Purpose Pituitary adenomas are the most common cause of an optic chiasmal syndrome, and treatment of these lesions is considerably different from the treatment of most of the other lesions in this region. Although the diagnosis of a pituitary adenoma is usually inferred from the results of neuroimaging, lesions other than pituitary adenomas can have an appearance that suggests an adenoma. The objective of our study was to determine whether there are clinical findings that suggest a lesion producing a chiasmal syndrome is something other than a pituitary adenoma. Design Retrospective, case-controlled, analysis of medical record data. Methods The records of the Neuro-Ophthalmology Unit of the Wilmer Eye Institute were searched for patients with a chiasmal syndrome who had been evaluated before treatment and for whom pathologic or laboratory confirmation of the etiology was available. Presenting clinical features of these patients were recorded, and analyses with both a single variable and multiple variables were performed to determine whether there were any features that could identify with a high degree of probability the etiology of the lesion producing the syndrome. Results The search revealed 149 patients who met the inclusion criteria, including 90 patients with pituitary adenomas and 59 patients with other lesions. Variables that were highly suggestive of an etiology other than pituitary adenoma included symptomatic visual loss, younger age, unilateral optic disk pallor, a relative afferent pupillary defect, and an absolute or a complete visual field defect or one was greater inferiorly than superiorly. Conclusion Although no single clinical feature can be used to determine the specific nature of a lesion that produces an optic chiasmal syndrome, certain features are highly suggestive of an etiology other than pituitary adenoma. When these features are present, the likelihood that a suprasellar lesion is a pituitary adenoma is much lower, regardless of the appearance on neuroimaging.
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