Cerebral aneurysm

Localization of saccular aneurysms

Most commonly, cerebral aneurysms form within the internal carotid artery (ICA) system and its branches. The frequency distribution is as follows:

• ICA territory: the internal carotid artery itself (A. carotis interna) — 30%, posterior communicating artery (A. communicans posterior) — 18%. Significantly less frequently (4% each) are the ICA bifurcation, anterior choroidal artery, and ophthalmic artery affected.
• Anterior cerebral artery system: anterior communicating artery (A. communicans anterior) — 25%, anterior cerebral artery (A. cerebri anterior) — 5%.
• Middle cerebral artery system: A. cerebri media — 25%.
• Vertebrobasilar system: basilar artery (A. basilaris) — 10% (primarily the bifurcation is affected), vertebral and posterior inferior cerebellar arteries — 3%, posterior cerebral artery (A. cerebri posterior) — 2%.

Aneurysm rupture and clinical presentation

Vessel rupture most commonly manifests as subarachnoid hemorrhage (SAH). In typical cases, the diagnosis is established based on the classic triad:

1. Sudden, extremely intense headache.
2. Meningeal signs (presence of Kernig's and Brudzinski's signs).
3. Altered mental status.

Additionally, arterial hypertension and a moderate temperature rise up to 37–38 °C may be observed. If SAH is suspected, emergency hospitalization of the patient is required.

Dynamics of focal symptoms: In the first days after SAH development, most patients do not exhibit focal neurological symptoms, as the extravasated blood does not directly penetrate the brain parenchyma. However, by the 2nd–3rd week, focal symptoms manifest in some patients due to secondary cerebral arterial vasospasm.

Differential diagnosis and the "spot sign"

The diagnosis is made after ruling out other conditions with similar manifestations (strokes, brain abscesses, tumors, chronic intracranial hematomas). Special attention is paid to instrumentally distinguishing active bleeding from vascular malformations (including unruptured aneurysms).

For this purpose, delayed CT angiography is used (performed a few minutes after contrast administration):

• "Spot sign": indicates active bleeding. The configuration and density of the lesion change on repeat scanning due to the mixing of contrast with the hematoma.
• Aneurysm vs. AVM: the density of the lesion remains stable and completely matches the density of adjacent healthy arteries.

Prognosis and specific complications

The prognosis for an aneurysm rupture is extremely grave. From 10 to 15% of patients die within minutes (before first aid can be provided). The overall mortality rate within the first 30 days of the disease is 30–50%.

If the acute period is successfully survived and the aneurysm has not been surgically excluded from the bloodstream, the probability of rebleeding remains at 5% per year.

Mycotic aneurysms: Can form as a neurological complication of infective endocarditis (IE), accounting for less than 10% of all CNS lesions in this pathology. In such cases, patients are strongly recommended to undergo brain MRI — an examination that allows detecting changes even in the absence of neurological clinical signs, which significantly affects the timing of cardiac surgery.

Class and exam questions

What else to study on this topic

• Meningeal syndrome: technique for checking Kernig's and Brudzinski's signs.
• The role of brain MRI in evaluating Duke criteria for infective endocarditis.
• Cerebral microbleeds as a small vessel pathology.
• Use of duplex ultrasonography to detect stenosis and occlusion of intracranial arteries.
• Pharmacotherapy of vascular dementia: dosages of acetylcholinesterase inhibitors.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.