Vascular Loop Syndrome As the Etiology of Abducens Nerve Palsy: A Case Report

Vascular loop syndrome, characterized by arterial loops or kinks causing compression of cranial nerves, can lead to a range of secondary side effects conditional on vascular morphology. This etiology has made standardization of treatment difficult, as confounding factors may take precedence over more interventional treatment. This case seeks to illustrate how vascular loop syndrome, specifically a dolichoectatic vertebrobasilar artery, can lead to left abducens nerve palsy. Here we present an 82-year-old female with reports of diplopia, who was seen previously for sixth nerve palsy. Imaging revealed no acute hemorrhage, restricted diffusion, hydrocephalus, intracranial space-occupying lesion, abnormal volume loss, vasogenic edema, mass effect, or abnormal CSF signal. Magnetic resonance angiography demonstrated an indentation of the left lower brainstem by the tortuous basilar artery, indicating that this vasculature may be abutting the abducens nerve exit zone. We demonstrate a case of vascular loop syndrome as an etiology of abducens nerve palsy and diplopia, raising awareness of these findings on imaging and encouraging the consideration of this etiology in radiological evaluation algorithms.