Fig 4.

Figure shows the result of an finger-tapping experiment on a T1-weighted reference image (block design, self-paced finger tapping of the left hand). The examination was performed in the context of presurgical evaluation of a patient after recurrence of a frontocentral astrocytoma (World Health Organization grade III) in the right hemisphere. The tumor margins reach the precentral gyrus close to the hand area of the primary motor cortex. The motor area, as detected with fMRI, is marked in white (a). The central sulcus can be identified by using five anatomic features: 1, The superior frontal sulcus ends in the precentral gyrus (b). 2, The lower part of the precentral sulcus and the inferior sulcus define the T sign (c). 3, The bracket sign defines the interception of the marginal part of the cingulate sulcus and the central sulcus close to the midline (d). 4, The omega shape of the precentral gyrus defines the hand motor area, the hand knob of the primary motor cortex (e). 5, The relative thickness of the precentral gyrus to the postcentral gyrus (pre > post) can help in identifying the central sulcus (e)