Strokes can be classified into two major categories: ¹
Ischaemic stroke (87%)
Haemorrhagic stroke (13%)
Ischaemic strokes occur when the blood supply to an area of the brain is reduced, resulting in tissue hypoperfusion.
There are several mechanisms which can result in an ischaemic stroke including:
Embolism: An embolus from somewhere else in the body (e.g. the heart) causes obstruction of a cerebral vessel, resulting in hypoperfusion to the area of brain the vessel supplies.
Thrombosis: A blood clot forms locally within a cerebral vessel (e.g. due to atherosclerotic plaque rupture).
Systemic hypoperfusion: Reduced blood supply to the entire brain secondary to systemic hypotension (e.g. cardiac arrest).
Cerebral venous sinus thrombosis: Blood clots form in the veins that drain the brain, resulting in venous congestion and hypoxia which damages brain tissue.
Haemorrhagic strokes occur when there is a rupture of a blood vessel or abnormal vascular structure within the brain.
There are two sub-types of haemorrhagic stroke:
Intracerebral haemorrhage: Bleeding within the brain itself secondary to a ruptured blood vessel.
Intraparenchymal (bleeding within the brain tissue)
Intraventricular (bleeding within the ventricles)
Subarachnoid haemorrhage: Bleeding that occurs outside of the brain tissue, between the pia mater and arachnoid mater.
Blood supply of the Cerebrum
The anterior, middle and posteriorcerebralarteries each supply a specific territory of the brain:
The anterior cerebral arteries supply the anteromedial area of the cerebrum.
The middle cerebral arteries supply the majority of the lateralcerebrum.
The posterior cerebral arteries supply a mixture of the medial and lateral areas of the posteriorcerebrum.
Bamford classification of ischaemic stroke
The most commonly used classification system for ischaemic strokes is the Bamford classification (or Oxford classification) system. This categorises stroke based on the initial presenting symptoms and clinical signs. This system does not require imaging to classify the stroke, instead, it is a purely clinical diagnosis.
Total anterior circulation stroke (TACS)
A total anterior circulation stroke (TACS) involves a large cortical stroke affecting the areas of the brain supplied by both the middle and anterior cerebral arteries.
All three of the following need to be present for a diagnosis of TACS:
Unilateral weakness (and/or sensory deficit) of the face, arm and leg