Intracranial aneurysms are pathological enlargements of cerebral arteries. Most aneurysms are congenital and continue to change and develop throughout life. They can become atherosclerotic. Aneurysms typically occur most frequently in the bifurcations of major vessels in the polygon of Willis. Multiple aneurysms are seen in 20% of the patients, and arteriovenous malformation (AVM) with aneurysm is seen in 1% of the patients. If aneurysms are located peripherally, secondary causes such as trauma or infection should be considered.
More than 85% of aneurysms occur in the carotid or “anterior” circulation. Approximately 30% of them occur in the intracranial segment of the internal carotid artery, usually at the exit of the posterior communicating artery or in its immediate vicinity. Another 30% is seen in the anterior communicating artery part. About 25% of it sits on the trifucation of the middle cerebral artery, where it gives its first major branches. The starting point here is the beginning of the bifurcation point of the vein. Vertebro-basilar or “posterior” circulation aneurysms are most commonly seen at the apex of the basilar artery, but may also occur in more proximal portions along its trunk. The origin of the posterior inferior cerebellar artery is the second most common location.
Cases with intracranial aneurysm most commonly present with signs and symptoms of subarachnoid hemorrhage (SAH). 80% of non-traumatic subarachnoid hemorrhages are due to aneurysm rupture. As a result of this rupture, the patient develops a severe headache, followed by nuchal rigidity and photophobia as a result of meningeal irritation caused by blood passing into the subarachnoid space. Temporary loss of consciousness may also occur. In some patients, focal neurological deficits and coma may occur due to sudden increase in intracranial pressure. The severity of SAH can be graded. Generally, the lower the grade, the better the prognosis.
Not all patients with aneurysms present with rupture-related symptoms. Internal carotid artery (ICA) aneurysms show a mass effect; It may cause blindness in one eye caused by compression on the optic nerve (II.) or diplopia, ptosis and pupil dilation as a result of compression on the oculomotor nerve (III.). An ICA aneurysm within the cavernous sinus n. Compressing the abducense causes double vision. A giant basilar-type aneurysm (more than 25 mm in diameter) may obstruct the cerebral aqueduct, producing hydrocephalus. Rarely, an aneurysm may be large enough to be mistaken for a tumor.
The diagnosis of SAH is usually made based on clinical findings. CT scan should be performed first, Entire cerebrovascular angiography helps to pinpoint and identify the aneurysm as well as reveal if multiple aneurysms are present or a concomitant AVM.
TREATMENT
After the diagnosis of aneurysm bleeding is confirmed, a certain protocol is applied to the patient against the risk of new bleeding. The ultimate goal in the treatment of aneurysm is to reach the aneurysm with craniotomy, dissect it microsurgically and close the neck with a clip. The timing of the surgery should be adjusted according to the clinical grade of the patient. Patients with grades I and II should undergo surgery within the first 72 hours after bleeding. Intensive medical intervention is applied to Grade III and IV patients, and their condition is improved and a lower grade is tried to be brought if possible, because the risk of mortality increases as the grade of the patient increases. If aneurysms that have not yet bled are detected, they should be operated under elective conditions without causing bleeding. Aneurysms that are difficult or even impossible to be surgically treated can be effectively treated with interventional neuroradiological techniques by emolizing them.
Complications of aneurysmal hemorrhages include a 30% risk of re-bleeding within the first 8 weeks in cases where the lesion is not treated, hydrocephalus, vasospasm, intracerebral hematomas, increased intracranial pressure, and epileptic seizures due to occlusion of arachnoid villi by subarachnoid blood clots. Of these, the most obvious but least understood is vasospasm. This phenomenon often occurs in the First 4-7 days after bleeding and causes narrowing of the involved cerebral arteries. Vasospasm can be seen on angiography without any clinical findings, or it can cause ischemia in the brain tissue supplied by the relevant vessels, which is severe enough to threaten the patient’s life.
Outcomes of cases with aneurysms clipped under elective conditions from bleeding are better than those with aneurysms clipped after bleeding, because the brain has not yet been damaged by subarachnoid haemorrhage. Besides, except for internal carotid artery aneurysms, complicated anterior communicating artery aneurysms; They are less risky than vertobrobasilar system aneurysms. Generally, patients recover when the aneurysm is successfully clipped and vasospasm can be relieved or prevented.
