Early neuroimaging beneficial in acute isolated ocular motor nerve palsy

This prospective, multicenter study found that brain MRI and lab work can be helpful in the initial evaluation of older patients with isolated acute ocular motor nerve palsies regardless of whether vascular risk factors are present.

Subjects were 109 patients aged 50 years or older presenting with neurologically isolated third, fourth or sixth cranial nerve palsies within 30 days of onset who were prospectively evaluated by neuro-ophthalmologists at 10 centers. Patients with a history of strabismus, orbital disease, head trauma, neurosurgical intervention or lumbar puncture, or those for whom an MRI could not be obtained were excluded.

A substantial number of patients (16.5 percent) had an identifiable cause other than presumed microvascular ischemia. Ten percent of patients with vasculopathic risk factors only and no other significant medical condition were found to have other causes, including midbrain infarction, neoplasms, inflammation, pituitary apoplexy and giant cell arteritis (GCA). Excluding patients with third cranial nerve palsies and GCA, there was an approximately 1 in 20 chance that a patient with vasculopathic risk factors alone had another cause found for fourth and sixth cranial nerve palsy. The presence of one or more vasculopathic risk factors was significantly associated with a presumed microvascular cause.

The authors write that given the higher incidence of other causes found in this cohort of patients, early neuroimaging is recommended in patients presenting with acute isolated ocular motor palsies, especially those who have previously presented to a nonspecialist who may have failed to elucidate a thorough history and may have lacked the expertise of a neuro-ophthalmologist.

While the overall yield of MRI scan in this cohort of patients was 16.5 percent, in patients with fourth and sixth nerve palsies who had vasculopathic risk factors alone, the yield from neuroimaging was significantly lower. In such patients, the decision to perform an immediate MRI scan could be weighed against observation alone, especially in patients with no insurance coverage, and MRI should be obtained if the palsy has not resolved.