Spontaneous Cranial Epidural Inflammatory Granuloma Mimicking Brain Tumor: A Case Report

Here, we report a case of spontaneous cranial epidural inflammatory granuloma occurring in an 87-year-old female patient. The patient had a longstanding history of diabetes, which was managed with insulin. She developed reading and speech difficulties 1 month prior to presentation, and on the day of her visit to the ER, she had a partial seizure. Non-contrast CT results showed an ill-defined iso- to mild hyperdense lesion on the left frontal lobe with severe perilesional edema, giving the impression of a brain tumor. Subsequent MRI results showed an irregular, rim-enhancing lesion involving the brain parenchyma and epidural space without diffusion restriction, suggestive of an infectious granuloma. An initial workup was performed, including various cultures and chest CT to rule out possible infectious sources, but all results were negative. Thus, an excisional biopsy was performed, and intraoperative findings revealed an epidural granulomatous lesion invading the dura and extending to the pial surface. Intraoperative tissue 16s rRNA polymerase chain reaction (PCR) was positive for Staphylococcus aureus, and tissue cultures later confirmed the strain to be methicillin-resistant S. aureus. After the PCR, the patient was additionally given vancomycin. She improved completely, regaining her previous average daily living function.