Aseptic meningitis syndrome is associated with symptoms, signs, and laboratory evidence of meningeal inflammation with spinal fluid findings that suggest a viral or noninfectious origin. Clinically, patients present with headache, nausea, meningismus, and photophobia, symptoms that are also common in patients with bacterial meningitis. A stiff neck, with or without a Brudzinski or Kernig sign, may be observed. Patients usually appear nontoxic but may have changes in mental status, including irritability. Other signs of possible viral infection may include pharyngitis, adenopathy, morbilliform rash, and evidence of systemic viral infection, including myalgia, fatigue, and anorexia. There are usually no signs of vascular instability, and the course is often self-limiting.

Aseptic meningitis is a syndrome of multiple etiologies, both infectious and noninfectious (Table 75.1). Infections are usually of viral origin but also may be due to mycobacteria, fungi, rickettsiae, and parasites. Group B Coxsackieviruses (mostly serotypes 2 through 5) and echoviruses (mostly serotypes 4, 6, 9, 11, 16, and 30) are responsible for more than 90% of cases of viral meningitis. Herpesvirus, arboviruses, lymphocytic choriomeningitis virus (LCM), Lyme disease, leptospirosis, and acute human immunodeficiency virus (HIV) are the etiologic agents that make up most of the remaining infectious cases. Noninfectious causes include drug reactions, collagen vascular diseases (i.e., lupus erythematosus, granulomatous arteritis), sarcoidosis, cerebral vascular lesions, epidermal cysts, meningeal carcinomatosis, serum sickness, and nonfocal lesions of the central nervous system (CNS). Specific syndromes (i.e., Mollaret's meningitis, Still's disease) may produce a similar clinical picture. The etiologic diagnosis of aseptic meningitis is often complicated by the numerous possible causes and the lack of specific diagnostic tests.