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The hypoglossal nerve (CN XII) may be placed at risk during posterior fossa surgeries. The use of intraoperative monitoring (IOM), including the utilization of spontaneous and triggered electromyography (EMG), from tongue muscles innervated by CN XII has been used to reduce these risks. However, there were few reports regarding the intraoperative transcranial motor evoked potential (MEP) of hypoglossal nerve from the tongue muscles. For this reason, we report here two cases of intraoperative hypoglossal MEP monitoring in brain surgery as an indicator of hypoglossal deficits. Although the amplitude of the MEP was reduced in both patients, only in the case 1 whose MEP was disappeared demonstrated the neurological deficits of the hypoglossal nerve. Therefore, the disappearance of the hypoglossal MEP recorded from the tongue, could be considered a predictor of the postoperative hypoglossal nerve deficits.
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To investigate the neurodevelopmental outcomes in children with developmental disorder according to visual evoked potential (VEP) results.
We retrospectively analyzed children who visited our Department of Pediatric Rehabilitation Medicine with a chief complaint of developmental disability from January 2001 to July 2015. Of the 549 medical records reviewed, 322 children younger than 42 months who underwent both Bayley Scales of Infant and Toddler Development second edition (BSID-II) and VEP studies were enrolled. We compared the development of 182 children with normal VEP latency and 140 children with delayed VEP latency results using the BSID-II results. The Mann-Whitney U-test was used to analyze the differences between the two groups.
There were no significant differences in baseline characteristics between the two groups. The delayed VEP latency group showed a significant delay in BSID-II index scores and developmental quotients compared with the normal VEP latency group. In addition, a comparative analysis of developmental quotients of mental and psychomotor domains according to age (younger than 12 months, 12–23 months, and 24–42 months) revealed significantly lower values in children with delayed VEP latency compared to children with normal VEP latency, younger than 12 months and from 12 to 23 months.
Children with delayed VEP latency showed more developmental delay than children with normal VEP latency. It is suggested that VEP can be easily applied to children with suspected developmental delay when physicians have concerns about visual impairment. Furthermore, it is proposed that VEP results could provide an insight into children's development and serve as early indicators for consultation with an ophthalmologist for the existing problem.
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Joubert syndrome (JS) is a rare genetic disorder characterized by a congenital malformation of the hindbrain, and accompanied by axonal decussation abnormalities affecting the corticospinal tract and the superior cerebellar peduncles. To the best of our knowledge, there are no reports of normal pyramidal decussation in JS. Here, we describe the case of an 18-year-old boy presenting midline-crossing corticospinal projections, which were considered normal corticospinal tract trajectories. Diffusion tensor imaging and motor evoked potential study analysis demonstrated the exclusive presence of decussating corticospinal projections in the patient. Based on these results, we suggest that JS might be associated with several, diverse corticospinal motor tract organization patterns.
To identify which combination of motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) is most reliable for postoperative motor deterioration during spinal cord tumor surgery, according to anatomical and pathologic type.
MEPs and SEPs were monitored in patients who underwent spinal cord tumor surgery between November 2012 and August 2016. Muscle strength was examined in all patients before surgery, within 48 hours postoperatively and 4 weeks later. We analyzed sensitivity, specificity, positive and negative predictive values of each significant change in SEPs and MEPs.
The overall sensitivity and specificity of SEPs or MEPs were 100% and 61.3%, respectively. The intraoperative MEP monitoring alone showed both higher sensitivity (67.9%) and specificity (83.2%) than SEP monitoring alone for postoperative motor deterioration. Two patients with persistent motor deterioration had significant changes only in SEPs. There are no significant differences in reliabilities between anatomical types, except with hemangioma, where SEPs were more specific than MEPs for postoperative motor deterioration. Both overall positive and negative predictive values of MEPs were higher than the predictive values of SEPs. However, the positive predictive value was higher by the dual monitoring of MEPs and SEPs, compared to MEPs alone.
For spinal cord tumor surgery, combined MEP and SEP monitoring showed the highest sensitivity for the postoperative motor deterioration. Although MEPs are more specific than SEPs in most types of spinal cord tumor surgery, SEPs should still be monitored, especially in hemangioma surgery.
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To investigate the relationship between motor evoked potential (MEP) response and the severity of motor paralysis, evaluated according to the Korean disability evaluation system in patients with spinal cord injury (SCI).
We analyzed 192 lower limbs of 96 SCI patients. Lower limbs were classified according to their motor scores, as determined by the International Standards for Neurological Classification of Spinal Cord Injury: motor score <10 (group 1); ≥10 and <15 (group 2); ≥15 and <20 (group 3); and ≥20 (group 4). MEP responses were classified as ‘normal’, ‘delayed’ or ‘absent’, based on their onset latency, which was compared between the different motor score groups.
MEP responses and limb motor scores were highly correlated (p<0.001). There was a significant difference of MEP responses between the motor score groups (p<0.001). MEP response was markedly poorer in motor group 1 (limb motor score <10) than in the other three groups (p<0.0001). However, there were no differences between the three groups with motor scores of 10 or above.
Clinical utility of MEP as a complimentary tool to manual muscle tests could be limited to discriminating motor score groups with severe paralysis, i.e., single lower limb motor power grades of 0 or 1, and from grade 2, 3, and 4, or above, in the Korean disability evaluation system.
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To investigate the clinical significance of quantitative parameters in transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEP) which can be adopted to predict functional recovery of the upper limb in stroke patients in the early subacute phase.
