Aseptic meningitis: causes, symptoms, diagnosis, and management

Aseptic meningitis is meninges inflammation with negative routine bacterial cultures. Most often viral and self-limited, it requires evaluation to exclude treatable causes and to guide therapy.

Overview

Aseptic meningitis describes inflammation of the membranes that surround the brain and spinal cord when routine bacterial cultures of cerebrospinal fluid (CSF) do not grow typical bacterial pathogens. The term emphasizes a negative standard bacterial culture rather than proving a viral cause. It is one category of meningitis and involves the protective layers around the brain, collectively called the meninges. The process involves inflammation, which produces symptoms similar to bacterial meningitis and therefore usually prompts urgent evaluation.

Common causes

Viral infections — Viruses are the most frequent cause of aseptic meningitis. Enteroviruses, including those that cause hand, foot and mouth disease, are common culprits (enterovirus). Other viral causes include herpesviruses, mumps, arboviruses such as West Nile, and infections associated with HIV. See general information on viral causes.
Partially treated bacterial infection — Prior or early antibiotic treatment can sterilize CSF cultures even when bacteria are responsible, so clinicians often consider possible bacterial infection until it is excluded.
Mycobacterial, fungal and other organisms — Tuberculosis (tuberculosis), certain fungi and slow‑growing organisms may give culture‑negative CSF initially.
Other infectious agents — Some systemic infections or atypical organisms (for example Mycoplasma associated with respiratory disease) have been linked to aseptic meningitis presentations.
Sexually transmitted and bloodborne infections — Some sexually transmitted infections and systemic infections such as sexually transmitted viruses and bacterial infections including syphilis may involve the meninges.
Noninfectious causes — Certain medications and immunologic conditions can cause meningitis without an identifiable bacterial pathogen. Drug‑associated cases include reactions to some nonsteroidal anti‑inflammatory drugs and other agents (drug-related). Autoimmune or inflammatory disorders such as sarcoidosis or Behçet disease may present with meningeal inflammation.

Symptoms and clinical features

Presentation commonly includes sudden headache, fever, neck stiffness, photophobia and sensitivity to bright light, nausea or vomiting, and general malaise. A rash may occur with some viral causes. Infants and young children may have nonspecific signs such as irritability, poor feeding, or lethargy. Focal neurologic deficits, seizures, or rapidly worsening consciousness suggest more severe disease (for example bacterial meningitis or encephalitis) and require urgent investigation.

Diagnosis

Definitive evaluation usually requires lumbar puncture to obtain CSF for cell count and differential, glucose, protein, Gram stain and routine culture. Modern molecular tests such as polymerase chain reaction (PCR) can detect viral genetic material and have reduced the proportion of cases labeled purely "aseptic." Typical viral CSF shows an increased white cell count with lymphocyte predominance and normal or mildly reduced glucose. Early viral meningitis may show more neutrophils. Imaging (CT or MRI) is used selectively before lumbar puncture when there are focal signs or elevated intracranial pressure concerns. Additional tests depend on the clinical context: blood cultures, specific serologic tests, and targeted PCRs for herpes simplex, enterovirus, or arboviruses.

Treatment and prognosis

Treatment is directed at the suspected cause. Many viral cases are self‑limited and treated supportively with fluids, analgesics and observation; patients typically recover over days to a couple of weeks. When herpesviruses are suspected, early antiviral therapy is indicated pending test results. Because bacterial meningitis can be life‑threatening and may yield negative cultures after antibiotics, empiric antibacterial therapy is often started until bacterial infection is confidently excluded. People who are immunocompromised, very young, or show severe or progressive neurologic signs may require hospitalization, broader testing and intensive treatment.

Risk factors, prevention and when to seek care

Risk factors include recent exposure to someone with a viral illness, close contact settings (daycare, dormitories, healthcare), immune suppression and certain drug exposures.
Prevention measures that reduce some causes include routine childhood vaccination (for infections such as mumps and measles), careful hand hygiene, and safer sexual practices to lower sexually transmitted risks.
Seek immediate medical attention for high fever, severe headache, neck stiffness, altered mental state, repeated vomiting, or signs of decreased consciousness. Early assessment can distinguish aseptic from bacterial meningitis and guide appropriate treatment.

For further general topics and patient information see links to basic resources: meningitis overview, brain anatomy, inflammation, meninges, bacterial infections, viral infections, enteroviruses, sexually transmitted infections, syphilis, HIV, pneumonia and Mycoplasma, tuberculosis, drug-related causes, and sarcoidosis and inflammatory disorders.