Stroke, Transient ischemic attack (TIA)

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Scheme of TIA symptoms.

Transient Ischemic Attack (TIA)

Definition

A Transient Ischemic Attack (TIA) is a brief episode of focal neurological dysfunction caused by transient cerebral, spinal cord, or retinal ischemia, without evidence of acute infarction.

The temporary reduction in blood flow leads to reversible ischemia, characterized by decreased oxygen and glucose delivery, accumulation of metabolic waste products, and transient neuronal dysfunction, but no permanent structural damage to neural tissue.

Clinical Presentation

TIA typically presents as a sudden-onset focal neurological deficit, reflecting the vascular territory involved. Common manifestations include:

• Unilateral weakness or paralysis (hemiparesis or hemiplegia)
• Unilateral facial drop
• Speech disturbances (aphasia or dysarthria)
• Sudden sensory loss
• Transient monocular blindness (amaurosis fugax)
• Visual field defects

Symptoms classically resolve completely within minutes to hours, and by definition within 24 hours, although most TIAs last less than 1 hour.

Unlike ischemic stroke, TIA involves ischemia without infarction. Cerebral perfusion is reduced below the threshold required for normal neuronal function but remains above the threshold for irreversible neuronal injury, allowing complete recovery once perfusion is restored.

Etiology of TIA

The most common mechanisms include:

• Thrombotic occlusion due to atherosclerotic plaque (especially carotid artery disease)
• Thromboembolism, typically originating from the heart (atrial fibrillation) or large arteries
• Small vessel disease
• Cryptogenic TIA, where no clear cause is identified despite investigation

Clinical Significance

Although symptoms are transient, TIA is a medical emergency and a strong predictor of future stroke. The risk of ischemic stroke is highest in the first 48 hours to 3 months following a TIA, making early evaluation and secondary prevention essential.

Stroke (Cerebrovascular Accident)

Definition

A stroke, or cerebrovascular accident (CVA), is a clinical syndrome characterized by sudden-onset focal (or occasionally global) neurological deficit lasting more than 24 hours or resulting in death, caused by disruption of cerebral blood flow.

In contrast to TIA, stroke results in irreversible ischemic injury and infarction of neural tissue.

Symptoms of Stroke

Clinical Features

The clinical presentation of stroke varies widely and depends on:

• The vascular territory affected
• The size of the lesion
• The rate of onset

Symptoms may range from mild focal deficits to:

• Hemiplegia
• Aphasia
• Visual loss
• Altered level of consciousness
• Coma or death

Classification of Stroke

1. Ischemic Stroke

Ischemic strokes account for most of the strokes and result from occlusion of a cerebral blood vessel, leading to cerebral infarction.

Causes include:

• Thrombotic stroke: in situ thrombosis, usually superimposed on an atherosclerotic plaque
• Embolic stroke: emboli originating from the heart (e.g., atrial fibrillation, mural thrombus) or proximal arteries
• Lacunar infarcts: occlusion of small penetrating arteries, commonly associated with chronic hypertension and diabetes

2. Hemorrhagic Stroke

Hemorrhagic strokes result from rupture of a blood vessel, causing extravasation of blood into or around the brain. The resulting mass effect and increased intracranial pressure (ICP) contribute to neuronal injury.

Types of Hemorrhagic Stroke

a) Intracerebral (Intraparenchymal) Hemorrhage

b) Subarachnoid Hemorrhage

c) Epidural Hematoma

d) Subdural Hematoma

Diagnostic Imaging

Neuroimaging is essential for the evaluation of suspected stroke:

• Non-contrast CT scan is the initial imaging modality of choice to differentiate ischemic from hemorrhagic stroke
• MRI is more sensitive for detecting early ischemic changes and small infarcts

References

1. Robbins and Cotran Pathologic Basis of Disease, 10th Edition Kumar V, Abbas AK, Aster JC. Elsevier – Chapter: Cerebrovascular Diseases
2. Pathophysiology of Disease: An Introduction to Clinical Medicine, 8th Edition McPhee SJ, Hammer GD. McGraw-Hill – Chapter: Stroke and Cerebrovascular Disease
3. Pathophysiology of Disease: An Introduction to Clinical Medicine 7th ed.  McPhee SJ, Hammer GD. New York: McGraw-Hill Education; 2014.
4. Harrison’s Principles of Internal Medicine, 21st Edition Jameson JL et al. McGraw-Hill – Sections on Stroke and Transient Ischemic Attack
5. Adams and Victor’s Principles of Neurology, 11th Edition Ropper AH, Samuels MA, Klein JP. McGraw-Hill – Cerebrovascular disorders
6. Cleveland Clinic Website: https://my.clevelandclinic.org/health/diseases/14173-transient-ischemic-attack-tia-or-mini-stroke