for diagnosis.429 In one study,345 contrast-enhanced MR imaging demonstrated focal thickening at the exit of the nerve in the interpeduncular cistern in five of six patients. The enhancement and thickening of the cisternal segment of the oculomotor nerve decreases as the episode resolves.48,405,439 Of cases demonstrating abnormal MR imaging, most show improved but persistent changes on repeat imaging.48

Mark et al345 hypothesized that ophthalmoplegic migraine may result from a benign viral infection (similar to Bell’s palsy), while others attribute it to a recurrent demyelinating neuropathy.316 Nazir et al395 reported a 11-month-old infant with recurrent parainfectious oculomotor palsy and enhancement of the proximal cisternal portion of the oculomotor nerve. The enhancing, thickened lesion may represent an inflammatory process similar to Tolosa–Hunt syndrome, occurring in the interpeduncular segment of the oculomotor nerve.406 The long potential duration of MRI changes and the scarcity of clinical episodes make feasible its incident discovery once the migraine attack has become a remote memory.439

In this context, however, it should be remembered that ocular motor schwannoma can rarely mimic ophthalmoplegic migraine with MR imaging showing an enhancing nodular lesion of the cisternal oculomotor nerve, but with persistence after resolution of the episode.54,403 Murakami et al392 described an 11-year-old girl with pathologically confirmed oculomotor schwannoma who had been suffering from symptoms that mimicked ophthalmoplegic migraines, and whose “migraine” attacks decreased following surgical excision of the tumor.

Enhanced MR imaging is also useful in distinguishing ophthalmoplegic migraine from Tolosa–Hunt syndrome in children.340 While persistent thickening of the oculomotor nerve on MR imaging supports the notion of an inflammatory mechanism with headache as a secondary and later feature of the condition,356 it is difficult to see how an inflammatory or demyelinating lesion restricted to oculomotor or abducens nerve could cause coincident severe headache, photophobia, nausea, and other visual disturbances.356

Despite its reclassification, migraine prophylactic medications such as beta blockers and calcium channel blockers continue to be used.329 Systemic steroids are also used with mixed results.329,406

Recurrent Isolated Third Nerve Palsy

Recurrent isolated third cranial nerve palsy has been described as a rare phenomenon in children.88,153,166 In such cases, the third nerve palsy resolves without deficit followed by an interval of normal ocular motility and one or more sub-

sequent recurrences. It has been suggested that this condition represents a variant of ophthalmoplegic migraine because symptoms of migraine become apparent later on in some affected children.153,419

Cryptogenic Third Nerve Palsy in Children

A number of children have been reported with acquired oculomotor palsies without evident cause, despite multiple neuroradiologic studies.481 Some children may develop an isolated, unremitting, painless, oculomotor palsy with pupillary involvement in the absence of any demonstrable systemic, neurologic, or neuroimaging abnormalities. Mizen et al380 described two such children who had normal cerebral arteriography and developed no additional signs or symptoms over more than 2 years of followup. We have managed similar children. In such cases, neuroimaging studies should be repeated at appropriate intervals before the designation of cryptogenic is applied, because some children may harbor intracranial tumors too small to detect on initial imaging studies.1 Nevertheless, it is important to recognize that acquired isolated oculomotor palsies in children are not always a harbinger of serious disease.

Vascular Third Nerve Palsy in Children

Cerebral aneurysms are rare but well recognized in children, and posterior communicating artery aneurysms are particularly rare.64,181 When they do occur, they almost always present with subarachnoid hemorrhage. Gabianelli et al181 have recommended that arteriography, not be obtained routinely in children under 10 years of age with acquired oculomotor palsies unless signs and symptoms of subarachnoid hemorrhage are present.

There have now been several documented cases of acquired oculomotor palsy in children with posterior communicating artery aneurysms.64,181,334,357,368,543,601 Even in infants, acquired isolated third nerve palsies can be the initial manifestation of an intracranial cerebrovascular malformation.543 Tamhankar et al543 described one infant with an acquired isolated third nerve palsies that were attributable to a partially thrombosed fusiform aneurysm of the internal carotid artery in one case, and another attributable to an arteriovenous fistula arising from the middle cerebral artery. DiMario and Rorke145 reported a 10-month-old child, who developed an isolated adduction deficit as a manifestation of transient third nerve palsy 7 days before fatal rupture of a congenital distal basilar artery aneurysm.