Isolated sixth nerve palsy

An isolated sixth nerve palsy may be a harbinger of underlying intracranial disease. Due to its long subarachnoid course, it may be damaged by downward shift of the brainstem as often occurs in increased or decreased intracranial pressure (“false-localizing sixth nerve palsy”). Alternatively, the sixth nerve may be involved in isolation by a compressive lesion in the cavernous sinus or along the clivus (“true-localizing sixth nerve palsy”), and specific attention on neuroimaging should be paid to these areas, especially in chronic or progressive cases. The most common causes of a sixth nerve palsy in an adult include ischemia, head trauma, and compression by a mass lesion, but inflammation, primary demyelination, and intracranial hypotension may also produce a sixth nerve palsy.