Focal neuro deficit caused by injury or dysfunction of medial longitudinal fasciculus
Paramedian Pontine Reticular Formation (PPRF) is the conjugate gaze center for horizontal eye movements. Innervates ipsilateral Abducens (CN VI) nucleus. Abducens nucleus signals ipsilateral lateral rectus to contract and sends a second via MLF to contralateral oculomotor (CN III) nucleus, causing contraction on the contralateral medial rectus.
Associated with one and one-half syndrome (lesion involving the PPRF and ipsilateral MLF)
Internuclear ophthalmoplegia
Multiple sclerosis 
Nystagmus
Stroke
Ocular palsy
Malignancy located in brainstem and 4th ventricle
Facial paralysis
CN III palsy would show additional deficit including weakness of elevation, ptosis, pupil dilation