Chronic meningitis is defined as inflammation of the cerebrospinal fluid (CSF) that persists for one month without spontaneous resolution. The etiologies can be grouped into categories of infectious, inflammatory, neoplastic or idiopathic. There is little literature available on defining the pathogens, risk factors, or mortality of patients with chronic meningitis.

Determine the infectious etiologies, comorbidities, and mortality of patients with chronic meningitis in central Pennsylvania

Cases were identified through retrospective review from our electronic medical record from 2004-2018, and were identified by having either two consecutive lumbar punctures (LP) with > 5 WBC/mL3 over 4 weeks, or by having 4 weeks of meningismus and one lumbar puncture with > 5 WBC/mL3. We excluded patients with diagnosis of human immunodeficiency virus (HIV). The study was approved by the institutional review board.

59 cases of infectious chronic meningitis were identified from this period. The most common pathogens were Borrellia burgdorferi (37%), Cryptococcus species (27%), and Candida species (10%). Viral etiologies were less common (13%), predominantly herpes simplex and varicella zoster viruses. Other bacteria included Streptococcus pneumonia and Pseudomonas species. One case was found to be secondary to prion disease. Comorbidities included diabetes (22%), renal disease (20%), and iatrogenic immunosuppression such as chemo/immunotherapy, steroids, or transplants (25%).

The study was done in a rural area endemic for Lyme disease and with a low prevalence of HIV infection. We found that Cryptococcus and Borrelia are the most common causes of chronic meningitis in this population, comprising 64% of all cases. Although it is a known pathogen among HIV-positive individuals, Cryptococcus should be considered even within HIV-negative individuals. We also found pathogens that are not typically associated with a chronic course (HSV/VZV, pneumococcus,  and Pseudomonas). This cohort had a high one year mortality (25%), with half these deaths associated with Cryptococcus but none from Lyme.