Definition and epidemiology
Ischaemic stroke accounts for 80% of stroke. We can differentiate five types:
- Large artery stroke
- Small artery/lacunar stroke
- Embolic stroke
- Watershed stroke
- Cryptogenic stroke
Symptoms, evaluation, and treatment are discussed in other topics.
Large artery stroke
Large artery stroke is due to occlusion of large arteries, most commonly the middle cerebral artery but also the internal carotid, vertebral, etc.
They’re often due to rupture of an atherosclerotic plaque with resulting thrombosis. Large artery stroke has the worst prognosis, as it causes large infarcts (> 1,5 cm in diameter). Ischaemia can occur in both cortical and subcortical regions.
Small artery stroke
Also called lacunar stroke, this type of stroke is due to occlusion of the so-called penetrating small arteries or lenticulostriate arteries. These are small arteries which arise at acute angles from larger arteries, which predispose them to turbulence in the context of hypertension. Chronic hypertension causes lipohyalinosis of these arteries, eventually causing occlusion.
These arteries are small in diameter (< 1,5 cm), and mostly affect subcortical regions. As such, they don’t cause cortical symptoms like aphasia. Typical symptoms include:
- Only hemiparesis
- Only hemisensory loss
- Ataxic hemiparesis
- Dysarthria-clumsy hand syndrome
These strokes occur due to embolism, most commonly from the heart. A cardiac source of the embolus must be identified by cardiological investigations, like atrial fibrillation, myocardial infarction, endocarditis, etc.
These strokes usually affect the cortical surfaces.
Watershed stroke refers to infarction of the region between the territory of two major arteries which occurs when there is a sudden decrease in blood flow through both of these arteries. This is usually due to systemic hypoperfusion rather than single artery occlusion.
Watershed stroke in the PCA-MCA watershed region causes bilateral visual loss, while ACA-MCA watershed stroke causes proximal limb weakness with sparing of the face, hands, and feet.
In cases where the etiology initially cannot be determined, the stroke is called cryptogenic. The underlying etiology is usually paroxysmal atrial fibrillation, patent foramen ovale with paradoxical embolism, or non-atherosclerotic vasculopathy.
26B. Subacute combined degeneration of the spinal cord (funicular myelosis)
27B. Wilson's disease