptoms were [107]:
•Ileus (42 percent)
•Hypertension (39 percent)
•Hypotension (37 percent)
•Fever (29 percent)
•Tachycardia or bradycardia (27 percent)
•Urinary retention (24 percent)
Patients with dysautonomia tended to have more frequent cardiogenic complications, hyponatremia, and a higher burden of disability [107]. Mortality in patients with dysautonomia was 6 versus 0 percent in those without dysautonomia. Severe autonomic dysfunction has also been associated with sudden death [108].
The syndrome of inappropriate antidiuretic hormone secretion (SIADH), which may be due to autonomic involvement, is an infrequent complication of GBS [109-111]. In the United States Nationwide Inpatient Sample data, SIADH was significantly more frequent in hospitalized patients with GBS compared with controls (5 versus <1 percent) [109].
●Uncommon features – Unusual features of GBS include papilledema with severely elevated cerebrospinal fluid (CSF) protein, facial myokymia, hearing loss, meningeal signs, vocal cord paralysis, and mental status changes [86].
In addition, posterior reversible encephalopathy syndrome, also known as reversible posterior leukoencephalopathy syndrome, has been associated with GBS in adults and children, likely related to acute hypertension from dysautonomia [112-114]. (See "Reversible posterior leukoencephalopathy syndrome".)
Variant forms of Guillain-Barré syndrome — Historically, GBS was considered a single disorder. It now is recognized as a heterogeneous syndrome with several variant forms [2]. Variant forms of GBS may be identified by distinguishing clinical, pathophysiologic, and pathologic features. Common variant forms include:
●Acute motor axonal neuropathy (AMAN)
●Acute motor and sensory axonal neuropathy (AMSAN)
●Miller Fisher syndrome (MFS)
●Bickerstaff brainstem encephalitis (BBE)
Uncommon forms of GBS that share some features with a more common variant or have features that overlap with more than one variant form of GBS have also been described. (See 'Rare variants' below.)
The clinical forms of GBS vary according to geographic region. In an analysis of the first 1000 patients enrolled in the International Guillain-Barré Outcome Study (IGOS), the sensorimotor variant was more common among patients from North and South America than those from Bangladesh or other Asian countries (69 versus 29 versus 43 percent) [31]. By contrast, the pure motor variant was more common among those from Bangladesh than patients from other Asian countries or North and South America (69 versus 24 versus 14 percent). MFS occurred in only 1 percent of patients from Bangladesh but 11 percent of patients from North and South America and in 22 percent of patients from other countries in Asia.
Acute inflammatory demyelinating polyneuropathy — AIDP is the most common form of GBS. In the United States and Europe, AIDP represents approximately 85 to 90 percent of cases. The typical clinical features are a progressive, symmetric muscle weakness accompanied by absent or reduced deep tendon reflexes. (See 'Clinical features' above.)
Acute axonal neuropathies — AMAN and AMSAN are primary axonal forms of GBS. These forms are frequently observed in China, Japan, and Mexico, but they also comprise an estimated 5 to 10 percent of GBS cases in the United States [31,115].
●Acute motor axonal neuropathy – AMAN was first recognized in 1986 [116]. Most cases are preceded by C. jejuni infection and occur in Asia, particularly in young people [21,31,117]. AMAN is more frequent in the summer. The pathology predominantly involves axon loss.
Deep tendon reflexes may be preserved in some patients with AMAN [118]. This form of GBS is distinguished from AIDP by its selective involvement of motor nerves. Sensory nerves are not affected. It may progress more rapidly, but the presenting clinical features of AMAN are otherwise similar to those of AIDP.
Evidence of early axonal involvement on electrodiagnostic studies is seen as a reduction of compound muscle action potential (CMAP) amplitudes on nerve conduction studies.
The development of AMAN has been associated with IgG antibodies to the gangliosides GM1, GD1a, GalNac-GD1a, and GD1b, which are present in peripheral nerve axons [21]. These antiganglioside antibodies can be induced by C. jejuni infection owing to molecular mimicry. The pathophysiology is due to antibody and complement-mediated nerve axon damage of varying severity.
●Acute motor and sensory axonal neuropathy – AMSAN is a more severe form of AMAN, in which both sensory and motor fibers are affected with marked axonal degeneration, frequently causing delayed and incomplete recovery [36]. Clinically, AMSAN resembles the AMAN variant but with additional sensory symptoms.
Electrodiagnostic studies on patients with AMSAN show severely reduced or absent CMAP and sensory nerve action potential (SNAP) amplitudes. Axon degeneration in these patients is demonstrated by extensive active denervation needle electrode electromyography (EMG) studies.
AMSAN is also associated with antiganglioside antibodies to GM1, GD1a, GalNac-GD1a, and GD1b [119].
