Cerebellar Infarction

Cerebellar infarction is ischaemic stroke in the territory of the posterior inferior, anterior inferior or superior cerebellar arteries. Swelling in the first 2 to 5 days can compress the brainstem and fourth ventricle, causing hydrocephalus and death.

It accounts for about 2% of ischaemic strokes. Posterior inferior cerebellar artery territory is the most common. Mean age is about 65 years.

Causes. Vertebral artery atherosclerosis or dissection, cardioembolism (atrial fibrillation), small artery disease and, less often, basilar occlusion.

Time course. Deterioration from mass effect typically occurs between days 2 and 4, with the risk higher in large infarcts involving more than one third of a hemisphere.

Pathophysiology.

Infarction of the cerebellar hemisphere causes cytotoxic then vasogenic oedema in a confined posterior fossa, with little room for expansion.

Upward herniation, tonsillar herniation and fourth ventricle compression lead to hydrocephalus and brainstem failure.

• Acute vertigo, vomiting, headache, gait and truncal ataxia, and nystagmus.
• Limb ataxia, dysarthria and loss of balance to the side of the lesion.
• Drowsiness, new headache, gaze palsy, pupillary change or respiratory pattern change signal swelling.
• Isolated vertigo with nausea may be the only sign in small infarcts.

Red flags.

• Decreasing level of consciousness.
• New headache with vomiting, or new cranial nerve palsy.
• Gaze palsy or abnormal breathing.

• Non-contrast CT shows hypodensity late and may be falsely normal in the first day; MRI with diffusion weighted imaging is far more sensitive.
• CT or MR angiography of the head and neck for vertebral and basilar disease and dissection.
• Repeat CT or MRI for any neurological decline, to assess oedema, fourth ventricle effacement and hydrocephalus.
• ECG and rhythm monitoring; echocardiography when a cardiac source is possible.

Differential diagnosis. Cerebellar haemorrhage, vestibular neuritis, benign paroxysmal positional vertigo, tumour, abscess, demyelination, Wernicke encephalopathy and drug toxicity.

• Admit to a monitored stroke or neurosurgical unit with frequent neurological observations for at least 5 days.
• Alteplase 0.9 mg/kg intravenously (maximum 90 mg), 10% as a bolus over 1 minute and the rest as an infusion over 60 minutes, within 4.5 hours of onset or last known well. Monitor neurological observations and blood pressure every 15 minutes for 2 hours, every 30 minutes for the next 6 hours, then hourly to 24 hours; keep blood pressure under 185/110 mmHg before and under 180/105 mmHg after treatment; repeat imaging at 24 hours or with deterioration. Contraindicated with previous intracranial haemorrhage, INR over 1.7, platelets under 100 x 10^9/L, glucose under 2.7 mmol/L, anticoagulant use within 48 hours or major surgery within 14 days; no renal adjustment.
• Tenecteplase 0.25 mg/kg intravenously as a single bolus over 5 to 10 seconds (maximum 25 mg), within 4.5 hours, with the same monitoring and contraindications as alteplase; no renal adjustment.
• Aspirin 300 mg orally once (300 mg rectally if swallowing is impaired), starting 24 hours after thrombolysis and a repeat scan, then 75 mg orally once daily. Maximum 300 mg daily. Monitor bleeding and full blood count. Avoid in active peptic ulcer, bleeding disorders and in children under 16 years; use caution when eGFR is under 10.
• Symptomatic vertigo and vomiting: ondansetron 4 mg intravenously or 4 to 8 mg orally every 8 hours for up to 48 to 72 hours. Maximum 24 mg daily orally, and 16 mg for any single intravenous dose. Monitor QTc, potassium and magnesium. Reduce to a maximum of 8 mg daily in severe hepatic impairment; no renal adjustment; avoid with other QT-prolonging drugs; acceptable in pregnancy after the first trimester or when benefit outweighs risk.
• Raised intracranial pressure: head elevation to 30 degrees, avoid hypotonic fluids and hypoxia, and osmotherapy as a bridge. Mannitol 0.25 to 0.5 g/kg intravenously over 15 to 20 minutes, repeated every 4 to 6 hours as needed for up to 48 to 72 hours. Maximum 1.5 g/kg in 24 hours. Monitor serum sodium and osmolality (stop if over 320 mOsm/kg), renal function and fluid balance. Avoid in anuria, severe dehydration and heart failure; use caution in renal impairment.
• Decompressive suboccipital craniectomy with or without external ventricular drainage for patients who deteriorate despite medical treatment (reduced consciousness, hydrocephalus or brainstem compression), done early before irreversible brainstem damage.
• Secondary prevention: antithrombotic by cause, atorvastatin 80 mg orally once daily with monitoring of lipids at 4 to 12 weeks and ALT at baseline (maximum 80 mg daily; avoid in active liver disease and pregnancy; limit to 20 mg daily with clarithromycin), blood pressure control under 130/80 mmHg, and diabetes and smoking control.
• Vestibular rehabilitation, physiotherapy and dysphagia care.

Monitoring. Neurological observations every 1 to 2 hours in the first 3 days, then less often; repeat imaging for any decline.

Referral and escalation. Early neurosurgical referral for all large infarcts; intensive care for reduced consciousness or respiratory pattern change.

Special groups. Older adults: frailty and reduced physiological reserve affect surgical decisions. Pregnancy: thrombolysis decisions need a multidisciplinary team.