17 Meningitis and Subarachnoid Haemorrhage

Question 1

Name the 4 important dural septa.

Answer 1

Tentorium cerebelli

Falx cerebri

Falx cerebelli

Diaphragma sellae

Question 2

What are cisterns?

Answer 2

Enlarged region of subarachnoid space (between arachnoid and pia)

Occur when brain moves away from skull

Question 3

What are the different stages of subarachnoid haemorrhage?

How common are they?

Who is more at risk? (age, gender, ethnicity)

Answer 3

How common are they?

9000 cases per year UK

Who is more at risk?

• 50-55yrs
• Females (1.6:1)
• Black, finnish, japanese populations

Question 4

The most common cause of a non-traumatic subarachnoid haemorrhage is a berry aneurysm.

Where do they occur?

Why do they occur?

What are the risk factors?

Answer 4

Where do they occur?

• Circle of willis- at bifurcations

Why do they occur?

• Pressures on arterial wall
• Intracranial arteries lack external elastic lamina- have thin adventitia

What are the risk factors?

• Same as CVS:
  
  • Hypertension, smoking, alcohol etc

Question 5

Give the typical presentation of a subarachnoid haemorrhage.

Answer 5

• Sudden onset, severe, diffuse headache
• Photophobia, neck stiffness
• Nausea and vomiting
• May have cranial nerve sign- right third nerve palsy

May have sentinel headaches in months preceding (minorleaks from aneurysms)

Question 6

What happens after a subarachnoid haemorrhage has occurred? (Ie consequences)

Answer 6

• Microthrombi- occlude smaller distal arteries
• Cerebral oedema
• Acute hydrocephalus (blood in subarachnoid space- blocking drainage)
• Cerebral ischaemia

Question 7

What should you do if you suspect a subarachnoid haemorrhage?

Answer 7

CT Scan ASAP

(93% detected if done within 24hours)

Question 8

What should you do if there is a convincing history of a subarachnoid haemorrhage but the CT scan is negative?

Answer 8

Do a lumbar puncture

• Should wait at least 6hrs
  
  • Need time for lysis of RBCs- bilirubin in CSF
  • Differentiate from traumatic tap by centrifuging
• CSF= high protein, low WBC, glucose normal

Question 9

What is the next step investigation once a subarachnoid haemorrhage has been confirmed?

Answer 9

Angiography to confirm location of anuerysm

Question 10

How is a subarachnoid haemorrhage treated?

Answer 10

• Airway support required?
• Monitor cardiovascular parameters
• Calcium channel blocker- Nimodipine
  
  • ​Prevent vasospasm and secondary ischaemia
• Operation (prevent rebleeding) :
  
  • Clipping (surgeons)
    
    • Clamping neck of aneurysm
  • Coiling (neuro-radiologists)
    
    • Insertion of wire into aneurysm sac

Question 11

What’s the prognosis like for a subarachnoid haemorrhage?

Answer 11

50 % mortality over 6 months

Question 12

Differentiate between meningitis and encephalitis.

Answer 12

Meningitis= infection of the meninges (usually leptomeninges)

Encephalitis= infection of parenchyma

(Meningitis can cause encephalitis)

Question 13

What are the signs and symptoms of meningitis? (think adults and babies)

Answer 13

• Develops over hours- bacterial cause*
• Develops over days- viral cause*

Signs:

• Fever
• Reduced conciousness
• Confusion

Symptoms:

• Photophobia
• Rash (non-blanching, petchial rash)
  
  • Microvascular thrombosis (more common in younger)
  • Trunk, legs, mucous membranes, conjunctivae
• Severe headache
• Joint pains
• Neck stiffness

Babies:

• Floppy
• Incosolable crying
• Reduced feeds
• Floppy

Question 14

Give 3 common bacterial causes of meningitis.

Answer 14

• Neisseria Meningitides
  
  • Menigococcal meningitis
• Haemophilus influenza
  
  • Hib meningitis
• Streptococcus pneumonia
  
  • Pneumococcal meningitis

Question 15

List some of the risk factors of acquiring meningitis.

Answer 15

• Immunocompromised
• Young and old
• Cochlear implants

Question 16

How does pneumococcus causing meningitis spread from the nasopharynx to the meninges? (3)

Answer 16

1. Colonisation of nasopharynx
   
   1. Bacteria ascends through eustacian tube to middle ear
      
      1. Through mastoid sinus
2. Colonisation of nasopharynx
   
   1. Seeding in lower respiratory tract (pneumonia)
      
      1. Invasion of CSF via capillaries
3. Neonates- from maternal source
   
   1. Placenta/reproductive tract secretions

Question 17

What complications can occur due to meningitis?

(bacteria multiply quickly in subarachnoid space- lots of leucocytes enter CSF)

Answer 17

• Encephalitis
• Permanent brain damage
• Septic shock
• Coma (raise ICP)
• DIC (bacteraemia)
• SeizuresHearing loss
• Hydrocephalus
• Focal paralysis (cerebral abscess)

Question 18

How is meningitis diagnosed? (What investigations are done?)

Answer 18

Diagnosis:

• Clinical history
• Signs:
  
  • Kernig sign
  • Brudzinski
• Lumbar puncture
  
  • ​CSF in bacterial meningitis=
    
    • Cloudy
    • Elevated protein
    • Low glucose (metabolised by bacteria)
    • Positive gram stain
  • CSF in viral meningitis=
    
    • Clear/cloudy
    • Normal/raised protein
    • Normal glucose

Question 19

Why might we delay a lumbar puncture when investigating meningitis? What are the best predictors of when to delay a lumbar puncture in suspected meningitis?

Answer 19

If raised ICP- risk of brain herniation

(occurs in 5% of patients with acute bacterial meningitis)

Performing LP= sudden decrease in pressure

Indicators:

• Decreasing conciousness
• Brainstem signs
• Recent seizure

May need to do a CT head to see but not always safe even if CT= normal

Question 20

Why would a PCR be carried out on blood and CSF from a patient with suspected meningitis?

Answer 20

Helpful to diagnose patients who received empiracal antibiotic treatment

Question 21

How is meningitis treated?

Answer 21