GQ1b syndromes — Variant forms of GBS characterized by clinical features of impairment of eye movement (ophthalmoplegia) and ataxia rather than limb weakness are frequently associated with seropositivity to antibodies against GQ1b. The GQ1b antibody is thought to have a direct effect on the neuromuscular junctions between cranial nerves and ocular muscles [120]. The GQ1b ganglioside is a component of oculomotor nerve myelin [23]. These forms may be called anti-GQ1b syndromes and include MFS, BBE, and pharyngeal-cervical-brachial (PCB) variants [121]. The pathology appears to be chiefly due to demyelination [122].
●Miller Fisher syndrome – The clinical variant MFS, characterized by ophthalmoplegia, ataxia, and areflexia, occurs in approximately 5 to 10 percent of cases in the United States and Europe and 20 percent of cases in Asia [31,123].
The typical presentation of MFS is that of ophthalmoplegia with ataxia and areflexia but about one-quarter of patients who present with MFS will develop some limb weakness [123,124]. Incomplete forms include acute ophthalmoplegia without ataxia and acute ataxic neuropathy without ophthalmoplegia [1,125]. Some patients with MFS develop fixed, dilated pupils [126].
Antibodies against GQ1b (a ganglioside component of nerve) are present in 85 to 90 percent of patients with MFS [127,128].
Electrodiagnostic studies in patients with MFS may reveal reduced or absent sensory responses without slowing of sensory conduction velocities [129]. Those with clinical weakness may show abnormalities on nerve conduction studies typical of AIDP, such as increased distal latencies or conduction block with temporal dispersion of motor responses.
●Bickerstaff brainstem encephalitis – BBE is a GQ1b syndrome characterized by encephalopathy with ophthalmoplegia and ataxia. In a series of 62 patients with BBE, facial weakness was present in 45 percent and bulbar symptoms including pupillary abnormalities were present in 34 percent [130]. In a review of 53 patients with BBE, approximately half were found to have mild limb weakness [121]. Reflexes were normal or brisk in 40 percent.
BBE is not only linked to MFS by shared clinical features but is also associated with anti-GQ1b antibodies and can respond to intravenous immune globulin (IVIG) or plasma exchange [131,132].
A retrospective review of the early electrophysiologic features (within 10 days) of 12 Spanish patients with BBE revealed reduced SNAP amplitudes in 5 (42 percent) patients, abnormal blink reflexes in 3 (25 percent), no signs of demyelination, and rare abnormalities in motor conductions. Interestingly, three of the patients showed normalization of SNAP amplitudes on serial neurophysiologic studies suggestive of reversible conduction failure similar to the observation in some AMAN variant cases [133].
●Pharyngeal-cervical-brachial weakness – The PCB variant of GBS is characterized by acute weakness of the oropharyngeal, neck, and shoulder muscles with swallowing dysfunction [134,135]. This form may overlap with MFS or BBE [134,136].
Patients with the PCB variant may also have facial weakness but may be distinguished from those with AIDP because leg strength and leg reflexes are usually [134,135], but not always [137], preserved.
There are no postmortem or clinico-pathologic correlates of PCB, but detailed serial nerve conduction studies indicate a localized pattern of neuronal damage similar to AMAN [1,134,135].
In a study of 100 PCB patients, half carried IgG anti-GT1a antibodies (associated with bulbar dysfunction), which often cross-react with GQ1b, and a quarter displayed IgG antibodies against GM1 or GD1a, which are often seen in AMAN [26,134].
Rare variants — There are a number of additional uncommon variants of GBS, including the following:
●Paraparesis – The paraparetic variant is typically a mild type of GBS characterized by weakness and hyporeflexia limited to the lower limbs at presentation [135,138]. In a cohort of nearly 500 patients with GBS, 40 patients were characterized by a paraparetic clinical course [138]. Among these patients, intact strength in the upper extremities was found in more than 70 percent of patients, but nerve involvement in the upper extremities was frequently identified by hyporeflexia (73 percent) and abnormal nerve conductions (89 percent).
●Acute pandysautonomia – Patients may present with isolated acute autonomic dysfunction and hyporeflexia consistent with GBS [139]. Symptoms include diarrhea, vomiting, dizziness, abdominal pain, ileus, orthostatic hypotension, urinary retention, pupillary abnormalities, an invariant heart rate, and decreased sweating, salivation, and lacrimation. Reflexes are absent or diminished, and sensory symptoms may be present.
Patients with pandysautonomia may respond to immunomodulatory therapies used for GBS, such as IVIG [139,140].
●Pure sensory GBS – GBS with isolated sensory abnormalities is a rare and heterogenous entity [141]. Reflexes are absent, and there may be minor motor involvement. An association with antibodies to GD1b has been noted [142].
Sensory GBS may be subcategorized by nerve fiber pathology into three subtypes: acute sensory demyelinating polyneuropathy, acute sensory large-fiber axonopathy-ganglionopathy, and acute sensory small-fiber neuropathy-ganglionopathy [141].
