Internuclear ophthalmoplegia is caused due to lesion in which of the following:

Internuclear ophthalmoplegia is caused due to lesion in the medial longitudinal fasciculus ascending from the abducens nucleus in the pons to the oculomotor nucleus in the midbrain. Damage to fibers carrying the conjugate signal from abducens interneurons to the contralateral medial rectus motoneurons results in a failure of adduction on attempted lateral gaze. Patient with a left internuclear ophthalmoplegia will show slowed or absent adducting movements of the left eye. Patients with bilateral injury to the medial longitudinal fasciculus will have bilateral internuclear ophthalmoplegia. One-and-a-half syndrome occur due to a combined lesion of the medial longitudinal fasciculus and the abducens nucleus on the same side. In this patient the only horizontal eye movement is abduction of the eye on the other side. Ref: Harrison's Principles of Internal Medicine, 18e chapter 28.