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Classification of stroke

Classification of stroke1

Stroke is a heterogeneous disease with more than 150 known causes. Strokes can broadly be divided into:

  • Ischaemic - restricted or interrupted blood and therefore oxygen supply to an area of the brain
  • Haemorrhagic - bleeding into an area of the brain, due to rupture of a blood vessel or abnormal vascular structure in the brain

This distinction between haemorrhagic and ischaemic stroke is critical for stroke management and treatment decisions.

Haemorrhagic strokes can further be distinguished into intracerebral and subarachnoid strokes.

Of all strokes, 88% are ischaemic and 12% are haemorrhagic in nature. Of the haemorrhagic strokes, 9% are due to an intracerebral haemorrhage, and 3% are due to a subarachnoid haemorrhage.

Classification of stroke

Stroke subtypes

There are various classification systems for the subtypes of ischaemic strokes, each with their own strengths and weaknesses.

Some of the most commonly used systems include:

1. Stroke Data Bank Subtype (NINDS) Classification2

Derived from the Harvard Stroke Registry classification, the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Data Bank recognised 5 major groups

  1. Infarction of unknown cause

  2. Infarction with normal angiogram

  3. Infarction in association with arterial pathology

  4. Embolism from a cardiac source

  5. Infarction due to atherosclerosis

  6. Lacune infarct

  7. Parenchymatous or intracerebral haemorrhage

  8. All other strokes

2. The Oxford Community Stroke Project classification (OCSP, also known as the Bamford or Oxford classification)3

Relies primarily on the initial symptoms; based on the extent of the symptoms, the stroke episode is classified as:

  1. Total anterior circulation stroke (TAC)

  2. Partial anterior circulation stroke (PAC)

  3. Lacunar stroke (LAC)

  4. Posterior circulation stroke (POC)

The type of stroke is then coded by adding a final letter to the above: 

I – for infarct (e.g. TACI)
H – for haemorrhage (e.g. TACH)
S – for syndrome; intermediate pathogenesis, prior to imaging (e.g. TACS)
These four entities predict the extent of the stroke, the area of the brain affected, the underlying cause, and the prognosis.

3. The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification4

Is based on clinical symptoms as well as results of further investigations. Based on this, a stroke is classified as being due to:

  1. Thrombosis or embolism due to atherosclerosis of a large artery

  2. Embolism of cardiac origin

  3. Occlusion of a small blood vessel

  4. Other determined cause

  5. Undetermined cause
    a. Two possible causes
    b. No cause identified
    c. Incomplete investigation

Determination of the subtype is important when5: 

  • Classifying patients for therapeutic decision-making in daily practice

  • Describing patients’ characteristics in a clinical trial

  • Grouping patients in an epidemiological study

  • Careful phenotyping of patients in a genetic study

References

  1. Thom et al. Heart disease and stroke statistics--2006 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. 2006;113(6):e85-151.

  2. Mohr JP, Barnett HJM: Classification of ischemic strokes, in Barnett HJM, Mohr JP, Stein BM, Yatsu FM (eds): Stroke: Pathophysiology, Diagnosis, and Management. New York, Churchill Livingstone, 1986, pp 281-291.

  3. Bamford et al. Classification and natural history of clinically identifiable subtypes of cerebral infarction. Lancet. 1991;337(8756):1521-1526.

  4. Adams et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke. 1993;24:35-41.

  5. Amarenco et al. Classification of stroke subtypes. Cerebrovasc Dis. 2009;27(5):493-501.

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