Functional MR Imaging of the Cervical Spinal Cord by Use of Median Nerve Stimulation and Fist Clenching
Walter H. Backesa,
Werner H. Messa and
Jan T. Wilminka
a From the Departments of Radiology (W.H.B., J.T.W.) and Clinical Neurophysiology (W.H.M.), University Hospital Maastricht, Maastricht, the Netherlands.
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FIG 1. Example of a compound muscle action potential recording evoked by electrical median nerve stimulation. The small signal deflection (left) represents the compound muscle action potential measured on the flexor carpi radialis muscle, and the strong zigzag pattern (right) is caused by the strong gradient switching of the running MR imaging system
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FIG 2. Example of the time course of the MR imaging signal evoked by median nerve stimulation in a spinal cord voxel. During execution, the paradigm proceeds as follows: rest, right hand stimulation, rest, left hand stimulation, and so on. In each 30-s epoch, five images were acquired. The black dots and lines represent the raw data; the red curve, the model function fitted to the responses. Note the considerable left-right differences in amplitude despite the standardized stimulus intensity
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FIG 3. Example of a statistical parametric map obtained in an fMR imaging session with median nerve stimulation. Sagittal views of the statistical parametric maps of the fMR imaging responses superimposed on the first acquired T2*-weighted image (A) and the spatially corresponding anatomic T1-weighted image section (B). The voxels displayed in colors of the activation pattern analyzed with a statistical threshold of P < .01. Vertebrae C7 and T1 are indicated. The color bar indicates the statistical Z values
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FIG 4. Transverse images in the lower cervical cord acquired during fMR imaging sessions.
A, fMR imaging responses evoked predominantly within the cord as well as on the cord surface during the fist-clenching task.
B, Illustration of the veins on the cord surface in a transverse cross-section. (Radiograph reproduced with permission by A.K. Thron.)
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