One hundred thirteen patients (61 men, 52 women; mean age 57.8±12.2 years) who suffered faiarst-ever stroke were included in this study. All participants underwent TMS-induced MEP session to assess the corticospinal excitability of both hand motor cortices within 3 weeks after stroke onset. After the resting motor threshold (rMT) was assessed, five sweeps of MEP were performed, and the mean amplitude of the MEP was measured. Latency of MEP, volume of the MEP output curve, recruitment ratios, and intracortical inhibition and facilitation were also measured. Motor function was assessed using the Fugl-Meyer Assessment scale (FMA) within 3 weeks and at 3 months after stroke onset. Correlation analysis was performed between TMS-induced MEP derived measures and FMA scores.
In the MEP response group, rMT and rMT ratio measures within 3 weeks after stroke onset showed a significant negative correlation with the total and upper limb FMA scores at 3 months after stroke (p<0.001). Multiple regression analysis revealed that FMA score and rMT ratio, but not rMT within 3 weeks were independent prognostic factors for FMA scores at 3 months after stroke.
These results indicated that the quantitative parameter of TMS-induced MEP, especially rMT ratio in the early subacute phase, could be used as a parameter to predict motor function in patients with stroke.
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To evaluate whether the combination of muscle motor evoked potentials (mMEPs) and somatosensory evoked potentials (SEPs) measured during spinal surgery can predict immediate and permanent postoperative motor deficits.
mMEP and SEP was monitored in patients undergoing spinal surgery between November 2012 and July 2014. mMEPs were elicited by a train of transcranial electrical stimulation over the motor cortex and recorded from the upper/lower limbs. SEPs were recorded by stimulating the tibial and median nerves.
Combined mMEP/SEP recording was successfully achieved in 190 operations. In 117 of these, mMEPs and SEPs were stable and 73 showed significant changes. In 20 cases, motor deficits in the first 48 postoperative hours were observed and 6 patients manifested permanent neurological deficits. The two potentials were monitored in a number of spinal surgeries. For surgery on spinal deformities, the sensitivity and specificity of combined mMEP/SEP monitoring were 100% and 92.4%, respectively. In the case of spinal cord tumor surgeries, sensitivity was only 50% but SEP changes were observed preceding permanent motor deficits in some cases.
Intraoperative monitoring is a useful tool in spinal surgery. For spinal deformity surgery, combined mMEP/SEP monitoring showed high sensitivity and specificity; in spinal tumor surgery, only SEP changes predicted permanent motor deficits. Therefore, mMEP, SEP, and joint monitoring may all be appropriate and beneficial for the intraoperative monitoring of spinal surgery.
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To examine the association between motor evoked potentials (MEPs) in lower limbs and ambulatory outcomes of hemiplegic stroke patients.
Medical records of hemiplegic patients with the first ever stroke who received inpatient rehabilitation from January 2013 to May 2014 were reviewed. Patient who had diabetes, quadriplegia, bilateral lesion, brainstem lesion, severe musculoskeletal problem, and old age over 80 years were excluded. MEPs in lower limbs were measured when they were transferred to the Department of Rehabilitation Medicine. Subjects were categorized into three groups (normal, abnormal, and absent response) according to MEPs findings. Berg Balance Scale (BBS) and Functional Ambulation Category (FAC) at initial and discharge were compared among the three groups by one-way analysis of variance (ANOVA). Correlation was determined using a linear regression model.
Fifty-eight hemiplegic patients were included. BBS and FAC at discharge were significantly (ANOVA, p<0.001) different according to MEPs findings. In linear regression model of BBS and FAC using stepwise selection, patients' age (p<0.01), BBS at admission (p<0.01), and MEPs (p<0.01) remained significant covariates. In regression assumption model of BBS and FAC at admission, MEPs and gender were significant covariates.
Initial MEPs of lower limbs can prognosticate the ambulatory outcomes of hemiplegic patients.
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To present a new stimulation method based on the use of a head-mounted display (HMD) during pattern reversal visual evoked potential (PR-VEP) testing and to compare variables of HMD to those of conventional cathode ray tube (CRT).
Twenty-three normal subjects without visual problems were recruited. PR-VEPs were generated using CRT or HMD stimuli. VEP outcome measures included latencies (N75, P100, and N145) and peak-to-peak amplitudes (N75–P100 and P100–N145). Subjective discomfort associated with HMD was determined using a self-administered questionnaire.
PR-VEPs generated by HMD stimuli showed typical triphasic waveforms, the components of which were found to be correlated with those obtained using conventional CRT stimuli. Self-administered discomfort questionnaires revealed that HMD was more comfortable in some aspects. It allowed subjects to concentrate better than CRT.
The described HMD stimulation can be used as an alternative to the standard CRT stimulation for PR-VEPs. PR-VEP testing using HMD has potential applications in clinical practice and visual system research because HMD can be used on a wider range of subjects compared to CRT.
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To investigate the clinical significance of upper and lower extremity transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs) in patients with parkinsonism.
Twenty patients (14 men, 6 women; mean age 70.5±9.1 years) suffering from parkinsonism were included in this study. All participants underwent single-pulse TMS session to assess the corticospinal excitability of the upper and lower extremity motor cortex. The resting motor threshold (RMT) was defined as the lowest stimulus intensity able to evoke MEPs of an at least 50 µV peak-to-peak amplitude in 5 of 10 consecutive trials. Five sweeps of MEPs at 120% of the RMT were performed, and the mean amplitude and latency of the MEPs were calculated. Patients were also assessed using the Unified Parkinson's Disease Rating Scale part III (UPDRS-III) and the 5-meter Timed Up and Go (5m-TUG) test.
