Meningitis

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Introduction

  • An infection of the meninges with the presence of pus and inflammatory cells in the cerebrospinal fluid
  • A medical emergency, and associated with considerable morbidity and mortality
  • May be bacterial (pneumococcus, meningococcus, tubercle bacilli, Haemophilus), viral, fungal, protozoal, neoplastic or chemical
  • Epidemics occur in the savannah region and are usually caused by Neisseria meningitidis

Clinical features

  • Neck stiffness and positive Kernig's sign
  • High grade fever
  • Headache
  • Vomiting
  • Photophobia with alteration in level of consciousness
  • If due to Pneumococcal and influenzae infection, additional features are jaundice, pneumonia and heart failure
  • Meningococcal infection presents additionally with joint pain, joint swelling, red eyes and skin rash
  • Tuberculous infection presents with weight loss, cough with blood in sputum while those with underlying immunosuppression (HIV infection) may manifest severe weight loss, diarrhoea, mouth lesions and skin rash

Other presentations:

  • Fever of unknown origin (chronic meningitis)
  • Mass lesion with focal neurological deficits (tuberculoma)
  • Stroke-like syndrome: resulting from vasculitis
  • Uncontrolled seizures (status epilepticus)
  • Acute psychosis (Organic Brain Syndrome) and dementia (chronic meningitis and pachymeningitis due to syphilis)

Differential diagnoses

  • Subarachnoid haemorrhage
  • Cerebral malaria
  • Septicaemia with meningism
  • Tetanus
  • Cerebral venous thrombosis

Complications

  • Cranial nerve palsies notably blindness and deafness
  • Subdural pus collection (empyema)
  • Stroke (from vasculitis)
  • Epilepsy
  • Syndrome of Inappropriate Anti-Diuretic Hormone secretion (SIADH)

Investigations

  • Lumbar puncture for CSF analysis
    • To demonstrate presence of inflammatory cells (after exclusion of raised intracranial pressure by fundoscopy or CT scan)
  • Full Blood Count and differentials; Blood culture, Erythrocyte sedimentation rate
  • Random blood glucose
  • Electrolytes, Urea and Creatinine
  • Chest radiograph
  • Mantoux test (if tuberculosis is suspected)
  • HIV screening after voluntary counselling

Treatment goals

  • Eliminate the organism
  • Reduce raised intracranial pressure
  • Correct metabolic derangements
  • Treat any complications

Non-drug treatment

  • Tepid-sponging
  • Attention to calories and fluid/electrolyte balance
  • Physiotherapy (for passive muscle exercises)
  • Nursing care (e.g. frequent turning and bladder care) to prevent decubitus ulcers and urinary tract infection

Drug treatment

Initial therapy will depend on the age of the patient and the causative agent, hence should be guided by microbiology results

Bacterial infections

  • acute conditions 8 g daily
    • Child: not recommended for use
  • Diazepam (for seizures)
    • Adult: 10 - 20 mg at a rate of 0.5 ml per 30 seconds, repeated, if necessary, after 30-60 minutes; may be followed by intravenous infusion to a maximum of 3 mg/kg over 24 hours
    • Child: 300-400 μg/kg (maximum 20 mg) by slow intravenous injection into a large vein for protracted or frequent recurrent (Note: Not required in single, short-lived convulsions) Intravenous therapy should be continued until the fever has settled and continued for another 3 days. Thereafter, oral medications can be used for a minimum treatment period of 10 -14 days
  • Vancomycin can  be  used  for  suspected  Methicillin-resistant Staphylococcus aureus infection (MRSA)
  • Intravenous penicillin G should be used with caution because of possible severe anaphylactic reaction that can lead to sudden death

Acute cerebral decompression

  • Furosemide
    • Adult: 40 - 80 mg every 8 hours by slow intravenous injection (for a maximum of 6 doses)
    • Neonate: 0.5-1 mg/kg every 12 - 24 hours (every 24 hours in neonates born before 31 weeks gestation)
    • 1 month - 12 years: 0.5 - 1 mg/kg (maximum 4 mg/kg), repeated every 8 hours as necessary
    • 12 - 18 years: 20 - 40 mg, repeated every 8 hours as necessary; higher doses may be required in resistant cases

Or:

  • Mannitol 20% solution
    • Adult: 50-200 g by intravenous infusion over 24 hours, preceded by a test dose of 200 mg/kg by slow intravenous injection
    • Neonate: 0.5-1 g/kg (2.5-5 mL/kg of 20% solution) repeated if necessary 1-2 times after 4-8 hours
    • 1 month - 18 years: 0.5 - 1.5 g/kg (2.5 - 7.5 ml/kg of 20% solution); repeat if necessary 1 - 2 times after 48 hours

Chemoprophylaxis

Treat contacts during meningococcal epidemics with either ciprofloxacin or rifampicin

  • Rifampicin
    • Adult: 600 mg orally every 12 hours for 5 days
    • Child: 10 mg/kg orally every 12 hours for 5 days
    • Under 1 year: 5 mg/kg orally every 12 hours for 5 days
  • Ciprofloxacin
    • Adult: 500 mg orally as a single dose
    • Child 5 - 12 years: 250 mg orally as a single dose

Notable adverse drug reactions, contraindications and caution

  • Diazepam: Must be administered slowly intravenously to avoid respiratory depression
  • Mannitol extravasation causes inflammation and thrombophlebitis. Contraindicated in congestive cardiac failure and pulmonary oedema

Prevention

  • Immunization of close contacts against communicable diseases:
    • Meningococcus,  Haemophilus,  Streptococcus  (especially  for homozygous sickle cell anaemia)
  • Chemoprophylaxis (rifampicin or ciprofloxacin)