Drug-induced aseptic meningitis

Lore & Background

Drug-induced aseptic meningitis (DIAM) presents with signs and symptoms similar to infectious meningitis, including headache, fever, neck stiffness, altered mental status, and neurological deficits such as numbness, paresthesias, seizure, or weakness. A key feature is recent exposure to a causative medication. The condition shows clinical improvement after cessation of the drug and a tendency to relapse upon resumption.

The pathogenesis of DIAM is poorly understood and may involve autoimmune hypersensitivity reactions, though it may vary depending on the inciting medication. For example, DIAM caused by OKT3 antibodies may be mediated by cytokine release. There is an association with underlying conditions such as systemic lupus erythematosus (SLE), Sjögren syndrome, idiopathic thrombocytopenic purpura, rheumatoid arthritis, HIV, and Crohn's disease.

Diagnosis involves ruling out infectious causes via lumbar puncture and CSF analysis, which in DIAM shows inflammatory changes such as elevated white blood cells and protein, with normal or low glucose. MRI and CT imaging may show blood-brain barrier disruption or cerebral edema. In patients with SLE, DIAM is distinguished from lupus aseptic meningitis by CSF neutrophilic predominance versus lymphocytic predominance, and by assessment of complement levels and signs of lupus flare.

Reader's Guide

Drug-induced aseptic meningitis (DIAM) is a clinically important condition because it mimics infectious meningitis but is reversible upon discontinuation of the causative medication. Its recognition prevents unnecessary antibiotic treatment and invasive procedures. The condition is associated with a wide range of drugs, including NSAIDs, biologic drugs like IVIG, antibiotics, antiepileptics, monoclonal antibodies, chemotherapeutic agents, and others. The pathophysiology remains uncertain, with possible autoimmune or cytokine-mediated mechanisms depending on the drug. Diagnosis relies on excluding infectious causes through CSF culture and PCR testing, and identifying recent drug exposure. Prognosis is excellent with prompt cessation of the offending agent. DIAM's significance lies in its role as a differential diagnosis in aseptic meningitis, particularly in patients with underlying autoimmune conditions or those on multiple medications.

Did You Know?

• Drug-induced aseptic meningitis (DIAM) is a noninfectious meningitis associated with medications such as NSAIDs and IVIG.
• DIAM generally shows clinical improvement after cessation of the medication and tends to relapse if the medication is resumed.

Defining the Condition and Its Diagnostic Overlap

Aseptic meningitis refers to inflammation of the meninges, the protective membranes that envelop the brain and spinal cord, occurring in patients whose cerebrospinal fluid tests return negative on routine bacterial cultures. Despite the term "aseptic," which might lead one to believe no infection is present, the condition frequently arises from pathogens such as viruses, mycobacteria, spirochetes, and fungi that standard laboratory techniques simply cannot detect. Medications and cancer-related complications also figure prominently among the recognized triggers. The diagnostic workup for aseptic meningitis largely mirrors that employed for bacterial meningitis: a lumbar puncture is performed to collect cerebrospinal fluid, which is then examined for elevated leukocyte levels and subjected to additional testing to pinpoint the true underlying cause. While the outward symptoms overlap considerably between the two forms, the severity of the illness and the appropriate therapeutic strategy ultimately hinge on identifying the specific agent responsible for the inflammation.

Clinical Presentation Across Age Groups

The clinical picture of aseptic meningitis shifts noticeably depending on the patient's age. Across the board, individuals may experience elevated body temperatures in the range of 38 to 40 degrees Celsius, vomiting, headaches, stiff neck pain, and diminished appetite. In infants, the presentation can be particularly alarming: meningeal inflammation may be accompanied by hepatic necrosis and myocarditis, and in severe cases, multi-organ failure can develop. Seizures and focal neurological deficits often serve as early warning signs in babies, where the mortality rate reaches a staggering 70 percent. Children tend to present with sore throat, rashes, and diarrhea alongside the classic signs. Adults generally experience a milder, shorter course of illness. Notably, the likelihood of developing aseptic meningitis rises in patients who have concurrent mumps or herpes infections. When the condition is triggered by an acute viral infection, symptoms typically persist for one to two weeks, though cytomegalovirus-related cases carry a 20 percent risk of mortality or significant morbidity, and untreated cases can impair hearing and learning abilities.

Etiology and the Drug-Induced Variant

Enteroviruses dominate the landscape of viral meningitis, accounting for approximately 90 percent of all viral cases. Other viral culprits include varicella zoster, herpes simplex types 1 and 2, human herpesvirus 6, mumps, and mosquito-borne flaviviruses such as West Nile virus and Saint Louis encephalitis. Bacterial agents responsible for Lyme disease, syphilis, and leptospirosis, as well as fungal infections including cryptococcal and coccidioidal disease, also feature in the differential. A distinct category is drug-induced aseptic meningitis, which arises when medications administered directly into the spinal canal or subarachnoid space irritate the meninges, provoking a hypersensitivity-driven immune response. Nonsteroidal anti-inflammatory drugs, certain antibiotics such as trimethoprim-sulfamethoxazole and amoxicillin, and antiepileptic medications have all been implicated. Autoimmune conditions like systemic lupus erythematosus, neoplastic meningitis affecting roughly 5 percent of cancer cases with a predominance in leukemias, and neurosarcoidosis round out the spectrum of recognized causes.

Diagnostic Workup and Therapeutic Approach

Diagnosing aseptic meningitis requires clinicians to weigh the season, the patient's and family's medical history, physical findings, and laboratory data together. The cornerstone of the workup is lumbar puncture, in which a needle is inserted between two vertebrae to extract cerebrospinal fluid. That fluid is then subjected to microscopic examination, cell counts, Gram staining, viral cultures, and polymerase chain reaction testing. PCR has notably expanded the ability to detect enterovirus, cytomegalovirus, and herpes virus within the fluid, though many viral agents still evade identification. Additional laboratory work includes blood, urine, and stool samples, while computed tomography or magnetic resonance imaging may be employed to visualize calcifications or abscesses. On the treatment side, patients with abnormal cerebrospinal fluid levels are typically hospitalized for antiviral therapy. When herpes simplex virus is identified as the causative agent, acyclovir is the prescribed antiviral. The condition was first described by Wallgren in 1925, and mumps-related cases have declined in the United States owing to widespread vaccination.