To the Editor.
—Aneurysmal compression of the third nerve produces an oculomotor nerve palsy with prominent pupillary involvement. Cerebral angiography is indicated in the workup of such third-nerve palsies if another cause is not promptly forthcoming. Pupil-sparing third-nerve palsies are often caused by local ischemia, and the risks of angiography are likely increased in such individuals. Unfortunately, occasional third-nerve pareses with limited pupillary participation do result from early aneurysmal compression,1 presenting the clinician with a management dilemma.A noninvasive test that could eliminate aneurysmal compression as the cause of a third-nerve palsy would be most valuable. Currently, lack of spatial resolution compared with conventional angiography and slow flow within the aneurysm preclude magnetic resonance angiography from replacing conventional angiography in the diagnosis of small cerebral aneurysms.2 However, aneurysms that produce oculomotor nerve palsies should be relatively easy to detect: their sites of involvement are known and they are
Keane JR, Ahmadi J. Third-Nerve Palsies and Angiography. Arch Neurol. 1991;48(5):470. doi:10.1001/archneur.1991.00530170030014