Anesthetic Fade in Intraoperative Transcranial Motor Evoked Potential Monitoring Is Mainly due to Decreased Synaptic Transmission at the Neuromuscular Junction by Propofol Accumulation.

BACKGROUND: We previously reported that normalization of motor evoked potential (MEP) monitoring amplitude by compound muscle action potential (CMAP) after peripheral nerve stimulation prevented the expression of anesthetic fade (AF), suggesting that AF might be due to reduced synaptic transfer in the neuromuscular junction. METHODS: We calculated the time at which AF began for each of craniotomy and spinal cord surgery, and examined whether AF was avoided by CMAP after peripheral nerve stimulation normalization in each. Similar studies were also made with respect to the upper and lower limb muscles. RESULTS: AF was observed in surgery lasting 160 minutes for craniotomy and 260 minutes or more for spinal surgery, and 195 minutes in the upper limb muscles and 135 minutes in the lower limb muscles. In all the series, AF could be avoided by CMAP after peripheral nerve stimulation normalization. CONCLUSION: AF of MEP occurred in both craniotomy and spinal cord surgery, and it was also corrected by CMAP after peripheral nerve stimulation. AF is considered to be mainly due to a decrease in synaptic transfer of the neuromuscular junction due to the accumulation of propofol because of the avoidance by CMAP normalization. However, it may be partially due to a decrease in the excitability of pyramidal tracts and α-motor neurons, because AF occurred earlier in the lower limb muscles than in the upper limb muscles.

Intravenous administration of mesenchymal stem cells derived from bone marrow after contusive spinal cord injury improves functional outcome.

Transplantation of mesenchymal stem cells (MSCs) derived from bone marrow has been shown to improve functional outcome in spinal cord injury (SCI). Systemic delivery of MSCs results in therapeutic benefits in a number of experimental central nervous system disorders. In the present study we intravenously administered rat MSCs derived from bone marrow at various time points after induction of a severe contusive SCI in rat to study their therapeutic effects. MSCs were systemically delivered at varied time points (6h to 28 days after SCI). The spinal cords were examined histologically 6 weeks after SCI. Stereological quantification was performed on the spinal cords to determine donor cell (MSCs transduced with the LacZ gene) density in the lesions. Light microscopic examination revealed that cavitation in the contused spinal cords was less in the MSC-treated rats. A limited number of cells derived from MSCs (LacZ(+)) in the injury site expressed neural or glial markers. Functional outcome measurements using the Basso-Beattie-Bresnehan (BBB) score were performed periodically up to 6 weeks post-SCI. Locomotor recovery improvement was greater in the MSC-treated groups than in sham controls with greatest improvement in the earlier post-contusion infusion times. The availability of autologous MSCs in large number and the potential for systemically delivering cells to target lesion areas without neurosurgical intervention suggests the potential utility of intravenous cell delivery as a prospective therapeutic approach in acute and subacute SCI.