Influence of placement sites of the active recording electrode on CMAP configuration in the trapezius muscle

When stimulating the accessory nerve, a current spread occurs to the C5 spinal nerve root and another CMAP originating from the supraspinatus muscle occurs in the supraspinous fossa. The volume conduction from the supraspinatus muscle affects the active recording electrode on the TM, resulting in an increase in CMAP amplitude.