gms | German Medical Science

Objective: Non-contrast enhancing gliomas are best depicted by fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). However, postoperative imaging likewise the standard procedure following resection of high-grade glioma, is prone to false positive FLAIR signal due to ischemia and edema of adjacent brain tissue.

Method: Patients who underwent resection of non-contrast enhancing gliomas within the last three years were included in this retrospective study. Patients were stratified for adjuvant therapy. Volumes of altered signals in FLAIR sequences were segmented (BrainLab), qualitative findings of diffusion and apparent diffusion coefficient (ADC) were captured and compared to first follow-up scans after 3 month.

Results: 42 patients met the inclusion criteria. Initial histology was astrocytoma in 20, oligoastrocytoma in 2, oligodendrogliom in 8, anaplastic astrocytoma in 7 and anaplastic oligodendroglioma in 5 cases. Mean volume of raised FLAIR signal in postop MRI was 21.1 ml (95% CI 10.7-31.5ml). According to 3 month MRI the mean volume of FLAIR was 14.9 ml (0-26.0ml). 12 patients (29%) revealed any raised diffusion signal with loss of ADC signal in postoperative MRI. The decrease in FLAIR intense volume consisted irrespective of diffusion and ADC findings. All but 2 patients (95%) revealed shrinkage of FLAIR intense volume after 3 month (p=0.015, paired-t-test).

Conclusions: Early postoperative MRI FLAIR sequences are unspecific. For determination of residual tumor delayed MRI after 3 month should be used.