Herpes Simplex Encephalitis initially erroneously diagnosed as glioma of the cerebellum. Case report and literature review

Background Herpes simplex encephalitis caused by herpes simplex has an estimated annual prevalence in the order of 1 in 250,000 to 500,000 patients and is considered to be the most usually encountered nonendemic pathogenic cause of lethal encephalitis in well-developed countries. There are a few cases reported in the literature in which a diagnostic dilemma between was raised between herpes simplex encephalitis and brain glioma and a definitive diagnosis was difficult to obtain. Case Description We report the case of a 5-year-old girl with a previous medical history of premature thelarche. As a part of her investigation, magnetic resonance imaging of the brain was performed, which revealed a space-occupying lesion of the posterior fossa. Magnetic resonance spectroscopy was performed, which advocated for the diagnosis of glioma. She was operated on, but the histopathologic analysis failed to verify the imaging findings. Herpes simplex virus (HSV) 1 was detected in cerebrospinal fluid (CSF) samples. Follow-up magnetic resonance imaging scans illustrated the progression of the disease. Conclusions The accumulation of data regarding CSF sample analysis, electroencephalography, brain biopsy, and imaging findings, along with the progression of the clinical picture of our patient, verified the diagnosis of HSV encephalitis. When confronted with confounding data that can pose a diagnostic dilemma between HSV encephalitis and glioma, brain biopsy and polymerase chain reaction of CSF samples could be able to verify the definitive diagnosis. When interpreting our results, we always have to consider the evolution of the clinical picture.