tcMEPtranscrancial Motor Evoked Potential
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Surgical damage was discarded by the surgeons as well as for TcMEPs loss on the upper extremities and hypotension, hypercapnia, hypoxemia or anaemia by the anaesthesiologist.
To our knowledge, there is no report in the literature regarding the effect of droperidol on TcMEPs by electrical stimulation, even more since this drug it is not currently used since it was banished by the FDA.
Droperidol used as prophylaxis for preventing postoperative nausea and vomiting at standard doses (0.6-1.25 mg IV) administered prior to the end of the surgery temporally abolishes TcMEPs. Eliciting TcMEPs by applying a double train of stimuli can partially solve the suppression caused by droperidol.
The surgeons operated at two hospitals and had access to all four modalities: SSEP, TcMEP, sEMG, and tEMG performed by an experienced neurophysiologist.
For both cervical and thoracic deformity surgeries, all surgeons used at least SSEP and TcMEP. For cervical surgeries, 47% of surgeons additionally used sEMG, while for thoracic 71% of surgeons additionally used sEMG and tEMG.
However, in patients undergoing ACDF with symptoms of myelopathy, most surgeons (31%) used SSEP and TcMEP with only 13% using SSEP only.
For both anterior and posterior thoracic decompression, most surgeons preferred to use SSEP and TcMEP. If these procedures involved fusion with or without instrumentation, all four modalities were used most frequently (Table 3).
(91) Traynelis and associates then estimated that per 4-hour surgery, the cost of SSEP monitoring is $941.82, of TcMEP monitoring $1,114.77, and of combined SSEP and TcMEP monitoring $1,423.27, thus by not monitoring the previous 720 cases, over one-million dollars were saved.
Table 1 Distribution of IOM Modalities Used for Deformity Surgery * Surgery SSEP TcMEP SSEP SSEP SSEP sEMG TcMEP TcMEP sEMG tEMG sEMG tEMG tEMG Cervical fusion/ 38 50 -- -- instrumentation Thoracic fusion/ 71 12 12 -- instrumentation Lumbar fusion/ 47 0 12 12 instrumentation Surgery SSEP SSEP SSEP sEMG TcMEP sEMG tEMG tEMG Cervical fusion/ 13 -- -- -- instrumentation Thoracic fusion/ 6 -- -- -- instrumentation Lumbar fusion/ 6 6 12 6 instrumentation * Values represent percentage of surgeons.
TcMEPs involves stimulating electrodes, usually ranging from 75 to 900 V in amplitude and currents up to 0.9 A depending the electrode type used, which is placed into the scalp over the motor cortex.
TcMEPs cannot be used in conjunction with neuromuscular blockade and are sensitive to the effects of anesthesia; therefore, concurrent use of D-wave monitoring is recommended, as D-waves are not affected by anesthesia.
TcMEPs do not allow for continuous monitoring but can measure corticospinal integrity immediately after a high-risk maneuver has been performed.