The brain is an extremely complex organ that controls various body functions. If stroke occurs and blood flow cannot reach the region that controls a particular body function, that part of the body will not work as it should.

The risk factors for stroke include hypertension, diabetes mellitus, increase of blood cholesterol level, certain heart diseases, smoking, obesity, sedentary lifestyle etc.

Types of stroke
There are two types of stroke -

1. Ischemic; and

2. Hemorrhagic

Ischemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis.

Hemorrhagic stroke results from a weakened vessel that ruptures and bleeds into the surrounding brain structure. The blood accumulates and compresses the surrounding brain tissue.

Transient ischemic attacks
Transient ischemic attacks (TIA) are minor or warning strokes. In case of TIA, conditions indicative of an ischemic stroke are present and the typical stroke warning signs develop.

However, the obstruction (blood clot) occurs for a short time and tends to resolve itself through normal mechanisms.

Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke. Steps should be taken immediately to prevent a stroke.

Symptoms of stroke

• Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• Sudden confusion, trouble speaking or understanding
• Sudden trouble seeing in one or both eyes
• Sudden trouble walking, dizziness, loss of balance or co-ordination
• Sudden severe headache. vomiting, loss of consciousness with no known cause

Diagnostic tests
Diagnostic tests examine how the brain looks, works and gets its blood supply. They can outline the injured brain area. Most of them are safe and painless.

CT scan (Computed Tomography) is a key imaging test. It is usually one of the first tests given to patients suspected of stroke. CT test results give valuable information about the cause of stroke and the location and extent of brain injury.

MRI (Magnetic Resonance Imaging) uses a large magnetic field to produce an image of the brain. Like the CT scan, it shows the location and extent of brain injury. The image produced by MRI is sharper and more detailed than a CT scan so it is often used to diagnose small, deep injuries.

What is a blood flow test?
Several blood flow tests exist; most use ultrasound technology. A probe is placed over the suspect artery -- especially arteries in the neck or at the base of the skull -- and the amount of blood flow is determined.

Examples of blood flow tests are B-mode imaging, doppler testing and duplex scanning. These tests give detailed information about the condition of arteries.

Another blood flow test is a medical procedure called angiography (arteriography or arteriogram). Special dyes are injected into the blood vessels and an X-ray is taken. Angio-graphy gives a picture of the blood flow through the vessels. This allows the size and location of blockages to be evaluated.

Treatments
Antiplatelets/Anticoagulants: Antiplatelet (aspirin like drugs) agents play an important role in preventing stroke.

Carotid endarterectomy: Carotid endarterectomy is a procedure in which blood vessel blockage is surgically removed from the carotid artery.

Angioplasty/Stents: Sometimes balloon angioplasty and stents are used in intervention procedure.

Surgical intervention: For hemorrhagic stroke, surgical treatment is often recommended which includes surgical evacuation of a haematoma, placement of a metal clip at the base (neck) of the aneurysm or to remove the abnormal vessels comprising an Arteriovenous Malformation (AVM) by Endovascular Procedures, e.g., "coils".

Endovascular procedures are less invasive and involve the use of a catheter introduced through a major artery in the leg or arm, guided to the aneurysm or AVM where it deposits a mechanical agent, such as a coil, to prevent rupture.

Common effects of stroke
Every stroke is individual, but there are a number of common ways in which stroke can affect someone. The disability from stroke depends on the size, extent and area of the brain affected. Stroke patients can have some disability such as motor, language dysfunction, swallowing problems, sensory deficit, visual disturbance, inco-ordination, behavioral disturbance etc.

Comprehensive rehabilitation which includes physical therapy, occupational therapy and speech therapy needs to be continued following stroke.

Maximum recovery following stoke occurs in the first 3-4 months which then gradually slows down. Regular follow up by the concerned consultant neurologist is very much essential so that the recovery is monitored and also the associated risk factors are controlled which prevents the chance of recurrence of stroke.

The writer is a Consultant and Head of the Department of Neurology of Apollo Hospitals Dhaka.