Aseptic Meningitis

Today we discussed a case of decreased level of consciousness and confusion in a 35-year old man.

We started by discussing the relatively young population we serve on general medicine we see here at St. Mike's. There are important factors that cause illness in this young patient population (more broadly social or societal determinants of health):

• Poverty
• Mental illness
• Substance use (often on the basis of mental illness)
• HIV prevalence in the community we serve
• An "early hit" - for example, traumatic brain injury or spinal cord injury leading to chronic illness.

The patient underwent a CT head and lumbar puncture, which demonstrated a lymphocytic pleocytosis. The differential diagnosis for a lymphocytic pleocytosis is actually broader than just viral meningitis:

• Viral meningitis (most commonly enteroviridae, arboviridae, HIV-1, and HSV-1 & 2)
• Less common viral etiologies include lymphocytic choriomeningitis virus and mumps, as well as EBV, CMV, influenza, measles, rubella, and VZV
• Mycobacterial and listeria infections
• Neurosyphilis
• Leptospira, toxoplasma, and fungi such as cryptococcus
• Lymphomatous meningitis & meningeal carcinomatosis
• Drug-induced aseptic meningitis

Diagnosis is made primarily with CSF analysis with cell count and differential, glucose, protein, CSF culture, and viral PCR (nucleic acid amplification of viral specific DNA or RNA, especially looking for HSV-1 and enteroviridae).