Final answer:
Internuclear ophthalmoplegia (INO) is a deficit of conjugate lateral gaze caused by a lesion in the medial longitudinal fasciculus (MLF), which disrupts communication between the abducens nerve and oculomotor nucleus. The MLF is a fiber pathway involved in eye and head position control.
Step-by-step explanation:
Internuclear ophthalmoplegia (INO) is a deficit of conjugate lateral gaze, resulting from damage to the abducens nerve or the medial longitudinal fasciculus (MLF). The MLF is a fiber pathway that connects structures involved in the control of eye and head position, from the superior colliculus to the vestibular nuclei and cerebellum. In INO, the MLF lesion affects the communication between the abducens nerve and the contralateral oculomotor nucleus, causing impaired lateral gaze in the affected eye.