Patients with suspected sensory GBS should be evaluated for acute paraneoplastic sensory neuronopathy, which is likelier to present with asymmetric sensory loss and severe ataxia. (See "Approach to the patient with sensory loss", section on 'Sensory neuronopathies'.)
●Facial diplegia and distal limb paresthesia – Case series have described patients with acute-onset bilateral facial weakness with paresthesias of the limbs [136,143,144]. Other bulbar symptoms are typically absent and electrodiagnostic studies show abnormalities suggestive of demyelinating pathology consistent with GBS.
●Acute bulbar palsy – Patients may also present with areflexia, ophthalmoplegia, ataxia, and facial palsy; neck and limb weakness are absent [145]. This rare form overlaps with both MFS and PCB variants of GBS.
DIAGNOSTIC EVALUATION — The initial diagnosis of GBS is based on the clinical features consistent with the syndrome: acute onset of progressive, mostly symmetric muscle weakness and reduced or absent deep tendon reflexes. The weakness can vary from mild difficulty with walking to nearly complete paralysis of all extremity, facial, respiratory, and bulbar muscles. Symptoms typically progress over days to four weeks. (See 'Clinical features' above.)
The clinical diagnosis of GBS is supported by results of diagnostic testing such as cerebrospinal fluid (CSF) and electrodiagnostic studies [75]. Lumbar puncture for CSF evaluation is performed in all patients. Electrodiagnostic studies and imaging are performed in patients with atypical symptoms and whenever the initial CSF evaluation is nondiagnostic (algorithm 1). These diagnostic tests may also help to exclude alternative diagnoses [146]. (See 'Cerebrospinal fluid analysis' below and 'Electrodiagnostic studies' below.)
Diagnostic criteria — Diagnostic criteria for GBS, originally proposed for research in 1978 by the National Institute of Neurological Disorders and Stroke (NINDS) [147], are widely used in clinical practice. These criteria are based on expert consensus and have been modified over time to reflect advances in the understanding of GBS [75,148].
Required features include:
●Progressive weakness of the arms and/or legs, ranging from minimal weakness of the legs to total paralysis of all four limbs, and including the trunk, bulbar and facial muscles, and external ophthalmoplegia.
●Areflexia or decreased deep tendon reflexes in weak limbs.
Supportive features include:
●Symptom progression over days to four weeks
●Relatively symmetric, bilateral symptoms
●Pain in the trunk or limbs
●Cranial nerve symptoms or signs
●Autonomic dysfunction
●Sensory dysfunction that is mild
●No fever at symptom onset
●CSF with elevated protein and normal to mildly elevated leukocyte count (usually <5 cells/mm3)
●Electrodiagnostic abnormalities consistent with GBS
●Recovery starting two to four weeks after progression halts
An epidemiologic study in Italy found that 84 percent of patients with GBS fulfilled the NINDS criteria and 16 percent had a variant syndrome [149]. Patients with GBS who do not meet the required criteria will typically have symptoms consistent with one of the other variant forms of GBS variants. As examples, patients with acute motor axonal neuropathy (AMAN) may have acute and progressive symmetric limb weakness but reflexes may be retained; those with Miller Fisher syndrome (MFS) may have acute and progressive ophthalmoplegia with reduced reflexes but no limb weakness. (See 'Examination findings' above and 'Variant forms of Guillain-Barré syndrome' above.)
Patients with symptoms that do not meet diagnostic criteria for GBS or a variant form should be evaluated for alternative causes. (See 'Additional diagnostic tests for some patients' below and 'Differential diagnosis' below.)
The World Health Organization recommends use of the Brighton criteria (table 1) for the case definition of GBS in regions affected by Zika virus transmission [150]. The Brighton criteria are developed for research studies and exclude most clinical variants of GBS. (See "Zika virus infection: An overview".)
Cerebrospinal fluid analysis — Lumbar puncture for CSF analysis should be performed in all patients to confirm the GBS diagnosis and exclude other sources to the symptoms. The typical finding with lumbar puncture in patients with GBS is an elevated CSF protein with a normal white blood cell count. This finding is called an albuminocytologic dissociation. The elevated protein may be due to increased permeability of the blood-nerve barrier at the level of the proximal nerve roots.
●CSF protein elevations varied in one study from 45 to 200 mg/dL (0.45 to 2.0 g/L) for most patients, but protein elevations as high as 1000 mg/dL (10 g/L) have also been described [86].
