Pachymeningitis Differential Diagnoses

Pachymeningitis refers to inflammation of the dura mater, the outermost meningeal layer covering the brain and spinal cord. The differential diagnoses for pachymeningitis can be categorized as follows:

• Single Most Likely Diagnosis
  • Tuberculous meningitis: This is a common cause of pachymeningitis, especially in regions with high tuberculosis prevalence. It often presents with chronic symptoms such as headache, fever, and neurological deficits.
• Other Likely Diagnoses
  • Bacterial meningitis (e.g., Streptococcus pneumoniae, Haemophilus influenzae): These infections can cause pachymeningitis, particularly in the context of sinusitis, otitis media, or following neurosurgical procedures.
  • Fungal meningitis (e.g., Cryptococcal meningitis): This is more common in immunocompromised patients and can cause chronic pachymeningitis.
  • Sarcoidosis: A systemic granulomatous disease that can involve the meninges, leading to pachymeningitis.
  • Rheumatoid pachymeningitis: A rare manifestation of rheumatoid arthritis, characterized by inflammation of the dura mater.
• Do Not Miss Diagnoses
  • Subdural empyema: An infection within the subdural space that can mimic pachymeningitis and requires urgent treatment to prevent severe neurological sequelae.
  • Malignant meningitis (e.g., carcinomatous meningitis, lymphomatous meningitis): These conditions have a poor prognosis and require prompt diagnosis and treatment.
  • Granulomatosis with polyangiitis (GPA): A vasculitic condition that can involve the meninges and present with pachymeningitis.
• Rare Diagnoses
  • IgG4-related pachymeningitis: A form of IgG4-related disease that can cause inflammation of the dura mater.
  • Eosinophilic pachymeningitis: A rare condition characterized by eosinophilic infiltration of the dura mater, often associated with parasitic infections or hypereosinophilic syndrome.
  • Syphilitic pachymeningitis: A manifestation of neurosyphilis that can cause inflammation of the dura mater, particularly in the tertiary stage of the disease.

Each of these diagnoses has distinct clinical and radiological features, and a thorough diagnostic workup, including imaging studies, cerebrospinal fluid analysis, and sometimes biopsy, is necessary to establish the correct diagnosis.