Medically Relevant Anatomy
At the base of the brain, the carotid and vertebrobasilar arteries form a circle of communicating arteries known as the Circle of Willis (see image listed below). From this circle, other arteries-- the anterior cerebral artery (ACA), the middle cerebral artery (MCA) and posterior cerebral artery (PCA)-- arise and travel to all parts of the brain.
Circle of Willis
The image listed below plainly reveals the function areas of the cortex that can be impacted following insufficiency of the blood supply.
Brain function associated to anatomy.jpg
Mechanism of Injury/ Pathological Process
[4] A stroke happens when there is a disturbance of the blood supply to a particular location of the brain, eventually resulting in cell injury and cell death.
Strokes can be categorized in two methods:
Ischaemic
Ischaemic strokes are the most typical, accounting for approximately 80% of strokes, and occur when there is an occlusion of a capillary hindering the flow of blood to the brain.
Ischaemic Strokes are divided into:
Thrombotic - Where a blood clot types in a main brain artery or within the small blood vessels deep inside the brain. The clot usually forms around atherosclerotic plaques.
Embolic - A blood clot, air bubble or fat globule forms within a blood vessel elsewhere in the body and is reached the brain.
Systemic Hypoperfusion - A basic decline in blood supply, eg. 1. 3 Watershed strokes see link.
Venous Thrombosis
According to the TOAST [5] category, there are 4 primary kinds of ischemic strokes.
Large vessel atherosclerosis,
Small vessel diseases (lacunar infarcts),.
Cardioembolic strokes.
Cryptogenic strokes.
Haemorrhagic.
Haemorrhagic Strokes occur when a capillary in the brain ruptures and bleeds.
Intracerebral Haemorrhagic Stroke-- there is bleeding from a blood vessel within the brain. High blood pressure is the primary reason for intracerebral haemorrhagic stroke.
Subarachnoid Haemorrhagic Stroke-- there is bleeding from a blood vessel in between the surface area of the brain and the arachnoid tissues that cover the brain.
Nb. Some professionals do not classify Subarachnoid Haemorrhage as Stroke because subarachnoid haemorrhages present differently from Ischaemic Strokes and Intracerebral Haemorrhagic Strokes.
Scientific Presentation.
Strokes can present in pre-determined syndromes due to the effect of reduced blood flow to particular locations of the brain that associate to exam findings. This allows clinicians to be able to forecast the location of the brain vasculature that can be affected.
Cortical Areas and their vascular supply:.