Targeting optimal biopsy location in basal ganglia germinoma using 11C-methionine positron emission tomography

Abstract

Background Approximately 5% to 10% of intracranial germinomas arise from the basal ganglia or thalamus. Diagnosis is usually made by stereotactic biopsy, and precise location of the biopsy target is crucial because germinoma in these sites is potentially curable. We herein describe a case with germinoma in the basal ganglia that showed nonspecific clinical and radiological findings. The usefulness of MET-PET in locating an optimal biopsy target and monitoring treatment efficacy in this case is presented. Case Description A 9-year-old boy presented with a 4-month history of dystonia in his left upper extremity. Magnetic resonance imaging of the brain showed abnormal signal intensity in the right basal ganglia, internal capsule, and corona radiata without mass formation and enhancement effect. He had been treated as having multiple sclerosis without improvements on clinical and radiological findings. The MET-PET study showed increased tracer uptake in the areas of abnormal signal intensity on the MR images, and the MRI-PET co-registered images exhibited the highest tracer uptake in the anterior limb of the internal capsule. A stereotactic biopsy targeting the highest tracer uptake lesion was performed with histologic verification of germinoma. He was intensively treated with combined chemotherapy and radiotherapy according to the MR images and MET-PET findings. After the treatment, the area of abnormal signal intensity significantly reduced in size on the follow-up MRI and lesional tracer uptake was also decreased on MET-PET images. Conclusion The MET-PET study is very useful for locating a precise biopsy target and provides useful information in monitoring treatment efficacy in the basal ganglia germinoma that showed nonspecific radiological findings.