The albuminocytologic dissociation varies by time since symptom onset. It may be present in 50 to 66 percent of patients in the first week after the onset of symptoms and ≥75 percent of patients in the third week [1,86,151,152]. In an analysis of 1231 patients from the International Guillain-Barré Outcome Study (IGOS), an albuminocytologic dissociation increased from 57 percent among patients ≤4 days from onset of weakness to 84 percent for those >4 days from onset of weakness [153]. GBS features associated with albuminocytologic dissociation included proximal or diffuse weakness and demyelinating subtype. In some series, a normal CSF protein is found in one-third to one-half of patients when tested earlier than one week from symptom onset and therefore does not exclude the diagnosis of GBS [99].
●The CSF cell count is typically normal (ie, <5 cells/mm3) but may be elevated up to 50 cells/mm3. However, a minority of patients with GBS have mildly elevated CSF cell counts [153]. In one study, the cell count was <5 cells/mm3 in 87 percent of patients, 5 to 10 cells/mm3 in 9 percent, and 11 to 30 cells/mm3 and >30 cells/mm3 in 2 and 2 percent of patients, respectively [86]. A review of 494 adult patients with GBS similarly found a mild CSF pleocytosis of 5 to 50 cells/mm3 present in 15 percent, and none had a pleocytosis >50 cells/mm3 [99].
A CSF pleocytosis is common in patients who have GBS and concurrent HIV infection [47].
The routine analysis of CSF for GBS includes cell count and differential, protein, glucose, Gram stain, and culture. Any remaining CSF should be retained for possible further analysis if the results of the initial routine analysis show a significant pleocytosis or other finding suggestive of an alternative diagnosis. (See 'Differential diagnosis' below.)
Electrodiagnostic studies — Electrodiagnostic studies consist of nerve conduction studies (NCS) and electromyography (EMG) and are performed in most patients to support the diagnosis of GBS as well as to provide prognostic information regarding the nature and severity of nerve dysfunction. They may be performed serially, at presentation and again several weeks later, to monitor recovery. However, electrodiagnostic testing may not be needed for the diagnosis of GBS in patients with typical symptoms who are found to have an albuminocytologic dissociation on CSF analysis. In addition, testing may be unavailable in some settings, and findings may be normal early in the disease course. Electrodiagnostic results may be limited in the intensive care or other inpatient settings due to technical and electrical artifacts or when patients are sedated and unable to participate in the assessment of volitional motor activity.
If electrodiagnostic testing performed at initial presentation is nondiagnostic, repeat testing may be performed one to two weeks after the first study. Abnormal findings are typically most pronounced approximately three to four weeks after the onset of weakness [154].
Progression of abnormal findings that support the diagnosis of the common demyelinating forms of GBS include [155-158]:
●Prolonged or absent F waves and absent H reflexes as the earliest findings
●Increased distal latencies and conduction blocks with temporal dispersion of motor responses
●Significant slowing or absent response on nerve conduction velocities not seen until the third or fourth week
●Needle EMG of weak muscles showing reduced recruitment or denervation
Sural sparing, when noted, also reinforces the suspicion for GBS since this finding is usually not observed in length dependent neuropathies [159]. Ancillary studies, such as facial NCS and blink reflex testing, may be used to show abnormal conduction in patients with GBS and bulbar symptoms.
Electrodiagnostic studies may also be useful to identify the main variants of GBS by identifying demyelinating (eg, acute inflammatory demyelinating polyneuropathy) or axonal (eg, AMAN) pathophysiology [75].
●Demyelinating forms of GBS are supported by features of demyelination, including increased F wave latency, prolonged distal motor latency, conduction blocks, temporal dispersion, and decreased motor nerve conduction velocity [154].
●Axonal forms of GBS are supported by decreased distal motor and/or sensory amplitudes [154]. In contrast with demyelinating forms, there is typically no sensory nerve involvement and F waves may be absent but are not significantly prolonged. In addition, there is no significant slowing of conduction velocities, increase in distal latencies, or temporal dispersion.
However, the low distal CMAP amplitudes in axonal forms may be associated with conduction block, a feature more typical of demyelinating forms of GBS [160]. Conduction block in axonal form is typically reversible, and the CMAP amplitudes rapidly improve with early recovery of function [160-162]. Electrophysiologic diagnosis to distinguish AMAN associated with reversible conduction block cases is more reliable when performed at three to six weeks after GBS onset rather than the first two weeks [163-165].
In 745 participants in the International Guillain-Barré Outcome Study classified by electrodiagnostic studies, 52 percent had a demyelinating pathophysiology, 10 percent axonal, 3 percent inexcitable nerves, while 29 percent were notably equivocal, and 7 percent had normal electrodiagnostic testing. Overall, patients with the axonal variants of GBS were younger than patients with demyelination [31].
Electrodiagnostic findings in patients with specific GBS variants are also discussed above. (See 'Variant forms of Guillain-Barré syndrome' above.)
