CEREBRAL ANEURYSM – Locations, Classification, Cause and Risk Factors, Pathophysiology, Clinical Manifestations, Diagnostic Evaluations and Management
A brain aneurysm, also called a cerebral or intracranial aneurysm, is an abnormal bulging outward of one of the arteries in the brain. Cerebral aneurysms can occur anywhere in the brain, but most are located along a loop of arteries that run between the underside of the brain and the base of the skull.
Brain aneurysms are often discovered when they rupture, causing bleeding into the brain or the space closely surrounding the brain called the subarachnoid space, causing a subarachnoid hemorrhage. Subarachnoid hemorrhage from a ruptured brain aneurysm can lead to a hemorrhagic stroke, brain damage and death
A common location of cerebral aneurysms is on the arteries at the base of the brain, known as the Circle of Willis. Approximately 85% of cerebral aneurysms develop in the anterior part of the Circle of Willis, and involve the internal carotid arteries and their major branches that supply the anterior and middle sections of the brain. The most common sites include the anterior cerebral artery and anterior communicating artery (30-35%), the bifurcation of the middle cerebral artery (20%), the bifurcation of the basilar artery, and the remaining posterior circulation arteries (5%).
CLASSIFICATION OF ANEURYSM
According to Size
- Fusiform Aneurysm: It is a diffuse dilation that involves the entire circumference of the arterial segment i.e. whole artery.
- Saccular Aneurysm: It is a distention of a vessel projecting form one side. Saccular aneurysm is a distinct, localized out pouching of the arterial wall.
- Dissecting Aneurysm: Hemorrhage or intramural hematoma, separating the layers of an arterial wall. Dissecting aneurysm commonly involves Arch of aorta.
According to Cause
- True Aneurysm: It is a result of the slow weakening of the arterial wall caused by long term diseases such as hypertension, artherosclerosis, etc.
- False Aneurysm: Pseudoaneurysm is caused by traumatic break in the arterial wall.
Causes and Risk Factors
An aneurysm occurs when the pressure of blood passing through part of a weakened artery forces the vessel to bulge outward, forming what you might think of as a blister.
- Atherosclerosis and Arteriosclerosis
- Heavy alcohol consumption
- Drug abuse, particularly the use of cocaine
- Lower estrogen levels after menopause
- Constant stress
- Intracranial arterio-venous malformation
- Family history of cerebral aneurysms
- Certain medical problems such as polycystic kidney disease and coarctation of the aorta
Due to etiological factors
Weakness of the vessel wall
Abnormal dilation of the wall of the artery
Rupture of a cerebral aneurysm due to intra-aneurysmal pressure and thinning of vessel wall
Blood leaks into the subarachnoid space may cause increased ICP and ischemia
Grading of Cerebral Aneurysm
Hunt – Hess Scale
Grade 0: Unruptured; asymptomatic discovery
Grade I Asymptomatic or minimal headache with slight nuchal rigidity
Grade II Moderate to severe headache, nuchal rigidity; no neurologic deficit other than cranial nerve deficit
Grade III Drowsiness, confusion or mild focal deficit (hemiparesis) or combination
Grade IV Stupor, moderate to severe deficit, decerebrate posturing
Ruptured Cerebral Aneurysm Symptoms
Sometimes patients describing “the worst headache in my life” are actually experiencing one of the symptoms of brain aneurysms related to having a rupture. Other ruptured cerebral aneurysm symptoms include:
- Nausea and vomiting
- Stiff neck or neck pain
- Blurred vision or double vision
- Dilated pupils
- Sensitivity to light
- Loss of sensation
Unruptured Cerebral Aneurysm Symptoms
Before an aneurysm ruptures, patients often experience no symptoms of brain aneurysms. In about 40 percent of cases, people with unruptured aneurysms will experience some or all of the following cerebral aneurysm symptoms:
- Peripheral vision deficits
- Thinking or processing problems
- Speech complications
- Perceptual problems
- Sudden changes in behavior
- Loss of balance and coordination
- Decreased concentration
- Short-term memory difficulty
Because the symptoms of brain aneurysms can also be associated with other medical conditions, diagnostic neuroradiology is regularly used to identify both ruptured and unruptured brain aneurysms
- History and physical examination
- Cerebral angiography or tomographic angiography
- Computed Tomographic Angiography (CTA)
- Electroencephalogram (EEG)
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
- Cerebrospinal fluid analysis
Administer nitroprusside or alternative IV antihypertensive agents and close monitoring of blood pressure. Administer calcium – channel blockers such as nimodopine to prevent vasospasm. Prophylactic antiepileptic drugs to prevent or control seizures such as phenytoin, Phenobarbital are preferred medications.
