Stroke I

Published on 10/04/2015 by admin

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Last modified 10/04/2015

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Stroke I

Stroke refers to damage to the brain caused by abnormalities of blood supply. This presents with a rapidly developing focal neurological deficit, which may lead to coma or death. If this deficit lasts less than 24 h it is referred to as a transient ischaemic attack (TIA; p. 70).

Stroke is the third most common cause of death in developed countries. The incidence of first stroke is 2 per 1000 per year. The incidence increases with age. It is rare below 45 years of age and increases from 2 per 1000 per year for people aged 45–54 years to 10 per 1000 per year for those aged 65–74 years and to about 30 per 1000 per year in those aged over 80 years. About a quarter of these patients will be dead within 6 months (the majority of these within 1 month). Stroke is a major cause of disability; after their first stroke, 40% of surviving patients will be dependent at 6 months.

Stroke is not a single diagnosis. Strokes differ in terms of their aetiology and pathogenesis, the area of the brain affected and the resulting clinical deficit. These differences have implications for investigation, treatment and prognosis.

Pathogenesis

Cerebral infarction accounts for 80% of strokes, 15% are primary intracerebral haemorrhages and 5% are due to subarachnoid haemorrhages (p. 72).

Cerebral infarction

Cerebral infarction results from an interruption in blood supply to an area of the brain. This can be due to (Fig. 1):

emboli (30% of all strokes)

thrombosis (30%)

small vessel disease (20%).

Fig. 1 Pathophysiology of common causes of cerebral infarction.

Atheroma

Atheroma is an important factor in both embolic and thrombotic strokes. A similar pathological process, occurring in patients with the same risk factors, produces intracerebral small vessel disease.

The risk factors for atheroma, and other disease resulting from it, are given in Table 1. The most important risk factor is hypertension, with the risk increasing with the blood pressure.

Table 1 Risk factors for atheroma and relative risk of stroke

Risk factors for atheroma	Relative risk of stroke
Hypertension	5
Diabetes	2
Smoking	3
Family history
Cholesterol
Excess alcohol intake	1–4

Atheroma commonly arises at the junctions of arteries, for example the carotid bifurcation and the point where the two vertebral arteries join to form the basilar artery (Fig. 2).

Fig. 2 Circle of Willis.

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