Chapter 28

DISEASES OF THE CHIASM

Chiasmal lesions often present with visual symptoms. Recognition of these symptoms is thus important, as it usually leads the clinician to discover an intracranial lesion with potential neurologic, endocrine, or systemic sequelae. Though the list of lesions that have been reported to occur in the chiasm is long, patterns of chiasmal disease are limited and easily localizable (Table 28–1).

URGENCY OF EVALUATION

The clinical course in patients with chiasmal lesions is usually one of progression over months. Evaluation by a neuro-ophthalmologist is recommended within 1 week unless there are signs of acute visual loss with severe headache or cavernous sinus involvement, suggesting pituitary apoplexy, which should be assessed emergently. Patients with known pituitary adenomas should be evaluated by an internist or endocrinologist for the possibility of hypocortisolemia, which can be life threatening.

DIAGNOSIS

SYMPTOMS

Visual Loss

The most frequent complaints are progressive visual loss. The patient may report a deterioration of central acuity and/or a dimming or loss of the temporal visual field.

Decreased Depth Perception and Diplopia

Patients may complain of difficulty with near tasks as a result of the hemifield slide phenomenon (see later). Such patients may experience diplopia at near vision. Diplopia may also result from cranial nerve palsy with cavernous sinus involvement.

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