Anterior Communicating Artery Aneurysms
In order to understand the anterior communicating artery, we have to first appreciate the anatomy of the anterior cerebral arteries. The anterior cerebral arteries are one of the two terminal branches of each internal carotid artery (the other being the middle cerebral artery). Each anterior cerebral artery has two sections: an A1 segment and an A2 segment.
Each A1 segment branches into an A2 segment and the anterior communicating artery. The anterior communicating artery connects each anterior cerebral arteries' A1 segment together to form a circle (see schematic below).
Anterior communicating artery aneurysms are the most common intracranial aneurysm. Patients at risk for developing anterior communicating artery aneurysms include those with atherosclerosis, those with a family history of intracranial aneurysms, those with a history of hypertension or collagen vascular disease, and those with polycystic kidney disease. Smokers are also at a higher risk of developing aneurysms.
Anterior communicating artery aneurysms form when the lining of the vessel wall is thinned.
The muscular layer of the wall - the tunica media - is weakened as a result of the reasons above.
This thinning allows turbulent blood flow to form out-pouchings in the vessel wall. Typically these outpouchings occur at branch points within arterial trees.
Anterior communicating artery aneurysms commonly present after a subarachnoid hemorrhage, which can cause a variety of signs and symptoms. The most common being a severe headache, although cranial nerve dysfunction, stroke, coma, and death can also occur.
Less commonly, aneurysms in this location can compress the optic chiasm or optic nerve leading to problems with vision.
Anterior cerebral artery aneurysms are most commonly diagnosed after a subarachnoid hemorrhage when a patient presents with the "worst headache of their life". The best imaging methods for diagnosing these aneurysms are CT angiograms (see image below) and formal cerebral angiograms.
Like other intracranial aneurysms, anterior communicating artery aneurysms may be clipped or coiled. Clipping of an aneurysm involves an open surgical procedure where the surgeon dissects down to the aneurysm and places a clip across its neck. This effectively excludes it from the circulation and prevents it from rupturing.
Aneurysms may also be treated from inside the blood vessel. In this procedure a catheter is threaded from the femoral artery in the groin up into the basilar artery. At this point the aneurysm is located and small metallic coils are placed within the dome of the aneurysm.
Regardless of how the aneurysm is treated - either with clipping or coiling - the end result is that the aneurysm is excluded from the normal circulation. This prevents it from rupturing.
The merits of clipping versus coiling are still under debate. Ultimately, the treatment depends on the size and location of the aneurysm, as well as other medical problems that the patient may have.
Anterior communicating artery aneurysms are the most common intracranial aneurysm. They typically present after rupturing into the subarachnoid space and/or adjacent frontal lobes. They are diagnosed using CT angiograms or formal cerebral angiography. Treatment is with clipping and/or coiling.
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