What is Hyperperfusion Syndrome?

Complication of Carotid Endarterectomy or Carotid Artery Stenting

Hyperperfusion syndrome, or cerebral hyperfusion syndrome (CHS) is a rare, serious complication of carotid revascularization either after carotid endarterectomy or carotid stent placement. Hyperperfusion syndrome may be fatal once an intracranial hemorrhage occurs. Hyperfusion syndrome, if not treated properly, can result in severe brain oedema, intracerebral hemorrhage, or death. 

How it Happens

Internal carotid artery stenosis is a narrowing of the artery frequently associated with strokes.

Decreased blood flow through the artery can reduce flow in areas of the brain that require the oxygen that blood supplies. The most common way of correcting the problem is with carotid endarterectomy (CEA) or carotid artery stenting (CAS), procedures that open the artery and thereby increase blood flow to the brain.

The risk of stroke and death associated with CEA is about 5.6 percent. The most common neurological problem after CEA is stroke, either because the carotid had to be occluded during the operation or because the plaque breaks up and spreads to other areas in the brain. However, sometimes the restored blood flow to the brain causes injury.

If the blood flow in the brain more than doubles after the artery is opened, the brain is said to be in a state of hyperperfusion. This happens as often as 9 to 14 percent of the time after a CEA, but only causes symptoms a small proportion of the time.

Those symptoms can include headache, seizures and focal neurological problems.

Hyperperfusion syndrome likely results from the brain being unable to manage the increased blood flow appropriately. The result is a leaking of fluid from the blood vessels that can result in brain swelling and sometimes bleeding.


Most studies report incidences of cerebral hyperfusion syndrome of 0-3 percent after carotid endarterectomy. CHS is most common in patients with increases of more than 100 percent in perfusion compared with baseline after carotid endarterectomy and is rare in patients with increases in perfusion less than 100 percent compared with baseline.

Risk Factors

The most important risk factors in cerebral hyperfusion syndrome are diminished cerebrovascular reserve, postoperative hypertension, and hyperperfusion lasting more than several hours after carotid endarterectomy.

Preventing Hyperfusion Syndrome

The best way to prevent hyperperfusion syndrome after CEA or CAS is to screen for it and identify the problem early, which can be done using imaging modalities like transcranial Doppler. Like many medical problems, blood pressure control is key to managing hyperperfusion syndrome.

Complete recovery happens in mild cases, but disability and death can occur in more severe cases. More information about cerebral hyperfusion syndrome and early institution of adequate treatment are of paramount importance in order to prevent these potentially severe complications.


Konstantinos G. Moulakakis; Spyridon N. Mylonas; Giorgos S. Sfyroeras; Vasilios Andrikopoulos. Hyperperfusion syndrome after carotid revascularization . Journal of Vascular Surgery.

Rothwell PM, Slattery J, Warlow CP. A systematic review of the risks of stroke and death due to endarterectomy for symptomatic carotid stenosis. Stroke 1996; 27:260-5.

Van Mook WN1; Rennenberg RJ; Schurink GW; van Oostenbrugge RJ; Mess WH; Hofman PA; de Leeuw PW. Cerebral Hyperfusion Syndrome. National Library of Medicine - National Institutes of Health.

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