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 non endemic 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 be obtained. Case presentation We report the case of a five year old female with previous medical history of premature thelarche. As a part of her investigation, an MRI of the brain was performed, which recognized a space-occupying lesion of the posterior fossa. An MRS was performed which advocated over the diagnosis of glioma. She was operated on but the histopathological analysis failed to verify the imaging findings. HSV 1 was detected in CSF samples. Follow up MRI scans illustrated the progression of the disease The accumulation of data regarding CSF sample analysis, EEG, brain biopsy and imaging findings, along with the progression of the clinical picture of our patient, verified the diagnosis of HSV encephalitis. Conclusions When confronted with confounding data that can pose a diagnostic dilemma between HSV encephalitis and glioma, brain biopsy and PCR of CSF samples could be able to verify the definite diagnosis. When interpreting our results, always we have to consider the evolution of the clinical picture.