Thoracolumbar multisegmental motor responses in the upper and lower limbs in healthy subjects

Abstract

Study design: Experimental design.Objectives: This descriptive study presents muscular responses from both the upper and the lower extremities during T11-12 segmental stimulation. Setting: Neuro Lab of the Texas Woman's University (School of Physical Therapy, TX, USA). Methods: A total of 13 healthy subjects were electrically stimulated using surface electrodes. In trial 1, signals were recorded from the flexor hallucis brevis, soleus, vastus medialis and gluteus medius in the lower right extremity. In trial 2, responses were recorded from the abductor digiti minimi, abductor pollicis brevis (APB), flexor carpi radialis and biceps brachii in the right upper extremity. In trial 3, stimulation was carried out and signals were recorded for both the upper and the lower extremities simultaneously, using different muscle combinations. Five traces per muscle were averaged for each step of the testing. Amplitude and deflection latency were the measured parameters and were compared using descriptive statistics. Results: Results showed signal amplitudes ranging from 85 to 821 mV in the upper extremity and from 582 to 3927 mV in the lower extremity, with the largest signal recorded in the soleus muscle and the APB. Response latency varies between 5.5 and 14 ms in the upper limbs and between 7.7 and 27 ms in the lower limbs and was comparable in bilateral recording. Conclusion: These muscular responses seem to be elicited from electrical stimulation of motor nuclei in lower limb muscles or from pathways to those nuclei in upper limb muscles, and could be useful in testing patients with spinal disorders.

Cervical multisegmental motor responses in healthy subjects

“…We recorded these potentials 11 This mild discomfort was only reported by our subjects at higher intensities, although such responses were also recorded at lower stimulus intensities.…”

“…No Hreflexes could be recorded from other muscles in upper limbs of relaxed subjects. 12 Response latency was comparable with bilateral recording for the APB and BB, and lend more support to direct spinal cord stimulation than to dorsal root stimulation. Root stimulation may result in longer latency on one side than the other.…”

“…In ADM and APB, active electrode was applied on the ball (motor point) of the muscle with the reference electrode distal to it (on the metacarpophalangeal (MP) joint). In FCR, the active electrode was applied on the motor point, about proximal 1/3 of the line drawn between the medial epicondyle and the radial styloid process, 12 with the reference electrode 2.5 cm lateral to it. In BB muscle, the active and reference electrodes were applied on the ball (motor point) of the muscle, midway between the shoulder and elbow levels.…”

“…12 In this method, the median nerve was electrically stimulated (1 msec, 0.2 pulses per second at H-max) at the cubital fossa using a surface electrode with the cathode proximal to the anode. FCR Hreflexes were recorded from the motor point of the muscle at the forearm with the reference electrode placed lateral to the active electrode.…”

“…It is hypothesized that, in healthy subjects, C7 electrical stimulation using surface electrodes will result in muscular responses in several upper limb muscles similar to T11-12 stimulation with lower limb multisegmental motor responses. 11 It is also hypothesized that muscular responses could be recorded in lower limb muscles with C7 electrical stimulation in healthy subjects.…”