There was a significant positive correlation between the RMTs of MEPs in the upper and lower extremities (r=0.612, p=0.004) and between the amplitude of MEPs in the upper and lower extremities (r=0.579, p=0.007). The RMT of upper extremity MEPs showed a significant negative relationship with the UPDRS-III score (r=–0.516, p=0.020). In addition, RMTs of lower extremity MEPs exhibited a negative relationship with the UPDRS-III score, but the association was not statistically significant (r=–406, p=0.075).
These results indicated that the RMT of MEPs reflect the severity of motor dysfunction in patients with parkinsonism. MEP is a potential quantitative, electrodiagnostic method to assess motor function in patients with parkinsonism.
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To compare diffusion tensor tractography (DTT) and motor evoked potentials (MEPs) for estimation of clinical status in patients in the subacute stage of stroke.
Patients with hemiplegia due to stroke who were evaluated using both DTT and MEPs between May 2012 and April 2015 were recruited. Clinical assessments investigated upper extremity motor and functional status. Motor status was evaluated using Medical Research Council grading and the Fugl-Meyer Assessment of upper limb and hand (FMA-U and FMA-H). Functional status was measured using the Modified Barthel Index (MBI). Patients were classified into subgroups according to DTT findings, MEP presence, fractional anisotropy (FA) value, FA ratio (rFA), and central motor conduction time (CMCT). Correlations of clinical assessments with DTT parameters and MEPs were estimated.
Fifty-five patients with hemiplegia were recruited. In motor assessments (FMA-U), MEPs had the highest sensitivity and negative predictive value (NPV) as well as the second highest specificity and positive predictive value (PPV). CMCT showed the highest specificity and PPV. Regarding functional status (MBI), FA showed the highest sensitivity and NPV, whereas CMCT had the highest specificity and PPV. Correlation analysis showed that the resting motor threshold (RMT) ratio was strongly associated with motor status of the upper limb, and MEP parameters were not associated with MBI.
DTT and MEPs could be suitable complementary modalities for analyzing the motor and functional status of patients in the subacute stage of stroke. The RMT ratio was strongly correlated with motor status.
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Terson syndrome refers to oculocerebral syndrome of retinal and vitreous hemorrhage associated with spontaneous subarachnoid hemorrhage or all forms of intracranial bleeding. Recent observations have indicated that patients with spontaneous subarachnoid hemorrhage have an 18% to 20% concurrent incidence of retinal and vitreous hemorrhages with about 4% incidence of vitreous hemorrhage alone. Clinical ophthalmologic findings may have significant diagnostic and prognostic value for clinicians. Here we report a 45-year-old female patient who suffered from blurred vision after subarachnoid hemorrhage. She was diagnosed as Terson syndrome. After vitrectomy, she recovered with normal visual acuity which facilitated the rehabilitative process. We also performed visual evoked potentials to investigate abnormalities of visual dysfunction. Based on this case, we emphasize the importance of early diagnosis of Terson syndrome.
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To determine the predictability of motor evoked potentials (MEP) in patients with putaminal hemorrhage (PH) according to the time of MEP from the onset of stroke.
Sixty consecutive patients with PH from January 2006 to November 2013 were retrospectively reviewed. Motor function of affected extremities was measured at onset time and at six months after the onset. Patients were classified into two groups according to the time of MEP from the onset of stroke: early MEP group (within 15 days from onset) and late MEP group (16-30 days from onset). Patients were also classified into two groups according to the presence of MEP on the affected abductor pollicis brevis (APB): MEP (+) group-patients (showing MEP in the affected APB) and MEP (-) group-patients (no MEP in the affected APB). Motor outcome was compared between the two early and late MEP groups or between the presence and absence of MEP in the affected APB groups.
For patients with MEP (+), a larger portion in the late MEP group showed good prognosis compared to the early MEP group (late MEP, 94.4%; early MEP, 80%). In contrast, in patients with MEP (-), a larger portion of patients in the late MEP group showed bad prognosis compared to the early MEP group (late MEP, 80%; early MEP, 71.4%). No significant improvement of MI between MEP (+) and MEP (-) was observed when MEP was performed early or late.
Our results revealed that the predictability of motor outcome might be better if MEP is performed late compared to that when MEP is performed early in patients with PH.
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To investigate the association between baseline motor evoked potential (MEP) and somatosensory evoked potential (SSEP) responses in the lower extremities and balance recovery in subacute hemiparetic stroke patients.
MEPs and SSEPs were evaluated in 20 subacute hemiparetic stroke patients before rehabilitation. Balance (static posturography and Berg Balance Scale [BBS]), motor function (Fugl-Meyer Assessment [FMA]) and the ability to perform activities of daily living (Modified Barthel Index [MBI]) were evaluated before rehabilitation and after four-weeks of rehabilitation. Posturography outcomes were weight distribution indices (WDI) expressed as surface area (WDI-Sa) and pressure (WDI-Pr), and stability indices expressed as surface area (SI-Sa) and length (SI-L). In addition, all parameters were evaluated during eyes open (EO) and eyes closed (EC) conditions.
