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Mechanism of brain damage
- A critical shortage of energy (energy crisis)
- Excitatory amino acid injury
- Cerebral oedema
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Stroke
Rapidly developing clinical symptoms and signs of focal and/or global loss of cerebral function, which are caused by vascular dysfunction, with symptoms lasting more than 24 hours or leading to death.
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Risk factors for stroke
- Hypertension (stress, familial)
- Diabetes
- Heart disease (atrial fibrillation particularly)
- Smoking
- Increased blood fat levels
- Obesity
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Stroke aetiology
- Ischaemic stroke 80-88%
- Haemorrhagic stroke- intracerebral 10%, subarachnoid 5-10%
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Ischaemic stroke
- Complete loss of blood flow resulting in inadequate oxygen and glucose to brain tissue leading to neuronal cell dysfunction and death (infarction). Caused by:
- Thrombus: atherosclerosis and subsequent plaque formation results in arterial narrowing or occlusion. Thrombus formation is most likely to occur in areas where atheroscelerosis and plaque deposition have caused the greatest narrowing of vessels
- Embolus: heart, extracranial vasculature
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Survival of cells in penumbra area depends on:
- Successful timing of return of circulation
- The volume of toxic products released by neighboring dying cells
- Degree of cerebral oedema
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Transient ischaemic attacks
- Small particles break off and wash from the neck into the arteries inside the brain (emboli)
- Particles often lodge into the cerebral artery and can cause temporary loss of blood, which are brief periods when normal nerve functions are interrupted
- Symptoms: blurred vision, loss of coordination, slurring of speech, or weakness or numbness in an arm or leg
- Symptoms usually last a few seconds but sometimes may last up to 1 hour
- Produce focal neurological deficits that lasts less than 1 hour. Neurological function is restored and there is no permanent
- tissue damage
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Lucunar infarct
- Small infarcts in deeper parts of the brain (basal ganglia, thalamus, white matter) and in the brainstem
- ~20% of strokes
- Caused by occlusion of deep penetrating branches of major cerebral arteries and are particularly common in hypertension and diabetes, which are associated with severe atherosclerosis of small vessels and small vessels disease
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Haemorrhagic stroke
- Rupture of vessels resulting in haemorrhage into brain tissue which results in oedema, compression of brain cells, spasm of adjacent blood vessels. Is a sudden event often associated with headache/vomiting.
- Causes: arterial hypertension, saccular aneurysms, arteriovenous malformations, vasculitis, drugs, trauma, neoplasms
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Anterior cerebral artery stroke
- Affects lower limb > upper limb
- Contralateral spasticity
- Contralateral paresis
- Contralateral sensory loss
- Lack of spontaneity/motor inaction
- Preservation
- Aphasia
- Apraxia
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Left middle cerebral artery
- Affects upper limb > lower limb
- Spasticity
- Right hemiparesis
- Right hemisensory loss
- Right homonymous hemianopia
- Global aphasia
- Ideomotor/ideational apraxia
- Behavioural observations
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Right middle cerebral artery stroke
- Affects upper limb > lower limb
- Contralateral spasticity
- Left hemiparesis
- Left hemisensory loss
- Left homonymous hemianopia
- Aprosodia of speech
- Constructional apraxia
- Dressing apraxia
- Visuospatial dysfunction
- Anosognia
- Asomatognosia/autotopagnosia
- Prosopagnosia
- Behavioural observations
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Right cerebral artery
- Hemisensory loss
- Homonymous hemianopia
- Cortical blindness
- Aphasia
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