Aneurysm precautions include – complete bed rest with head elevated 30 degree, intravenous fluids, avoidance of Valsalva maneuver and neck flexion, decreasing environmental stimuli, limitations of visitors and administration of analgesics and sedatives.
There are two common treatment options for a ruptured brain aneurysm
- Surgical Clipping: Surgical clipping is a procedure to close off an aneurysm. The neurosurgeon removes a section of skull to access the aneurysm and locates the blood vessel that feeds the aneurysm. Then he or she places a tiny metal clip on the neck of the aneurysm to stop blood flow to it.
- Endovascular Coiling: Endovascular coiling is a less invasive procedure than surgical clipping. The surgeon inserts a hollow plastic tube (catheter) into an artery, usually in your groin, and threads it through your body to the aneurysm. He or she then uses a guide wire to push a soft platinum wire through the catheter and into the aneurysms. The wire coils up inside the aneurysm, disrupts the blood flow and causes blood to clot. This clotting essentially seals off the aneurysm from the artery.
- Ventricular or lumbar draining catheters and shunt surgery: ventricular or lumbar raining catheters and shunt surgery can lessen pressure on the brain from excess cerebrospinal fluid (hydrocephalus) associated with a ruptured aneurysm. A catheter may be placed in the spaces filled with fluid inside of the brain (ventricles) or surrounding brain and spinal cord to drain the excess fluid into an external bag. Sometimes, it may then be necessary to introduce a shunt system – which consists of a flexible silicone rubber tube (shunt) and a valve – that creates a drainage channel starting in brain and ending in abdominal cavity.
- Monitor neurological status carefully every hour, and immediately notify the physician of any changes in the patient’s condition
- Establish and maintain a patient airway as needed. Administer supplemental oxygen as ordered
- Position the patient to promote pulmonary drainage and prevent upper airway obstruction. Avoid placing the patient in the prone position as well as hyper extending his neck.
- Suction secretions from the airway as necessary to prevent hypoxia and vasodilation from carbon dioxide accumulation
- Monitor pulse oximetry levels and arterial blood gas level as ordered. Use these levels as a guide to determine appropriate needs for supplemental oxygen
- Prepare the patient for emergency craniotomy, if indicated. If surgery can’t be performed immediately, institute aneurysm precautions to minimize the risk of rebleeding and to avoid increasing the patient’s intracranial pressure.
- Administer hydralazine or another antihypertensive agent as ordered
- Turn the patient often. Encourage deep breathing and leg movement
- Discourage and control any measure the initiates Valsalva’s maneuver, such as coughing, straining at stool, pushing up in bed with the elbows, turning with the mouth closed.
- Apply elastic stockings or compression boots to the patient’s legs to reduce the risk of deep vein thrombosis.
- Assist with hygienic care as necessary. If the patient has a facial weakness, assist her or him during meals
- Give fluids as ordered and monitor I.V. infusions to avoid over hydration, which may increase ICP.
- If the patient has facial weakness, assist him during meals, assess his gag reflex and place the food in the unaffected side of his mouth
- Implement a bowel elimination program based on previous habits. Raise the bed’s side rails to protect the patient from injury
- Provide emotional support to the patient and his family. Encourage the patient to verbalize fears of dependency and of becoming a burden