The MEP (+) group showed significant improvements in balance except WDI-Sa (EC), FMA, and MBI, while the MEP (-) group showed significant improvements in the BBS, FMA, and MBI after rehabilitation. The SSEP (+) group showed significant improvements in balance except SI-Sa (EO), FMA, and MBI, while the SSEPs (-) group showed significant improvements in the BBS, MBI after rehabilitation. The changes in the SI-Sa (EO), SI-L (EO), total MBI, and several detailed MBI subscales in the MEP (+) group after rehabilitation were significantly larger than those in the MEP (-) group.
Our findings suggest that initial assessments of MEPs and SSEPs might be beneficial when predicting balance recovery in subacute hemiparetic stroke patients.
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To investigate whether motor evoked potential (MEP) amplitude ratio measurements are sufficiently objective to assess functional activities of the extremities. We also delineated the distribution between the presence or absence of MEPs and the Medical Research Council (MRC) scale for muscle strength of the extremities.
We enrolled 183 patients with first-ever unilateral hemiplegia after stroke. The MEP parameters were amplitude ratio (amplitude of affected side/amplitude of unaffected side) recorded at the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. We performed frequency analyses using the MRC scale for muscle strength and the presence or absence of evoked MEPs. Change on the MRC scale, hand function tests (HFTs), and the Modified Barthel Index (MBI) subscore were compared between the evoked MEP and absent MEP groups using the independent t-test. Receiver operating characteristic curves were used to determine the optimal cutoff scores for the MEP amplitude ratio using the HFT results and MBI subscores. Correlations between the MEP amplitude ratio and the MRC scale, HFTs, and MBI subscore were analyzed.
About 10% of patients with MRC scale grades 0-2 showed evoked MEPs at the FDI muscle, and 4% of patients with MRC scale grades 3-5 did not show MEPs. About 18% of patients with MRC scale grades 0-2 showed evoked MEPs at the TA muscle, and 4% of patients with MRC scale grades 3-5 did not show MEPs. MEP amplitude increased with increasing MRC scale grade. The evoked MEP group had more significant changes on the MRC scale, HFT, and the climbing stair score on the MBI than those in the group without MEPs. Larger MEP amplitude ratios were observed in patients who had more difficulty with the HFTs and ambulation. The MEP amplitude ratio was significantly correlated with the MRC scale, HFT, and MBI subscore.
We conclude that the MEP amplitude ratio may be useful to predict functional status of the extremities in patients who suffered stroke.
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Although spinal cord injury without radiographic abnormality (SCIWORA) literally refers to the specific type of spinal cord injury, however, some extents of spinal cord injuries can be detected by magnetic resonance imaging (MRI) in most of cases. We introduce an atypical case of spinal cord injury without radiologic abnormality. A 42-year-old male tetraplegic patient underwent MRI and computed tomography, and no specific lesions were found in any segments of the spinal cord. Moreover, the tetraplegic patient showed normal urodynamic function despite severe paralysis and absent somatosensory evoked potentials from the lower limbs.
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To investigate the normal data of pain-related evoked potentials (PREP) elicited with a concentric surface electrode among normal, healthy adults and the relationship between PREP and pain intensity.
Sixty healthy volunteers (22 men and 38 women; aged 36.4±10.7 years; height, 165.4±7.8 cm) were enrolled. Routine nerve conduction study (NCS) was done to measure PREP following electrical stimulation of hands (C7 dermatome) and feet (L5 dermatome). Negative peak (N), positive peak (P) latencies, peak to peak (NP) amplitudes, conduction velocity (CV), and verbal rating scale (VRS) score were obtained. Linear regression analysis tested for significant relevance between variables of PREP and VRS score.
Normal NCS results were obtained in all subjects. N latency of hand PREP was 163.8 ±40.0 ms (right) and 161.0±39.9 ms (left). N latency of foot PREP was 178.0±43.9 ms (right), 180.4±43.4 ms (left). NP amplitude of hands was 20.6±10.6 µV (right) and 21.9±11.6 µV (left). NP amplitude of feet was 18.8±8.3 µV (right) and 19.0±8.4 µV (left). The calculated CV was 13.2±4.7 m/s and VRS score was 3.8±1.0. A highly significant positive correlation was evident between VRS score and NP amplitude (y=0.1069x+1.781, r=0.877, n=60, p<0.0001).
PREP among normal, healthy adults revealed a statistically significant correlation between PREP amplitude and VRS score.
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To evaluate whether an initial complete impairment of spinal cord injury (SCI) contributes to the functional outcome prediction, we analyzed the relationship between the degree of complete impairment according to the American Spinal Injury Association impairment scale (AIS), the posterior tibial nerve somatosensory evoked potential (PTSEP) and the changes of functional indices.
Sixty subjects with SCI were studied who received rehabilitative management for over 2 months. The degree of completeness on basis of the initial AIS and PTSEP were evaluated at the beginning of rehabilitation. Following treatment, several functional indices, such as walking index for spinal cord injury version II (WISCI II), spinal cord independence measure version III (SCIM III), Berg Balance Scale (BBS), and Modified Barthel Index (MBI), were evaluated until the index score reached a plateau value.
The recovery efficiency of WISCI and BBS revealed a statistically significant difference between complete and incomplete impairments of initial AIS and PTSEP. The SCIM and MBI based analysis did not reveal any significant differences in terms of the degree of AIS and PTSEP completeness.
AIS and PTSEP were highly effective to evaluate the prognosis in post-acute phase SCI patients. BBS and WISCI might be better parameters than other functional indices for activities of daily living to predict the recovery of the walking ability in post-acute SCI.
