Stroke (Cerebral infarction - Transient ischaemic attack (TIA))

Epidemiology

In clinical practice stroke is usually considered to imply infarction. Cerebral infarction accounts for about 80% of all strokes, followed by intracerebral haemorrhage in about 15% and subarachnoid haemorrhage in about 5%.

The annual incidence of stroke in the UK is about 1:500; the incidence of TIA (a "stroke" lasting less than 24 hours) is about 1:2000. Stroke is commoner in males. The risk of stroke increases 5 fold between the 6th and 9th decade, up to around 25%.

Pathophysiology

Atheroma is the commonest cause of stroke; it is present in many cerebral and extracerebral arteries. Atheroma is often located at sites where an artery divides, notably at the carotid bifurcation in the neck, at the origen of the internal carotid artery.

Atheroma may cause stoke by blocking the vessel locally with thrombus or by producing emboli, which occlude a smaller vessel further down the arterial tree. Emboli are also produced in the heart, especially in association with atrial fibrillation, myocardial infarction or disorders of the heart valves. Rare causes of stroke include: arteritis, trauma, infection, irradiation, coagulation disorders, venous sinus thrombosis.

Risk Factors for Stroke Include:

• age
• hypertension
• heart disease
• diabetes
• peripheral vascular disease
• obesity
• cigarette smoking
• hyperlipidaemia
• excess alcohol (especially binge drinking)
• drug abuse

Clinical Features

A stroke may be defined clinically as a sudden loss of localised neurological function, due to vascular disease, which lasts longer than 24 hours. The symptoms are defined by the artery which is affected.

Generalised loss of neurological function, eg diffuse cerebral hypoxia due to hypotension, is usually classified separately. There is usually no warning. The onset is sudden; sometimes symptoms may progress over a few minutes. Progression over several hours is unusual and progression over days should raise serious doubt over the diagnosis.

The patient's symptoms can be dramatic and frightening. "I was eating my lunch and my fork dropped out of my hand; my arm was useless. I tried to stand, but I couldn't move my right leg." "I woke up this morning and my left side felt dead."

Carotid artery territory stroke features: hemiparesis, hemisensory loss, monocular visual loss, speech and language loss (dominant hemisphere), visuo-spatial loss (non-dominant hemisphere).

Vertebro-basilar territory stroke features: hemianopic visual loss, hemiparesis, sensory loss, ataxia, nystagmus, cranial nerve palsies, dysarthria and dysphagia. These features can occur in a variety of combinations and there may be loss of consciousness.

If a large vessel is occluded, more than one clinical feature is produced. For example, occlusion of the middle cerebral artery may cause hemiparesis, hemisensory loss and aphasia (loss of speech). Conversely, obstruction of a small artery or arteriole (such a one of the lenticulostriate arteries in the basal ganglia region) may cause a single clinical feature, eg hemiparesis or hemisensory loss; the term lacunar infact may be applied to this category.

Investigation

The diagnosis of stroke is made on the typical clinical presentation. Investigation is indicated to assess potential causes of stroke ( eg hypertension, heart disease, diabetes, hyperlipidaemia, haematological parameters) and monitor clinical progress (respiratory function, fluid balance, swallowing, nutrition).

Specific neurological investigation may include a head scan (CT or MRI ); imaging the brain is essential if the<