Meningitis

Clinical Description

Infection of the brain meninges. Microorganisms reach the meninges through the bloodstream or by direct extension from the ears, nasopharynx, cranial injury and congenital meningeal defects. Immunocompromised patients are at risk of infection with unusual organisms.

• Causes can be infective or non-infective (malignant meningitis, intrathecal drugs and blood following subarachnoid hemorrhage).
• Can be acute or chronic

Infective Causes

• Bacterial: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenza, Staphylococcus aureus, Escherichia coli (neonates), Mycobacterium tuberculosis
• Viral: Herpes simplex virus, Epstein Barr virus, Mumps
• Fungi: Cryptococcus neoformans, rarely – Candida albicans, Histoplasma capsulatum, Coccidioides immitis

Signs and Symptoms

• Triad of headache, neck stiffness and fever
• Photophobia
• Vomiting
• Petechial or nonspecific blotchy, red rash (meningococcal)
• Positive Kernig’s sign
• Reduced level of consciousness, lateralizing signs, cranial nerve palsies
• Less severe cases e.g., viral meningitis may have less symptoms and signs

Complications of Meningitis

• Brain abscess
• Seizures
• Hydrocephalus
• Cranial nerve palsies
• Syndrome of inappropriate ADH secretion (SIADH)

Investigations

• FBC, malaria tests, urea, electrolytes and creatinine
• Random blood glucose
• HIV test (+/-CD4, urine TB LAM and serum CRAG, Focused Abdominal Sonographer in HIV (FASH) if HIV positive
• lumbar puncture (under aseptic technique)
• CXR where indicated (if bacterial or TB suspected)

Typical CSF Changes in Normal, Viral, Bacterial, Cryptococcal and Tuberculous Meningitis

Normal Viral Bacterial Cryptococcal TBM

Appearance crystal clear clear/turbid turbid/slash clear (high opening pressure) clear/cloudy

Lymphocytes <5/mm3 10 - 100/mm3 < 50/mm3 10 - 100/mm3 0 - 300/mm3

Polymorphs Nil nil 200 – 300/ mm3 nil - <50/ mm3 0 -200/ mm3

Protein 0.2 – 0.4 g/L 0.4 – 0.8 g/L 0.5 – 2.0 g/L 0.4 – 1 g/L 0.5 – 3 g/L

Glucose 2/3 – 1⁄2 blood glucose >1⁄2 blood glucose (low/normal) < 1⁄2 blood glucose low/normal < 1⁄2 blood glucose (low)

Cryptoccal antigen test (CRAG) negative negative negative positive negative

India Ink negative negative negative positive negative

Cell count may be low in severely immunocompromised patients

Bacterial meningitis

• CSF is predominantly neutrophils (polymorphs)
• in partially treated bacterial meningitis, cell count may be lower or predominantly lymphocytes
• Gram stain can be used to identify some organisms
• Streptococcus pneumoniae as gram positive diplococci
• Neisseria meningitidis as gram negative diplococci
• gram negative bacilli eg Haemophilus influenzae, Non typhoidal salmonella
• gram positive bacilli – Listeria monocytogenes

TB meningitis

• neutrophils may predominate in early TB meningitis
• AFBs are rarely seen in CSF hence their absence does not exclude the diagnosis of TB meningitis
• Gene XPert /Xpert RIF can be done on CSF

Cryptococcal meningitis

• India ink sensitivity is 60% hence negative result does not exclude cryptococcal meningitis
• CSF CRAG and culture are more sensitive and specific

Treatment Objective

• Identify and treat the causative organisms
• Prevent complications
• Prevent spread to contacts
• Maintain good nutrition

Non-pharmacological

• Secure the airway
• Nasogastric tube feeding if applicable

Pharmacological

Bacterial Meningitis

Adult

• Ceftriaxone 2g IV 12 hourly for 10 - 14 days

Alternatively

• Benzylpenicillin 4MU 6 hourly + Chloramphenicol 1g 6 hourly for 10 – 14 days
• Adjust antibiotic treatment as per CSF results.
• TB meningitis - treat as per Malawi TB Treatment guidelines
• Cryptococcal meningitis – refer to Cryptococcal Meningitis management in 2021

Clinical Management of HIV in Children and Adults (5th edition, 2021)

Viral Meningitis

• Herpes Simplex Virus
• Acyclovir 10mg/kg IV 8 hourly for 14 – 21 days

Complications and Referral Criteria

Refer all patients not responding to treatment within the first 48 hours for specialist care.

Neonates

• Give Benzyl Penicillin and Gentamycin IM or IV
• When a lumber puncture cannot be done prior to referral, this should be done as soon as possible after admission