Anatomy of blood flow in CNS and consequences of disruption Flashcards
Define stroke
Cerebrovascular accident (CVA) Rapidly developing focal disturbance of brain function of presumed vascular origin lasting more than 24 hours
Define transient ischaemic attack
Rapidly developing focal disturbance of the brain function of presumed vascular origin that resolves completely within 24 hours
What percentage of stroke is due to infarction and haemorrhage?
85% - infarction
15% - haemorrhage
Define infarction
Degenerative changes that occur in tissue following occlusion of an artery
Define cerebral ischaemia
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly due to hypoxia/anoxia
What are the causes of occlusion?
Embolism - plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid
Thrombosis - formation of a blood clot (thrombus)
Where does the posterior cerebral artery supply?
Supplies the lateral and medial parts of the posterior part of the hemisphere
What does the anterior cerebral artery supply?
The medial part of the hemisphere
What is associated with the disturbance of the anterior cerebral artery?
- Paralysis of contralateral leg > arm, face
- Disturbance of intellect, executive function and judgement (abulia)
- Loss of appropriate social behaviour
What is associated with the disturbance of the middle cerebral artery?
- “Classic stroke”
- Contralateral hemiplegia: arm > leg
- Contralateral hemisensory deficits
- Hemianopia
- Aphasia (L sided lesion)
What is associated with the disturbance of the posterior cerebral artery?
- Visual deficits
- homonymous hemianopia (loss of visual field on the same side in both eyes)
- Visual agnosia
Define hemianopia
Blindness in over half the field of vision
Define Aphasia
Loss in being able to speak
What are lucunar infarcts?
Stroke that causes small holes to appear in the brain tissue. They appear in deep structures as a result of small vessel occlusion therefore symptoms can vary depending on the anatomical location of the vessel that has been occluded
Caused by hypertension
What are the types of haemorrhagic stroke?
Extradural - Trauma, immediate effects. Arterial blood
Subdural - Trauma, delayed effects. Venous blood
Subarachnoid - usually caused by a ruptured aneurysm
Intracerebral - spontaneous hypertensive rupture of small vessels
What are the differences in the dura between the skull and in the spine?
Skull two layers - periosteal and meningeal
Spine one layer
What is the superior sagittal sinus formed by?
The peeling apart of the two layers of the dura in the skull
What can found in the SSS?
Arachnoid granulations - subarachnoid space that protrude into the SSS.
Why do extradural haemorrhages have a rapid onset?
Because it is usual due a rupture of a meningeal artery. Arteries carry blood at a high BP whereas veins are at a lower pressure so onset of symptoms is much slower
What is the difference in vessels that rupture between a subdural and extradural haemorrhage?
Subdural - vein. Between dura mater and arachnoid layer
Extradural - artery. Between the dura mater and the skull
What are the main risk factors for stroke?
- Age
- Hypertension
- Cardiac disease
- Smoking
- DM
Draw and describe the arterial and venous blood supply to the brain.
Kenhub/Netters/slides
Where does the middle cerebral artery supply?
The lateral parts of the hemisphere