Laboratory testing — We perform initial screening laboratory testing in all patients to screen other causes of acute weakness. This includes:
●Complete blood count and differential
●Comprehensive metabolic profile
●Erythrocyte sedimentation rate (ESR)
●Serum glucose and glycosylated hemoglobin
Additional testing to evaluate for other causes of acute weakness may be indicated by specific symptoms, risk factors, and clinical settings (table 2). (See 'Differential diagnosis' below and "Overview of polyneuropathy".)
Additional diagnostic tests for some patients — For patients with atypical clinical features or those with equivocal results on CSF analysis and electrodiagnostic studies, antibody testing and neuroimaging are obtained to support the diagnosis of GBS and to exclude alternative possibilities.
Autoantibody testing — Antiganglioside antibody testing may be useful in clinical practice to help identify patients with atypical symptoms that may be suggestive of a variant form of GBS. (See 'Variant forms of Guillain-Barré syndrome' above.)
The serum of patients with acute axonal neuropathies such as AMAN and acute motor and sensory axonal neuropathy (AMSAN) have frequently been found to have anti-GM1 IgG and anti-GD1a antibodies [21,166]. Anti-GalNac-GD1a and anti-GD1b have also been associated with axonal forms of GBS [167,168]. Anti-GM2 IgM antibodies have been noted in 30 to 50 percent of patients with cytomegalovirus (CMV)-associated GBS, but anti-GM2 antibodies also occur in patients with CMV who do not have GBS [169,170]. (See 'Acute axonal neuropathies' above.)
Serum IgG antibodies to GQ1b are useful for the diagnosis of MFS, having a sensitivity of 85 to 90 percent. GQ1b is a component of oculomotor nerve myelin and may also be present in patients with Bickerstaff brainstem encephalitis, the pharyngeal-cervical brachial (PCB) variant, and other patients with GBS with ophthalmoplegia [127,128]. Anti-GT1a antibodies that cross-react with GQ1b have been reported in patients with the PCB variant [26]. (See 'GQ1b syndromes' above.)
Some patients with PCB form of GBS may have antibodies against GM1 or GD1a, which are more frequently seen in patients with AMAN who also present with prominent motor weakness [26,134].
Diagnostic imaging — Diagnostic imaging is typically reserved for patients with atypical symptoms to exclude alternative causes. This includes patients with prominent early bowel or bladder dysfunction, those who present with a sensory level, and those who reach a clinical nadir within 24 hours of symptom onset. Imaging is also warranted for patients with clinical symptoms of GBS when CSF and electrodiagnostic studies are not confirmatory. (See 'Differential diagnosis' below.)
For most patients with symptoms of GBS who are evaluated with diagnostic imaging, we obtain magnetic resonance imaging (MRI) of the brain and spine with contrast. MRI of the brain and cervical spine imaging is typically performed for patients with bulbar weakness and/or quadriparesis, while MRI of the thoracic and lumbar spine imaging is performed for those with lower extremity weakness to evaluate for transverse myelitis or another cause for myelopathy.
In addition, features consistent with GBS may be identified on imaging of the spine or nerves:
●MRI – Spinal MRI (image 1) may reveal thickening and enhancement of the intrathecal spinal nerve roots and cauda equina [171-174]. The anterior spinal nerve roots may be selectively involved, but, in other cases, both the anterior and posterior spinal nerve roots are involved.
In exceptional cases of MFS, abnormalities of the spinal cord posterior columns have been described [174]. On brain MRI, enhancement of the oculomotor, abducens, and facial nerves may be seen (image 1) [172,173,175].
●Ultrasound – Peripheral nerve ultrasound may identify structural changes associated with GBS. Patients with GBS may have enlarged cervical nerve roots acutely and show progressive improvement of cross-sectional area of peripheral nerves on serial ultrasound studies during recovery [176-178]. Sparing of sensory nerves on ultrasound and transient enlargement of nerve roots and the vagus nerve may help differentiate GBS from chronic inflammatory demyelinating polyradiculoneuropathy, and ultrasonographic normalization of nerves evaluated at six months lends further confirmation of the diagnosis of GBS [179].
DIFFERENTIAL DIAGNOSIS — The differential diagnosis of GBS includes chronic inflammatory demyelinating polyneuropathy (CIDP) and other acute polyneuropathies as well as diseases of the spinal cord, neuromuscular junction, and muscle (table 3).
The differential diagnosis of variant forms of GBS characterized by prominent ophthalmoplegia and ataxia additionally includes cerebral and brainstem pathologies. (See 'Differential diagnosis of Miller Fisher syndrome' below.)
