Session 10 Subarachnoid Haemorhage And Meningitis Flashcards
(29 cards)
What are the risk factors for subarachnoid haemorrhage?
Hypertension Smoking Excess alcohol consumption Predisposition to aneurism formation Family history Associated conditions: CDK (resultant effect on vessel wall), Marfan’s syndrome (effect on connective tissues of vessels), Neurofibromatosis Trauma Cocaine use
Why do subarachnoid haemorrhages usually occur?
Following rupture of an aneurism in the circle of Willis
What is an aneurism?
A weakness in a vessel (usually artery) wall which can cause an abnormal bulge
What causes aneurisms?
Genetic predisposition
Haemodynamic effects at branch points in the circle of Willis(e.g. higher resulting flow rate in progressively smaller branches, turbulence)
What type are most aneurisms?
Berry aneurisms
What are the common sites all aneurisms?
anterior communicating artery / proximal anterior cerebral artery (30%)
- these can compress the optic chiasm and may affect frontal lobe or pituitary
Posterior communicating artery (25%)
- can compress the adjacent oculomotor nerve causing an ipsilateral third nerve palsy
Bifurcation of the middle cerebral artery as it splits into superior and inferior divisions (20%)
What does bleeding into the subarachnoid space cause? 3 key points
Early brain injury
Cellular changes
Systemic complications
Early brain injury is caused by bleeding into the subarachnoid space. How does this occur?
Microthombi may occlude more distal branches
Vasoconstriction: as a result of blood in the CSF irritating cerebral arteries
Cerebral oedema: general inflammatory response to tissue hypoxia and extravasated blood
Apoptosis of brain cells
Cellular changes occur due to bleeding into the subarachnoid space. Why does this occur?
oxidative stress - could be related to reperfusion
Release of inflammatory mediators - can activate many pathways as well as activation of microglia
Platelet activation - formation of thrombi
What systemic complications can occur due to bleeding into subarachnoid space?
Sympathetic activation (early cushing response)
Myocardial necrosis (due to sympathetic activation)
Systemic inflammatory response that can affect multiple symptoms
What are the clinical features of subarachnoid haemorrhage?
Thunderclap headache
- explosive in onset and SEVERE
- diffuse pain
- can last from 1 hr to a week
Frequently loss of consciousness and confusion
Meningism
- neck stiffness
- photophobia
- headache
Focal neurology
History of sentinel bleed (previous headache)
May present as cardiac arrest if intracranial pressure rises rapidly following bleed leading to profound cushing’s response
What investigations would you perform if you suspected subarachnoid haemorrhage?
CT head
- prominent filling of the basal cisterns in a five pointed star pattern
- blood may be seen within the ventricles (maybe due to reflex from subarachnoid space)
CT angiogram if bleed confirmed
- allows direct visualisation of bleeding aneurysm of aneurysm sac
- vital for planning surgery
Lumbar puncture
Describe the technique of performing a lumbar puncture
- Identify iliac crest (L4-L5 level)
- Give local anaesthetic
- Insert needle between spinous processes and through the supraspinous and interspinous ligaments
- Feel give as pass through ligamentum flavum and dura
- Remove needle styles and collect CSF in sterile containers (allow to drip - don’t aspirate!)
What would LP findings show in SAH?
Increased opening pressure (as there is now additional volume in the subarachnoid space)
Frank blood or xanthochromia seen
High protein (blood constituents and Hb)
High red cell count
NB:
White cells are often normal
Glucose not affected
What is xanthochromia?
When would this be seen ?
Why is this useful?
Yellow colouring of the CSF due to metabolism of Hb to bilirubin within the subarachnoid space
Seen at least 12 hours POST bleed
More specific than frank blood for SAH (helps exclude a bloody or traumatic tap)
Treatment of SAH in 3 main points?
ABC approach
- support airway if diminished conscious level
- give oxygen
- support circulation: fluids, nimodipine to alleviate cerebral vasospasm
Neurological observations - look for trends which may be suggestive of increasing ICP
Neurosurgery
What are the types of surgery you can perform to treat SAH?
Decrompressive surgery (craniectomy)
Coiling: insertion of a platinum wire into the aneurism sac which causes thrombosis of blood within the aneurism itself
(Neuroradiologist)
Clipping: placement of a spring clip around the neck of the aneurism, causing it to lose blood supply and shrivel up
(Neurosurgeons)
What typical organisms cause meningitis in neonates?
E.coli
Group B streptococcus
Listeria monocytogenes
What typical organisms cause meningitis in children?
Haemophilus influenzae type B (HiB vaccine)
Neisseria meningitidis
What typical organisms cause meningitis in the elderly?
Streptococcus pneumoniae
Listeria monocytogenes
What are the risk factors for meningitis?
CSF defects (e.g. spina bifida)
Spinal produced results
Endocarditis
Diabetes
Alcoholism
Splenectomy
Crowded housing
What is the triad of meningism with fever?
Headache
Neck stiffness
Photophobia
What are some associated symptoms of meningitis?
Flu-like symptoms Joint pains and stiffness Seizure Meningococcal rash (non blanching) Drowsiness Shock Babies: inconsolable crying, rigidity, bulging fontanelle (late sign)
How does meningitis occur (pathophysiology)?
Bugs that normally live in the NOSE gain entry to the circulation and cause a bacteraemia
This bacteraemia causes damage to vessel walls in the brain and meninges, allowing pathogen to enter the subarachnoid space
Once in this 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 ICP