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To investigate neuroradiological and neurophysiological characteristics of patients with dyskinetic cerebral palsy (CP), by using magnetic resonance imaging (MRI), voxel-based morphometry (VBM), diffusion tensor tractography (DTT), and motor evoked potential (MEP).
Twenty-three patients with dyskinetic CP (13 males, 10 females; mean age 34 years, range 16-50 years) were participated in this study. Functional evaluation was assessed by the Gross Motor Functional Classification System (GMFCS) and Barry-Albright Dystonia Scale (BADS). Brain imaging was performed on 3.0 Tesla MRI, and volume change of the grey matter was assessed using VBM. The corticospinal tract (CST) and superior longitudinal fasciculus (SLF) were analyzed by DTT. MEPs were recorded in the first dorsal interossei, the biceps brachii and the deltoid muscles.
Mean BADS was 16.4±5.0 in ambulatory group (GMFCS levels I, II, and III; n=11) and 21.3±3.9 in non-ambulatory group (GMFCS levels IV and V; n=12). Twelve patients showed normal MRI findings, and eleven patients showed abnormal MRI findings (grade I, n=5; grade II, n=2; grade III, n=4). About half of patients with dyskinetic CP showed putamen and thalamus lesions on MRI. Mean BADS was 20.3±5.7 in normal MRI group and 17.5±4.0 in abnormal MRI group. VBM showed reduced volume of the hippocampus and parahippocampal gyrus. In DTT, no abnormality was observed in CST, but not in SLF. In MEPs, most patients showed normal central motor conduction time.
These results support that extrapyramidal tract, related with basal ganglia circuitry, may be responsible for the pathophysiology of dyskinetic CP rather than CST abnormality.
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To investigate the somatosensory findings of pusher syndrome in stroke patients.
Twelve pusher patients and twelve non-pusher patients were enrolled in this study. Inclusion criteria were unilateral stroke, sufficient cognitive abilities to understand and follow instructions, and no visual problem. Patients were evaluated for pusher syndrome using a standardized scale for contraversive pushing. Somatosensory finding was assessed by the Cumulative Somatosensory Impairment Index (CSII) and somatosensory evoked potentials (SEPs) at 1 and 14 weeks after the stroke onset. Data of SEPs with median and tibial nerve stimulation were classified into the normal, abnormal, and no response group.
In the baseline characteristics (sex, lesion character, and side) of both groups, significant differences were not found. The score of CSII decreased in both groups at 14 weeks (p<0.05), but there were no significant differences in the CSII scores between the two groups at 1 and 14 weeks. There were no significant differences in SEPs between the two groups at 1 and 14 weeks after the stroke onset.
It appears that somatosensory input plays a relatively minor role in pusher syndrome. Further study will be required to reveal the mechanism of pusher syndrome.
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To investigate the effectiveness of the daily living activity and motor evoked potential (MEP) in the subacute stroke patients.
Nineteen subjects with subacute ischaemic/hemorrhagic stroke developed in the last three months were enrolled, and MEP was measured with transcranial magnetic stimulation. Functional Independence Measure (FIM) score were evaluated in both groups before and 4 weeks after comprehensive rehabilitative management. According to the presence of MEP response in the affected hemisphere, subjects were divided into MEP positive and negative group.
There was no significant difference between the two groups in age, sex, and post-onset duration. Four weeks later, the change in total FIM and self-care score improved significantly in the MEP-positive group, when compared to the MEP-negative group (p<0.05). However, cognitive improvement had no relationship with MEP responsiveness.
We concluded that initial measurement of MEP is a useful assessment tool in predicting functional outcome of subacute stroke patients.
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Method: Thirty eight complete peripheral nerve injuries, diagnosed by motor and sensory nerve conduction studies (NCS) and needle electromyography (nEMG), were studied. Nerve injuries were grouped into two groups with and without SEP recorded at the time of initial evaluation. Outcome of nerve injuries was graded from 0 to 3 based on the results of NCSs and nEMG, followed up for more than six months. Grade 0 was designated for those with no evidence of recovery, and grade 3 for those with recovery in nEMG and both motor and sensory NCSs.
Results: At the time of initial electrodiagnosis, SEP study showed no response in 25 cases, but SEP could be observed in 13 cases, although they were attenuated or delayed. Recovery of nerve injury was observed in 22 cases, despite the findings compatible with complete injury in initial NCSs and nEMG. The group in which SEPs were recorded showed significantly higher grades of recovery, compared to no re sponse group.
Conclusion: In predicting the prognosis of complete peripheral nerve injuries, SEP study could be useful as a supplementary electrodiagnostic method.
Method: The subjects were 57 patients with first stroke. Somatosensory evoked potential study was performed at the time of transfer to the rehabilitation department. Data of somatosensory evoked potential with median and tibial nerve stimulations were obtained and classified as normal (group 1), abnormal (group 2), and no response group (group 3). Modified Barthel index (MBI), motor and sensory functions were evaluated at the time of transfer and discharge.
Results: MBI score was statistically different among the 3 groups based on the findings of median and tibial nerve SSEP at the time of transfer, but not different at the time of discharge. Motor function was statistically different among the 3 groups at the time of transfer and discharge. Sensory function was statistically different among the 3 groups at the time of transfer, but not different at the time of discharge.
Conclusion: Even though SSEP study reflects the functional status of the patients and correlates well with the findings of brain image, it has limitation in predicting outcome of the patients with stroke. (J Korean Acad Rehab Med 2003; 27: 355-360)
Objective: The purpose of this study is to evaluate the relationship between cognitive function and findings of evoked potential study in chronic renal failure patients.
