meningitis

Question 1

definition

Answer 1

Inflammation of the leptomeningeal (pia mater and arachnoid) coverings of the brain, most commonly caused by infection.

Question 2

aetiology

Answer 2

Bacterial

Neonates: Group B streptococci, Escherichia coli, Listeria monocytogenes.
Children: Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae.
Adults: Neisseria meningitidis (meningococcus), Streptococcus pneumoniae, tuberculosis.
Elderly: Streptococcus pneumoniae, Listeria monocytogenes.

Viral: Enteroviruses, mumps, HSV, VZV, HIV.

Fungal: Cryptococcus (associated with HIV infection).

Others: Aseptic meningitis, Mollaret’s meningitis

Question 3

risk factors

Answer 3

Close communities (e.g. dormitories), basal skull fractures, mastoiditis, sinusitis,
inner ear infections, alcoholism, immunodeficiency, splenectomy, sickle cell anaemia, CSF shunts, intracranial surgery.

Question 4

symptoms

Answer 4

signs of meningism:

• Photophobia
• neck stiffness (Kernig’s sign: with hips flexed, pain/resistance on passive knee extension; Brudzinski’s sign: flexion of hips on neck flexion).
• nausea and vomiting

Signs of infection:

• Fever
• tachycardia and hypotension
• skin rash (petechiae with meningococcal septicaemia),
• altered mental state, confusion

Question 5

investigations

Answer 5

Blood: Two sets of blood cultures (do not delay antibiotics).

Imaging: CT scan to exclude a mass lesion or raised intracranial pressure before LP, (may lead to cerebral herniation during subsequent CSF removal).
A CT scan of the head must be done before LP in patients with: immunodeficiency, history of CNS disease, reduced consciousness, fit, focal neurologic deficit or papilloedema.

Lumbar puncture: Note opening CSF pressure. Send CSF for microscopy with, culture, sensitivity and Gram staining (Streptococcus pneumoniae: Gram-positive diplococcic, Neisseria Meningitidis: gram-negative diplococcic), PCR, biochemistry and cytology.

FBC
Metabolic profiile
coagulation profile (check for DIC)

Question 6

treatment

Answer 6

Bacterial:
antibiotics (ceftriaxone) + dexamethasone + any supportive treatment as needed

Viral:
antiviral – acyclovir (for HSV, CMV, herpes zoster. all others don’t need antiviral) + supportive treatment