Transient Binocular Visual Loss

What causes it?

Migraine has the following characteristics:

• flickering zigzags that migrate across the visual hemifield of both eyes over a 20- to 30-minute period
• zigzags are not consistently in the same hemifield in successive attacks
• headache follows visual symptoms
• onset usually within first three decades

The less the patient's description conforms to the features of migraine, the more you should consider vertebrobasilar ischemia as the cause. There are two mechanisms:

• embolism originating in the vertebrobasilar arterial system or heart
• severe vertebrobasilar stenosis with a brief dip in blood pressure

What to do?

If age 40 years or above, dismiss as migraine only if the vision loss is accompanied by marching scintillations or is followed by headache. Otherwise, evaluate for cardiac sources of emboli, overtreated hypertension, atherosclerosis, and hypercoagulable states. Carotid surgery is not indicated, even for high grade stenosis.

If under age 40, dismiss as migraine unless history is very atypical, in which case evaluate for ischemia as in those aged 40 years and older.

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