Cerebral Hyperperfusion Syndrome

Cerebral hyperperfusion syndrome is a rare complication of carotid revascularisation in which cerebral blood flow rises by more than 100% from baseline, causing ipsilateral headache, seizures, focal deficit and, in severe cases, intracerebral haemorrhage.

It occurs in about 1 to 3% of patients after carotid endarterectomy and 1 to 5% after carotid stenting. Onset ranges from hours to 4 weeks, usually within the first week.

Risk factors. Severe stenosis (over 90%), contralateral occlusion, poor collateral flow, impaired cerebrovascular reactivity, postoperative hypertension, recent contralateral revascularisation, older age, and diabetes.

Course. Many cases are mild and resolve with blood pressure control; intracerebral haemorrhage is rare but carries a high mortality.

Pathophysiology.

Chronic ischaemia causes maximal arteriolar vasodilation and loss of autoregulation. After flow is restored the vessels cannot constrict, so perfusion pressure transmits directly to capillaries.

Hyperaemia causes oedema, blood brain barrier breakdown and haemorrhage.

• Unilateral frontotemporal or periorbital headache, often the first sign.
• Seizures, focal or generalised, and focal deficits.
• Confusion, visual disturbance and reduced consciousness, with hypertension.
• Intracerebral haemorrhage with sudden deterioration.

Red flags.

• Sudden severe headache or deterioration in the first week.
• Seizure after carotid revascularisation.
• Severe hypertension that persists.

• Urgent CT or MRI to exclude infarction and haemorrhage; vasogenic oedema in the ipsilateral hemisphere supports the diagnosis.
• Transcranial Doppler: increase of middle cerebral artery velocity by more than 100% from baseline; perfusion imaging (SPECT, CT or MR perfusion) shows hyperperfusion.
• Ultrasound or CT angiography to confirm stent or endarterectomy patency.
• EEG in seizures; blood pressure monitoring.

Differential diagnosis. Ischaemic stroke from thrombosis or embolism, intracerebral haemorrhage, posterior reversible encephalopathy syndrome, seizure, post-operative pain and migraine.

• Strict blood pressure control: systolic pressure under 140 mmHg (under 120 mmHg in some units after stenting), avoiding hypotension.
• Labetalol 10 to 20 mg intravenously over 1 to 2 minutes, repeated or doubled every 10 minutes to a maximum of 300 mg, or an infusion of 0.5 to 2 mg/minute. Monitor blood pressure, heart rate (stop if under 55 beats/minute) and ECG. Avoid in asthma, severe chronic obstructive disease, second or third degree heart block and decompensated heart failure; reduce dose in hepatic impairment; no renal adjustment; acceptable in pregnancy.
• Seizures: levetiracetam 500 mg orally or intravenously twice daily, increased as needed to a maximum of 1500 mg twice daily. Monitor mood and renal function. Reduce dose when creatinine clearance is 50 to 80 mL/min (500 to 1000 mg twice daily), 30 to 50 mL/min (250 to 750 mg twice daily) and under 30 mL/min (250 to 500 mg twice daily).
• Cerebral oedema: head elevation, avoid hypotonic fluids, and osmotherapy for mass effect. Haemorrhage: neurosurgical review; reverse antithrombotic therapy when indicated.
• Prevention: continuous blood pressure monitoring for 24 to 48 hours after revascularisation, early treatment of hypertension, and delayed staging of contralateral procedures.
• Avoid antiplatelet intensification during active haemorrhage; resume when stable.

Monitoring. Neurological observations and blood pressure every 15 to 30 minutes in the first 6 hours, then hourly; repeat imaging with any change; follow up at 4 weeks.

Referral and escalation. Vascular surgery or neuroradiology team for suspected cases; neurocritical care for haemorrhage.

Special groups. Older adults: tailor blood pressure targets to avoid hypoperfusion in other territories.