21. STROKE

Introduction

Stroke is a serious medical condition that happens when the brain does not receive enough blood supply. According to the World Health Organization (WHO), stroke is defined as a neurological deficit caused by a problem in the brain’s blood vessels that lasts for more than 24 hours or results in death within 24 hours. When the blood flow stops due to blockage or bleeding, the affected brain cells start to die, leading to loss of function.

Transient Ischaemic Attack (TIA)

Transient Ischaemic Attack, commonly called a “mini-stroke,” is a temporary episode where the patient may experience weakness, loss of speech, or vision problems lasting from a few seconds up to 24 hours. Complete recovery happens after a TIA, but these attacks act as a warning sign for future stroke. TIAs usually occur suddenly and tend to repeat.

Epidemiology

  • There are over 4.6 million stroke survivors in the United States alone.
  • Stroke is one of the leading causes of adult disability.
  • Nearly 20% of nursing home residents have had a stroke.
  • Higher risk is seen in older adults, males, and African-Americans.
  • Some regions of the southeastern United States show double the average stroke mortality rate. These areas are often referred to as the “Stroke Belt.”

Classification of Stroke

Stroke is mainly classified into two major types:

  • Ischaemic Stroke (85%) – caused by blockage of a blood vessel.
  • Haemorrhagic Stroke (15%) – caused by bleeding inside or around the brain.

1. Ischaemic Stroke

An ischaemic stroke occurs when a blood vessel supplying the brain becomes blocked. Due to this blockage, the brain does not get oxygen and nutrients, leading to tissue death known as infarct.

Types of ischaemic stroke:

  • Thrombotic Stroke: A blood clot forms inside the blood vessels of the brain.
  • Embolic Stroke: A blood clot or debris forms elsewhere in the body and travels to the brain.

2. Haemorrhagic Stroke

This type of stroke occurs when a blood vessel ruptures and bleeds into the brain tissues. It is less common but more dangerous and has a higher death rate.

Types of haemorrhagic stroke:

  • Subarachnoid Haemorrhage: Bleeding occurs in the subarachnoid space, usually due to trauma or rupture of an aneurysm or AVM.
  • Intracerebral Haemorrhage: Bleeding occurs inside the brain tissue. Common causes include uncontrolled high blood pressure and use of blood-thinning medicines.
  • Subdural Haematoma: Blood collects under the dura layer of the brain, mostly due to head injury.

Etiology (Causes)

Ischaemic Stroke

  • Blood clot formation
  • Atherosclerosis
  • Emboli travelling from the heart or major vessels

Haemorrhagic Stroke

  • Subarachnoid Haemorrhage: Trauma, rupture of aneurysm, AVM rupture
  • Intracerebral Haemorrhage: High blood pressure, trauma, vessel rupture
  • Subdural Haematoma: Trauma leading to rupture of bridging veins

Pathophysiology

The brain needs a continuous supply of oxygen and glucose to function. When blood flow stops, the following happens:

  • Neurological metabolism changes within 30 seconds.
  • Brain metabolism completely stops in 2 minutes.
  • Brain cell death begins in 5 minutes.

Atherosclerosis is one of the major causes of ischaemic stroke. Fat and inflammatory cells deposit inside blood vessel walls, forming plaques. When these plaques rupture, they attract platelets and form a clot. This clot may block the vessel or travel to smaller vessels, causing an embolic stroke.

In cardiogenic embolism, clots form in the heart chambers due to blood stagnation (e.g., in atrial fibrillation) and travel directly to the brain.

The final effect of both thrombosis and embolism is blockage of a cerebral artery, leading to reduced blood flow and lack of oxygen in the affected brain area.

Clinical Presentation

Symptoms

  • Weakness on one side of the body
  • Inability to speak
  • Loss of vision
  • Vertigo or sudden imbalance
  • Severe headache (more likely in haemorrhagic stroke)

Signs

  • Hemi- or monoparesis
  • Sensory deficits
  • Aphasia (in anterior circulation stroke)
  • Double vision or vertigo (posterior circulation stroke)
  • Speech difficulty (dysarthria)
  • Altered level of consciousness

Risk Factors

Non-Modifiable

  • Age above 60 years
  • Family history
  • Gender (women have higher mortality)
  • Race (African-Americans at higher risk)

Modifiable

  • Hypertension
  • Diabetes mellitus
  • Atrial fibrillation
  • High cholesterol
  • Smoking and heavy alcohol use
  • Obesity and lack of exercise
  • Use of oral contraceptive pills
  • Sickle cell disease

Diagnosis

Laboratory Tests

  • Tests for hypercoagulable conditions such as protein C and S deficiency
  • Antiphospholipid antibody tests

Imaging & Other Tests

  • CT Scan: Shows bleeding immediately and infarction after some time.
  • MRI: Shows ischemic areas with higher clarity.
  • DWI (Diffusion Weighted Imaging): Detects very early infarcts.
  • Carotid Doppler: Checks for carotid artery narrowing.
  • ECG: Detects atrial fibrillation.
  • TTE/TEE: Evaluates heart for clots or structural abnormalities.
  • Transcranial Doppler: Checks for intracranial arterial disease.

Prevention

  • Eat a balanced and healthy diet
  • Maintain a healthy weight
  • Exercise regularly
  • Avoid smoking
  • Limit alcohol intake
  • Keep blood pressure under control
  • Manage diabetes effectively
  • Treat sleep apnea if present

Detailed Notes:

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