10.3 subarachnoid haemorrhage Vs Meningitis Flashcards
what are the risk factors for a subarachnoid haemorrhage?
- hypertension
- smoking
- excess alcohol consumption
- predisposition to aneurysm formation
- family history
- associated conditions e.g CKD, marfans syndrome
- trauma
- cocaine use
what is the pathophysiology of a subarachnoid haemorrhage?
usually occur following rupture of an aneurysm in the circle of willis, most are berry aneurysms
what physiological response does bleeding into the subarachnoid space cause?
early brain injury
- early brain injury via micro thrombi that may occlude more distal branches
- vasoconstriction as a result of blood in the CSF irritating cerebral arteries
- cerebral oedema, generally inflammatory response to tissue hypoxia and extravasated blood
- apoptosis of brain cells
cellular changes
- oxidative stress
- release of inflammatory mediators
- platelet activation and thrombi
systematic complications
- early cushings response
- myocardial necrosis due to sympathetic activation
- systemic inflammatory response
what are the clinical features of a subarachnoid haemorrhage?
- thunderclap headache, diffuse pain, can last from an hour to a week
- frequent loss of consciousness and confusion
- meningism = neck stiffness, photophobia, headache
- history of sentinel bleed
- may present as cardiac arrest if ICP rises rapidly flowing bleed = big cushings repsonse
what investigations would you to in a subarachnoid haemorrhage?
- CT head scan for blood
- CT angiogram is bleed confirmed = can directly visualise bleed
- lumbar puncture at L4/L5 (by identifying illiac crests). May see xanthochromia = yellow colouring of CSF as haemoglobin is metabolised to bilirubin in this space. Seen at least 12 hours post bleed. may see frank blood. Also may find high protein, and red cell count.
what is the treatment for a subarachnoid haemorrhage?
ABC approach
- support airway
- give o2
- support circulation e.g fluids and nimodipine to alleviate cerebral vasospasm
- decompressive surgery = craniotomy
- clipping surgery
what are the common sites for a subarachnoid haemorrhage?
common sites are
- Anterior communicating artery/ proximal anterior cerebral artery: can compress nearby optic chasm, frontal lobe or pituitary
- posterior communicating artery: can compress adjacent oculomotor nerve causing an ipsilateral third nerve palsy
- bifurcation of MCA as it splits into superior and inferior divisions
what is the epidemiology of a subarachnoid haemorrhage
more females than males
about 6% of all strokes
most under 50
50% mortality
what typical organisms cause meningitis in
- neonates
- children
- elderly
neonates
- E coli
- group B strep
- listeria monocytogenes
children
- haemophilus influenzae B
- Neisseria meningitidis
elderly
- strep pneumoniae
- listeria monocytogenes
what are the risk factors for meningitis?
risk factors include
- CSF defects e.g spina bifida
- spina procedures e.g surgery/lumbar puncture
- endocarditis as focus of bacteriaemia
- diabetes (immunosuppression)
- alcoholism
- splenectomy (immunosuppresion)
- crowded housing (students at risk)
what do patients with meningitis present with and what other associated symptoms?
present with
- headache
- stiff neck (nuchal rigidity)
- photophobia
associated symptoms
- flu like symptoms
- joint pains and stiffness
- seizure
- meningococcal rash (non blanching)
- drowsiness
- patients may be in shock
babies
- inconsolable crying
- rigidity/floppiness
- bulging fontanelles
what is the pathophysiology of meningitis?
bugs which normally live in the nose gain entry to the circulation and cause a bacteraemia
the bacteraemia causes damage to vessel walls in the brain and meninges, allowing pathogen to enter the sub arachnoid space
once in the subarachnoid space, pathogens multiply rapidly causing purulent CSF and severe meningeal inflammation
vasospasm of cerebral vessels can cause cerebral infarction
oedema of brain parenchyma can cause raised intracranial pressure
why would you see a non blanching rash in meningitis?
micro vascular thrombosis is occurring due to
- sluggish circulation
- impaired fibrinolysis
- increased tissue factor expression in endothelial cells
what is kernigs sign?
To look for Kernig’s sign:
1) Lie face up.
2) Flex your knee and hip in a 90˚ angle while someone else slowly extends your knee.
this will stretch the meninges. If there is any pain/resistance, a sign of meningitis.
comes hand in hand with nuchal rigidity (cant flex neck as stretching meninges)
what investigations would you do in a patient with suspected meningitis?
- bloods including sepsis screen and PCR
- chest X ray or mid stream urine if suspected septal focus point
- lumbar puncture
