subarachnoid haemorrhage Flashcards
epidemiology of subarachnoid heamorrhage
~6% of all strokes
▪ Slightly more females 1.6:1
▪ Most are under 50
▪ 50% mortality, 60% suffer some longer term morbidity following
the event
risk factors for subarachnoid heamorrhage
- Hypertension
- Smoking
- Excess alcohol consumption
- Predisposition to aneurysm formation
- Family history
- Associated conditions
o Chronic kidney disease (resultant effect on vessel wall)
o Marfan’s syndrome (effect on connective tissues of vessels)
o Neurofibromatosis (unclear mechanism, if any link) - Trauma
- Cocaine use
pathophysiology of subarachnoid heamorrhage
-> berry aneurysm (genetic, haemodynamic effects)
what are some sites of a berry anyerysm in circle of willis
Anterior communicating artery / proximal anterior
cerebral artery (30%)
▪ Can compress the nearby optic chiasm and may affect frontal lobe or even pituitary
Posterior communicating artery (25%)
▪ Can compress the adjacent oculomotor nerve causing an ipsilateral third nerve palsy
o Bifurcation of the middle cerebral artery as it splits into superior and inferior divisions (20%)
what can bleeding into the subarachnoid space cause
Early brain injury
o Microthrombi: These may occlude more distal branches.
Vasoconstriction
▪ As a result of blood in the CSF ‘irritating’ cerebral arteries
Cerebraloedema
▪ General inflammatory response to tissue hypoxia and extravasated blood
Apoptosis of brain cells
what cellular changes can in a subarachnoid heamorrhage
- Oxidative stress: related to reperfusion?
- Release of inflammatory mediators: Can activate many pathways as well as activation of microglia
- Platelet activation: Formation of thrombi
what are some systemic complications of a subarachnoid heamorrhage
- Sympathetic activation: Early Cushing response
- Myocardial necrosis: Due to sympathetic activation, Interestingly, SAH has typical ECG features
- Systemic inflammatory response: Can affect multiple systems
Describe features of the thunderclap headache that a subarachnoid heamorrhage causes
Explosive in onset and severe, often reported as worst headache ever or even ‘like being hit on the head with a cricket bat’
* Diffuse pain
* Can last from an hour to a week
clinical features of subarachnoid heamorrhage
- Frequently loss of consciousness and confusion
- Meningism:
* Neck stiffness
* Photophobia
* Headache
▪ focal neurology
▪ history of sentinel bleed (previous headache)
▪ present as cardiac arrest (if intracranial pressure rises
rapidly following bleed leading to profound Cushing response)
what Does CT Do to help subarachnoid heamorrhage
- Prominent filling of the basal cisterns in a five pointed ‘star’ pattern
- Blood may be seen within the ventricles (maybe due to reflux from subarachnoid space)
▪ CT angiogram if bleed confirmed - Will allow direct visualisation of bleeding aneurysm of aneurysm sac
- Vital for planning surgery
what is the process of a lumbar puncture
o Identify iliac crests (giving L4-L5 level)
o Give local anaesthetic
o Insert LP needle between spinous processes and through the supraspinous and interspinous
ligaments
o Feel give as pass through ligamentum flavum and dura
o Remove needle stylet and collect CSF in sterile
containers (allow to drip, don’t aspirate!)
what are lumbar puncture findings in a SAH
Increased opening pressure (as there is now additional volume in the subarachnoid space)
* Frank blood or xanthochromia may be seen
* High protein (blood constituents and haemoglobin)
* White cells often not raised o Glucose not affected
* High red cell count
what is xanthochromia
Xanthochromia is a yellow colouring of the CSF due to metabolism of haemoglobin to
bilirubin within the subarachnoid space
* Seen at least 12 hours post bleed
* More specific than frank blood for
SAH (helps exclude a
bloody/traumatic tap)
Treatment of SAH
▪ ABC approach: Support airway if diminished conscious, Give oxygen, Support circulation
* **Fluids: ** nimodipine to alleviate cerebral vasospasm
* Neurological observations: increasing intracranial pressure
* **Neurosurgery: ** Decompressive surgery (craniectomy), Coiling
* Insertion of (frequently) a platinum wire into the aneurysm sac, which causes thrombosis of blood within the aneurysm itself
* Clipping: Placement of a spring clip around the neck of the aneurysm, causing it to lose blood supply and ‘shrivel up’
typical organisms involved meningitis
o E. coli
o Group B streptococcus
o Listeria monocytogenes
risk factors for meningitis
- CSF defects (e.g. spina bifida)
- Spina procedures (e.g. surgery, lumbar puncture)
- Endocarditis (as a focus of bacteraemia)
- Diabetes (immunosuppression)
- Alcoholism
- Splenectomy (immunosuppression)
- Crowded housing (students at risk)
what are some conditions in children and elderly that can cause meninigits
Children
o Haemophilus influenzae type B (HiB vaccine
given, ‘meningococcus’)
o Neisseria meningitidis (vaccines given for some
strains
* Elderly
o Streptococcus pneumoniae (vaccines now given)
o Listeria monocytogenes
triad of symptoms associated with meningitis
- Headache
- Neck stiffness (nuchal rigidity)
- Photophobia
symptoms of meningits
- Flu-like symptoms
- Joint pains and stiffness
- Seizure
- Meningococcal rash (non blanching)
- Drowsiness
- Patient may be in shock
- Babies
o Pathophysiology
o Inconsolable crying / off feeds o Rigidity / floppiness
o Bulging fontanelle (late sign)
pathophysiology of meningitis
- Bugs which normally live in the nose gain entry to the circulation and cause a bacteraemia
- bacteraemia causes damage to vessel walls in the brain and meninges, allowing pathogen to enter the subarachnoid space
- pathogens multiply rapidly causing purulent CSF and severe meningeal inflammation
- Vasospasm of cerebral vessels = cerebral infarction
- Oedema of brain parenchyma can cause raised intracranial
pressure - Maculopapular rash seen in meningococcal septicaemia
- Caused by microvascular thrombosis due to many factors, including
o Sluggish circulation
o Impaired fibrinolysis
o Increased tissue factor expression in endothelial
cells
investigations for meningitis
-> blood
-> chest x-ray
-> Lumbar puncture
what lumbar puncture results show Bacterial meningitis
o Cloudy CSF
o High protein (immune proteins etc.)
o High white cells, primarily neutrophils (which
phagocytose bacteria)
o Low glucose as bacteria (and white cells)
metabolise it
what lumbar puncture results show Viral meningitis
o Maybe clear but can be cloudy (due to immune cells and proteins)
o Protein level may be normal or raised (as above) o High white cells, primarily lymphocytes to mount
an adaptive response
o Normal glucose (>60% plasma)
Treatment for meningitis
▪ Supportive
* Analgesia
* Antipyretics
*Fluids if shocked
▪ Medical
* IV ceftriaxone
* Dexamethasone to prevent hearing loss (due to swelling of vestibulocochlear nerve or effect on cochlea)
* If viral
o Aciclovir for Herpes
o Ganciclovir for CMV
complications of meningitis
what does a subarachnoid heammaorage look like on a CT
-> starshaped
the white lines in the middle is blood
where does blood collect in a subarachnoid heammorhage
-> basal cisterns
in a CT what colour does blood show up as
white
in a CT what colour does CSF show up as
black
