Isolated Abducens Nerve Palsy Caused by a Meningohypophyseal Trunk Aneurysm Treated with Endovascular Coiling: A Case Report

Aneurysms of the meningohypophyseal trunk are rare and usually asymptomatic, but because of the close anatomical relationship between the meningohypophyseal trunk and cranial nerves within the cavernous sinus, they can cause neurological deficits. We describe an 80-year-old woman who presented with acute horizontal diplopia exacerbated on rightward gaze. Neurological examination revealed isolated right abducens nerve palsy. Magnetic resonance angiography demonstrated an aneurysm arising from the right meningohypophyseal trunk in close proximity to the abducens nerve. Endovascular coil embolization was performed under dual antiplatelet therapy, and the aneurysm was successfully occluded while preserving meningohypophyseal trunk patency. The procedure was uneventful, although postoperative diffusion-weighted imaging revealed multiple small cerebral infarctions suggestive of distal embolism. The patient remained neurologically stable, and her diplopia gradually improved. At the 6-month follow-up, she exhibited complete recovery of abducens nerve function. This case highlights the anatomical vulnerability of the abducens nerve to compression by meningohypophyseal trunk aneurysms and underscores the importance of considering vascular lesions in the differential diagnosis of isolated cranial nerve palsies. Despite radiographic evidence of silent embolic infarction, endovascular coil embolization resulted in full clinical recovery, supporting its role as a safe and effective therapeutic option in appropriately selected symptomatic meningohypophyseal trunk aneurysms.