Similarities and differences in cervical and thoracolumbar multisegmental motor responses and the combined use for testing spinal circuitries

STUDY DESIGN

Experimental study.

OBJECTIVE

To determine similarities and differences of C7 and T11-12 multisegmental motor responses (MMR) studies for the upper limbs (UL) and lower limbs (LL).

SETTINGS

Neuroscience Lab, TWU (School of Physical Therapy, TX, USA).

METHODS

C7 and T11-12 percutaneous electrical stimulations were applied while recording muscle action potentials from ULs and LLs.

RESULTS

The procedure of cervical MMR (CMMR) was easier in application than thoracolumbar MMR (TMMR), requiring less current intensities but cause more "jolts" in the trapezius/shoulder complex, due to close proximity of the stimulation electrodes. CMMR evoked large amplitude motor responses in the millivolts range in (UL) muscles, but smaller amplitude signal in (LL) muscles (in microvolts). TMMR evoked large amplitude motor responses in both UL and LL (in millivolts). The MMR amplitude was generally larger in the UL as compared to the LL, in the distal limb muscles more than in the proximal limb muscles. CMMR and TMMR for the UL were comparable in amplitude, latencies and action potential shapes. Signal latencies were longer for distal limb muscles as compared to proximal limb muscles and were slightly longer for LL as compared to UL muscles. MMR signals were either biphasic or triphasic in shape.

CONCLUSION

CMMR and TMMR have similarities and differences in the methods and recording signal that must be considered during its clinical applications. Comparing the signal of the UL muscles with CMMR and TMMR could be a useful test for the integrity of the ascending and descending spinal pathways in patients with spinal cord injuries and diseases.

Intersession reliability of thoracolumbar multisegmental motor responses

STUDY DESIGN

Experimental design. Objective To determine test-retest reliability across sessions of the thoracolumbar multisegmental motor responses (MMR) in the upper and lower limbs of healthy subjects. Test-retest reliability of MMR has not been established or examined in previous studies.

SETTINGS

Neuro Laboratory of the Texas Woman's University (School of Physical Therapy, Houston, TX, USA).

METHODS

The MMR of 15 healthy subjects were tested over two sessions. T11-12 vertebral segments were electrically stimulated using surface electrodes. MMR signals of the upper and lower limbs were recorded, using surface electrodes, from the upper extremity muscles (abductor pollicis brevis, flexor carpi radialis, biceps brachii, triceps brachii), and from the lower extremity muscles (vastus medialis obliqus, medial hamstring, soleus, tibialis anterior). The peak-to-peak maximum amplitude and deflection latency were the dependent parameters. Data from the first session was compared with a second session (on a different day), using interclass correlation coefficient (ICC), to evaluate the reliability across sessions. In addition, data from the right limbs were compared with the left limbs.

RESULTS

MMR of the right and left, upper and lower extremities were comparable between limbs in all subjects. Further, signals were highly correlated between days of testing (ICC = 0.58-0.99) and was not statistically different between the two sessions in the same subject.

CONCLUSION

These results indicate that MMR studies could be useful for serial testing of patients with neurological disorders, such as spinal cord injuries and diseases.