Differentials
Sepsis
SIGNS / SYMPTOMS
Think 'Could this be sepsis?' based on acute deterioration in a patient in whom there is clinical evidence or strong suspicion of infection.[39] Sepsis (and septic shock) may also be present in children with bacterial meningitis as part of the severe infection.
INVESTIGATIONS
Blood or other body fluid cultures are diagnostic.[39]
Encephalitis
SIGNS / SYMPTOMS
Abnormal cerebral function, such as altered behaviour and speech or motor disorders, particularly when associated with fever, suggests encephalitis.
INVESTIGATIONS
MRI scan.
Electroencephalogram (EEG).
Cerebrospinal fluid (CSF) analysis.
Viral meningitis
SIGNS / SYMPTOMS
Relevant exposure history.
No differentiating symptoms and signs.
INVESTIGATIONS
Cerebrospinal fluid (CSF) pressure is usually normal.
CSF WBC count may be normal or 10-500/microlitre and has a lymphocytic differentiation.
CSF glucose is normal and CSF protein is slightly elevated.
Bacterial culture of CSF is negative.
Polymerase chain reaction (PCR) for enteroviruses and herpes viruses.
Cerebral malaria
SIGNS / SYMPTOMS
Relevant travel history to endemic region.
INVESTIGATIONS
Blood film (thick and thin) for microscopy.
Rapid diagnostic tests.
Drug-induced meningitis
SIGNS / SYMPTOMS
No differentiating symptoms and signs.
History of culprit drug use (e.g., non-steroidal anti-inflammatory drugs, trimethoprim/sulfamethoxazole, amoxicillin, ranitidine).
INVESTIGATIONS
This is a diagnosis of exclusion. Cerebrospinal fluid typically shows a neutrophilic pleocytosis. Symptoms resolve once the causative drug is stopped.
Tuberculous meningitis
SIGNS / SYMPTOMS
History of contact or residence in an endemic area.
Symptoms and signs of pulmonary and extraneural disease.
INVESTIGATIONS
Cerebrospinal fluid (CSF) smear and culture: sensitivity of smear >50% if repeated drops of CSF sediment dried on a slide and then stained and examined at length. Culture requires large volume for maximum sensitivity.
Skin testing or interferon gamma-based blood tests for exposure to Mycobacterium tuberculosis are supportive, but negative results do not exclude diagnosis of tuberculosis.
CSF may show a neutrophil rather than a lymphocytic infiltrate early in the infection.[15][50]
Fungal meningitis
SIGNS / SYMPTOMS
Presentation is often insidious with onset of headache and fever over weeks or months. A rash resembling molluscum contagiosum may be present in disseminated cryptococcal disease.
Rare in healthy children; consider if the child is immunocompromised.
INVESTIGATIONS
Testing cerebrospinal fluid (CSF) for cryptococcal antigen has a sensitivity of almost 100% for cryptococcal meningitis.
In patients who are HIV-positive the fungal burden is high, leading to high CSF pressures. CSF leukocyte count may be low. India ink stain or cryptococcal antigen is usually positive.
Patients who are HIV-negative have higher CSF leukocyte counts, and India ink stain is positive in only half of cases.
Non-central nervous system infections
SIGNS / SYMPTOMS
Includes retropharyngeal abscess, tonsillitis, cervical lymphadenitis, otitis media, and mastoiditis. Can present with symptoms that mimic meningitis such as fever, irritability, neck stiffness, or headache.
INVESTIGATIONS
Usually identified on examination
Other cause of reduced conscious level
SIGNS / SYMPTOMS
Includes seizures, toxin or drug ingestion, neurotrauma, metabolic disturbance, and neurovascular events.
INVESTIGATIONS
History and examination.
Blood tests.
Neuroimaging.
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