Clinical Significance of MRI Contrast Enhancement of the Oculomotor Nerve in Ischemic Isolated Oculomotor Nerve Palsy

BACKGROUND AND PURPOSE: Contrast enhancement of the oculomotor nerve in MRI was recently noticed in patients with clinical ischemic isolated oculomotor nerve palsy (iIONP). The opinions about whether this is a sign of inflammation and whether or not to administer steroids vary between doctors. The study aimed to determine the associations between this enhancement and vascular-disease risk factors (VRFs) and inflammatory factors in iIONP patients. METHODS: The study recruited patients who had experienced iIONP during the previous 2 years. They were divided into groups A and B based on whether or not they exhibited an enhanced oculomotor nerve in MRI of the cavernous sinus using thin-section, fat-suppressed, and contrast-enhanced sequences. VRFs, inflammatory factors, and improvement scores were compared between the two groups. RESULTS: Most (71.1%) of the 45 included iIONP patients had enhanced oculomotor nerves in MRI. VRFs, periorbital pain, elevated C-reactive protein and erythrocyte sedimentation rate, the neutrophil-to-lymphocyte ratio, and the platelet-to-lymphocyte ratio were not significantly associated with the enhancement. Four of the five patients in group A exhibited an elevated cerebrospinal fluid (CSF) IgG synthesis rate. The improvement score of eight patients who received 80 mg of methylprednisolone in addition to the routine therapy was not significantly different from the scores of the other patients (p=0.485). CONCLUSIONS: More than half of the iIONP patients had an enhanced oculomotor nerve in MRI. A few of them also had elevated CSF IgG synthesis rate, but no further evidence for inflammation was found. The administration of steroids seemed to have no benefit other than increasing the blood glucose level.