L16 - Meningitis and subarachnoid haemorrhage

Question 1

Dural septa

Answer 1

Falx cerebri
Falx cerebelli
Tentorium cerebelli
Diaphragma sella - layer of dura with a hole for the pituitary stalk

Question 2

Cisterns

Answer 2

Enlarged spaces between the brain and the skull where CSF can collect

Functions:

• Render brain weightless
• Excretion of brain metabolites
• intracerebral transport of hormone releasing factors

Question 3

What percentage of strokes are subarachnoid

Answer 3

6%

Question 4

Who is more likely to get a subarachnoid stroke?

Answer 4

Women 1.6:1
50- 55 yr olds
Black, Finnish and Japanese’s people

Question 5

Prognosis of subarachnoid haemorrhage

Answer 5

50% mortality

60% longer term morbidity

Question 6

Risk factors of subarachnoid haemorrhage

Answer 6

Hypertension 
Smoking 
Trauma
Cocaine 
Family history 
Excess alcohol consumption 
Predisposition to aneurysm formation - Marfan’s

Question 7

Presentation of subarachnoid haemorrhage

Answer 7

Thunderclap headache 
Nausea and vomiting 
Dizziness
Orbital pain 
Diplopia 
Visual loss 
Meningism - bleeding into the subarachnoid space cause if inflammation

Question 8

Pathophysiology of subarachnoid haemorrhage

Answer 8

Rupture of berry aneurysm in the circle of Willis usually at bifurcation points

Question 9

Common sites of Berry aneurysms

Answer 9

Anterior communicating artery - 40%
- can compress the optic chiasm

Posterior communicating artery - 25%
- compress CN III

Middle cerebral artery as it bifurcates into superior and inferior - 20%

Question 10

Why are intracerebral arteries prone to aneurysm

Answer 10

Lack external elastic lamina

Thin adventitia

Question 11

Sentinel headaches

Answer 11

Headaches month prior to the subarachnoid haemorrhage due to small leaks from the aneurysm

Question 12

What happens after a subarachnoid bleed?

Answer 12

Microthrombi can occlude distal arteries
Vasoconstriction of cerebral arteries as the CSF is irritated
Cerebral oedema
Myocardial damage due to sympathetic activation
Early rebleeding
Acute hydrocephalus - blood blocks CSF drainage
Global cerebral ischaemia

Question 13

How does cerebral oedema occur?

Answer 13

Decreased oxygen delivery to an area of the cerebral cortex causes ischaemia
Less ATP produced therefore less Na+/K+ ATPase activity
Higher Na+ conc inside the cell causes depolarisation
Na+ influx
K+ efflux
Water follows sodium therefore influx of water causing oedema

Question 14

Investigations of a subarachnoid haemorrhage

Answer 14

1st line - CT without contrast

If there is a convincing Hx but negative CT, do a lumbar puncture at L3/L4 or L4/L5

Question 15

Lumbar puncture

Answer 15

Wait at least 6 hours
Preferably 12+ hours

For the blood in the CSF to lyase, therefore can detect the bilirubin
CSF has a yellow tinge after centrifugation - xanthochromia

Question 16

Traumatic tap

Answer 16

Needle inadvertently enters an epidural vein

Question 17

Xanthochromia

Answer 17

Yellow tinge of the CSF due the presence of bilirubin

Question 18

CSF contents of subarachnoid haemorrhage

Answer 18

High protein (plasma proteins from blood)
No WCC ( not infection)
Normal glucose
High RBC

Question 19

After diagnosis

Answer 19

Angiography is performed to confirm the location of the aneurysm

Question 20

Treatment of a subarachnoid haemorrhage

Answer 20

Stabilisation

Airways - Assess whether they need airway support
Breathing- Give oxygen
Circulation - fluids and nimodopine

Possibly operate

Question 21

When to operate

Answer 21

Within 72 hours of bleed
On patients with good neurological status
Prevents rebleeding

Question 22

Types of surgical procedures

Answer 22

Decompression - craniotomy

Clipping - surgeon clamps base of the aneurysm with spring clip (open craniotomy) cutting off the blood supply causing it to shrivel

Coiling - neuro radiologists insert a platinum wire into the aneurysm sac which causes thrombosis of blood within the aneurysm which doesn’t occlude the artery

Question 23

Subarachnoid CT

Answer 23

Prominent filling of the basal cisterns in a 5 point star pattern
Blood may be seen within the ventricles - reflux from subarachnoid space

