Distinguish reasons for the variety of intraoperative transcranial magnetic motor evoked potential: the anaesthesia or the operative injury / 中华外科杂志

<p><b>OBJECTIVE</b>To find a way to discriminate operative reason from anaesthesia reason for the changes of intraoperative transcranial magnetic motor evoked potentials (MEPs).</p><p><b>METHODS</b>In 26 patients under Etomidate/Fentanyl anesthesia from February 2001 to June 2004, MEPs elicited by transcranial magnetic stimulation were recorded from tibialis anterior muscles, simultaneously bispectral index (BIS) and train-of-four stimulation (TOF) were used to monitor the anesthesia depth and neuromuscular blockade respectively. MEP, BIS and measurements of TOF at different anesthesia depth and muscular relaxation were recorded synchronously, statistical analysis of this data set was done in order to find the inherent relationship between these variables.</p><p><b>RESULTS</b>Under anesthesia, MEP amplitude was always positively correlated with the corresponding BIS and TOF value. A regression equation could be built, with which the MEP amplitude could be reckoned based on realtime BIS and T(1)/T(c). In case of spinal cord injury, the measured amplitude value would significantly deviate from predicted one, which suggested that the change of MEP was because of the operation, but not the anaesthesia or neuromuscular blockade. Each patient had his or her own regression equation, which was different from each other.</p><p><b>CONCLUSIONS</b>The establishment of regression equation from MEPs, BIS and TOF is very useful to distinguish reasons of the changes of transcranial magnetic MEPs during surgery, and with this technique, the intraoperative MEP monitoring should be more reliable and practicable.</p>

The utility of neuronavigation in the microsurgery for cerebral cavernous malformations / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the utility of neuronavigation in the microsurgery for cerebral cavernous malformations.</p><p><b>METHODS</b>In a retrospective study, 47 patients with cavernous malformations were involved from January 1995 to December 2010. Fourteen cases admitted into hospital from January 1995 to December 2002 were treated without neuronavigation (conventional group), the focus localization was based on magnetic resonance imaging (MRI) images, anatomic landmarks, and the experiences of the neurosurgeon. In the other 33 cases admitted after February 2002 to December 2010, surgeries were performed with neuronavigation using the Medtronic Stealth Station TREON or TRIA system (neuronavigation group). Excision of the cavernomas were all performed microsurgically, surrounding gliotic rim and hemosiderin stained tissue were resected in the case of epilepsy, and a few patients underwent extended hippocampal resection or multiple subpial transection.</p><p><b>RESULTS</b>With the use of neuronavigation, the extent of craniotomy reduced from 5.2 cm to 3.6 cm (P < 0.01), and deeper cavernoma focuses could be treated surgically. There were no changes with regard to the mean size of the cavernomas, the mean time of surgery and hospital stay (P > 0.05), but the mean time of anaesthesia was prolonged from 164 min to 197 min (P < 0.01). Cavernomas were resected completely in all 47 cases, which was confirmed by postoperative MRI recheck. The conditions of all patients were improved or remain unchanged, and no significant differences in the clinical outcome could be evaluated between the two groups.</p><p><b>CONCLUSIONS</b>Application of neuronavigation-assisted microsurgery of intracranial cavernous malformations surgery, helps reduce the surgical trauma, and has security and reliability.</p>