Method: Thirty chronic renal failure patients with cognitive dysfunction were recruited, whose mini-mental state examination (MMSE) scores were less than 24 points. According to the underlying diseases of chronic renal failure, we categorized thirty patients into diabetic group (11 patients) and non-diabetic group (19 patients), and the control-group was composed of 15 normal volunteers. Somatosensory evoked potential (SEP) on stimulating median and posterior tibial nerves, and cortical and spinal conduction time of the motor pathways were valuated.
Results: In tibial nerve SEP, N22-P38 interpeak latencies (IPL) were 18.1⁑4.2 msec in the patient group and 15.7⁑1.9 msec in the control group, respectively. In MEP, cortico-lumbar central motor conduction times (CMCT) were 19.5⁑2.7 and 16.5⁑3.0 msec, respectively. CMCT were prolonged in patients than controls (p＜0.05). There was significant correlation between serum creatinine concentration and N22-P38 IPL (r=0.64, p＜0.05), but, there were no correlations between the underlying diseases of chronic renal failure, duration of disease, MMSE score and cortico-lumbar CMCT, N22-P38 IPL (p＞0.05).
Conclusion: Evoked potentials will be helpful in evaluating the patients with cognitive dysfunction in chronic renal failure.
Objective: The aim of this study is to identify the ipsilateral motor evoked potentials (iMEPs) from unaffected cerebral hemisphere after stroke via transcranial magnetic stimulation, especially in acute stage (within 1 week from attack), and to evaluate the characteristics of iMEPs compared with the crossed contralateral motor evoked potentials (cMEPs).
Method: Thirty patients were recruited, who had suffered their first ischemic stroke and consequent motor deficits and mean duration from attack to examination was 6.0⁑3.3 days. They were tested with round coil stimulator in order to record motor evoked potentials from both contralateral and ipsilateral abductor pollicis brevis (APB) muscles. For the purpose of hand motor cortex mapping, we designed specialized cap, which was marked using international 10∼20 systems by 1 cm interval. In addition, we observed the changes in onset latency and amplitude of MEPs during the isometric contraction of thenar muscle guided by visual and auditory feedback.
Results: iMEPs were generally absent in normal subjects, but they were obtained in 17 (56.7%) of 30 patients by stimulating the unaffected hemisphere. Different from contralateral MEPs, ipsilateral MEPs were obtained with higher stimulation intensity, significantly delayed latencies and lower amplitudes. And we noticed shorter latencies and larger amplitudes of MEPs by the isometric contraction of thenar muscle.
Conclusion: Our results will reflect the compensatory role by the unaffected cerebral hemisphere with respect to motor recovery, if contralateral route is damaged. We provided neurophysiologic evidences of cerebral neuroplasticity, proven by the ipsilateral unaffected hemispheric activation in early phase stroke patients.
Objective: The purposes of this study were to evaluate the diagnostic value of dermatomal somatosensory evoked potentials (DSEPs) in the unilevel/unilateral lumbosacral radiculopathies.
Method: The study was performed on 41 patients with herniated lumbosacral disc which was confirmed by magnetic resonance imaging, and the patients with clinical lumbosacral radiculopathies (L5 radiculopathy in 33 cases and S1 radiculopathy in 8 cases). Stimulation sites were over the dorsum of the foot on the distal fifth metatarsal bone for the S1 dermatome and at the interdigital web space between first and second toe for the L5 dermatome. Recordings were made at Cz' and reference to Fz. Conventional nerve conduction study, needle EMG and H-reflex were also examined.
Results: While the needle EMG showed abnormalities in 32 patients (78.0%), the abnormalities of DSEPs were in 13 patients (31.7%): 33.3% for the L5 radiculopathy and 25.0% for the S1 radiculopathy, respectively. Moreover, there was no significant relationship between the abnormal findings of needle EMG and DSEPs (p＞0.05). The H-reflexes were abnormal in 6 of 7 patients (85.7%). And then two of them were found abnormal in S1 DSEPs.
Conclusion: The conventional needle EMG appears to be the more useful electrophysiological technique in the diagnosis of lumbosacral radiculopathies. The ultimate diagnostic value of DSEPs in lumbosacral radiculopathies is doubtful and controversial.
Objective: To investigate the effect of peripheral nerve stretching on motor evoked potentials (MEP) as a method of facilitation.
Methods: Twenty three normal healthy volunteers were enrolled. Transcranial magnetic stimulation (TMS) was applied to the contralateral scalp at 7 cm lateral to Cz using 90 cm round coil. Intensity of stimulation was adjusted to 90% of maximal stimulation intensity. Recording was done on the abductor pollicis brevis muscle in three different conditions; firstly resting state, secondly voluntary contraction of abductor pollicis brevis muscle, and lastly with stretching of median nerve. The onset latency and amplitude were obtained and compared between three conditions.
Result: The amplitude of MEP was significantly increased in the condition with muscle contraction and peripheal nerve stretching compared with resting state. The latency was shortened in the condition with muscle contraction with statistical significance and with peripheral nerve stretching without significance.
Conclusion: We concluded that stretching of peripheral nerve can be used as a method of facilitation of MEP. This method is considered to be useful especially for the patients with motor paralysis or poor cooperarion for voluntary contraction.
