False and non-localizing signs in neuro-ophthalmology.

The absolute reliance on abnormal neuro-ophthalmologic findings as signposts for particular lesions of the neuraxis must be tempered by a working knowledge of false and nonlocalizing signs and symptoms. Transient monocular visual loss or complex visual hallucinations may lead to neuroanatomic ambiguity, and elevated intracranial pressure is not the most common cause of swollen optic disks in late life. Sixth nerve palsy associated with increased intracranial pressure is possibly the best-known false localizing sign, but other ocular motility disturbances (divergence paresis, convergence insufficiency, and skew deviation) also elude localization. Lastly, the localizing pitfalls of anisocoria--Horner and Raeder syndromes, physiologic anisocoria, pupil-involving third nerve palsy, and benign pupillary dilation--are discussed.