How does a stroke affect the brain?

Posted on 1 September 2017

The human brain influences most of our day-to-day activities, both directly and indirectly. And while its optimal function is paramount to healthy living, the danger of an ischemic stroke is ever present.

‘Cases of ischemic strokes are a fairly common occurrence, particularly in people over the age of fifty,’ says Dr Sarel Spies, a neurosurgeon based at Mediclinic Tzaneen. ‘Ranked right up there with heart disease and most cancers as potentially fatal medical conditions, ischemic strokes are influenced primarily by hypertension and elevated cholesterol.’

An ischemic stroke occurs when oxygen and glucose supply to the brain is cut off by an arterial blockage, or blood clot. Loss of feeling in one side of the body signals the onset of an ischemic stroke, as does dizziness and a feeling of imbalance. These varied symptoms distinguish which of the part of the brain is affected.

‘The brain is divided into left and right hemispheres,’ explains Dr Spies. ‘The left hemisphere controls the right side of the body and vice versa, and the same applies to strokes. A stroke in the left side of the brain affects the right side of the body, often in the form of slurred speech and confusion. Loss of feeling in the left arm and leg is indicative of the right side of the brain being affected.

‘Loss of consciousness and whole body paralysis are the hallmarks of a brain stem stroke,’ he continues. ‘A sensation of feeling “locked in” predominates, where only the eye muscles are able to move. Severe nausea and vomiting characterise a cerebellar stroke. Headaches and vertigo are also tell-tale warning signs.’

Dr Spies cautions that, while the acute effects of an ischemic stroke are indeed treatable, it is also important to think long term.

‘One should be wary of depression, memory loss and urinary dysfunction in the aftermath of an ischemic stroke. All important factors in the healing process.’

Important notes:

Stroke warning signs. 

  • Sudden weakness or numbness on one side of the body.
  • Sudden unusual, severe and persistent headache.
  • Sudden difficulty speaking or loss of sight in one or both eyes


Smile, or show your teeth. Does one side of the face droop?
Close your eyes, and hold your arms out for 10 seconds. Does one arm drift down?
Repeat any sentence. Is speech slurred, wrong words used or unable to speak?
Note the time and get to the nearest stroke unit as soon as possible. Every minute counts.

For emergency services, call 084 124.


Published in Healthy Life

In the interest of our patients, in accordance with SA law and our commitment to expertise, Mediclinic cannot subscribe to the practice of online diagnosis. Please consult a medical professional for specific medical advice. If you have any major concerns, please see your doctor for an assessment. If you have any cause for concern, your GP will be able to direct you to the appropriate specialists.

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2 Responses to “How does a stroke affect the brain?”

  1. johan trotskie says:

    most interesting. helped me better understand the death of my friend last year.

Leave a reply to Frances Bailey