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Türkçe Aneurysms
Intracranial aneurysms are pathological enlargements of the cerebral arteries. Most of the aneurysms are congenital and continue by changing and developing. They may gain atherosclerotic form. Typically, aneurysms occur most commonly in the bifurcations of the main arteries in the circle of Willis. Multiple aneurysms are seen in 20% of the patients, arteriovenous malformation (AVM) with aneurysm is seen in 1% of the patient. If aneurysms have peripheral localization, secondary causes such as trauma or infection should be taken into consideration.
More than 85% of aneurysms occur in the carotid or "anterior" circulation. Approximately 30% of them show up at the intracranial segment of the internal carotid artery, usually at the origin of posterior communicating artery or in the neighbourhood. The other 30% of them are seen in the anterior part of communicating artery. Approximately 25% of them settle in the trifurcation of major branches of the middle cerebral artery. The initial point here is the origin of the branching point of the artery. Although vertebrobasilar or "posterior" circulation aneurysms occur most commonly at the top of the basilar artery, they may also occur along its trunk or in more proximal parts. The origin part of the posterior inferior cerebellar artery is the second most common localization.
Intracranial aneurysm cases come up most commonly with signs and symptoms of subarachnoid hemorrhage (SAH). 80% of non-traumatic subarachnoid hemorrhages are caused by aneurysm rupture. As a result of this rupture, a severe headache and following that, neck stiffness and photophobia developed due to meningeal irritation that is caused by the blood moving to the subarachnoid space. Transient loss of consciousness may also occur. In some patients, focal neurological deficits and coma state may occur due to sudden increase of intracranial pressure. The severity of SAH can be graded. Generally, a lower grade represents a more favourable prognosis.
Patients with aneurysms may not always come up with rupture related symptoms. Internal carotid artery (ICA) aneurysms may cause mass effect thus may cause sight loss in one eye as a result of compression on the optic nerve (II.) or diplopia, ptosis and pupil dilatation as a result of compression on oculomotor nerve (III). An ICA aneurysm in the cavernous sinus may cause diplopia by compressing on the nervus abducens. A giant aneurysm (larger than 25 mm in diameter) may develop hydrocephalus by occluding the cerebral aqueduct. Rarely, an aneurysm can be large enough to be mistaken for a tumour.
The SAH is usually diagnosed according to clinical findings. Firstly, CT scan should be performed. An angiography that is an examination involving all blood brain vessels of the brain helps identify the aneurysm precisely and at the same time reveal whether there are multiple aneurysms or not, or an accompanying AVM.
Treatment
After confirming the diagnosis of aneurysmal hemorrhage, a specific protocol is carried out against the risk of a new hemorrhage in the patient. The ultimate goal in the treatment of aneurysm is to reach the aneurysm by craniotomy and to dissect it microsurgically, and close up the neck with a clip. The timing of the surgery should be adjusted according to the clinical grade of the patient. Patients with grade I and II should be operated within the first 72 hours after the hemorrhage. Intense medical intervention is performed for patients with grade III and IV and by improving their conditions, the grade is tried to be lowered if possible, since the grade of a patient increases, the risk of mortality increases. If aneurysms that has not bled yet are detected, they should be operated under elective conditions before causing an hemorrhage. Aneurysms, surgery of which is difficulty, even impossible, can be effectively treated by interventional neuroradiological techniques by embolization.
Complications of aneurysmal hemorrhage include the risk of recurrence of hemorrhage by 30% within the first 8 weeks in case the lesion is untreated, hydrocephalus developing as a result of occlusion of the arachnoid villi (granulations) by subarachnoid blood clots, vasospasm, intracerebral hematomas, intracranial pressure increase and epileptic seizure. The most significant but least understood one among these is the vasospasm. This phenomenon often come up within the first 4-7 days after bleeding and causes the stenosis (narrowing) of the relevant cerebral arteries. Vasospasm may be visualized during angiography without any clinical finding, on the other hand it may cause ischemia in the brain tissue, which is fed by the relevant blood vessels at a level of seriousness that threatens the life of the patient.
The results of aneurysm cases clipped electively before hemorrhage are better than those with clipped aneurysm after hemorrhage because the brain has not yet been damaged by subarachnoid hemorrhage. Besides that, internal carotid artery aneurysms, except for complicated anterior comminian artery aneurysms, are less risky than system aneurysms. Usually, in cases in which the aneurysm is clipped by a successful surgery and vasospasm can be removed or prevented, the recovery of the patient is ensured.
