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Fig 1. A, Axial SPGR images showing truncation of the left precentral gyrus (upper row) and activation to sequential finger tapping (white arrows). The left postcentral gyrus (red arrow) extends anteriorly around a truncated precentral gyrus, and comes near the posterior aspect of the left middle frontal gyrus (yellow arrow). Nearly continuous activity spanning from truncated precentral gyrus to overlapping postcentral gyrus is notable. Demarcating the boundary between M1 and S1 cortex is not possible at preoperative functional MRI (fMRI). B, Activation (white arrow) to right ankle movement is shown superimposed onto fluid-attenuated inversion recovery (FLAIR) images, yielding only slight activity. Slighter than typically observed activity to the lower-extremity task may be due to a combination of tumor-induced neurovascular uncoupling and the limitations of the task, and probably underestimates the actual distal lower-extremity M1 cortical field. In A and B, the proximity of eloquent lower-extremity and upper-extremity M1 cortex to the anterior-medial and anterior-lateral borders of the mass, respectively, are notable.
