Diplopia-Supranuclear and nuclear causes

When evaluating a patient with diplopia, it is critical to differentiate monocular diplopia (diplopia present in one eye) from binocular diplopia (diplopia resolves with closure of either eye). Binocular diplopia is typically related to ocular misalignment and often has a neurologic cause. Although the supranuclear ocular motor system is primarily associated with generation of bilateral eye movements, certain supranuclear processes can cause ocular misalignment and binocular diplopia. Skew deviation, the most common supranuclear cause of diplopia, presents with binocular vertical diplopia due to a hypertropia and full ductions in each eye. Oculomotor nuclear lesions have distinct clinical characteristics related to the unique anatomy of the third cranial nerve nuclei, which may present with combinations, including bilateral ptosis and contralateral or bilateral ocular elevation deficits. Trochlear nuclear lesions clinically appear identical to fascicular or trochlear axonal lesions, but abducens nuclear lesions produce ipsilesional gaze palsies rather than unilateral cranial nerve VI palsies.