Strokes and Brain Bleeds – Dr. Gnana sankaralingam
Stroke is said to have occurred when blood supply to an area of brain has been interrupted resulting in damage to that part, leading to loss of function of the corresponding regions of the body controlled by the diseased brain segment. Since it involves blood vessels and brain cells, it is called Cerebro-Vascular accident (CVA). It is a medical emergency due to either blockage or rupture of artery to the brain causing death of cells if not treated quickly, due to lack of oxygen and nutrients. About 60% are ischaemic strokes due to blocked artery in brain while around 40% are haemorrhagic strokes due to burst artery in brain. Important risk factors for a stroke are diabetes, high blood pressure and atrial fibrillation. In Transient Ischaemic attack (TIA) or mini stroke, symptoms resolve itself within 24 hours.
To understand strokes, brief knowledge of blood circulation of brain is helpful. Brain requires lot of energy to function compared to other tissues. Though brain is only 02% of the body, it receives about 20% of blood pumped by the heart. Main supply to the brain is through right and left Carotid arteries along either side of the neck. Other source is through right and left vertebral arteries lying beside the vetebral column. Two vertebral arteries join together to form a single basilar artery after entering the skull. Carotid arteries connect with basilar artery forming circle of Willis, on the under surface of brain. This set up comes handy when there is impairment of blood flow in one vessel, where other arteries compensate for it. Though blood from these separate arteries mix, main supply to anteriror part of the brain is by carotids while brain stem and posterior parts are mainly by basilar artery.
One may be curious as to how when strokes affect one side of the brain, effect is seen on the opposite side of the body. Every part of the body has its representation in the brain and the nerves are transmitted from the brain through the spinal cord, to the areas of supply. In the brain stem, the nerves cross so that right side of the brain controls left side of the body and vice versa. Right and left cerebral cortices form anterior part of the brain, each divided into frontal, parietal, temporal and occipital lobes, while cerebellum and brain stem consisting of mid brain, pons and medulla form the posterior part of the brain. Frontal lobes are responsible for intelligence, thinking and decision making. Parietal lobes are responsible for receiving and processing sensory information and for voluntary muscle activity. Occipital lobes are concerned with vision and colour recognition while Temporal lobes are concerned with speech and emotional response. Hind brain is associated with balance, coordination of movement and through vital centres in medulla for breathing and heart beats.
Symptoms of stroke depend on affected area of the brain. Common presenting ones are loss of movement with weakness or paralysis and loss of sensation with numbness and tingling of arm or leg and weakness of facial muscles on one side of body, with drooling and speech problem. Strokes affecting posterior parts of brain could present with dizziness, double vision and problems of balance, swallowing and breathing. Drowsiness, confusion or collapse may be seen in the elderly. CT scan will differentiate the type and demonstrate the region affected. Echo cardiogram is done to exclude clots in the heart and ultrasound of the neck is done for narrowing of carotid arteries. In the CT scan pictures, haemorrhages would be seen as white areas and ischaemic regions would be seen as greyish areas.
Immediate treatment differs according to type of stroke. In Ischaemic variety, if the patient is brought within four hours of suffering a stroke, blocks could be relieved either by infusion of drugs IV to dissolve the clots or by removal of clots (thrombolectomy) through catheter. In haemorrhagic variety, which may present with severe headache and nausea and vomiting due to raised pressure within the skull and swelling of brain, first step is to stop the bleeding and reduce the pressure. They might require surgery to remove blood or repair the burst aneurysm. Once recovered from acute phase, rehabilitation regimen is commenced to get the patient to regain their pre-stroke activity as much as possible. Physiotherapy is given to improve strength of limbs and walking, occupational therapy is given to adapt to the new situation and speech therapy is given to relearn talking and assist swallowing.
Locked in syndrome is due to stroke affecting part of brain stem, where there is total paralysis of voluntary muscles, but consciousness and cognitive abilities are preserved. Patient is aware but unable to communicate. They could blink and move eyes up and down and not sideways, hear, sleep, think and reason and comprehend people talking or reading to them. However, they cannot speak, make facial expressions, chew, swallow or feel pain. In the incomplete form they can feel pain and other sensations in certain parts of the body. As vital centres are not damaged, breathing and heart beats are not affected.
Bleeding in the brain due to other causes such as burst aneurysm or past head injury can mimic stroke. Brain has three layers of covering, termed pia, arachnoid and dura and enclosed in the skull. Bleeding between pia and brain substance is called cerebral bleed, bleeding in the space between arachnoid and pia is called sub-arachnoid bleed, bleeding in the space between dura and arachnoid is called sub-dural bleed and bleeding between dura and skull is called extra dural bleed. They all present with same symptoms due to pressence of blood compressing brain, to raise the pressure inside the skull cavity. Common ones are headache not responding to simple pain killers, vomiting several times and disturbances in vision such as blurring and double vision. Dizziness may be due to blood loss.
Chronic sub-dural haematoma (cSDH) is collection of blood over several weeks or months, following trivial head injury in older people, which at the time of impact had not produced substantial symptoms and been allowed to pass unattended. Unfortunately even after the lapse of time, it presents with vague symptoms such as failing of memory to recent events, mild headache, listlessnes, drowsiness and falls. Elderly are at higher risk of cSDH as the brain shrinkage due to ageing causes tiny veins to be more stretched and vulnerable to tearing. It could also occur in those on anti-coagulants and anti-platelets and heavy drinkers. Blood is evacuated surgically in those with large clots causing neurological compromise, and those with small ones not having neurological deficit are treated with drugs to reduce brain swelling and to prevent seizures and kept under observation. Those over 60 years must take extra caution in daily activities, to avoid accidents causing injury to the head.
