N Alexeeva1, J G Broton, B Calancie. 1. The Miami Project to Cure Paralysis, University of Miami School of Medicine, FL 33136, USA.
Abstract
OBJECTIVES: To examine the basis for delay in the excitatory effects of transcranial magnetic stimulation (TMS) of motor cortex on motoneuron pools of muscles left partially-paralyzed by traumatic spinal cord injury (SCI). METHODS: The effect of subthreshold transcranial magnetic stimulation (TMS) on just-suprathreshold H-reflex amplitude was examined in subjects (n = 10) with incomplete cervical SCI, and in able-bodied (AB) subjects (n = 20) for comparison. EMG activity was recorded from the soleus and the abductor hallucis muscles, and H-reflex was elicited by stimulation of the tibial nerve behind the knee. Comparison of the peak-to-peak amplitude of the TMS-conditioned H-reflex to that of the H-reflex alone (i.e. unconditioned H-reflex) was made for different conditioning-test intervals with multivariate analysis of variance and (when called for) t testing. RESULTS: The absolute latencies of motor responses to suprathreshold TMS delivered during a weak voluntary contraction of the soleus and abductor hallucis were significantly prolonged in the SCI group relative to AB subjects. For the TMS-conditioned H-reflex, the time-course effect of TMS on the H-reflex amplitude in different AB subjects included an early effect (typically facilitation, but occasionally inhibition) seen between -5 and 0 ms, followed by a later period (i.e. >5 ms) of H-reflex facilitation. In contrast, the earliest indication of a TMS effect on H-reflex excitability in SCI subjects was between 5 and 10 ms after TMS. This difference between SCI and AB subjects of approximately 10 ms was similar to the prolongation of TMS-evoked response latencies in the soleus and the abductor hallucis muscles of the SCI subjects. CONCLUSIONS: The results suggest that motor conduction slowing after traumatic SCI most likely occurs across the population of the descending tract axons mediating the TMS-evoked motor responses.
OBJECTIVES: To examine the basis for delay in the excitatory effects of transcranial magnetic stimulation (TMS) of motor cortex on motoneuron pools of muscles left partially-paralyzed by traumatic spinal cord injury (SCI). METHODS: The effect of subthreshold transcranial magnetic stimulation (TMS) on just-suprathreshold H-reflex amplitude was examined in subjects (n = 10) with incomplete cervical SCI, and in able-bodied (AB) subjects (n = 20) for comparison. EMG activity was recorded from the soleus and the abductor hallucis muscles, and H-reflex was elicited by stimulation of the tibial nerve behind the knee. Comparison of the peak-to-peak amplitude of the TMS-conditioned H-reflex to that of the H-reflex alone (i.e. unconditioned H-reflex) was made for different conditioning-test intervals with multivariate analysis of variance and (when called for) t testing. RESULTS: The absolute latencies of motor responses to suprathreshold TMS delivered during a weak voluntary contraction of the soleus and abductor hallucis were significantly prolonged in the SCI group relative to AB subjects. For the TMS-conditioned H-reflex, the time-course effect of TMS on the H-reflex amplitude in different AB subjects included an early effect (typically facilitation, but occasionally inhibition) seen between -5 and 0 ms, followed by a later period (i.e. >5 ms) of H-reflex facilitation. In contrast, the earliest indication of a TMS effect on H-reflex excitability in SCI subjects was between 5 and 10 ms after TMS. This difference between SCI and AB subjects of approximately 10 ms was similar to the prolongation of TMS-evoked response latencies in the soleus and the abductor hallucis muscles of the SCI subjects. CONCLUSIONS: The results suggest that motor conduction slowing after traumatic SCI most likely occurs across the population of the descending tract axons mediating the TMS-evoked motor responses.
Authors: Qilin Cao; Xiao-Ming Xu; William H Devries; Gaby U Enzmann; Peipei Ping; Pantelis Tsoulfas; Patrick M Wood; Mary Bartlett Bunge; Scott R Whittemore Journal: J Neurosci Date: 2005-07-27 Impact factor: 6.167
Authors: Kelsey A Potter-Baker; Daniel P Janini; Yin-Liang Lin; Vishwanath Sankarasubramanian; David A Cunningham; Nicole M Varnerin; Patrick Chabra; Kevin L Kilgore; Mary Ann Richmond; Frederick S Frost; Ela B Plow Journal: J Spinal Cord Med Date: 2017-08-07 Impact factor: 1.985
Authors: Qilin Cao; Qian He; Yaping Wang; Xiaoxin Cheng; Russell M Howard; Yiping Zhang; William H DeVries; Christopher B Shields; David S K Magnuson; Xiao-Ming Xu; Dong H Kim; Scott R Whittemore Journal: J Neurosci Date: 2010-02-24 Impact factor: 6.167