The Great Imposter: An Unusual Case of Giant Vertebral Artery Aneurysm Presenting as Unilateral Ptosis

Background: Vertebral artery aneurysms are uncommon vascular lesions of the posterior circulation.While they may present with subarachnoid haemorrhage, ischaemic stroke, or progressive neurological deficits, isolated neuro-ophthalmic manifestations are rare.Ptosis typically results from oculomotor nerve dysfunction or disruption of sympathetic pathways and is most commonly associated with anterior circulation aneurysms.Presentation of a vertebral artery aneurysm with unilateral ptosis is therefore unusual and may mimic more common neurological conditions.Case presentation: We report a 55-year-old man with hypertension and a previously treated left vertebral artery (V4 segment) aneurysm who presented with new-onset right-sided ptosis, gait imbalance, facial deviation, and decreased hearing in the left ear.Two years earlier, he had undergone flow-diverter embolisation for a 22 × 24 mm aneurysm and had remained on dual antiplatelet therapy.Neurological examination revealed right-sided ptosis without ophthalmoplegia or pupillary asymmetry, left lower motor neuron facial weakness, sensorineural hearing loss, and ipsilateral limb ataxia.Digital subtraction angiography demonstrated interval enlargement of the aneurysm to approximately 28 × 22 mm with partial thrombosis, significant mass effect on the brainstem, perilesional oedema, and a small subacute perianeurysmal bleed.Imaging findings suggested compression of cranial nerves VII and VIII along with distortion of midbrain structures.The patient was managed conservatively with high-dose corticosteroids to control oedema, continuation of dual antiplatelet therapy, vestibular rehabilitation, and close neuro-imaging surveillance.Discussion: Giant vertebral artery aneurysms may produce neurological deficits through multiple mechanisms, including direct cranial nerve compression, ischemia due to compromised arterial flow, and inflammatory oedema associated with aneurysm thrombosis.In this case, contralateral ptosis likely resulted from brainstem distortion affecting oculomotor pathways.Conclusion: This case highlights an atypical presentation of a vertebral artery aneurysm manifesting as contralateral ptosis with multiple cranial nerve deficits.Recognition of such unusual presentations is essential, as early diagnosis and multidisciplinary management are critical to prevent neurological deterioration.