A cliniconeuroradiologic approach to third cranial nerve palsies

Sixty-three patients with third cranial nerve palsies (CNPs), either isolated (31) or in association with other neurologic deficits (32), underwent neuroophthalmologic and neuroradiologic evaluation. Discrepancies between the clinical and radiologic evaluations were analyzed and useful clinical presenting symptoms were identified. Microvascular infarction secondary to diabetes mellitus and/or hypertension was the most common cause in patients with isolated third CNP, and extensive neuroradiologic evaluation is not indicated in this subgroup. The overall diagnostic yield of high-resolution CT for isolated third CNPs was low (30%), but improved to 60% if diabetes and hypertension were excluded. However, CT was highly sensitive (90%) in those patients with third CNPs associated with additional neurologic deficits. The status of the pupil in and of itself cannot be the sole determinant as to whether angiography is indicated to exclude an aneurysm. Careful ophthalmologic observation and relating the severity of pupillomotor dysfunction to extraocular ophthalmoplegia is mandatory to determine the logical sequence of radiologic evaluation. Retroorbital pain taken in isolation is a nonspecific presenting symptom and has differential diagnostic value only if it is correlated temporally with the onset of third CNP and the presence or absence of additional cranial nerve deficits.