Causes, symptoms, treatment of cerebral hyperperfusion syndrome

CHS is a potential risk of carotid artery revascularization surgeries. These surgeries aim to increase blood flow in the carotid artery to prevent strokes in people with carotid artery disease. Blockages in the carotid arteries account for 15% of all strokes.

CHS was first discovered as a risk of a type of surgery called carotid endarterectomy, but it can also occur after stenting the carotid artery. It can develop immediately after surgery or up to a month later.

The exact reason why some people develop CHS remains unclear. Several factors are thought to contribute to this.

Loss of self-regulation

Normally, your brain regulates itself to maintain constant pressure when blood flow changes. Researchers believe that in some people with chronically low blood flow in the carotid artery, the brain may lose its ability to self-regulate and the blood vessels may remain chronically relaxed.

When blood flow increases after surgery, the brain may not constrict blood vessels appropriately to protect the beds of tiny blood vessels called capillaries.

Chronic high blood pressure

People with severe narrowing of the carotid artery often have high blood pressure. It is thought that high blood pressure that is already present may contribute to the development of CHS. Chronic high blood pressure can damage small blood vessels and lead to a breakdown of the blood-brain barrier.

Researchers found evidence of leakage of the protein albumin after breakdown of the blood-brain barrier in animal studies. This leakage can potentially activate a pathway that causes brain swelling and seizures.

Damage caused by nitric oxide and free radicals

Nitric oxide is a vasodilator, which means it relaxes blood vessels and lets more blood flow through.

It’s thought nitric oxide may contribute to autoregulatory and blood-brain barrier dysfunction in CHS. The buildup of harmful molecules called free radicals can damage brain tissue to 48 hours.

Dysfunction of baroreceptors

Baroreceptors are specialized receptors that sense blood pressure and send signals to your brain to up-regulate or down-regulate blood flow. During surgery, the nerves that carry information from these receptors can be damaged. This damage can lead to increased blood pressure that is difficult to control, even with medication. Fluctuations in blood pressure due to baroreceptor damage can last up to 12 weeks.

Most people with CHS have mild symptoms, but they can progress to severe and life-threatening symptoms if left untreated. The most common symptoms are:

Less common symptoms include:

This condition can be fatal in some cases.

CHS is a rare risk of carotid surgery. A study of 4,689 people undergoing carotid endarterectomy and 4,446 people undergoing carotid artery stenting found an incidence of 1.9% and 1.16%, respectively.

What can increase the risk of getting CHS?

Extensive studies have revealed that the three most common conditions associated with the development of CHS are:

• more than 90% blockage of the carotid artery
• severe blockages (or plaques) of blood vessels in the brain
• long-standing pre-existing high blood pressure

Studies have also identified the following as risk factors for developing CHS after carotid surgery:

• to be assigned female at birth
• chronic kidney disease
• left carotid disease
• progressive neurological disorders
• recurrent hemorrhaging (bleeding)
• brain damage (tumors or damaged areas)
• microvascular disease (disease of small blood vessels)
• reduced ability of blood vessels in the brain to respond to changes in blood flow

What risks does CHS pose to your health?

If left untreated, CHS can lead to severe brain swelling, bleeding, permanent disability, or death.

A 2018 review of studies noted that 47% of CHS cases resulted in stroke, and more than half of strokes were fatal or disabling.

Treatment for CHS often includes intravenous drugs to lower blood pressure, such as labetalol and clonidine.

Antiepileptic drugs may be given to prevent seizures or to treat seizures if they occur.

Mannitol and hypertonic saline solution can be used to treat brain swelling. However, if these treatments are effective in the long term is not clear.

Surgery may be needed if bleeding occurs.

Taking steps to keep your blood pressure within a healthy range can help prevent CHS, as high blood pressure is considered a risk factor for its development.

Prompt identification and treatment of CHS is essential to prevent life-threatening complications. It is recommended that blood pressure be monitored by medical professionals continuously at least every 15 minutes for 24 hours or more after surgery.

Management of CHS focuses on reducing swelling, seizures, and bleeding, which are major causes of brain damage.

In the early stages, the swelling is usually reversible, but if it progresses to hemorrhage, the outlook is not as good. Until 30 percent people remain at least partially disabled and the mortality rate reaches 50%.

CHS is a rare risk of surgeries used to increase blood flow in the carotid artery. It is defined as an increase of more than 100% in blood flow in the carotid artery compared to baseline.

CHS can lead to serious complications such as permanent disability or death. Early recognition of CHS is key to receiving prompt treatment. Common early symptoms include headache, facial pain, or eye pain on one side. Seek immediate medical attention if you experience any of these symptoms within a month of carotid surgery.