The recent developments of new devices and advances in anesthesiology have greatly improved the utility and accuracy of intraoperative neurophysiological monitoring (IOM). Herein, we review the basic principles of the electrophysiological methods employed under IOM in the operating room. These include motor evoked potentials, somatosensory evoked potentials, electroencephalography, electromyography, brainstem auditory evoked potentials, and visual evoked potentials. Most of these techniques have certain limitations and their utility is still being debated. In this review, we also discuss the optimal stimulation/recording method for each of these modalities during individual surgeries as well as the diverse criteria for alarm signs.
Electroencephalography ; Electromyography ; Evoked Potentials, Motor/physiology ; Evoked Potentials, Somatosensory/physiology ; Humans ; Intraoperative Neurophysiological Monitoring ; Muscle, Skeletal/*physiology ; Spinal Cord/*physiology

PURPOSE: To investigate the influence of 2 phases of short interval intracortical inhibition (SICI) on the cortical silent period (SP). MATERIALS AND METHODS: Single- and paired-pulse transcranial magnetic stimulations (TMSs) at 1 and 2.5ms interstimulus intervals (ISIs) were applied to the left motor cortex in 12 healthy subjects while their right hand muscles were moderately activated. Conditioning stimulation intensity was 90% of the active motor threshold (AMT). Test stimulation intensities were 120, 140, 160, 180, 200, 220, 240, 260% of the AMT and at 100% of the maximal stimulator output, the order of which was arranged randomly. The rectified electromyography area of motor evoked potential (MEP) and duration of the SP were measured off-line using a computerized program. RESULTS: At high-test stimulation intensities, MEP areas were saturated in both single- and paired-pulse stimulations, except that saturated MEPs were smaller for the paired-pulse TMS at 1ms ISI than for the other conditions. As the test stimulation intensity increased, SP was progressively prolonged in both single- and paired-pulse stimulations but was shorter in paired-pulse than single-pulse TMS. Overall, the ratio of SP duration/MEP area was comparable between single- and paired-pulse TMS except for the paired-pulse TMS at 1 ms ISI with a test stimulation intensity at 140-180% of the AMT, in which the ratio was significantly higher than in the single pulse TMS. CONCLUSION: These results suggest that 2 phases of SICI modulate MEP saturation and SP duration differently and provide additional evidence supporting the view that 2 phases of SICI are mediated by different inhibitory mechanisms.
Adult ; Evoked Potentials, Motor/*physiology ; Female ; Humans ; Male ; Motor Cortex/*physiology ; Transcranial Magnetic Stimulation

PURPOSE: To evaluate whether intraoperative neurophysiologic monitoring (IONM) with combined muscle motor evoked potentials (mMEPs) and somatosensory evoked potentials is useful for more aggressive and safe resection in intramedullary spinal cord tumour (IMSCT) surgery. MATERIALS AND METHODS: We reviewed data from consecutive patients who underwent surgery for IMSCT between 1998 and April 2012. The patients were divided into two groups based on whether or not IONM was applied. In the monitored group, the procedures were performed under IONM using 75% muscle amplitude decline weaning criteria. The control group was comprised of patients who underwent IMSCT surgery without IONM. The primary outcome was the rate of gross total excision of the tumour on magnetic resonance imaging at one week after surgery. The secondary outcome was the neurologic outcome based on the McCormick Grade scale. RESULTS: The two groups had similar demographics. The total gross removal tended to increase when intraoperative neurophysiologic monitoring was used, but this tendency did not reach statistical significance (76% versus 58%; univariate analysis, p=0.049; multivariate regression model, p=0.119). The serial McCormick scale score was similar between the two groups (based on repeated measure ANOVA). CONCLUSION: Our study evaluated combined IONM of trans-cranial electrical (Tce)-mMEPs and SEPs for IMSCT. During IMSCT surgery, combined Tce-mMEPs and SEPs using 75% muscle amplitude weaning criteria did not result in significant improvement in the rate of gross total excision of the tumour or neurologic outcome.
Adult ; Evoked Potentials, Motor/physiology ; Evoked Potentials, Somatosensory/*physiology ; Female ; Humans ; Male ; Middle Aged ; Retrospective Studies ; Spinal Cord Neoplasms/*surgery

OBJECTIVEThe local field potential (LFP) is a summation of dendritic potentials. The main objective of the present work is to view the features of LFP in M1 during the experimental rat pushed a paddle with the right forelimb.

METHODSFour rats were trained to press a paddle with the right forelimb for water. Then Two bundle micro-electrode with four channels were implanted into the rat's left and right primary motor cortex (M1)(AP + 3.0 mm, ML +/- 1.6 mm, H-1.6 mm) with stereotaxic apparatus. After three days recovery, 8-channel Deep-EEG and the pulse signal of paddle pressed were recorded during the rats were in operant chamber, and at the same time, the behavior were also recorded with video recorder.

RESULTSThe LFP in left M1 were defined as the substance between two channel deep-EEG. It is found that low frequency, high amplitude signal appear aligned with the paddle pressed pulse signals. With threshold detect method, about 80% press-paddle behavior could be detected.

CONCLUSIONThe result indicates that LFPs in this position in M1 are relative to forelimb's movement, and a powerful brain-computer interface system maybe developed with the LFPs.

Animals ; Brain-Computer Interfaces ; Evoked Potentials, Motor ; physiology ; Male ; Microelectrodes ; Motor Cortex ; physiology ; Movement ; physiology ; Rats ; Rats, Sprague-Dawley

Animals ; Evoked Potentials, Motor ; physiology ; Male ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Spinal Cord ; physiology

OBJECTIVETo investigate the effect of electrical stimulation to sacral spinal nerve 3 (S₃ stimulation) on gastrointestinal dysfunction after spinal cord injury (SCI).

