Abstract
BACKGROUND: We present the rare case of a spontaneous intracranial subdural empyema caused by Helicobacter cinaedi in a preexisting chronic subdural hematoma (CSDH). CASE DESCRIPTION: A 72-year-old man with a history of the right CSDH that remained radiologically unchanged for the past 2 years with conservative management was transferred to our hospital because of fever and convulsive seizure. Systemic sources of infection were not identified. Fever and extremely high levels of serum C-reactive protein (CRP) spontaneously improved without antibacterial therapy. One month after the fever disappeared, brain computed tomography (CT) showed an increase in CSDH size. Mildly elevated CRP levels persisted without fever. Interval changes in shape on CT and hyperintense signals on diffusion-weighted magnetic resonance imaging (DWI) within the CSDH were observed with no neurological deficits. Five months later, the patient underwent craniotomy for a progressively enlarged CSDH. An infected organized hematoma was found, and copious pus was evacuated. Subsequently, an infected subdural hematoma (ISH) was diagnosed. Although bacterial cultures of the purulent specimen were negative, H. cinaedi was identified by gene sequencing analysis. Six months post antibiotic therapy, the ISH was under control, and abnormal DWI signals disappeared. CONCLUSION: To the best of our knowledge, this is the first report of ISH caused by H. cinaedi. This case suggests that ISH can follow a chronic course, mimicking the progressive expansion of subdural hematoma, and that H. cinaedi should be considered as a causative organism of ISH especially when conventional cultures are negative.