Meningitis

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This is inflammation of the meningeal covering of the brain or spinal cord. Both brain and meninges can be involved. This inflammation could be caused by bacteria, viral or fungal infections, malignancies, chemical reaction, intrathecal infections and also due to injury or trauma.

Clinical Features

Clinical presentation is the same despite different causative agents; but the commonest causative agent is bacteria and these include, Gram-negative organisms i.e. E. coli in children, H. influenzae type b, group B Streptococcus, Streptococcus pneumoniae, Neisseria meningitidis and Cryptococcus in immune-compromised patients. Factors such as age, head trauma, and compromised immunity may help predict causative agents.

The relative incidence of meningitis for children remains high in the first 2 years of life. The incidence of meningitis is high during the 1st month of life with most infections being due to gram-negative organisms i.e. E-Coli in children and group B Streptococcus.

Presentation of patients with meningitis varies according to age group.

Adults and older children  (**Common Presentations)

  • Headache  **
  • Neck stiffness/ache   **
  • Fever
  • Vomiting
  • Seizures
  • Confusion
  • Drowsiness
  • Loss of consciousness
  • Vascular collapse (Waterhouse - Friderichsen syndrome)

In infants

  • Fever
  • Vomiting
  • Irritability
  • Convulsions
  • High-pitched cry and
  • Bulging of the anterior fontanel is commonly present
  • Stiffness of the neck may be absent
  • There may be enlarging of head size

Signs of Meningitis
Other signs elicited during a physical examination that suggest meningitis include:

  • Neck stiffness
  • Positive kernig's sign
  • Brudzinski' s sign
  • Cranial nerves abnormality may occur (facial nerve palsy, oculomotor nerve palsy and occasional deafness).

Complications

These include:

  • seizures
  • loss of consciousness
  • hydrocephalus, thrombophlebitis
  • cranial palsies
  • hemiplegia and
  • death.

Long term complications include mental retardation, hearing loss, sometimes blindness, epilepsy.

Diagnosis

This is confirmed by laboratory investigations. Perform a lumbar puncture for gram-stain culture and sensitivity for glucose and protein.

Cerebral spinal fluid may be cloudy, indicating bacterial meningitis.

Management

Bacterial Meningitis

Initial therapy should be guided by the patient's age, the clinical circumstances, and suspected pathogen and later by the CSF results. Antibiotics are the mainstay of therapy and should be instituted parenterally at the initial stage. Benzylpenicillin or Ampicillin is given I.V.

Adults:

  • Benzylpenicillin 4 mega units I.M or Ampicillin 100mg - 200mg/kg I.V. 6 hourly.
  • The Penicillin is usually given with Chloramphenicol injection at a dosage of 50 - 100mg/kg every 6 hours.
  • Intravenous antibiotic injection should be put in place for the first 72 hours or for as long as the patient is unconscious and then changed to the oral form.
  • Treatment should generally be continued for at least 1 week after the fever subsides and the CSF returns towards normal.
  • The various antibiotics and combinations used in bacterial meningitis include:

In infants:

  • Ampicillin 100 -150mg/kg I.V (0 - 7 days old) 8- 12 hourly or 150 - 200mg/kg I.V (> 7 days old) 6 - 8 hourly plus Cefotaxime 200mg/kg I.V. every 6 hours.
  • Ampicillin, as above plus Gentamycin, 7.5mg/ kg I.V (0 - 7 days old) 8 hourly or 5mg/kg I.V. (> 7 days old) 12 hourly.

In children >1 month-old,

  • Cefotaxime, as above or Ceftriaxone 20 -50mg/kg daily as a single dose can be increased up to 80mg/kg as a single dose in severe infection or Ampicillin 100 - 200mg/kg IV 6 hourly + Chloramphenicol 50 - 75mg/kg I.V. 6 hourly.

 

Fungal Meningitis

Fungal meningitis is usually caused by Cryptococcal neoformans. This is commonly seen in immunocompromised individuals such as people with HIV/AIDS or individuals with malignancies or on immunosuppressant drugs.

The drug of choice is Amphotericin-B and Fluconazole for at least 10 days and followed by daily Fluconazole.

The Amphotericin-B dosage is 0.7mg/kg IV daily by slow infusion over 4 hours. Current treatment guidelines do not support the slow dose escalation of amphotericin B and are associated with poorer patient outcomes.

Caution

Amphotericin-B the daily dosage should not exceed 1mg/ kg for adults or children.

Flucytosine is added at 150mg/kg/day every 6 hours for 6 weeks, but this is associated with increased risk of bone marrow toxicity and clinical research showed no increased benefit when compared to Amphotericin-B and Fluconazole.

Fluconazole is also effective for cryptococcus infection, but should not be used as monotherapy, particularly in the initial period of treatment.

Treatment of Cryptococcal Meningitis:
Amphotericin-B 0.7mg/kg IV + Fluconazole 800mg PO daily for at least 10 - 14 days, followed by daily maintenance Fluconazole 800mg for 8 – 10 weeks, then daily chronic suppression with 200mg until CD4 count >200 for at least 6 months for HIV+ patients.

Management of intracranial pressure is essential and may require repeated lumbar punctures to drain CSF to reduce the pressure. Children can be treated with 3 to 6mg/kg/ day.

Tuberculous meningitis may complicate pulmonary tuberculosis especially in patients with immunodeficiency, also in children between 1 and 5 years and in the elderly. These should be treated with anti- tuberculosis therapy, which should be prolonged for an extra 3 months.

Supportive Fever, dehydration, and electrolyte disorders require correction.

Care must be taken not to over hydrate patients with cerebral oedema.

Convulsion and status epilepticus are treated appropriately.

All patients with presumed bacterial meningitis (of unknown aetiology) should be isolated for the first 24 hours of therapy.

Viral meningitis may complicate viral infection in other parts of the body e.g. herpes meningitis. Most common causes of viral meningitis or encephalitis are herpes viruses.

Human Herpes Virus (HHV3 or Varicella Zoster Virus): commonly causes Chickenpox or shingles. If you suspect a VZV meningitis or encephalitis:   

Acyclovir IV 10mg/kg q8 hours for 14 - 21 days in adults, but can use higher doses in neonates up to 20mg/kg IV q8hrs to reduce rates of relapses. Oral Acyclovir should not be used, as therapeutic levels will not be achieved. Children 5mg/kg 8 hourly.

Prevention• Avoid overcrowding
• Immunisation against Meningococcal Meningitis.