Cervical multisegmental motor responses in healthy subjects

Study design: Experimental design. Objectives: This descriptive design study presents multisegmental motor responses in the upper extremities after stimulation of cervical spinal vertebrae. Setting: Neuro Lab of Texas Woman's University, School of Physical Therapy, Texas, USA. Methods: In trial 1, C7 spinal segment was electrically stimulated in 13 healthy subjects using surface electrodes while recording responses from abductor digiti minimi (ADM), abductor pollicis brevis (APB), flexor carpi radialis (FCR) and biceps brachii ( BB) in the right upper extremity. In trial 2, C7 stimulation was carried out while recording responses from the APB and BB bilaterally. In trial 3, C7 stimulation was carried out while recording responses from the flexor hallucis brevis (FHB), soleus, vastus medialis (VMO) and gluteus medius (GM) in the right lower extremity. The amplitude of the signal and the deflection latency were the measured parameters. Descriptive statistics were completed on the data. Results: Results showed response amplitudes in all muscles of the upper extremities ranging from 328 to 1239 mu V, with the largest recorded from the APB and ADM, then the FCR and BB. Muscular responses were recorded simultaneously in bilateral muscles. Response latency was comparable, in bilateral similar muscles, and was varied from 6 to 16.5 msec, being longer in the ADM and APB, shorter in FCR and shortest in the BB. No lower limb muscles responded to C7 spinal stimulation, using current setup/method. Conclusion: These responses appear to be caused by stimulating the dorsal roots or motor nuclei of the cervical region and could be useful in testing patients with cervical spinal disorders. Spinal Cord (2012) 50, 432-439; doi:10.1038/sc.2011.166; published online 17 January 2012