The following features make the diagnosis of GBS doubtful:
●Weakness progresses to nadir <24 hours or >4 weeks from symptom onset
●Sensory level (decrement or loss of sensation below a spinal cord root level)
●Asymmetric weakness
●Bowel and bladder dysfunction at onset or that becomes severe and persistent
●Pulmonary dysfunction with little or no limb weakness at onset
●Sensory signs that are isolated or with no weakness at onset
●Fever at onset
●Cerebrospinal fluid (CSF) leukocyte count >50/mm3
Patients with any of these features should be evaluated for alternative sources to symptoms. As examples, brain and/or spine magnetic resonance imaging (MRI) may be warranted when central etiologies are suspected by the presence of a sensory level, prominent bowel/bladder dysfunction, or weakness progressing to nadir <24 hours from symptom onset. By contrast, additional laboratory testing may be indicated for patients with prominent sensory signs and those with fever at onset (table 2). Evaluation for inflammatory conditions such as transverse myelitis are warranted for patients with a CSF leukocyte count >50 mm3 (table 4). (See 'Additional diagnostic tests for some patients' above.)
Chronic inflammatory demyelinating polyneuropathy — There is a temporal continuum between acute inflammatory demyelinating polyneuropathy (AIDP), the demyelinating form of GBS, and CIDP.
●AIDP is a monophasic subacute illness that typically reaches its nadir within two to four weeks. (See 'Time course of symptoms' above.)
●Subacute inflammatory demyelinating polyneuropathy (SIDP) is the term used by some authors for symptoms that reach a nadir between four and eight weeks.
●CIDP continues to progress or has relapses for greater than eight weeks. (See "Chronic inflammatory demyelinating polyneuropathy: Etiology, clinical features, and diagnosis".)
This arbitrary temporal delineation between GBS and CIDP can occasionally be difficult to ascertain in practice. Examination of the patient over time and serial electrodiagnostic studies or peripheral nerve ultrasound can help clarify whether the clinical course is that of AIDP or CIDP [179]. (See 'Electrodiagnostic studies' above and 'Diagnostic imaging' above.)
Features may be useful to distinguish GBS from CIDP:
●The onset of GBS is usually easily identified, while the precise onset of CIDP is typically less clear.
●Antecedent events are identified more frequently with GBS than CIDP (approximately 70 percent of GBS cases versus <30 percent of CIDP cases).
●Clinical features in the first few weeks after onset of symptoms suggestive of CIDP over GBS include [180]:
•Acute relapse or deterioration occurs ≥3 times
•Deterioration occurs ≥8 weeks after symptom onset
•Mild symptoms with retained ability to walk independently throughout course
•Lack of either cranial neuropathies or frequent respiratory involvement
About 2 to 5 percent of patients initially diagnosed with AIDP will develop the chronic relapsing weakness of CIDP. (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Approach to patients who relapse or worsen'.)
Other polyneuropathies — Several polyneuropathies may mimic GBS by presenting with an abrupt symptom onset. The combination of data from the clinical setting, screening laboratory tests indicated by presentation and risk factors, and cerebrospinal fluid analysis and nerve conduction studies, are usually sufficient to identify or rule out these other causes of polyneuropathy.
Specific etiologies include:
●Thiamine (vitamin B1) deficiency – Adults with thiamine deficiency from nutritional deficiencies or chronic alcohol use typically present with a symmetric, distal motor and sensory polyneuropathy. (See "Overview of water-soluble vitamins", section on 'Deficiency'.)
●Acute arsenic poisoning – Patients with arsenic poisoning may present with distal, sensory-predominating neurologic symptoms. A history of environmental exposure and associated skin or nail changes may be seen. Urine testing is useful to identify arsenic toxicity. (See "Arsenic exposure and chronic poisoning", section on 'Neurologic'.)
●Toxic neuropathies – Exposure to toxic substances such as n-hexane exposure (in "glue sniffing neuropathy") may lead to an acute polyneuropathy. (See "Overview of polyneuropathy", section on 'Toxic'.)
●Lyme disease – Neurologic manifestations of borreliosis are varied and include peripheral polyneuropathy, cranial nerve palsies (eg, facial nerve palsy), and ataxia. Laboratory and CSF testing identifies Lyme disease. (See "Clinical manifestations of Lyme disease in adults", section on 'Neurologic manifestations'.)
●Tick paralysis – Patients with tick paralysis may present with bulbar or limb weakness. Symptoms may be asymmetric. Laboratory and CSF testing is typically normal. Symptoms typically improve promptly following removal of the embedded tick. (See "Tick paralysis", section on 'Clinical manifestations'.)
●Systemic vasculitis – Peripheral nerve vasculitis may present with mononeuritis multiplex of sensory and motor fibers in the distribution of individual peripheral nerves. Although the pathology of the disease is asymmetric, the clinical picture can mimic GBS with symmetric ascending weakness when the vasculitis is rapidly progressive with confluent nerve involvement. Patients may also have severe limb pain and systemic symptoms such as fever, weight loss, and other organ involvement. Serological testing, electrophysiologic testing, and biopsy of nerve and muscle lead to the diagnosis. (See "Clinical manifestations and diagnosis of vasculitic neuropathies".)
