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

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 mu V in the upper extremity and from 582 to 3927 mu V 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. Spinal Cord (2011) 49, 741-748; doi:10.1038/sc.2010.165; published online 21 December 2010