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 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

Adult ; Aged ; Aging ; physiology ; Evoked Potentials, Somatosensory ; physiology ; High-Frequency Ventilation ; Humans ; Middle Aged ; Somatosensory Cortex ; physiology

Acute sensorimotor polyneuropathy that resembles Guillain-Barre syndrome (GBS) is rarely accompanied with nephrotic syndrome, and its underlying immunological mechanisms are unclear. A 56-year-old man presented with simultaneous acute progressive symmetric sensorimotor polyneuropathy and proteinuria. A kidney biopsy revealed focal segmental glomerulosclerosis. Serial electrophysiologic studies showed only a transient proximal conduction block in the median nerve, stimulated somatosensory evoked potential and prolonged terminal latencies of the median and peroneal nerves. The patient's neurologic deficits and kidney dysfunction recovered with corticosteroid treatment. Our case showed that somatosensory evoked potential study can be an important objective tool in the diagnosis of acute polyneuropathy with normal distal nerve conduction and that corticosteroids should be considered in the initial treatment of GBS-resembling polyneuropathy associated with nephrotic syndrome.
Evoked Potentials, Somatosensory/physiology ; Humans ; Male ; Middle Aged ; Nephrotic Syndrome/*diagnosis/*physiopathology ; Polyneuropathies/*diagnosis/*physiopathology

BACKGROUNDParoxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent brief episodes of chorea and dystonia induced by sudden movement. Whether the central nervous system is hyper- or hypoexcitable in PKD remains undetermined. The aim of our study was to compare the somatosensory evoked potential (SEP) recovery cycle, a marker of somatosensory system excitability, in PKD patients and controls.

METHODSTwenty-four PKD patients (mean age of (20.0±5.3) years; 21 males, 3 females) and 18 control age-matched subjects (mean age of (22.0±5.0) years; 17 males, 1 female) were studied. The stimuli were delivered to the median nerve in the affected dominant arm in patients and in the dominant arm in controls. The change in SEP amplitude was measured after paired electrical stimulation at interstimulus intervals (ISIs) of 5, 20, and 40 ms. The SEPs evoked by S2 (test stimulus) were calculated by subtracting the response to S1 (the conditioning stimulus) from the response to a pair of stimuli (S1+S2), and their amplitudes were compared with those of the control response (S1) at each ISI. Analysis of variance (ANOVA) or equivalent was used for non-parametric data.

RESULTSIn patients, the P27 amplitude after the single stimulus (S1) was significantly larger than that after the control stimulus. The (S2/S1)×100 ratio for P14 and N30 SEPs did not differ significantly between PKD patients and normal subjects at ISI of 5 ms but were significantly higher in patients at ISIs of 20 and 40 ms (P<0.05).

CONCLUSIONSSomatosensory system disinhibition takes place in PKD. The finding of reduced suppression of different SEPs, each thought to have a different origin, suggests an abnormality of intracortical and subcortical inhibitory circuits.

Adolescent ; Adult ; Case-Control Studies ; Dystonia ; physiopathology ; Evoked Potentials, Somatosensory ; physiology ; Female ; Humans ; Male ; Young Adult

This study was directed at extracting the rabbit somatosensory evoked potential (SEP), locating and analyzing the waveform of rabbit SEP. The rabbit was narcotized and stimulated by 0.5 Hz electric pulse. Potential of scalp was sampled at 3.764 Hz. Rabbit somatosensory evoked potential was extracted by one-dimension multi-resolution analysis, and continuous wavelet transform (CWT) was employed to locate and analyze the wave of SEP. The study results showed that Single-trail SEP can be extracted by Daubechies wavelet, when wavelet transform result of single-trail was compared with the result of averaged SEP. Wave component of SEP can be located precisely through the method of continuous wavelet transform. Frequency feature of SEP can also be analyzed by CWT. The technique of continuous wavelet transform, which can project a one-dimension signal into a two-dimension time-frequency space, shows good application prospect of processing medical electronic signal.
Algorithms ; Animals ; Electric Stimulation ; Evoked Potentials, Somatosensory ; physiology ; Fourier Analysis ; Rabbits ; Signal Processing, Computer-Assisted

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

This experiment was carried out to analyze the time-frequency feature of rabbit cortical somatosensory evoked potential (SEP). Rabbit was narcotized and subjected to craniotomy. SEP was from sensory and motor cortex. Stimulation was continuing many times and signal was sampled at 3 800 Hz. The peak latency of each waveform was measured. Power spectrum of SEP was analyzed. The time-frequency feature of single-trial was compared with that of average SEP. It was found that the variability of single-trial SEP latency enlarges with time in a stimulation period. The spectrum of SEP includes three main frequency spectrum packages. The technique of summation makes a lot of signal aberration such as waveform confluence, new waveform emerging and after-discharging components dismissing.
Animals ; Cerebral Cortex ; physiology ; Electric Stimulation ; Evoked Potentials, Somatosensory ; physiology ; Female ; Fourier Analysis ; Male ; Rabbits ; Signal Processing, Computer-Assisted

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

Sensory evoked potential (SEP) studies have contributed to the greater accuracy of diagnosis and evaluation in neuropathy. Normal values of SEP serve as a helpful reference in evaluating neuropathy, whether SEP or a conventional diagnostic study is employed. The conduction velocity of the median sensory nerve in 46 normal, healthy Korean individuals was determined, using SEP, and the findings compared with the findings of investigators in other countries. The mean conduction velocity was 63.15 +/- 5.00m/sec; the mean latency following stimulation at the wrist was 18.27 +/- 1.35 msec, and at the elbow 14.58 +/- 1.23 msec. Significant positive correlation of N20 latency with subject's height were found.
Adult ; Body Height ; Comparative Study ; Evoked Potentials, Somatosensory* ; Female ; Human ; Korea ; Male ; Median Nerve/physiology* ; Middle Age ; Neural Conduction*