Gliomatosis cerebri mimicking acute viral encephalitis and with malignant transformation of partial lesions: A case report

Gliomatosis cerebri (GC) is a rare glial neoplasm, characterized by extensive diffuse brain infiltration and relative preservation of the underlying architecture. In the present case report, a patient with type 2 GC, which mimicked the clinicoradiological course of acute viral encephalitis, is presented. A 56-year-old male presented with fever, dizziness, headache and numbness in the right extremities three days prior to admission to hospital. The cerebrospinal fluid (CSF) showed mild pleocytosis. Brain magnetic resonance imaging (MRI) revealed hyperintensity on fluid-attenuated inversion recovery images in the left frontal, temporal, insular lobes and in the left thalamus. No signal enhancement was observed following gadolinium administration. The patient was diagnosed with acute viral encephalitis of unknown cause and received a 10-day course of acyclovir, intravenously. At the follow-up three months later, the patient had personality changes and memory deterioration. The results from the follow-up MRI revealed no remarkable changes. At the follow-up six months after presentation, the patient had expressive aphasia and severe headaches. Subsequently, the patient had two tonic-clonic seizure onsets. The results from the MRI showed an increase in lesion size, more edema around the lesion and irregular enhancement in the left frontal lobe. However, the lesions in the left temporal and insular lobes and in the left thalamus were nearly unchanged. Magnetic resonance spectroscopy (MRS) showed elevated choline (Cho)/creatine (Cr) and Cho/N-acetylaspartate (NAA) ratios, as well as decreased NAA/Cr ratios. Surgery was performed and the neuropathological diagnosis of WHO grade III astrocytoma was confirmed. Thus, it is important to pay attention to the differential diagnoses of GC and acute viral encephalitis in patients who have widespread MRI lesions. A brain biopsy is recommended for a diagnosis in this case.