Oculomotor nerve palsies are typically associated with posterior communicating artery (PcommA) aneurysms. We report a rare case of an oculomotor nerve palsy caused by a PcommA infundibular dilatation. Although there are cases of infundibular dilatations causing cranial nerve palsies, only reports of three involving the PcommA exists. We review these reported cases in the literature and discuss their treatments as well as other non-aneurysmal compressive etiologies that may cause oculomotor nerve palsies. We present the case of a 53-year-old female with transient oculomotor nerve palsy that was initially diagnosed with a PcommA aneurysm. She underwent a craniotomy with plans of microsurgical clipping; however, the dilatation was identified correctly as an infundibulum intraoperatively. The operation was completed as a microvascular decompression and her oculomotor nerve palsy has not returned at the 1-year follow-up. We provide a detailed microsurgical report and video detailing the operative technique and relevant anatomy for this operation. Although rare and not as life-threatening as aneurysms, infundibular dilatations as a cause of oculomotor nerve palsy should remain as a differential diagnosis. Given the difference in natural history and treatment of these two entities, it is important to diagnose and treat them appropriately. Multimodal imaging such as thin-sliced computed tomography angiogram (CTA) and 3-dimensional (3D) rotational angiography can aid in diagnosis.
Keywords: Infundibulum; microvascular decompression; oculomotor nerve; posterior communicating artery.