Brain Aneurysm

Causes, Warning signs and Symptoms

 A brain aneurysm is defined as any abnormal enlargement or dilatation of the lumen of a cereb  ral artery. The cerebral aneurysms according to their morphology identified as Saccular and Fusiform,and the most common form is Saccular. In other words a sac is formed at a weak point in the artery with a stem which joins it to the rest of the artery. They usually develop in arterial junction areas. In a Fusiform brain aneurysm, the aneurysm takes a long narrow shape which includes all the wall of the artery on both sides. The size and the anatomical position of the aneurysm are the factors which usually define the clinical manifestation. Usually the rupture of the aneurysm manifests with subarachnoid hemorrhage (SAH) and more often with intraventricular hemorrhage or intraparenchymal.

 The Symptoms of a ruptured aneurysm are:

• Severe unprecedented headache
• Stiff neck
• Vomiting
• Photophobia
• Diplopia
• Pain in eye
• Drooping eyelids
• Disturbance- deterioration in level of consciousness
• Palsy or paralysis of a cranial nerve
• Pupil dilation
• Numbness, paresthesias dysesthesias of half of the face

Non ruptured aneurysms are accompanied by focal neurological signs (reduced visual acuity, ophthalmology, psychology and cognitive disorders etc.) or with epileptic seizures. Often preceding minor leaks of the aneurysm cause persistent headache.

Demographic data:

 The incidence of subarachnoid hemorrhage (SAH) is 1:10.000 residents annually. Based on this figure, for Cyprus, approximately 100 patients are expected annually. In 80-90% of these patients the subarachnoid hemorrhage (SAH) is caused by ruptured aneurysm, while 5% by rupture arteriovenous malformation. While at a rate of 10% -20% no pathology is found, the SAH may be due to coagulopathy, thrombocytopenia, leukemia, vasculitis, or neoplasms and vascular diseases of the spine.

Postmortem studies have shown that the incidence of cerebral aneurysms in the general population is 2 % while half of these will occur with rupture of the aneurysm that occurs between the ages of  45 and 65. The majority of aneurysms, 80%, are less than 1 cm in size. In most cases however, there is either a family history of aneurysm or a congenital abnormality in the arterial wall.

With regards to the hereditary correlation it has been proved that there is a 10-15% chance of the development of a cerebral aneurysm among first degree relatives. Hence the extreme importance of precautionary screening with digital subtraction angiography or non-invasively by three-dimensional angiography or MRA. The same diagnostic procedure is applied to determine the existence of an aneurysm in cases of subarachnoid hemorrhage. In some cases the aneurysm showed up randomly in a screening by CT or MRI brain performed for another indicated disease.

About 20% of patients with a ruptured cerebral aneurysm die before they reach a hospital while 20% with ruptured cerebral aneurysm have a severe clinical picture which negatively affects both the outcome and rehabilitation of patients. The remaining 50-60% of patients tested are in relatively good neurological condition and able to undergo timely treatment of the aneurysm with a metal staple. This procedure excludes the possibility recurrence of hemorrhage and development of cerebral ischemia due to vasospasm.

Aneurysm Treatment:

The most contemporary non-invasive method of treatment for aneurysms is that of embolization of the aneurysm.

Microcatheters are inserted usually through the femoral artery and navigated to the area of the aneurysm and special coils are placed in the sac which helps block the flow of blood into the aneurysm. In many cases it is necessary to use special expandable stent catheters which ensure the anatomical structure of the vessel.

If however embolization of the aneurysm is not possible, surgical clipping must be performed with aneurysm clips to prevent blood flow into the aneurysm and new rupture of the aneurysm.

Factors that increase the risk of formation of a brain artery aneurysm are:

• Smoking
• High blood pressure
• Drug abuse, cocaine in particular
• Brain Tumors
• Infections
• Family history of brain aneurysms
• Head trauma
• Congenital brain aneurysm due to abnormalities in the arterial wall
• Dysgenesis of the circulatory system of the brain such as arteriovenous malformation
• Inherited conditions such as polycystic kidney disease, Marfan syndrome,Ehler’s syndrome

Arteriovenous malformations:

These are a cluster of abnormal blood vessels where the arteries flow directly without the intervention of capillaries and veins and without brain parenchyma  present in the "nest" of the cluster. These are congenital lesions that gradually increase in size. They are usually diagnosed due to:

• Bleeding
• Epileptic seizures caused by ischemia
• Persistent headache
• Symptoms indicative of increased intracranial pressure (ICP)

If hemorrhage or dysplasia is also present there is a 10% mortality rate per episode of hemorrhage and 30-50% chance of neurological deficit per episode of hemorrhage. The bleeding is intraparenchymal  less frequently spontaneous subarachnoid, or intraventricular  or spontaneous subdural hematoma.

These dysplasias are evaluated according to the size, the location in relation to structures and their venous drainage.

Therapy:

Usually endovascular embolization is preferred followed by radiotherapy or stereotactic radiotherapy for small lesions less than 3 cm or conventional radiotherapy in larger lesions. The surgical treatment of dysplasias eliminates the risk of hemorrhage immediately and improves the control of epileptic seizures.