Central Nervous System Actinomycosis-A Clinicoradiologic and Histopathologic Analysis

Actinomycosis is an uncommon chronic suppurative infection that rarely affects the central nervous system (CNS). It is caused by filamentous Gram-positive anaerobic bacteria that is a normal commensal but causes suppurative and granulomatous inflammation after disruption of anatomical barriers. We report the largest series of 17 histologically confirmed cases of CNS actinomycosis and review clinical, imaging, and histopathologic features.

All histologically confirmed cases of CNS actinomycosis diagnosed between January 2010 and June 2016 were retrieved from the neuropathology records. The demographic profile, clinical, radiologic, microbiologic, and histologic features, treatment, and clinical outcomes were reviewed.

Seventeen cases were histopathologically diagnosed to have CNS actinomycosis. Nine of these were primarily admitted and managed in our institute, whereas the remaining 8 were referred to us for histopathologic diagnosis. Mean age at presentation was 31.4 years, with male predilection (3.25:1). Mean duration of symptoms was 2.95 months. Systemic symptoms were noted in 5 patients, although no systemic focus was detectable. Pachymeningitis was most common type (9; 52.94%), and chronic abscess was identified in 7. History of previous surgery for osteomyelitis was forthcoming in 3. All patients underwent surgical excision/aspiration of the lesions. Histologically, lesions revealed characteristic suppurative granulomatous response with giant cells and actinomycotic colonies were detected within necrotic centers. Cultures failed to grow Actinomyces in all. Follow-up data were available in 9 patients managed in our institute, and all had good outcomes at the median follow-up period of 32 months after antibiotic treatment for mean period of 8.4weeks.

Histopathology remains the cornerstone for diagnosis of actinomycosis as on culture confirmation is very rare.