Use of a Brain Navigator to Identify the Precentral Knob of the Precentral Gyrus in Normal Subjects

BACKGROUND: The precentral knob of the precentral gyrus is the original site for hand somatotopy in the corticospinal tract, and it is considered an important target for neuromodulation. However, little is known about the anatomical location of the precentral knob for easy clinical use. This study aimed to describe the use of an optical tracking brain navigator to identify the anatomical location of the precentral knob in the precentral gyrus in normal subjects. MATERIAL/METHODS: Twenty healthy right-handed subjects were enrolled for this study. The locations of target and surface points in each subject were determined using a brain navigator. The target and surface points were defined as the precentral knob and the area of the scalp in the vertical direction from the target point, respectively. Then, by placing a marked 1-cm grid on each subject’s head, the horizontal and vertical distances from the midline central (Cz) were measured using the point marker. RESULTS: The average distance from Cz to the location of the precentral knob in the horizontal direction was 30.75 mm in the right hemisphere, 31.25 mm in the left hemisphere, and 31.00 mm in both hemispheres. The average distance from Cz to the location of the precentral knob in the vertical direction was −12.75 mm in the right hemisphere, −14.50 mm in the left hemisphere, and −13.62 mm in both hemispheres. CONCLUSIONS: This study showed that the anatomical location of the precentral knob in normal subjects could be identified using a brain navigator and this method may be used clinically for patients requiring neuromodulation.