Magnetic resonance imaging findings of isolated abducent nerve palsy induced by vascular compression of vertebrobasilar dolichoectasia

If the origin of isolated abducent nerve palsy cannot be found on neuroradiological examinations, diabetes mellitus is known as a probable cause; however, some cases show no potential causes of isolated abducent nerve palsy. Here, we report a 74-year-old male who suffered from diplopia due to isolated left abducent nerve palsy. Magnetic resonance angiography and fast imaging employing steady-state acquisition imaging clearly showed a dolichoectasic vertebrobasilar artery compressing the left abducent nerve upward and outward. There were no abnormal lesions in the brain stem, cavernous sinus, or orbital cavity. Laboratory data showed no abnormal findings. We concluded that neurovascular compression of the left abducent nerve might cause isolated left abducent nerve palsy. We observed him without surgical treatment considering his general condition with angina pectoris and old age. His symptom due to the left abducent nerve palsy persisted. From previous reports, conservative treatment could not improve abducent nerve palsy. Microvascular decompression should be considered for abducent nerve palsy due to vascular compression if patients are young, and their general condition is good. We also discuss interesting characteristics with a review of the literature.