The utility of transcranial magnetic motor evoked potential monitoring during spinal surgery / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the practicability and validity of transcranial magnetic motor evoked potential monitoring (TMS-MEP) during spinal surgery.</p><p><b>METHODS</b>From February 2001 to June 2004, 37 patients undergoing spinal surgery were involved, anaesthesia was maintained with volatile anesthetics in 11 operations and etomidate in 26. Analgesia was provided with fentanyl, and non-depolarizing muscle relaxant was given intermittently. MEPs elicited with transcranial magnetic stimulations were recorded from tibialis anterior muscles, simultaneously bispectral index (BIS) and train-of-four stimulation (TOF) were used to monitor the anesthesia depth and neuromuscular blockade respectively. The variety of MEP and its effect on surgical operation at different anesthesia depth and muscular relaxation were observed, and the muscle strength of the patients before and after operation were compared.</p><p><b>RESULTS</b>The 11 cases anesthetized with isoflurane or enflurane gave no response to TMS, the other 26 cases in which anaesthesia was maintained with etomidate and fentanyl gave satisfactory TMS-MEPs, but with significantly attenuated amplitudes and prolonged latencies (P < 0.05). Intraoperative MEP showed a grossly unchanged waveform, and its amplitude and latency had little fluctuation when anaesthesia and neuromuscular blockade maintained stable. When T(1) value of TOF at 40% - 60%, a steady MEP could be acquired and the muscular contraction after TMS should not interfere the operation.Seven of 26 cases had a MEP amplitude drop up to 50% or more during the operation, the surgical team was notified to avoid further spinal injury, at last only 1 case had a worsen muscle power after operation.</p><p><b>CONCLUSIONS</b>Myogenic TMS-MEP is a valid and practicable technique for intraoperative monitoring, and the etomidate + fentanyl technique is adequate for its anesthesia. BIS and TOF monitoring are helpful to maintain the steadiness of the anesthesia and MEPs, which is very important for monitoring the changes of the MEPs.</p>

Treatment of multisegmental intramedullary cervical spinal cord ependymomas / 中华外科杂志

<p><b>OBJECTIVE</b>To discuss the possibility of microneurosurgery techniques in the treatment of multisegmental intramedullary cervical spinal cord ependymomas.</p><p><b>METHODS</b>The clinical data of 26 cases of multisegmental intramedullary cervical spinal cord ependymomas patients was reviewed and analyzed.</p><p><b>RESULTS</b>There were 14 cases of cervical spinal cord ependymomas, 12 cases of cervical and thoracic spinal cord ependymomas. 4.5 spinal cord segments were involved in average. Incompletely inferior paraplegia was in 18 cases, incompletely high paraplegia in 8 cases, dyspnea in 6 cases, sphincter dysfunction in 10 cases. MRI detected syringomyelia formation in 24 cases. Vertebral lamina reposition were done in 20 cases. Muscle strength recovered in 21 cases, no change in 4 cases, aggravated in 1 case. All cases had total resection and 1 cases vertebral had instability in MRI.</p><p><b>CONCLUSIONS</b>Total resection of intramedullary cervical spinal cord ependymomas can be achieved by microneurosurgery. Most of the symptoms can be released after microsurgical treatment. After multisegmental laminotomy, the vertebral plate reposition should be done to ensure the stability.</p>

Experimental research of myogenic motor evoked potentials to transcranial magnetic stimulation for spinal cord monitoring / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the validity of intraoperative magnetic MEP (motor evoked potentials) monitoring in a spinal-cord-menaced surgery.</p><p><b>METHODS</b>32 rabbits were employed in weight-drop spinal cord contusion model. After anesthetized with a combination of Ketamine and Droperidol the spinal cords were surgically exposed with the dura intact, and the contusion injuries were delivered except the rabbits in control group. The MEPs were recorded and the relationship between the variation of the MEPs and the residual locomotor capacity after spinal cord injury was analyzed.</p><p><b>RESULTS</b>The 6 rabbits in mild-spinal-cord-injury group experienced transient attenuation of their TMS-MEPs, and the locomotor capacity remained intact (scores of 5) in almost all rabbits (5 of 6) when assessed 24 hours later; In the moderate-spinal-cord-injury group the 8 rabbits lost their TMS-MEP immediately after the weight-drop contusion, but they regained them partly in 1 hour one after another and scored 4 or 5 in the assessment of muscle power next day except for one score of 2; 8 rabbits had their spinal cords impaired severely in the contusion procedure and lost their TMS-MEP too but without recovery, their locomotor capacity outcomes were very poor, 5 of them had no response to transcranial magnetic stimulation next day, and in the other 3 rabbits we only found some polyphase waves with variant latency and lower amplitude which did not resemble common compound muscle action potential (CMAPs) evoked by TMS.</p><p><b>CONCLUSIONS</b>Myogenic TMS-MEPs was very sensitive to the spinal cord injury and should be a valid technique for intraoperative monitoring, and a slight change of them, even if a transient lose, should be unnecessarily related to a severe movement disorder. The warning threshold for a given patient should depend on the malady itself.</p>