Differential Diagnosis for a 3-year-old girl with symptoms of fever, lethargy, and cervical rigidity

The patient's presentation and laboratory results guide the differential diagnosis. Here's the organized differential diagnosis:

• Single most likely diagnosis

  • B. Bacterial meningitis: The high fever, lethargy, cervical rigidity, elevated WBC count in the CSF with a predominance of neutrophils, low glucose, and high protein levels are all indicative of bacterial meningitis. The absence of organisms on the Gram stain does not rule out this diagnosis, as the sensitivity of Gram stain can be low, especially if the sample is not properly prepared or if the organism is difficult to stain.

• Other Likely diagnoses

  • C. Viral meningitis: Although the CSF profile (high neutrophil count, low glucose) is more suggestive of bacterial meningitis, some cases of viral meningitis can present with atypical CSF findings, especially early in the course of the disease. However, the glucose level is typically not as low as in bacterial meningitis.
  • D. Subdural hematoma: While less likely given the CSF findings, a subdural hematoma could cause increased intracranial pressure and potentially lead to symptoms like lethargy and cervical rigidity. However, the CSF findings would not typically show such a significant inflammatory response unless there was an associated infection.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Bacterial meningitis (already discussed): Given its high mortality and morbidity if not promptly treated, ensuring the coverage of bacterial meningitis is crucial.
  • Subdural hematoma: Due to its potential for severe consequences if not promptly diagnosed and treated, it's essential to consider and rule out subdural hematoma, possibly with imaging studies.
  • Brain abscess or empyema: These conditions can present with similar symptoms and CSF findings to bacterial meningitis and require urgent diagnosis and treatment to prevent severe outcomes.

• Rare diagnoses

  • A. Brain tumor: While brain tumors can cause increased intracranial pressure and lead to symptoms like lethargy, they would not typically cause the acute onset of fever, cervical rigidity, and the specific CSF findings seen in this patient.
  • Fungal or tuberculous meningitis: These are less common causes of meningitis, especially in immunocompetent children, but should be considered in the appropriate clinical context (e.g., immunocompromised state, exposure history).
  • Other infectious causes (e.g., Lyme disease, syphilis): Depending on the geographic location and exposure history, other infectious causes could be considered, though they are less likely given the acute presentation and CSF findings.