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A 24 year old man suffers severe head trauma from a fall. Weeks later, he reports lingering diplopia to his caregivers at a rehabilitation center. Your examination shows a comitant esotropia with full ocular ductions. He is wheelchair-bound. He has saccadic pursuit and gaze-evoked horizontal nystagmus, lingering cognitive impairment, ataxia of speech and extremities, and spastic quadriplegia.

  • Review Topic

    Where is the lesion causing the esotropia?

    Correct! The comitant misalignment of the eyes is not consistent with damage to the ocular motor cranial nerves. Damage to those nerves should create incomitance, in which the misalignment is greatest in the field of action of the dysinnervated extraocular muscles. Ductional deficits will often be apparent. The comitant misalignment in this case suggests a breakdown in the balance between convergence and divergence caused by a lesion within the brain—usually in the diencephalon or cerebrum. Such a lesion—it can be of any cause—may interfere with the brain’s ability to maintain bifoveal fixation. In that case, the eyes drift apart, either into inappropriate convergence or divergence, setting up comitant esodeviation or exodeviation.