gms | German Medical Science

Diffuse glial tumors with bithalamic involvement are rare in children and sometimes difficult to differentiate from non tumorous disorders due to unspecific radiological findings. Stereotactic biopsy in these cases not always proves a glial tumor but unspecific reactive changes.

In order to enhance the diagnostic yield we performed image fusion with the recently described amino acid analogue O-(2-(¹⁸F)-fluoroethyl)-thyrosine-(FET)-PET and MRI. Stereotactic biopsy was planned with neuronavigation and stereotaxy system simultaneously and additional information from MRI-spectroscopy and CT.

Since 2002 we saw two children presenting with signs of raised intracranial pressure. MRI showed symmetric expansion of the thalamic structures with diffuse hyperintensity on T2/FLAIR sequences. No contrast uptake was observed. In one child additional hyperintensity was found in the right temporal lobe and right cerebellar hemisphere. MRI spectroscopy (thalamic voxel) was typical for glial tumors in both children. In the first patient FET-PET revealed an unexpected hot spot in the left cerebellar hemisphere with a brain/tumor ratio of 3.8 compared to 1.8 in the thalamus. Accordingly stereotactic biopsy was taken there and an anaplastic astrocytoma was diagnosed. The other patient showed a higher uptake (brain/tumor ratio 2.0) in the left dorsal thalamus compared to a homogeneous hyperintensity of the bilateral thalamus on MRI. Stereotactic biopsy resulted in astrocytoma WHO grade II. Target point planning was realized with both neuronavigation and stereotaxy system.

Image fusion with FET-PET, MRI and CT for multimodal planning can enhance the diagnostic yield of stereotactic biopsies in diffuse glial tumors in children.