Objective: To investigate the association of the muscle contraction with gating of the sensory input at central and peripheral levels according to the intensity of muscle contraction and location of the muscles, somatosensory evoked potentials (SSEPs) studies were evaluated at different levels of isometric contraction in the different muscles.
Method: Median nerve SSEPs were recorded at Erb's point and scalp in the ten healthy adult subjects with isometric contraction of ipsilateral abductor pollicis brevis (APB), ipsilateral abductor digiti minimi (ADM) and contralateral APB. Median nerve SSEPs were recorded in each of these conditions during precontraction, weak contraction, strong contraction and 4 minutes after contraction.
Results: 1) N9 amplitudes of median SSEPs recorded at Erb's point were augumented during weak contraction and these amplitude augumentations were statistically significant in the ipsilateral APB contraction (p＜0.05). 2) N20 amplitudes recorded at scalp were inhibited during strong isometric contraction and these amplitude inhibitions were statistically significant in the ipsilateral APB contraction (p＜0.05). 3) The latencies of N9 and N20 potentials were not significantly changed during isometric contraction.
Conclusion: Therefore peripheral nervous system as well as central nervous system is responsible for gating, so the subject should be asked for the best relaxation possible for higher reliability of SSEPs.
Objective: The present study was undertaken to determine the value of developmental assessment, multimodality evoked potentials, brain magnetic resonance image (MRI) and electroencephalography (EEG) and to identify correlations between each evaluation.
Method: Developmental assessments such as Bayley scales of infant development and Vineland social maturity scale, brain MRI, EEG and evoked potentials findings were evaluated in 45 children with spastic cerebral palsy to assess the developmental level and abnormalities of the anatomical structure of the brain and to elucidate the relationship between the test methods.
Results: 1) Mean mental developmental index (MDI) and psychomotor developmental index (PDI) were 69.6 and 68.6, respectively and mean Vineland social maturity quotient (SQ) was 76.1 and there was a significant correlation between the MDI, PDI, and SQ in cerebral palsied children. 2) Abnormal findings of brain MRI and EEG were found in 73.3% and 44.4% of the cases, respectively. 3) There was significant correlation between findings of brain MRI, auditory evoked potentials, visual evoked potentials, median somatosensory evoked potentials and social quotient.
Conclusion: Developmental assessment, multimodality evoked potentials, EEG, and brain MRI would be a useful method to evaluate the maturity of brain and estimate the level of development.
Objective: To identify the existence of ipsilateral responses by magnetic stimulation, and to elucidate the influences of ipsilateral tonic contraction on bilateral MEP responses, and to attain the proper facilitation technique for bilateral MEP responses.
Method: Ten normal healthy volunteers who were right handed, were recruited. They performed the voluntary contraction of thenar muscle via lateral prehension with three stage, contralateral, bilateral, ipsilateral contraction by 70 mm bipolar coil stimulator (figure-of-eight shaped). The excitability threshold (ET) at rest was determined, and then, three facilitation techniques with combination of both voluntary contraction and stimulus intensity were also performed: A technique, minimal facilitation (10% of MVC) with ET intensity; B technique, moderate facilitation (30% of MVC) with 110% of ET intensity; C technique, minimal facilitation (10% of MVC) with 140% of ET intensity. Contralateral, bilateral and ipsilateral voluntary contractions were performed in each technique. In 90 mm circular coil stimulator, same procedure as above was followed.
Results: There were no differences of ET between the two coil stimulators. Ipsilateral MEP responses were not detected after bipolar coil stimulation except one case in C technique, but they were developed over 70% in B and C technique with ipsilateral muscle contraction. However, only 2 cases of ipsilateal responses could be detected in C technique, and not detected in A and B technique. The latency of ipsilateral responses were similar to that of contralateral responses, but the amplitude was much lower than that of contralateral responses. Ipsilateral muscle contraction reduced the amplitude of contralateral MEP in moderate facilitation (B technique). Especially, ipsilateral response was never evoked in B technique with contralateral contraction.
Conclusion: In normal subjects, ipsilateral MEPs can't be obtained in focal magnetic stimulation. Ipsilateral tonic contractions are regarded as reducing facilitative effects of contralateral MEP responses. Bilateral responses should be attained when contralateral target muscle is contracted with moderate facilitation (30% of MVC and 110% of threshold intensity). In this facilitation, the stimulation by circular coil is no less effective than focal stimulation by 70 mm bipolar.
Objective: The aim of this study was to evaluate the clinical usefulness of motor evoked potentials (MEPs) in predicting functional motor recovery of acute stroke patients.
Method: Nineteen acute stroke patients were assessed clinically by manual muscle test (MMT) & modified Barthel index (MBI) and SEP & MEP at about 10 days after stroke. Follow up clinical assessments were performed by MMT, MBI & gait evaluation after two months of rehabilitation program.
Results: 1) In the acute phase of stroke, there was a significant relationship between MEP and motor function. 2) The presence of MEPs in hemiparetic upper & lower extremities was correlated with better functional outcome than the absence of MEP in at least one extremity. MEP was better than SEP in predicting functional outcome following acute stroke. 3) The presence of MEP in hemiparetic abductor pollicis brevis muscle was correlated with a better functional improvement, contrarily the absence of MEP in abductor hallucis muscle was correlated with a worse functional outcome.
Conclusion: We concluded that MEP study is a useful assessment tool in predicting functional outcome of acute stroke patient. However, the absence of MEP does not necessarily indicate a poor prognosis. So further study is needed to clarify this controversy.
