Oculomotor circuitry for horizontal eye movements

During horizontal saccades, the paramedian pontine reticular formation (PPRF) burst cells innervate the abducens nucleus, which contains two distinctive sets of neurons. Axons from the abducens motor neurons innervate the ipsilateral lateral rectus muscle, while the axons of the abducens interneurons cross the midline to become the medial longitudinal fasciculus (MLF) and subsequently innervate the medial rectus subnucleus of the oculomotor complex (cranial nerve nucleus III).
Internuclear ophthalmoplegia (INO) is characterized by slowing and/or limitation of the adducting eye during horizontal saccades and is the result of damage to the MLF within the dorsomedial pontine or midbrain tegmentum, adjacent to the fourth ventricle and cerebral aqueduct, respectively.