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A 25 year old man noticed slowly failing vision in his right eye. He had no pre-existing medical problems. Visual acuity was 20/25 (6/7, 0.9) in the right eye and 20/20 (6/6, 1.0) in the left eye. There was a mild afferent pupil defect in the right eye. The rest of the examination was normal. Here are his visual fields.
Where is the lesion?
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Correct!
This is the most easily recognized visual field abnormality—a bitemporal hemianopia. It is the signature of an extrinsic or intrinsic lesion compressing, inflaming,
infarcting, or expanding the optic chiasm.
By far the most common cause of chiasmal damage is a mass lesion: pituitary adenoma, meningioma, and aneurysm in adults; craniopharyngioma and pilocytic astrocytoma in children. Why do lesions of the optic chiasm produce this defect pattern? Because the crossing axons in the optic chiasm are especially vulnerable.
Patients are slow to notice these bitemporal defects because the nasal field of each eye almost completely covers the temporal field of the other eye. Although patients may eventually sense that peripheral vision is compromised, more often they present with decreased vision in one eye because the lesion has also compromised the function of an optic nerve. In those patients, visual fields often show a combination of nerve fiber bundle defects and temporal hemianopic defects (“junction pattern”) There are even some patients who present with unilateral temporal hemianopic defects from lesions located at a more anterior position of the optic nerve-optic chiasm junction. Expect to find an afferent pupil defect in patients with these junctional defect patterns.
This patient had a pituitary tumor. The serum prolactin level was markedly elevated, implicating prolactinoma. Prolactinomas are treated initially with cabergoline, a dopamine agonist that can dramatically shrink the tumor, restoring vision and pituitary function
Therefore, cabergoline is usually the first line of treatment, even if vision is markedly impaired. Should treatment fail or be poorly tolerated because of gastrointestinal side-effects, surgery would be undertaken. Unfortunately, cabergoline treatment must be maintained indefinitely or the tumor will recur. That is why some patients will take surgery as the first option. Either way, early diagnosis of this condition unquestionably improves visual outcome.
By far the most common cause of chiasmal damage is a mass lesion: pituitary adenoma, meningioma, and aneurysm in adults; craniopharyngioma and pilocytic astrocytoma in children. Why do lesions of the optic chiasm produce this defect pattern? Because the crossing axons in the optic chiasm are especially vulnerable.
Patients are slow to notice these bitemporal defects because the nasal field of each eye almost completely covers the temporal field of the other eye. Although patients may eventually sense that peripheral vision is compromised, more often they present with decreased vision in one eye because the lesion has also compromised the function of an optic nerve. In those patients, visual fields often show a combination of nerve fiber bundle defects and temporal hemianopic defects (“junction pattern”) There are even some patients who present with unilateral temporal hemianopic defects from lesions located at a more anterior position of the optic nerve-optic chiasm junction. Expect to find an afferent pupil defect in patients with these junctional defect patterns.
This patient had a pituitary tumor. The serum prolactin level was markedly elevated, implicating prolactinoma. Prolactinomas are treated initially with cabergoline, a dopamine agonist that can dramatically shrink the tumor, restoring vision and pituitary function
Therefore, cabergoline is usually the first line of treatment, even if vision is markedly impaired. Should treatment fail or be poorly tolerated because of gastrointestinal side-effects, surgery would be undertaken. Unfortunately, cabergoline treatment must be maintained indefinitely or the tumor will recur. That is why some patients will take surgery as the first option. Either way, early diagnosis of this condition unquestionably improves visual outcome.
Incorrect
Incorrect