●HIV/AIDS – Patients with HIV and severe immunosuppression or AIDS may develop acute and progressive lumbosacral polyradiculopathy. This may be due to opportunistic infections such as cytomegalovirus. Weakness may be asymmetric and patients may develop bowel and/or bladder dysfunction. CSF typically shows a lymphocytic pleocytosis. (See "Polyradiculopathy: Spinal stenosis, infectious, carcinomatous, and inflammatory nerve root syndromes", section on 'Polyradiculopathy in HIV and AIDS'.)
●Sarcoidosis – Patients with sarcoidosis may present with peripheral polyneuropathy and/or cranial neuropathies, sometimes in the absence of other systemic symptoms. An elevated angiotensin converting enzyme level in the blood or CSF and meningeal enhancement on brain or spine imaging supports the diagnosis. (See "Neurologic sarcoidosis".)
●Porphyria – Acute intermittent porphyria may present with a progressive sensory and motor neuropathy. Symptoms may begin in the upper limbs and can be associated with autonomic dysfunction as well as abdominal pain. A spot urine test for porphobilinogen in a sample obtained at the time of symptoms will identify most patients with acute porphyria. (See "Acute intermittent porphyria: Pathogenesis, clinical features, and diagnosis".)
●Leptomeningeal lymphoma – Malignant involvement of the meninges may present with a peripheral neuropathy but may have other neurologic symptoms such as headache, encephalopathy, or cranial nerve palsies. (See "Secondary central nervous system lymphoma: Clinical features and diagnosis".)
●Paraneoplastic syndromes – Peripheral motor or sensorimotor neuropathies can occur in patients with systemic cancer. The diagnosis may be suspected in patients with known systemic cancer and patients with other neurologic manifestations such as encephalopathy. Diagnostic evaluation may include imaging for malignancy, CSF analysis, and specific antibody testing. (See "Overview of paraneoplastic syndromes of the nervous system".)
Spinal cord disorders — Acute myelopathies can be confused with GBS since reflexes can be depressed in the acute stage of spinal cord disease. Examples include:
●Acute transverse myelitis (see "Transverse myelitis: Etiology, clinical features, and diagnosis")
●Spinal cord compression from fracture or epidural abscess (see "Spinal epidural abscess")
●Spinal cord infarction (see "Spinal cord infarction: Clinical presentation and diagnosis")
Distinguishing features favoring a spinal cord disorder include early bowel and bladder dysfunction, a sensory level on examination, and/or an elevated CSF leukocyte count (table 4). Spine MRI is usually helpful in identifying a focal spinal cord lesion consistent with acute myelopathy. (See "Disorders affecting the spinal cord".)
Motor neuron disorders such as amyotrophic lateral sclerosis, progressive spinal muscular atrophy, and poliomyelitis may also mimic GBS. These are discussed separately. (See "Clinical features of amyotrophic lateral sclerosis and other forms of motor neuron disease" and "Diagnosis of amyotrophic lateral sclerosis and other forms of motor neuron disease" and "Spinal muscular atrophy" and "Poliomyelitis and post-polio syndrome", section on 'Poliomyelitis'.)
Neuromuscular junction disorders — Diseases of the neuromuscular junction including botulism, myasthenia gravis, and Lambert-Eaton myasthenic syndrome can all present with acute weakness, but sensory signs or symptoms are lacking. Botulism is associated with large, unreactive pupils and constipation, though similar pupillary abnormalities may occur in a subset of patients with GQ1b syndromes. Electromyography with repetitive nerve stimulation and appropriate laboratory tests help clarify the diagnosis. (See "Diagnosis of myasthenia gravis" and "Lambert-Eaton myasthenic syndrome: Clinical features and diagnosis" and "Botulism" and 'GQ1b syndromes' above.)
Muscle disorders — Acute polymyositis, dermatomyositis, necrotizing myopathy, and critical illness myopathy can present with acute and symmetric weakness similar to GBS. Patients with myopathies may report muscle or joint pain and characteristic skin findings. A myopathic cause to weakness is supported by laboratory and electrodiagnostic testing and by muscle biopsy. The myopathy of critical illness (often combined with neuropathy) presents as an acute paralysis, typically in patients receiving intensive care. (See "Clinical manifestations of dermatomyositis and polymyositis in adults" and "Overview of and approach to the idiopathic inflammatory myopathies" and "Neuromuscular weakness related to critical illness".)
Differential diagnosis of Miller Fisher syndrome — The Miller Fisher syndrome (MFS) may be mistaken for a brainstem stroke due to prominent ophthalmoplegia with ataxia often without associated limb weakness found in other forms of GBS. The gradual onset and progressive nature of MFS symptoms may help to distinguish from an acute stroke. (See 'GQ1b syndromes' above.)
