Identification of the primary motor cortex: value of T2 echo-planar imaging, diffusion-weighted imaging and...

To investigate the primary motor cortex (PMC) concerning T2 shortening on T2 echo-planar imaging (EPI-T2) and the double-layer sign on diffusion-weighted imaging (DWI), and also to measure its apparent diffusion coefficient (ADC).

3-T MR DWI was performed in 134 adult volunteers and 64 patients. T2 shortening was graded as hypointense or isointense compared with the signal of the superior frontal cortex (SFC). The double-layer sign of the PMC was graded as present or absent. Both findings (T2 shortening and double-layer sign) were evaluated independently by two authors. ADC of the PMC and the SFC were calculated using manually selected ROIs.

T2 shortening was found in 131 adults and 62 patients by author 1 and in 132 adults and 61 patients by author 2 (kappa = 0.96 and 0.91). The double-layer sign was found in 131 adults and 61 patients by author 1 and in 127 adults and 58 patients by author 2 (kappa = 0.94 and 0.91). ADC values of the PMC and the SFC were different for all subjects (p < 0.01).

T2 shortening and/or the double-layer sign on 3-T MR can be used to locate the PMC. The difference in ADC values between PMC and SFC is a distinguishing feature.