The brain is a wondrous thing. It is the source of joy, and greed, sloth, envy, pride, wrath, lust and gluttony, and any other sins one could think of. But every once in a while things don’t go as planned. One of those events is a stroke.
A stroke very simply is a sudden event occurring in relation to the blood vessels that supply the brain. This maybe blockage of the vessel, similar to what happens in a heart attack, or sometimes bursting of fragile vessels such as aneurysms or due to a sudden rise in blood pressure.
Historically, these conditions were termed apoplexy (Greek for ‘strike away’). Apoplexy however was used to describe any sudden loss of consciousness with usually rapid deterioration and death. Today we know that there many causes of such symptoms including rupture of aortic aneurysms, massive heart attacks, or catastrophic bleeding into the brain or a large ischemic stroke.
The use of the word stroke to describe this condition began around the 17th century largely as a translation of the Greek origin but some believed it to refer to a divine retribution and chose to refer to it as such.
Before we go in to strokes, however, a brief overview of the brain and its parts and their function is warranted.
The brain largely has 3 main divisions – the cerebral hemispheres, the cerebellum, and the brainstem.
The cerebral hemispheres are the important parts that make us WHO we are. They control limb movement, speech, memory, consciousness, sensation, intelligence, thought and pretty much every thing that we associate with being, well, human. There is some amount of side specificity with the left cerebral hemisphere being the dominant hemisphere in a majority of right (and left) handed people and it controls the right half of the bodyand speech and language, reasoning, math, logic, etc. The right half of the brain controls the left side and also has a bunch of areas that deal with association and transformation of thought from a logical concept to an abstract one and with imagination and thus art.
The cerebellum controls coordination of limbs and its what makes movement smooth and in some of us, graceful. It also controls balance while sitting, standing or walking. And also, since it controls the smoothness of movement it also has a role to play in the clarity of speech.
The brainstem is like the set of cables that go in and out of a computer. Pretty much every tract that sends sensations into the brain from the body and every tract that descends down from the brain to the body run through it. It also has centres that regulate heart rate, breathing and motor functions of the head and face.
This forms the basis of how people are affected by strokes depending on which part of the brain is involved.
Blood – too little or too much
Strokes are classified in multiple ways, the simplest is on the basis of the cause – ischemic (lack of blood) or hemorrhagic (bleeding). Strokes may also be transient or permanent. Doctors will diagnose and stratify strokes further depending on the area of the brain affected.
Ischemic strokes are the most common type of stroke. It is caused by the obstruction of blood flow to a part of the brain. Like a heart attack. In fact, there is reason to call it a brain attack to give it the importance that it deserves. The symptoms of stroke are dependent on the area of the brain most affected. While heart attacks have a common set of symptoms irrespective of which part of the heart is affected – like chest pain, left arm pain, shortness of breath, etc. the brain strokes, on the other hand, can manifest themselves in a host of ways.
The common acronym FAST – Face, Arm, Speech, Time; gives a reasonable outline of the common symptoms of stroke occurring in either of the cerebral hemispheres. There may be asymmetry of the face or paralysis of one side; On asking the individual to lift both arms, one may drift downwards and lastly there maybe impairment of speech – either complete inability to speak or garbled incoherent speech. T is Time, which is of essence. It is important to note that these are the earliest symptoms of stroke and treatment is required urgently. More urgently than in a heart attack since the brain is less resilient to ischemia than the heart is.
It’s also important to realize that early symptoms may just be any altered sensation or a “weird feeling” in the limbs which should prompt a FAST evaluation and medical treatment.
These signs and symptoms are for strokes involving the cerebral hemispheres, a right brain stroke leading the left sided weakness and a left brain stroke causing right sided weakness and often impaired speech. But what of strokes affecting the cerebellum or the brainstem even? Cerebellar strokes cause incoordination of the limb on the same side as the stroke. Clumsiness while attempting to reach out and grab and object, a drunken gait, persistent giddiness are some of those features. These are however not as common as cerebral strokes. Brainstem strokes, thankfully are rare. They have various symptoms depending on which of the nerve fibers are affected and largely are the cause of many a sleepless night during neurosurgery training trying to remember the exact components of Claude’s, Bernard’s, Webber’s, Foville’s, Millard-Gubler’s, Wallenberg’s syndromes. Needless to say we shall not deal with them at length here.
What of TIA?
Sometimes, in very lucky situations, the universe gives us a warning. Transient Ischemic Attacks are strokes in their own right. They involve a block in a small artery to the brain that the body somehow manages to dissolve before it’s too late. TIAs are usually short lived but can take upto 24 hours to fully resolve. They may have the same symptoms as a stroke – limb weakness on one side of the body, facial asymmetry, loss of vision (amaurosis fugax), speech arrest or difficulty, incoordination, and sometimes seizures.
A TIA is often followed by a stroke. It’s a warning that should not be ignored and evaluation of stroke risk factors and preventive treatment is imperative to reduce the risk of a large/major stroke.
Hemorrhagic strokes are where instead of blood not flowing into the affected part of the brain, a small blood vessel bursts open a causes a blood clot within the brain. The commonest cause of this is hypertension. And a fragile hemorrhaging artery of Charcot. And while we’re dropping names, another cause is Moya Moya disease.
But names apart, hemorrhagic strokes are a problem. The sudden bleeding often causes unconsciousness and if the bleeding is large, coma even. Most commonly the bleeds occur deep in the cerebral hemispheres in close proximity to the nerve fibres that control movement leading to paralysis of the opposite half of the body.
The next most common site of a hypertensive bleed is the cerebellum. Here the symptoms may just be a sudden giddiness and incoordination and gradually worsening drowsiness. Cerebellar bleeds require urgent evaluation and possible surgery since the cerebellum and the brain stem lie next to each other with rigid bone and membranes all around. A blood clot in the cerebellum thus can cause increased pressure on the brain stem and create substantial risk to life.
The bottom line in this case is if there’s a possible suspicion that someone nearby is having a stroke then they need to be shifted urgently to a healthcare facility that is equipped to deal with strokes. It would also help to know which hospitals in your city have a dedicated stroke unit that can give effective treatment. The next post will cover treatment of strokes in an emergent setting, long term rehabilitation, and the assessment and need for preventive therapy for patients who maybe at a high risk for a stroke.