Meningitis and subarachnoid haemorrhage Flashcards
4 important dural folds
- falx cerebri (between cerebral hemispheres)
- falx cerebelli (between cerebellar hemispheres)
- tentorium cerebelli
- diaphragm sella
Role of CSF
Physical support Excretion of brain metabolites Intracerebral transport (hormone releasing factors) Control chemical environment Volume changes - compensate
What are cisterns?
Enlarged regions in subarachnoid space where brain moves away from skull - collect CSF
Flow of CSF
Formed by choroid plexuses and extra- choroidal structures
Lateral ventricles
3rd ventricle
Aqueduct of Sylvius
4th ventricle
Median and lateral apertures
Subarachnoid space (small amount into spinal cord)
Arachnoid granulations project into dural Sinuses -> circulation
Propelled by new fluid, ciliary action, ventricular ependyma, vascular pulsation
What is a subarachnoid haemorrhage? Risk factors, symptoms
Extravasated new of blood is to subarachnoid space - non-traumatic spontaneous (can also occur in trauma)
Risks: 6% of all strokes, female, black, Finnish, Japanese, 50-55yrs
Aneurysms risk: hypertension, smoking, alcohol, CT disorder, polycystic ovaries
Symptoms: headache 1/2, dizziness, orbital pain, diplopia, visual loss
Subarachnoid haemorrhage cause
Rupture of saccular (berry) aneurysms 80% of non-traumatic
(Rupture arterial/ venal malformations - 10%)
Usually at bifurcation points
Often large cerebral arteries circles of willis
Subarachnoid haemorrhage clinical signs
Signs of meningism
(Neck stiff, photophobia)
Right third nerve palsy - PCA aneurysm
Sentinel headaches in months preceding 40% - minor leaks
What can occur after the bleed in subarachnoid haemorrhage?
Micro thrombi which can occlude smaller distal arteries
Vasoconstriction from CSF irritant
Cerebral oedema (response to hypoxia & extravasated blood)
Sympathetic activation - myocardial damage (ECG ST elevation, troponin increased)
Earl rebleeding common
Acute hydrocephalus (blood in subarachnoid space may block drainage CSF)
Global cerebral ischaemia
Subarachnoid haemorrhage investigations before diagnosis
1st lime - CT scan detects 93% if done within 24hrs or bleed (without contrast so not confused blood)
If convincing history but negative CT scan: lumbar puncture (should wait at least 6hrs, need time lysis RBCs - release bilirubin in CSF - yellow tinge (xanthochromia) in centrifuging, different from just blood from traumatic tap of procedure)
What is xanthochromia
Yellow tinge to CSF that occurs >6hrs after bleed in subarachnoid space
Subarachnoid haemorrhage investigations post diagnosis
Angiography confirm location of aneurysm -
digital subtraction angiography (inject contrast-> vasculature, fluoroscope (x-ray) real-time)
Subarachnoid haemorrhage treatment
Stabilisation - May need airway support - monitor CVS parameters
✅CCB - nimodipine (selective cerebral vasculature- prevents vasospasms and secondary ischaemia)
✅operate within 72hrs if gd neurological status prevent re-bleeding
- clipping (clamp aneurysm)
- coiling (insertion wire into aneurysm sac-> thrombosis of blood)
What two broad categories can infections of the CNS be divided into?
Infections focused on parenchyma (encephalitis)
Infections focused on meninges (meningitis) - usually inflammation of leptomeninges (arachnoid, pia)
Signs and symptoms meningitis
Triad of meningism with a fever 44%
- headache
- neck stiffness
- photophobia
- flu like
- joint pains
- rash
- reduced GCS/ seizures
Babies: Inconsolable crying/ high pitched Reduced feeds Floppy Bulging fontanelle
What is the meningitis rash most common with, what causes it and what does it look like?
Most common with meningococcal meningitis
Caused by bleeding into skin/ mucosa (microvascular thrombosis)
- non- blanching rash
Larger lesions - purpuric
Smaller lesions (1-2mm) - petechial (bbs can get from distress above clavicle)
Usually trunk/ legs/ mucous membranes/ conjunctivae/ palms/ soles
Causes of meningitis
Most often infectious bacterial/
viral (most common)
Common bacteria cause:
1st Streptococcus pneumonia (vaccine for 13 variants)
2nd neisseria meningitides
3rd haemophilus influenza (Hib vaccine)
- occasionally from fungal disease or trauma/ surgery
Risk factors for meningitis
Young and old <5 >65yrs
Crowding
Immune problems
Cochlear implants
How does bacteria reach the CNS to cause meningitis?
- colonisation nasopharynx
- ascent through Eustachian tube -> middle ear (otitis media)
- prolonged infection -> directly CSF (mastoid sinuses)
OR
- colonisation nasopharynx
- seeding to LRT (pneumonia)
- lung inflammation bacteria enters blood (bacteraemia)
- invasion of CSF via capillaries or subarachnoid space
Neonates can get pathogens from maternal source (placenta/ reproductive tract secretions)
Effects of meningitis - pathophysiology & complications
Bacteria quickly multiply in subarachnoid space - inflammatory mediators induced - lots leukocytes enter CSF -> inflammatory cascade -> cerebral oedema ⬆️ICP
Complications: Specific shock Disseminated IV coagulation Coma Seizures Hearing loss Hydrocephalus Focal paralysis
Diagnosing meningitis
Symptoms/ signs
Physical examination
Kernig sign - supine patient with thigh flexed 90degrees -> extension knee met with resistance (more common children -53%)
Brudzinski sign - neck flexed involuntary flexion knees and hips (children 66%)
Due to meningeal irritation (stretching)
Meningitis investigations and when to be cautious
Lumbar puncture - untreated bacterial CSF: cloudy, elevated protein, low glucose, positive gram stain
Viral CSF: clear or cloudy, normal/ raised protein, normal glucose
But performing Lp increases chance brain herniation (occurs 5% with acute bacterial meningitis anyway)
Signs:
Decreasing consciousness, Brainstem signs, recent seizure (delay LP)
CT head find contraindications to LP but normal may not mean safe
Can also do PCR:
Blood and CSF - helpful diagnose patients who received empirical antibiotic treatment, distinguish bacterial from viral causes
Blood culture - results can be inflicted previous antibiotic treatment
Treatment meningitis
Admit to hospital
- empirical antibiotics e.g. Vancomycin + (Ceftriaxone OR cefotaxime)
- supportive therapy (intubation if altered consciousness, fluids if shocked, O2)
- dexamethasone (prevent hearing loss)
If viral: aciclovir for herpes, supportive fluids, antipyrexial, painkillers, rest
