What are the causes of aseptic meningitis?

Causes of Aseptic Meningitis

Aseptic meningitis is primarily caused by viral infections, with enteroviruses and herpes viruses being the most common etiological agents, accounting for at least 50% and up to 80% of all cases. 1

Definition

Aseptic meningitis is defined as a syndrome characterized by:

• Acute onset of meningeal symptoms
• Fever
• Cerebrospinal fluid pleocytosis
• Bacteriologically sterile cultures 1

Viral Causes

Viral agents are the predominant cause of aseptic meningitis:

• Enteroviruses - Most common cause, accounting for more than half of all cases 2

  • Coxsackie viruses
  • ECHO viruses
  • Over 90 different enterovirus serotypes exist 1

• Herpes viruses - Second most common cause 1

  • Herpes simplex virus type 2 (HSV-2) - More common than HSV-1 for meningitis 1
  • Varicella zoster virus (VZV) - Can occur with or without rash of chickenpox or shingles 1
  • HSV-1 - More commonly associated with encephalitis than meningitis 1

• Other viral causes - Less common but important to consider 1, 3

  • Cytomegalovirus (CMV)
  • Epstein-Barr virus (EBV)
  • Mumps virus
  • Lymphocytic choriomeningitis virus
  • Influenza viruses
  • Human herpesvirus type 6 (HHV-6)
  • Human immunodeficiency virus (HIV) 4

Non-Viral Infectious Causes

Several non-viral infectious agents can cause aseptic meningitis:

• Bacterial causes (culture-negative or partially treated) 5

  • Mycobacterium tuberculosis
  • Leptospira species
  • Brucella species
  • Borrelia burgdorferi (Lyme disease agent)
  • Other unusual bacterial organisms

• Fungal causes - May present initially with aseptic meningitis picture 4

Non-Infectious Causes

Aseptic meningitis can also result from non-infectious etiologies:

• Drug-induced meningitis 2

  • Various medications can trigger an aseptic meningitis syndrome

• Malignancy-related meningitis 2

  • Carcinomatous meningitis
  • Leukemic meningitis

• Systemic illnesses with meningeal involvement 2

  • Autoimmune disorders
  • Inflammatory conditions

Epidemiology

• Aseptic meningitis is the most common form of meningitis with an annual incidence of 7.6 per 100,000 adults 6
• Viral meningitis accounts for at least 50% and possibly up to 80% of all meningitis cases 1
• In the UK, enteroviruses and herpes viruses (predominantly HSV-2 and VZV) are the most common causes 1

Clinical Considerations

• Distinguishing between viral meningitis and bacterial meningitis is crucial due to differences in treatment and outcomes 1
• Viral meningitis is generally self-limited with a good prognosis 6
• Examination findings such as Kernig sign or Brudzinski sign have variable sensitivity and specificity for differentiating bacterial from aseptic meningitis 6
• Diagnosis relies on examination of cerebrospinal fluid obtained from lumbar puncture 6
• CSF should be tested for enteroviruses, HSV-1, HSV-2, and VZV by PCR when viral meningitis is suspected 1

Treatment Approach

• Most cases of viral aseptic meningitis require only supportive care 2, 6
• Specific antiviral therapy is indicated for certain causes:
  • VZV meningitis: Intravenous aciclovir at 10-15 mg/kg three times daily for 10-14 days 7
  • Consider corticosteroids for VZV meningitis with vasculitic component 7
• Non-viral infectious causes require targeted antimicrobial therapy 5

Important Pitfalls

• Failure to consider treatable causes of aseptic meningitis (e.g., tuberculosis, fungal infections, herpes simplex encephalitis) 4
• Delayed recognition of bacterial meningitis masquerading as aseptic meningitis 6
• Overlooking parameningeal infections that may initially present with aseptic meningitis features 4