MEPs above the injury site.

<p>MEPs recorded from the resting BB and FDI of representative patients with a T3-T5 (A) and T6-T12 (B) injury, while the other side remained at rest or performed 70% of index finger abduction or elbow flexion. Group data (C, healthy controls, n=17 and T3-T5, n=6; D, healthy controls, n=17 and T6-T12, n=14). The abscissa shows the muscle tested (BB and FDI). The ordinate shows the size of FDI and BB MEPs as a % of the baseline FDI and BB MEPs. Note that the increase in FDI and BB MEP size during contralateral index finger abduction and elbow flexion in both groups of patients was similar to healthy controls. Error bars indicate SEs. *p<i><</i>0.05.</p

Experimental Set-up.

<p>Diagrams show the posture of the hand, elbow, and foot used during testing. Three motor tasks were randomly tested. In task 1 (A), subjects were seated in an armchair with both arms flexed at the elbow by 90° with the forearm pronated and the wrist and forearm restrained by straps. In this task, crossed motor evoked potential (MEP) facilitation was examined in the first dorsal interosseous (FD, motoneurons located at C8-T1) muscle. In task 2 (B), subjects were seated in an armchair with both shoulders and elbows flexed by 90°. In this task crossed MEP facilitation in the biceps brachii (BB, motoneurons located at C5-C6) muscle was tested. In task 3 (C), subjects were seated in an armchair with both feet attached to a footplate. Here crossed MEP facilitation was tested in the tibialis anterior (TA, motoneurons located at L4-L5) muscle. During all tasks subjects were at rest while the contralateral side remained at rest or performed 70% of MVC into index finger abduction (A), elbow flexion (B), and ankle dorsiflexion (C).</p

Segmental level of injury and MEPs.

<p>Schematics of the spinal cord illustrating segments above the injury (white area), at the injury site (black shaded area), within 5 segment below the injury (dark gray shaded area) and greater than 5 segments below the injury site (5-8 segments light shaded area; 17-23 segments light gray-striped area). (B) MEPs recorded from the BB, FDI, and TA in all motor tasks and patients tested are plotted as a function of the segmental level of injury. The abscissa shows the number of segments (grouped by 3 segments) from all muscles tested. The ordinate shows the size of MEPs as a % of the baseline MEPs in all muscles. Note that when the muscle tested was at or within 5 segments below the injury the size of MEPs remained unchanged during 70% of MVC compared to rest. Whereas, when the muscle tested was more than 5 segments below the injury the size of MEPs was increased and aberrantly high at longer distances during 70% of MVC compared to rest. Error bars indicate SEs. </p

MEPs below the injury site.

<p>MEPs recorded from the resting BB, FDI, and TA of representative patients with a C2-C4 (A) and C5-C7 injury (B), while the other side remained at rest or performed 70% of index finger abduction, elbow flexion, or ankle dorsiflexion. Group data (C, healthy controls, n=17 and C2-C4, n=7; D, healthy controls, n=16 and C5-T7, n=11). The abscissa shows the muscle tested (BB, FDI, and TA). The ordinate shows the size of BB, FDI, and TA MEPs as a % of the baseline BB, FDI and TA MEPs. Note the increase in FDI and TA MEP size during contralateral index finger abduction and elbow flexion, but not in BB MEPs during elbow flexion in patients with C2-C4 injuries. Interestingly, TA MEPs size was increased in both groups of patients more than in healthy controls. Error bars indicate SEs. *p<i><</i>0.05.</p

MEPs at the injury site.

<p>(A) MEPs recorded from the resting BB and FDI of representative patients with a C5-C6 and C8-T1 SCI, while the other side remained at rest or performed 70% of elbow flexion or index finger abduction. Group data (B, healthy controls, n=17; C5-C6, n=9, C8-T1, n=5). The abscissa shows the muscle tested (BB and FDI). The ordinate shows the size of BB and FDI MEPs as a % of the baseline BB and FDI MEPs. Note the increase in BB and FDI MEP size during contralateral index finger abduction and elbow flexion in healthy controls, but not in patients with C5-C6 and C8-T1 SCI. Error bars indicate SEs. *p<i><</i>0.05.</p