Stroke II

Published on 10/04/2015 by admin

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Last modified 10/04/2015

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Stroke II

Clinical features

A common feature of all strokes is the onset. The neurological deficit comes on over a short time, from seconds to a progression over hours. This contrasts with space-occupying lesions, which develop over weeks or months, and inflammatory lesions (such as plaques of demyelination in multiple sclerosis), which usually come on over days or weeks.

The clinical manifestations of stroke depend on the area of the brain affected, which in turn depends on which blood vessel is affected. The anatomy of the blood vessels supplying the brain can be subdivided according to vessel size (large or small) and vessel site (anterior or posterior) (Fig. 1):

image Anterior circulation:

– large vessels: the internal carotid artery (ICA) and its main branches, the middle (MCA) and anterior (ACA) cerebral arteries
– small vessels: branches from the MCA and ACA.

image Posterior circulation:

– large vessels: the vertebral arteries, which join to form the basilar artery and its main branches, the posterior cerebral arteries
– small vessels: branches from all these vessels.

image

Fig. 1 Anterior and posterior arterial circulation.

The anterior circulation supplies the anterior two-thirds of the cerebrum, while the posterior circulation provides the supply for the occipital lobes of the cerebrum and the brain stem and cerebellum (Fig. 1).

A simple syndromic classification divides strokes into the following categories, which have important differences in terms of pathogenesis, treatment and prognosis:

image Total anterior circulation stroke.
image Partial anterior circulation stroke.
image Posterior circulation stroke.
image Lacunar stroke.

Anterior circulation large vessel strokes

The MCA supplies most of the motor and sensory cortex, including that controlling the contralateral arm and face, both Wernicke’s and Broca’s areas in the dominant hemisphere, the internal capsule and optic radiation. The ACA supplies the motor cortex controlling the leg, the frontal lobe and the corpus callosum.

Total anterior circulation stroke

This can arise from a complete MCA infarct, from internal carotid disease or massive intracerebral haemorrhage.

Complete infarction of the area produces a devastating deficit. There is a dense flaccid hemiparesis, affecting the arm, face and leg and a homonymous hemianopia. The patient may be drowsy initially with eyes averted away from the hemiparetic side. There is a complete aphasia if the dominant hemisphere is affected and a marked inattention or neglect if the non-dominant side is involved. There may be a transient dysarthria and swallowing may be impaired. The patient may be incontinent. These strokes carry a high mortality and severe long-term morbidity.

Partial anterior circulation stroke

Infarction in the territory of one of the branches of the MCA produces different combinations of deficits depending on the affected hemisphere (Fig. 2). Some of the common ones are: inferior branch = hemianopia – Wernicke’s aphasia if dominant, or constructional apraxia if non-dominant; superior branch = hemiparesis – Broca’s aphasia if dominant or neglect if non-dominant. Distal branches lead to cortical infarcts with weakness only of one limb or isolated higher function deficits.

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