Meningitis

Question 1

Most common bacterial pathogens

Answer 1

Streptococcus pneumoniae (pneumococcus)
Neisseria meningitidis (meningococcus) –> non-blanching rash
Haemophilus influenzae
Listeria monocytogenes (often in patients at extremes of age)

Question 2

Most common viral pathogens

Answer 2

enteroviruses such as Echoviruses, Coxsackie viruses A and B, poliovirus are the most common causes of viral meningitis.

Other viruses include herpes viruses:

HSV2 (more associated with meningitis)
HSV1 (more associated with meningoencephalitis/encephalitis, particularly affecting the temporal lobes).
Paramyxovirus: can be a complication of mumps infection
Measles and rubella viruses: can cause meningoencephalitis
Varicella Zoster Virus: can be a complication of chicken pox
Arboviruses - arthropod-borne viruses, cause meningoencephalitis
Rabies virus - can cause meningo-encephalitis

Question 3

Fungal meningitis

Answer 3

Fungal (particularly Cryptococcus neoformans) and mycobacterial meningitis are rare, except in the immunosuppressed population.

Question 4

Parasitic meningitis

Answer 4

Amoeba: Acanthamoeba - associated with keratitis and meningitis associated with contact lens fluid contamination.
Toxoplasma gondii

Question 5

Non-infective causes of meningitis

Answer 5

Malignancy (leukaemia, lymphoma and other tumours)
Chemical meningitis
Drugs (NSAIDs, trimethoprim)
Sarcoidosis
Systemic Lupus Erythematosus
Behcet’s disease

Question 6

Specific clinical signs in meningitis

Answer 6

KErnigs –> Unable to Knee Flex due to stifness of hamstring
brudziNsKi –> Neck flexion leads to Knee flexion

Question 7

Empiric mx of meningitis

Answer 7

2g of IV ceftriaxone twice daily (twice the standard dose to ensure CNS penetration)
+ IV amoxicillin in young/old patients to better cover listeria,
+ IV aciclovir if viral encephalitis is suspected

IV dexamethasone

Question 8

CSF: bacterial meningitis

Answer 8

May be clear or turbid
100-200 PMNs
Culture results positive (may be negative depending on how heavily infected the meninges are)
Protein raised due to bacterial protein contamination
LOW GLUCOSE as bacteria use as an energy source

Also consistent with brain abscess

Question 9

CSF: (viral) aseptic meningitis

Answer 9

Misnomer: usually due to viral infection (or treated bacterial meningitis)
Clear or slightly turbid
15-500x109 LYMPHOCYTES
Negative culture results
0.5-1g/l protein
glucose normal (viruses use cell machinery to replicate)

Question 10

CSF: tubercular meningitis

Answer 10

Clear or slightly turbid
Fibrin web may develop.
30-500x109 lymphocytes +/- PMNs, negative gram stain (need Auramine staining)
Protein 1-6g/L
Glucose 0-2.2.

Question 11

CSF: cryptococcal meningitis

Answer 11

very high opening pressure (poor prognostic sign)
May give any of the results above, so should consider as a differential in any HIV or immunocompromised patient.
Cryptococcal antigen testing or India Ink staining should be requested.

Question 12

Complications of meningitis

Answer 12

Septic shock
Disseminated Intravascular Coagulation
Coma
Subdural effusions
Syndrome of inappropriate antidiuretic hormone secretion
Seizures
Delayed: Hearing loss, cranial nerve dysfunction, hydrocephalus, intellectual deficits, ataxia, blindness
Death

Question 13

When not to do lp

Answer 13

Signs of raised ICP
- focal neurological signs
- papilloedema
- continuous or uncontrolled seizures
- GCS ≤ 12