Purpose To estimate the proportion of patients presenting with isolated third, fourth or sixth cranial nerve palsies of presumed microvascular origin versus other causes. Design Prospective, multi-center observational case series. Participants One hundred and nine patients, 50 years of age or older with acute isolated ocular motor nerve palsy. Testing Magnetic resonance imaging (MRI) of the brain Main outcome measures Causes of acute isolated ocular motor nerve palsy (presumed microvascular or other) as determined with early MRI and clinical assessment. Results Among 109 patients enrolled in the study, there were 22 patients with cranial nerve III palsy, 25 patients with cranial nerve IV palsy and 62 patients with cranial nerve VI palsy. A cause other than presumed microvascular ischemia was identified in 18 patients (16.5 %, 95% confidence interval (CI): 10.7–24.6%). The presence of one or more vasculopathic risk factors (diabetes, hypertension, hypercholesterolemia, coronary artery disease, myocardial infarction, stroke and smoking) was significantly associated with a presumed microvascular cause (p=0.003, Fisher’s exact test). Vasculopathic risk factors were also present in 61% of patients (11/18) with other causes. In the group of patients who had vasculopathic risk factors only, with no other significant medical condition, 10% of patients (8/80) 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 those with GCA the incidence of other causes for isolated fourth and sixth cranial nerve palsies was 4.7% (3/64). Conclusions In our series of patients with acute isolated ocular motor nerve palsies, substantial proportion of patients had other causes including neoplasm, GCA and brainstem infarction. Brain MRI and laboratory work–up has a role in the initial evaluation of older patients with isolated acute ocular motor nerve palsies regardless of whether vascular risk factors are present or not.

Most GCA-positive TAs contained VZV in skip areas that correlated with adjacent GCA pathology, supporting the hypothesis that VZV triggers GCA immunopathology. Antiviral treatment may confer additional benefit to patients with GCA treated with corticosteroids, although the optimal antiviral regimen remains to be determined.