Walsh & Hoyt: Persistent Deficits Caused by Large Unilateral Lesions

Persistent ocular motor deficits caused by lesions such as hemidecortication for intractable seizures are summarized. Although there may be no resting deviation of the eyes, forced eyelid closure may cause a contralateral spastic conjugate eye movement, the mechanism of which is not understood. This tonic deviation (Cogans sign) differs from the tonic deviation associated with Wallenbergs syndrome, because in the former, active or attempted eyelid closure is necessary to cause the eyes to deviate, whereas in the latter, the deviation occurs even with eyes open in darkness. Cogans sign occurs most frequently with parietotemporal lesions.