Hyperintense signal in pyramidal tract neurons in postoperative brain tumor: wallerian degeneration or neoplastic dissemination?

A 46-year-old man presented with behavioral changes and partial seizures over 20 days. Neurological examination showed mental confusion. Brain MRI showed a ringshaped lesion in the left frontal lobe (A and B). Surgery was performed (C) and pathology confirmed glioblastoma multiforme. The patient underwent radiotherapy and che motherapy. A control MRI (eight months later) showed hyperintense signal in the left pontine base (D and E), suggesting wallerian degeneration or neoplastic dissemination. Four months later, there was a marked increase in lesion size, confirming that the hyperintense signal in the pyramidal tract was neoplastic dissemination (F). Follow-up imaging may differentiate wallerian degeneration from tumor spread1,2.