Abstract Number: Esoc2026a1575 Isolated Oculomotor Nerve Palsy as a Stroke Mimic Associated With a Persistent Trigeminal Artery

Abstract Background and aims Persistent trigeminal artery (PTA) is the most common embryonic carotid–vertebrobasilar anastomosis, with a reported prevalence of 0.1–0.6%. It is usually asymptomatic but may be associated with neurovascular compression or ischemic events. Cranial nerve involvement is rare, and isolated oculomotor nerve palsy related to PTA without aneurysmal dilation has been only exceptionally reported. Methods: Case Presentation A 67-year-old woman presented with acute onset dizziness, binocular diplopia, and left periorbital pain following physical exertion with neck extension. Neurological examination revealed left ptosis, limitation of left eye abduction, and right-beating nystagmus on right gaze, with preserved consciousness and no focal motor or sensory deficits. Laboratory tests were unremarkable except for mild hypercalcemia. Brain CT and CT angiography demonstrated a persistent left trigeminal artery arising from the internal carotid artery and supplying the basilar artery, with associated hypoplasia of the vertebral and basilar arteries and no aneurysmal changes. Results Neuroimaging demonstrated a persistent left trigeminal artery with vertebrobasilar hypoplasia and no aneurysm or ischemia. No alternative etiology was identified. Symptoms resolved spontaneously and the patient remained stable on follow-up. Conclusions Persistent trigeminal artery may represent a rare cause of isolated oculomotor nerve palsy through transient neurovascular compression or altered posterior circulation hemodynamics, even in the absence of aneurysmal dilation. Recognition of this anatomical variant is important in patients presenting with acute diplopia or brainstem symptoms in order to avoid misdiagnosis, unnecessary interventions, and inappropriate secondary prevention strategies. This case highlights the value of detailed vascular imaging in the diagnostic work-up of atypical cranial neuropathies. Conflict of interest Oneda Cibuku: nothing to disclose Figure 1 - belongs to Methods Figure 2 - belongs to Methods