Hypertrophic olivary degeneration as the initial presentation of midbrain arteriovenous malformation

Hypertrophic olivary degeneration as the initial presentation of midbrain arteriovenous malformation Dear Editor,An arteriovenous malformation (AVM) is a tangle of dysplastic vessels (nidus) fed by arteries and drained by veins without intervening capillaries, thereby creating a high-flow, low-resistance shunt between the arterial and venous systems. 1 It predominantly manifests as headache, epilepsy, ischemic or hemorrhagic symptoms.Some AVMs may be complicated by hypertrophic olivary degeneration (HOD).A 63-year-old male was admitted due to progressive dizziness and gait instability of 2 years with a history of hypertension.After the onset of symptoms, the patient was admitted to the Department of Neurosurgery and diagnosed with incomplete obstructive hydrocephalus.Following ventriculoperitoneal shunt surgery, the patient's dizziness improved slightly, yet bilateral upper extremity motor dysfunction, blurred vision, and vertical oscillopsia subsequently developed.Physical examination revealed dysarthria, palatal tremor, arrhythmic, bilateral pendular vertical nystagmus (consistent with oculopalatal tremor),impaired coordination bilaterally in the upper and lower extremities, unsteady stance and gait, inability to ambulate independently, and positive Romberg sign.Laboratory examinations were unremarkable, including blood tests, cerebrospinal fluid analysis, autoimmune antibodies, paraneoplastic antibodies, and genetic testing for spinocerebellar ataxia.Magnetic resonance imaging (MRI) showed abnormal signals in the bilateral ventral medulla oblongata, vascular malformation around the cerebral aqueduct, and chronic hydrocephalus.Contrast-enhanced MRI showed vascular malformation around the cerebral aqueduct complicated by chronic hydrocephalus involving the lateral and third ventricles.(Fig.1).Computed tomography angiography (CTA) and digital subtraction angiography (DSA) confirmed midbrain AVM(Fig.2).Taken together, the patient was diagnosed with bilateral HOD secondary to midbrain AVM, and treated with gabapentin and other medications but refused further interventional embolization for midbrain AVM.Follow-up examination conducted six months after discharge showed that the patient's dizziness, nystagmusand oscillopsia were ameliorated, whereas gait unsteadiness had