METHODSSix rabbits were taken as normal controls to record their gastrointestinal multipoint biological discharge, colon pressure and rectoanal inhibitory reflex. Electrodes were implanted into S₃ in another 18 rabbits. Then the model of SCI was conducted following Fehling's method: the rabbit S₃ was clamped to induce transverse injury, which was claimed by both somatosensory evoked potential and motion evoked potential. Two hours after SCI, S₃ stimulation was conducted. The 18 rabbits were subdivided into 3 groups to respectively record their gastrointestinal electric activities (n=6), colon pressure (n=6), and rectum pressure (n=6). Firstly the wave frequency was fixed at 15 Hz and pulse width at 400 μs and three stimulus intensities (6 V, 8 V, 10 V) were tested. Then the voltage was fixed at 6 V and the pulse width changed from 200 μs, 400 μs to 600 μs. The response was recorded and analyzed. The condition of defecation was also investigated.

RESULTSAfter SCI, the mainly demonstrated change was dyskinesia of the single haustrum and distal colon. The rectoanal inhibitory reflex almost disappeared. S₃ stimulation partly recovered the intestinal movement after denervation, promoting defecation. The proper stimulus parameters were 15 Hz, 400 μs, 6 V, 10 s with 20 s intervals and 10 min with 10 min intervals, total 2 h.

CONCLUSIONS₃ stimulation is able to restore the intestinal movement after denervation (especially single haustrum and distal colon), which promotes defecation.

Animals ; Disease Models, Animal ; Electric Stimulation ; Electrodes, Implanted ; Evoked Potentials, Motor ; physiology ; Evoked Potentials, Somatosensory ; physiology ; Gastrointestinal Tract ; physiopathology ; Rabbits ; Sacrum ; innervation ; Spinal Cord Injuries ; physiopathology

It is the intent of this paper to locate the activation point in Transcranial Magnetic Stimulation (TMS) efficiently. The schemes of coil array in torus shape is presented to get the electromagnetic field distribution with ideal focusing capability. Then an improved adaptive genetic algorithm (AGA) is applied to the optimization of both value and phase of the current infused in each coil. Based on the calculated results of the optimized current configurations, ideal focusing capability is drawn as contour lines and 3-D mesh charts of magnitude of both magnetic and electric field within the calculation area. It is shown that the coil array has good capability to establish focused shape of electromagnetic distribution. In addition, it is also demonstrated that the coil array has the capability to focus on two or more targets simultaneously.
Algorithms ; Brain ; physiology ; Electric Stimulation ; instrumentation ; Electromagnetic Fields ; Equipment Design ; Evoked Potentials, Motor ; physiology ; Humans ; Neurons ; physiology ; Transcranial Magnetic Stimulation

Electrophysiologic examination of dorsal spinal cord injury (DSCI) is focused on transcranial magnetic stimulation induced motor evoked potentials. It were recorded at thenar muscles, exector spinae muscle, intercostals muscle, and internal oblique muscles. In complete spinal cord injury, the exector musle motor evoked potentials may occur although clinically that muscle shows no recovery. The ipsilateral exector and internal oblique muscles may be distributed by non-cross fibers in cerebrospinal tract. The progress in clinical sensory examination includes cutaneous electrical perceptional sensory threshold and quantitative sensory test. The former is more sensitive than two-points discrepentive test. Quantitative sensory test includes light touch threshold, vibration perceptual threshold, thermal threshold, pain, and cutaneous axon flare respone. It has been used in DSCI patients above and below the injury level. The thermal threshold elevates above the injury level in complete and incomplete DSCI patients.
Electric Stimulation ; Electromagnetic Fields ; Electromyography ; Evoked Potentials, Motor ; Evoked Potentials, Somatosensory ; Humans ; Neurologic Examination ; methods ; standards ; Sensory Thresholds ; physiology ; Spinal Cord Injuries ; physiopathology ; Thoracic Vertebrae

The local field potentials (LFPs) underlying specific behavior were recorded and analyzed in this paper from primary motor cortex (M1) with several medium, such as the self-made single channel micro-electrodes, the system of multi-channels physiological signal acquisition and processing and so on. During the experiment, the specific behavior was divided into four periods according to the changes of the recorded LFPs and the changes of the specific behavior recorded simultaneously in rats. The four periods were named prophase of catching period, planning period, catching period and the completion period, respectively. Then several methods were used for the analysis of the LFPs by MATLAB, such as time domain analysis, power spectral distribution analysis and time-frequency analysis. The results suggested that the LFPs which were caused by different behavior from a large number of movement-related neurons of M1 during the specific behavior in the process of catching play an important part in the "code" guiding role in rats. The results demonstrat that the LFPs of M1 may provide a feasibility to discriminate the motor behavior of forelimb.
Animals ; Brain-Computer Interfaces ; Electrodes, Implanted ; Evoked Potentials, Motor ; physiology ; Feeding Behavior ; physiology ; Male ; Microelectrodes ; Motor Cortex ; physiology ; Rats ; Rats, Wistar

Our objective is the designing of a functional electrical stimulation (FES) system on event related desynchronization (ERD) and event related synchronization (ERS) signals. When the brain images the left-and right-leg movements, the ERD/ERS signals will appear. By characterization and characteristic classification, the ERD/ERS will be translated into the response control signal for operating the FES system to electrically stimulate the legs of motor disability. The result shows that the experiment is successful in electrically stimulating the legs of motor disability.
Brain ; physiopathology ; Cortical Synchronization ; Electric Stimulation ; methods ; Electroencephalography ; Evoked Potentials, Motor ; physiology ; Hemiplegia ; physiopathology ; rehabilitation ; Humans ; Motor Activity ; physiology ; User-Computer Interface