Stroke: Definition, Classification, its Effects with Different Brain Centers

Stroke is defined as a medical emergency arising due to a partial or complete loss of blood supply to a part of the brain.

In medical terms, you can define a stroke as an infarct in the brain due to a vascular causes namely ischemia or hemorrhage. It is also referred to as a cerebrovascular accident (CVA).

Stroke is characterized as a neurological deficit due to an acute focal injury in the brain by a vascular cause and includes cerebral infarction, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH).

World Health Organization (WHO) definition of stroke (introduced in 1970 and still used) is

“rapidly developing clinical signs of focal (or global) disturbance of cerebral function, lasting more than 24 hours or leading to death, with no apparent cause other than that of vascular origin.”

Due to the interruption in the blood supply, the concerned part of the brain is deprived of nutrients and oxygen. And, there is a sudden loss of function of the affected part of the brain.

Two million brain cells die every minute during a stroke. This increases the risk of irreversible brain damage, permanent disability, or death. These ischemic changes involved in stroke begins within seconds to minutes of the loss of oxygen and nutrients to the neurons (brain cells).

This situation is similar to that arising in a heart attack and therefore, stroke is referred to as a “brain attack”.

A stroke is a life-changing event that contributes to a sense of frustration, helplessness, and depression in a person.

What does all this about stroke mean?

The repercussions arising out of the loss of blood supply are sudden and serious and often result in a disability of the person and at times, instant death.

What happens is that, due to the deprivation of oxygen, the cells of the brain tissue begin to die. This damage to the nervous tissue is irreversible and irreparable.

Therefore, that part of the body controlled by the affected area of the brain loses its function. It could be anything such as loss of muscle ability or loss of memory or speech.

Therefore, the manifestations of a stroke depend very much on where the disruption of blood supply has occurred in the brain and the part of the brain affected.

The effects of stoke could be minor or major and this depends on the amount of brain tissue that is affected by the interruption of blood supply.

For example, a mild stroke can result in temporary muscle weakness in one extremity, while a major stroke can cause paralysis of one half of the body.

Again, what disabilities occur depends on where the stroke has occurred in the brain. That is explained further below.

Classification of Stroke according to its cause

Stroke is classified into types according to the vascular cause that may lead to a stroke:

Ischemic stroke

Blockage of an artery due to clot or an embolus disrupting blood supply distally

Hemorrhagic stroke

Loss of blood supply to part of the brain due to the bursting of a blood vessel leading to brain hemorrhage.

Transient ischemic attacks (TIA)

These are, as the name suggests, transient or temporary lasting from a few minutes to a few hours leaving no permanent damage. They are often referred to as mini-strokes and are benign in nature. They are caused by a temporary blockage of an artery in the brain. The blockage may due to temporary clot formation or due to cholesterol build up in the walls of an artery or its branches in the brain (atherosclerosis).

Effects of stroke occurring in the various brain control centers

A stroke can affect any or all functions of the brain center.

A brief overview:

Effects of stroke in the right hemisphere of the cerebrum

  • Left-sided weakness or paralysis along with sensory impairment
  • Inability to see the left visual field of each eye
  • Inability to localize or recognize body parts and find objects such as clothing
  • Loss of memory
  • Behavioral changes, such as lack of concern about the circumstances and depression

Effects of a left hemisphere stroke in the cerebrum

These are the same as those that occur in the right hemisphere except that they relate to the right side of the body.

Effects of stroke in the cerebellum

Strokes in the cerebellum are less common but the complications can be severe.

The cerebellum receives sensory information from all parts of the body via the spinal cord. It regulates motor movement, helps fine-tunes muscle control and muscle action.

It coordinates voluntary movements such as fine movements, posture, balance, and speech, which results in an overall smooth and balanced muscular activity.

Effects include

  • Inability to walk due to trouble with coordination and balance (ataxia)
  • Dizziness
  • Headache
  • Nausea and vomiting

Effects of stroke in the brainstem

The brainstem controls many of the body’s vital functions such as heartbeat, blood pressure, and breathing.

It also controls the nervous transmission of functions concerning eye movement, hearing, speech, chewing, and swallowing.

Stroke effects include problems relating to:

  • Breathing and heart functions
  • Body temperature control
  • Balance and coordination
  • Chewing, swallowing, and speaking
  • Vision
  • Coma
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