The differential diagnosis of MFS also includes other cerebral disorders. These include:
●Wernicke encephalopathy – Patients with Wernicke encephalopathy usually have encephalopathy and nystagmus, features not usually associated with MFS. Of note, nystagmus has been reported in an acute vestibular syndrome associated with anti-GQ1b antibodies [181]. Neuroimaging studies can be helpful to exclude stroke and to demonstrate the acute lesions of the diencephalon, midbrain, and periventricular regions that are sometimes found in patients with Wernicke encephalopathy. (See "Wernicke encephalopathy".)
●Myasthenia gravis – Myasthenia gravis and other neuromuscular junction disorders that may present with cranial nerve abnormalities may be mistaken for MFS. Appropriate laboratory and electrodiagnostic testing with repetitive nerve stimulation help differentiate MFS from neuromuscular junction disorders. (See "Clinical manifestations of myasthenia gravis" and "Diagnosis of myasthenia gravis" and "Electrodiagnostic evaluation of the neuromuscular junction".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Guillain-Barré syndrome".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Guillain-Barré syndrome (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Definition and pathogenesis – The acute immune-mediated polyneuropathies are classified under the eponym Guillain-Barré syndrome (GBS). The acute polyneuropathy of GBS is triggered when an immune response to an antecedent event cross-reacts with shared epitopes on peripheral nerve (molecular mimicry). (See 'Introduction' above and 'Pathogenesis' above.)
●Antecedent triggers – Most patients report an antecedent infection or other event in the four weeks prior to GBS. Upper respiratory tract infection and gastroenteritis are the most common infections, and Campylobacter jejuni gastroenteritis is the most commonly identified precipitant of GBS. (See 'Antecedent events' above.)
●Epidemiology – GBS occurs worldwide with an overall incidence of 1 to 2 cases per 100,000 per year. The incidence increases by approximately 20 percent with every 10-year increase in age. (See 'Epidemiology' above.)
●Clinical features – The typical clinical features of GBS include progressive and symmetric muscle weakness with absent or depressed deep tendon reflexes. Patients may also have sensory symptoms and dysautonomia. (See 'Clinical features' above.)
•GBS symptoms typically progress over a period of two weeks. If the nadir is reached within 24 hours or after 4 weeks of symptom onset, alternative diagnoses must be considered. (See 'Time course of symptoms' above.)
•GBS is a heterogeneous syndrome with variant forms that may be identified by distinguishing clinical and pathologic features. Acute inflammatory demyelinating polyneuropathy is the most common form of GBS. Common variant forms include acute motor axonal neuropathy, acute motor and sensory axonal neuropathy, Miller Fisher syndrome, and Bickerstaff brainstem encephalitis. (See 'Examination findings' above and 'Variant forms of Guillain-Barré syndrome' above.)
●Diagnostic evaluation – The initial diagnosis of GBS is based on the clinical features consistent with the syndrome: acute onset of progressive, mostly symmetric muscle weakness, and reduced or absent deep tendon reflexes. The clinical diagnosis of GBS is confirmed if cerebrospinal fluid (CSF) and electrodiagnostic studies show typical abnormalities (algorithm 1). (See 'Diagnostic evaluation' above.)
•CSF findings in patients with GBS is an albuminocytologic dissociation consisting of an elevated CSF protein (typically 45 to 200 mg/dL [0.45 to 2.0 g/L]) with a normal white blood cell count (typically <5 cells/mm3 but may be elevated up to 50 cells/mm3). (See 'Cerebrospinal fluid analysis' above.)
•Electrodiagnostic studies may show prolonged or absent F waves and absent H reflexes, increased distal latencies and conduction blocks with temporal dispersion, significant slowing or absent response on nerve conduction velocities, and reduced recruitment or denervation on needle electromyography of weak muscles. (See 'Electrodiagnostic studies' above.)
•Laboratory testing is performed for all patients to screen other common causes of acute weakness. We reserve ganglioside autoantibody testing for patients with symptoms suggestive of a variant form of GBS. Neuroimaging is typically used for patients with atypical symptoms to exclude alternative etiologies. (See 'Additional diagnostic tests for some patients' above.)
●Differential diagnosis – The differential diagnosis of GBS includes chronic inflammatory demyelinating polyneuropathy, other acute polyneuropathies, and diseases of the spinal cord, neuromuscular junction, and muscle (table 3). Patients with features atypical for GBS should be evaluated for alternative sources to symptoms (algorithm 1). (See 'Differential diagnosis' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Francine J Vriesendorp, MD, who contributed to earlier versions of this topic review.
10 : Early nodal changes in the acute motor axonal neuropathy pattern of the Guillain-Barrésyndrome.
42 : Guillain-Barrésyndrome following primary cytomegalovirus infection: a prospective cohort study.
137 : Guillain-barrésyndrome presenting pharyngeal-cervical-brachial weakness in the recovery phase.
177 : Ultrasonography of the peripheral nervous system in the early stage of Guillain-Barrésyndrome.
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