Sensitivity and specificity in transcranial motor-evoked potential monitoring during neurosurgical operations

Abstract

Background:Intraoperative transcranial motor-evoked potential (TCMEP) monitoring is widely performed during neurosurgical operations. Sensitivity and specificity in TCMEP during neurosurgical operations were examined according to the type of operation.Methods:TCMEP monitoring was performed during 283 neurosurgical operations for patients without preoperative motor palsy, including 121 spinal operations, 84 cerebral aneurysmal operations, and 31 brain tumor operations. Transcranial stimulation at 100–600 V was applied by screw electrodes placed in the scalp and electromyographic responses were recorded with surface electrodes placed on the affected muscles. To exclude the effects of muscle relaxants on TCMEP, compound muscle action potential (CMAP) by supramaximal stimulation of the peripheral nerve immediately after transcranial stimulation was used for compensation of TCMEP.Results:In spinal operations, with an 80% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 100% and 96.4%, respectively. In aneurysmal operations, with a 70% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 100% and 94.8%, respectively. Compensation by CMAP was especially useful in aneurysmal operations. In all neurosurgical operations, with a 70% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 95.0% and 90.9%, respectively.Conclusions:Intraoperative TCMEP monitoring is a significantly reliable method for preventing postoperative motor palsy in both cranial and spinal surgery. A 70% reduction in the compensated amplitude is considered to be a suitable alarm point in all neurological operations.

Intraoperative monitoring during decompression of the spinal cord and spinal nerves using transcranial motor-evoked potentials: The law of twenty percent

“…Our CMAP normalization was shown to be effective under the constant administration of anesthetics. Although CMAP normalization provided only a very minor improvement in the sensitivity and specificity of MEP monitoring, as previously reported [19], CMAP normalization is necessary when using MEP to predict functional recovery from compressive spinal and spinal nerve disease.…”

“…Langeloo et al also showed that an 80% reduction in amplitude was the threshold point in MEP with EMG recording in spinal surgery [3]. We previously reported that in 121 spinal operations for patients without preoperative motor palsy (MRC grading P 3/5), the sensitivity and specificity of MEP by EMG recording with CMAP normalization was 100% and 96.4%, respectively, using a criterion of an 80% reduction in amplitude [19,20]. These results are consistent with those of Langeloo et al [3].…”

“…CMAP by single, bipolar supramaximum stimulation (20-50 milliamps), which had been determined at the beginning of the operation, usually on the median nerve at the wrist 2 seconds before or after each transcranial stimulation of the motor area, was recorded in all operations as previously described [19,20]. The amplitudes of MEP and CMAP after peripheral nerve stimulation were measured.…”

“…The other method involves high voltage (several hundred volts) transcranial stimulation using screw electrodes that have been placed in the scalp [11,[14][15][16]. Transcranial stimulation of the motor area with recording of the peripheral electromyogram (EMG) is the most popular method of MEP monitoring during spinal surgery and it has also been shown to be very sensitive [17][18][19].…”

Diagnostic accuracy of motor evoked potentials to detect neurological deficit during idiopathic scoliosis correction: a systematic review

“…It is well known that MEPs are highly sensitive compared to SSEPs, but while they seem to be influenced by the same systemic factors, MEPs are more vulnerable to ischemic injuries, and thus experience more changes in amplitude than SSEPs due to the nature of their blood supply [12,21,25]. The anterior spinal artery (ASA) supplies around 75% of the spinal cord, which includes gray matter and anterior horn cells [26,27].…”