10.3.1 Subarachnoid Haemorrhages Flashcards
What two layers make up the dura mater?
Periosteal
Meningeal
Why can dementia increase the risk of chronic subdural haemorrhage?
Dementia causes brain atrophy, placing additional strains on bridging veins
What structures are within the arachnoid mater?
Arachnoid granulations- evaginations into dural venous sinuses to reabsorb CSF
Arachnoid trabeculae- pass through space and blend with pia
What are the 4 main dural septae?
Falx cerebri- between hemispheres
Falx cerebelli- between cerebellar hemispheres
Tentorium cerebelli
Diaphgrama sella
What are the two types of dural bleeds?
Extradural (epidural)
Between endosteal layer and skull
- Caused by trauma to MMA
- Lemon shaped
Subdural
Between meningeal layer and arachnoid
- Trauma to bridging veins
- Banana shaped
How do extradural haemorrhages present?
LOC
Lucid interval
Sudden decline, loss of consciousness
What are cisterns?
Enlarged regions where the brain moves away from the skull
Located in the subarachnoid space
What is present in the subarachnoid space?
CSF
What is the function of CSF?
Physical support of neural structures
Excretion of brain metabolites
Intracerebral transport (hormone releasing factors)
Control of chemical environment
Volume changes reciprocally with volume of intracranial contents
What forms CSF?
Choroid plexuses (and extra-choroidal structures)
Outline the flow of CSF
Choroid plexuses
Lateral ventricles
Interventricular foramen
3rd ventricle
Aqueduct of sylvius/ cerebral aqueduct of the midbrain
4th ventricle
Central canal, medial apeture and two lateral apetures
Subarachnoid space, small amount into spinal cord
What propels CSF through the ventricular system?
Newly formed fluid
Ciliary action of ventricular ependyma
Vascular pulsations
What causes subarachnoid haemorrhages?
Trauma
Spontaneous
Who is affected commonly by subarachnoid haemorrhages?
6% of all strokes
Females 1.6:1
More likely in black, Finnish and Japanese populations
50-55 years old
What does a subarachnoid haemorrhage present with?
Headache
Dizziness
Orbital pain
Diplopia
May have visual loss (due to anterior communicating artery aneurysm)
What can cause spontaneous subarachnoid haemorrhages?
Rupture of succular aneurysms (berry aneurysms)
80% of non-traumatic
Ruputure of arteriovenous malformations- 10%
Label the image
ACA- may compress optic chiams and affect frontal lobe or pituitary gland
PCA- compresses oculomotor nerve, third nerve palsy
What causes aneurysms to develop?
Pressures on the arterial wall (vessels in subarachnoid space)
Intracranial arteries lack external elastic lamina and have thin adventitia
Hypertension, smoking, alcohol, PCKD, Marfan’s, cocaine etc..
Where do aneurysms tend to develop?
Usually at bifurcation points
Large cerebral arteries in anterior circle of Willis mostly affected
What are the symptoms of a subarachnoid haemorrhage?
Worst headache of life
Nausea and vomiting
Loss of consciousness at onset, short
What are the examination findings for subarachnoid haemorrhages?
- Normal mental state
- Meningism- stiff neck, photophobia
- Third nerve palsy
- No motor or sensory deficit
What are sentinel headaches?
Bad headaches in the months preceding
Caused by minor leaks from aneurysm
What happens after subarachnoid haemorrhages?
- Microthrombi-can occlude smaller distal arteries
- Vasoconstriction- CSF irritates cerebral arteries
- Cerebral oedema- Response to hypoxia and extravasated blood
- Sympathetic activation- early cushing response
- Myocardial necrosis- due to sympathetic activation
- Early rebleeding
- Acute hydrocephalus -blood in subarachnoid space may block normal drainage of CSF
- Global cerebral ischaemia
What are the cellular changes in subarachnoid haemorrhages?
Oxidative stress
Release of inflammatory mediators- activation of microglia
Platelet activation
