What Is a Posterior Communicating Aneurysm?

A posterior communicating aneurysm, also known as a posterior communicating artery aneurysm, is an out-pouching of the wall of the posterior communicating artery — a blood vessel located in the brain. Although the reason why certain people develop these blood vessel abnormalities is not entirely understood, risk factors can include smoking, high blood pressure, or having certain inherited conditions. Symptoms of the condition can include problems with eye movements or headaches. Surgical treatment is recommended in some people in hopes to prevent complications such as rupture of the aneurysm.

Often the reason why a posterior communicating aneurysm develops is poorly understood. Certain genetic diseases can predispose people to developing this condition, including Ehlers-Danlos syndrome, autosomal dominant polycystic kidney disease, and familial aldosteronism type I. Other risk factors could include smoking, high blood pressure, and low levels of estrogen in the blood.

Some of the most recognizable symptoms of a posterior communicating aneurysm are problems with vision. The aneurysm compresses the oculomotor nerve, also known as cranial nerve III, which transmits signals from the brain to the eye. This compression can cause problems with the movement of the eye, resulting in the eye remaining in a fixed position looking down and away from the body. Some patients also have a dilation of the affected eye as a result of the compression of the oculomotor nerve. Since patients would typically only have one posterior communicating aneurysm, usually these symptoms would only be present in one eye.

The most feared consequence of a posterior communicating artery aneurysm is rupture. When this occurs, the blood vessel breaks open, spilling blood into the brain. Having blood in this region of the brain is called a subarachnoid hemorrhage, and if enough blood accumulates this can be life-threatening because it can shift the brain out of the cranium, compressing the brain stem region that is responsible for critical body functions such as breathing. A subarachnoid hemorrhage could also cause neurologic deficits, such as weakness in half of the body, because the blood interferes with the normal function of the brain.

Treatment of an unruptured posterior communicating aneurysm can be difficult. Typically, doctors recommend that patients with aneurysms larger than 0.4 inches (1 centimeter) in diameter have their aneurysms surgically repaired. A patient with a smaller aneurysm might be monitored by regular imaging studies to look for an increase in the diameter of the aneurysm. If a patient has symptoms related to the aneurysm, however, surgical intervention is typically recommended regardless of the size.