Subarachnoid Haemorrhage & Meningitis Flashcards
Describe the epidemiology of SAH
- 6% of all strokes
- Slightly more females (x1.6)
- 50% mortality, 60% have long term morbidity afterwards
List 8 risk factors for SAH
- Hypertension
- Smoking
- Excess alcohol
- Predisposition to aneurysm formation
- Family history
- Trauma
- Cocaine
- Associated conditions (CKD, Marfan’s, Neurofibromatosis)
SAHs usually occur after rupture of an Aneurysm in the Circle of Willis.
What is an Aneurysm?
A weakness in a vessel wall which can cause an abnormal bulge
Most SAHs come from Berry Aneurysms
List 3 common sites where these form, making up 75% of all aneurysms
Proximal ACA/ Ant. Comm. Artery;
- 30%
- (Can affect Optic Chiasm, Frontal Lobe, Pituitary)
Post. Comm. Artery;
- 25%
- (Can compress CNIII-> CNIII palsy)
MCA Bifurcation (as it splits into S + I divisions); - 20%
List 6 Clinical Features/ Signs/ Symptoms of SAH
- Thunderclap headache
- Loss of consciousness + confusion
- Meningism (Neck stiffness, Photophobia, Headache)
- Focal neurology
- Possible sentinel bleed/ headache
- May present as cardiac arrest (Rapid rise in ICP-> Cushing’s response)
What 3 groups of things can happen after an SAH
- Early brain injury
- Cellular changes (Oxidative stress, inflammatory mediator release, platelet activation)
- Systemic complications (Cushing’s response, Myocardial damage, Systemic inflammatory response)
What are 4 examples of Early brain injury due to SAH
- Microthrombi (can occlude more distal branches)
- Vasoconstriction (cerebral arteries)
- Cerebral oedema (Inflammatory response)
- Brain cell apoptosis
List SAH investigations
- CT head
- CT angiogram
- Lumbar Puncture (if CT inconclusive but history strongly suggests)
Describe the CT appearance of a SAH
- Filling of cisterns in a ‘5-pointed star pattern’
- Blood may be seen in ventricles
How long you should you wait after the onset of symptoms, before doing an LP to diagnose SAH?
Why?
- At least 6 hours, preferably 12
- Need time for lysis of RBCs in SA space, to allow Bilirubin to accumulate in CSF, giving it a yellow tinge (Xanthrochromia)
If SAH has happened describe the following results of a CSF sample;
- Protein
- WBCs
- Glucose
- RBCs
- Protein: High (because blood constituents)
- WBCs: Not rasied
- Glucose: Normal
- RBCs: Raised
Describe the technique of an LP
- Find Iliac Crests (giving L4-L5 level)
- Local anaesthetic
- Insert needle between Spinous Processes and through InterS and SupraS ligaments
- Feel ‘give’ as needle passes through Ligamentum Flavum and Dura
Outline the treatment of SAH patients
- Airway monitoring, O2, Fluids (Nimodipine to alleviate cerebral vasospasm)
- Neurological observations
- Neurosurgery (Decompresive Craniectomy, Coiling, Clipping)
Describe the process of Coiling to treat SAH
- Insertion of a Platinum wire into aneurysm sac
- Causes thrombosis of blood within aneurysm
Describe the process of Clipping to treat SAH
- Clamping neck of the aneurysm with a spring clip
- Causes it to looses blood supply and shrivel up
Who does Coiling and Clipping procedures
Coiling: Done by Neuroradiologists
Clipping: Done by neurosurgeons
Why do we operate on SAH patients with a good neurological status within 48 hours?
To prevent re-bleeding (a risk of previous SAH)
Describe the typical presentation of Meningitis
- Fever + Meningism (Neck stiffness, Photophobia, Headache)
- Flu like symptoms
- Rash (non-blanching, Petechiae and Purpura)
- Joint pain/ stiffness
- Seizure
- Drop in GCS
- Shock
How can meningitis present in babies?
- Inconsolable crying
- Rigidity/ floppiness
- Bulging fontanelle (late sign)
Compare the development of Meningitis if due to a Bacterial and Viral cause
Bacterial cause: Over hours
Viral: Over days
List 6 risk factors for Meningitis
- Cochlear implants (easier route of bacterial entry into brain)
- Crowding
- Young and old
- Immunosuppression
- Spinal procedures
- CSF defects
Describe 2 ways bacteria can reach the CNS
- Bacteria ascend Nasopharynx-> Middle ear
- Prolonged infection here allows them to spread directly into CSF
- Bacteria accumulate in LRT
- Lung inflammation allows entry into blood
- Invasion of CSF via capillaries allows entry into CSF
(Neonates can get bacteria from their mothers)
Describe the pathophysiology of Meningitis
- Cause damage to vessel walls in Brain and Meninges, allowing pathogen to enter SA space
- In here, they cause Meningeal inflammation and CSF becomes purulent
- Inflammatory cascade-> Cerebral Oedema and Raised ICP
Suggest complications of Meningitis
- Septic shock
- DIC
- Coma (raised ICP)
- Seizures
- Death (herniation, sepsis)
- Hydrocephalus
- SIADH
- Hearing loss
- Focal paralysis
- Intellectual deficits
