Stroke, demystified

^{_{Written by Dr. Ko Yiu Kwan, Cyril, Specialist in Cardiology}}

There are two main types of stroke: ischaemic stroke and haemorrhagic stroke. Haemorrhagic stroke is the rupture of blood vessels and accounts for about 20% of all stroke cases only. The remaining 80% are cases of ischaemic stroke, otherwise known as cerebral vascular thrombo-embolism (blood clot in cerebral vessel). 

Both blockage and haemorrhage of cerebral vessels can cause brain cells to receive insufficient nutrients and lose oxygen supply. This will cause damage to brain tissues and affect activities they control.

Doctors often get asked whether numbness in fingers means a stroke is imminent. In most cases, a stroke affects rather large sections of the body. Numbness that is limited to the fingers or the hand, and especially numbness that occurs in both hands without any other accompanying symptoms, might not necessarily mean a stroke is forthcoming.

Different parts of the brain control different bodily functions. Depending on which part of the brain is damaged, the symptoms will vary. The acronym “FAST” is used for quick identification of stroke symptoms:

“F” stands for face drooping;

“A” stands for arm weakness;

“S” stands for speech difficulty; and

“T” stands for time to call.

The local medical profession uses a Chinese-based mnemonic “SSSS” (談笑用兵) instead:

Speech (談): show difficulty in communicating or speaking;

Smile (笑): have asymmetrical facial expressions;

Strength in limbs (用): experience weakness in arm and leg on one side of the body; and 

Seek help (兵): seek medical help as soon as possible if the above appears.

The brain is extremely dependent on a stable supply of nutrients and glucose for normal operation. Despite accounting for only 2% of the body weight, the brain consumes 20% of the oxygen used by the entire body! Brain cells quickly become damaged or die when a stroke happens because of the lack of blood supply carrying nutrients and glucose. The longer the time delay, the more serious the brain damage might be. Irreversible death of the brain cells might even happen. Therefore, when a stroke occurs, seeking medical help at once is vital.

The medical profession often uses the phrase “the three ‘golden’ hours of stroke treatment”, which originated from a clinical trial report published by the National Institute of Neurological Disorders and Stroke (NINDS) of the United States in 1995. The study involved a clinical trial performed on about 300 patients who suffered ischaemic stroke. It was found that when those who were administered recombinant tissue plasminogen activators (rt-PA) to dissolve the clot within three hours of the stroke, their chances of making a full recovery in three months or developing only very mild forms of disabilities were at least 30% higher than those sufferers who were not given the clot-busting drug (N Eng J Med. 1995; 333:1581-1587).

Then, does it mean that all hopes are gone if the 3 “golden” hours has passed? The answer is a definite no. A study has shown that rt-PA administered within 4.5 hours can still reduce the sequelae of stroke (Lancet 2014; 384:1929-1935). According to a more recent study, if rt-PA is administered within 4.5 hours to 9 hours after a stroke has happened, it can still lessen the damage done to nerves (N Engl J Med 2019; 380:1795-1803).

If it is just a case of blood clot blocking the blood flow and the brain is not yet dead, then an “angioplasty” surgery for the brain can be performed: a catheter is inserted to remove the obstructing blood clot to resume blood supply for the brain (N Engl J Med 2018; 378:708-718).

Seizing the 3 “golden” hours of stroke treatment is undoubtedly the best scenario; however, even if this window is passed, timely treatment can still reduce the risks involved. Therefore, if you suspect a stroke has happened, do not hesitate and seek medical attention immediately.