Question 24

Nimodopine

Answer 24

Calcium channel blocker prevents secondary vasospasm and secondary ischaemia

Question 25

Meningitis

Answer 25

inflammation of the meninges commonly due to infection | Often the leptomeninges

Question 26

Encephalitis

Answer 26

Infection (often viral) of the brain parenchyma | Meningitis can lead to encephalitis

Question 27

Signs and symptoms of meningitis

Answer 27

``` Signs: Non blanching rash Fever Reduced GCS Kernig sign Brudzinski sign ``` ``` Symptoms: Photophobia Neck stiffness Headache Joint pains Seizures ```

Question 28

Meningitis in children

Answer 28

Insoluble crying Reduced feeds Floppy Bulging fontanelle

Question 29

Non blanching rash

Answer 29

Due to bleeds into the skin or mucosa - microvascular thrombosis - slow circulation - impaired fibrinolysis - increased tissue factor expression in endothelial cells 1-3mm - petechia (pin prick like) Larger than 3mm - purpura Usually found on legs, trunk, mucosal membranes and conjunctivae Occasionally palms and soles More common in younger patients

Question 30

Conjugate vaccine for meningitis

Answer 30

PCV13 - pneumococcal conjugate vaccine for 13 worst variants - given to under 60s PCV20 - given to the elderly

Question 31

Risk factor for community acquired meningitis

Answer 31

Young and old - less that 5 yrs old and over 65 years old Crowding Immunocompromised- non vaccinated, asplenic, cancer, diabetes Cochlear implants - physical conduit to meninges CSF defects - spina bifida Spinal procedures - lumbar puncture Endocarditis - bacteraemia Alcoholism

Question 32

How does pneumococcal bacteria reach the meninges

Answer 32

- commensal of nasopharynx - ascends through the Eustachian tube to middle ear (otitis media) - prolonged otitis media can lead to bacteria spread directly to CSF through the mastoid sinus - seeds to the lower resp tract (pneumonia) - lung inflammation causes vessels to become more leaky therefore bacteria enters the blood stream causing bacteraemia - invasion of CSF via capillaries the traverse the choroid plexus or subarachnoid space - neonates can get pathogen from mother (Ecoli)

Question 33

Effects of meningitis

Answer 33

Once bacteria is in the subarachnoid space, it multiplies exponentially as no resistance - inflammatory mediators are induced - leukocytes enter the CSF - inflammatory cascade causes cerebral oedema and raised ICP

Question 34

Complications of meningitis

Answer 34

Septic shock - meningococcal sepsis due to bacteraemia DIC - disseminated intravascular coagulation - bacteraemia Coma - raised ICP Seizures - irritation of brain parenchyma Hearing loss - cochlea swelling or CN VIII lesion Hydrocephalus Focal paralysis - cerebral abscess

Question 35

Positive Kernig sign

Answer 35

Supine patient with thigh flexed to 90 degrees Resistance to knee extension as stretches meninges More common in children

Question 36

Positive brudzinski sign

Answer 36

When neck is flexed, involuntary flexion of the knees and hips More common in children

Question 37

Investigations of meningitis

Answer 37

Lumbar puncture - compare with blood culture PCR - blood and CSF - distinguishes between viral and bacterial Blood culture - May be influenced by antibiotic treatment Sepsis screen If septic: - mid stream urine sample - CXR

Question 38

CSF in meningitis

Answer 38

Bacterial: - WCC present - lymphocytes and neutrophils - cloudy due to WCC - elevated protein - immune proteins - low glucose - bacteria metabolism it - positive gram stain Viral meningitis: - clear of cloudy - WCC - normal or raised protein - normal glucose

Question 39

Risk of lumbar puncture

Answer 39

Raised ICP increases the likelihood of brain herniation | Performing the LP increases this chance due to a sudden decrease in pressure from removal of the CSF

Question 40

When should a lumbar puncture be delayed

Answer 40

- decreased consciousness - brainstem signs - recent seizures CT can identify contraindications but a normal CT may not mean LP is safe

Question 41

Meningitis treatment

Answer 41

Admit to hospital - empirical antibiotics asap - vancomycin + IV ceftriaxone or cefotaxime (neonatal meningitis) Supportive therapy: - airways - intubation - altered consciousness - breathing - oxygen - circulation - fluids if sepsis shock - caution with raised intracranial pressure Dexamethosone (corticosteroid) - prevents hearing loss by reducing swelling Viral - acyclovir for herpes - ganciclovir - CMV Supportive: - fluids if sepsis shock - analgesia - antipyretic