Object: The isolated posterior femoral cutaneous nerve (PFCN) neuropathy has rarely been described in the literature and documented electrophysiologically, based on the paucity of published report. The purpose of this study was to assess the reference value of somatosensory evoked potentials (SSEP) in posterior femoral cutaneous nerve.
Method: Both legs of twenty healthy adults were tested. Somatosensory evoked potentials were obtained with the active recording electrode placed at Cz', 2 cm posterior to CZ, and the reference electrode at FZ (international 10∼20 system). The posterior femoral cutaneous nerve was excited 14 cm proximal to the midpopliteal fossa between the long head of the biceps femoris and the semitendinosus muscles.
Results: The mean latency of right P1 were 35.35⁑3.17 msec, N1 were 45.28⁑2.71 msec and mean peak amplitudes were 1.42⁑0.98 μV. In the left side, mean latency of P1 were 34.54⁑2.89 msec, N1 were 43.87⁑2.44 msec and mean peak amplitudes were 1.20⁑0.53 μV.
Conclusion: Based on the result of this study, the reference values could be used to differentiate and detect the lesion in the case of isolated dysfunction of the posterior femoral cutaneous nerve.
Objective: To investigate the change of peak latency, interpeak latency and amplitude of auditory brainstem evoked potentials (AEPs) in normal preterm infants in accordance with the age, and to find out the correlation between reproducibility of AEPs and high risk of premature infants.
Method: AEP studies were performed on 266 premature infants (male 143, female 123) within a month of the birth. Acquired potentials were grouped by the reproducibility of waveforms, and latency, interpeak latency and amplitude were measured in each group of potentials to interpret age appropriate changes of AEPs.
Results: 1) Peak latency of peak I, III and V were shortened in accordance with the age, especially latency of peak V was significantly decreased from 7.42 msec to 6.84 msec. 2) There was no significant change in interpeak latency or amplitude of AEPs according to the postmenstrual age. 3) Reproducibility of AEPs was worse in premature infants with history of asphyxia.
Conclusion: Considering the results, the latency of peak V can be used as one of the useful parameter to investigate and follow up the premature infants. Significant negative correlation between low grade reproducibility and history of neonatal asphyxia was found.
Objective: Intraoperative monitoring using somatosensory evoked potential (SEP) study has been used increasingly to monitor neurological function during scoliosis surgery and other high-risk spinal surgeries. However, there are few studies related to this intraoperative monitoring, particularly in severe spinal deformity surgery, in Korea. So we evaluated the clinical efficacy of intraoperative SEP monitoring and considered the risk factors related to spinal surgery.
Method: We performed a posterior tibial nerve somatosensory evoked potential study for intraoperative monitoring during surgical procedures in 101 patients (male 46, female 55).
Results: Neurologic damage occurred in 16 patients (10 congenital scoliosis cases, 5 tuberculous kyphosis cases, and 1 degenerative spondylosis case) after surgical procedures. Delayed postoperative neurologic damage occurred in 4 patients (2 mild damage cases, 2 severe damage cases) among 85 cases which showed normal responses during surgical procedures. Sensitivity of this study was 75%, and specificity was 95.3%.
Conclusion: Somatosensory evoked potential study for intraoperaive monitoring is a sensitive and very useful method to detect iatrogenic lesions during spinal deformity surgery with satisfactory specificity. However, to improve the sensitivity and specificity of the intraoperative monitoring, combination of motor evoked potentials is recommended.
Objective: This study was performed to investigate the prognostic value of multi-sensory evoked potentials (MSEPs) in neonatal period for the early diagnosis of delayed motor development, especially cerebral palsy.
Method: The MSEPs studies composed of auditory brainstem evoked potentials (AEPs), visual evoked potentials (VEPs) and somatosensory evoked potentials were taken on 237 neonates, 136 boys and 101 girls, using Viking IVⰒ machine. Follow up MSEPs were repeated in every 4 or more weeks for those who showed abnormal responses in any of the MSEPs. Each neonate was also evaluated for motor development as an outpatient or by telephone interview.
Results: Among 237 neonates, 6.4% showed delayed development, and 4.6% were cerebral palsy: 3.8%, spastic type; 0.8%, athetoid type, and the others revealed normal motor development. AEP was useful method to predict motor development when this was done at 39.7⁑0.4 weeks of postmenstrual age (PMA). VEPs failed to show the validity, but there was the typical waveform change in accordance with increase of the postmenstrual age. Median nerve SEPs were valuable for prediction of motor development which were taken at PMA 40.7⁑0.6 weeks. After 45.3⁑1.5 weeks of PMA, median nerve SEPs did not reflect motor development outcome significantly. However, posterior tibial SEPs significantly reflect motor outcome regardless of the time of examination.
Conclusion: Median and posterior tibial SEPs done before 40weeks of PMA are useful tool to predict motor development outcome. When any of these tests showed abnormal findings, follow up study is recommended and posterior tibial SEP study is thought to be the most useful for its predictability. It is necessary to correlate the AEPs and VEPs with hearing and vision whenever abnormal findings are found.
Objective: This study was designed to investigate the effect of different sites of recording electrodes on auditory evoked potentials (AEPs) in healthy adults and to analyse these potentials properly.
Method: Eleven healthy adults, 7 males and 4 females, without any history of disease or conditions causing hearing difficulties were selected. AEPs were performed on these subjects with 4 different methods, i.e. different recording sites, Cz-Ai, Cz-Fpz, Ai-Ac, and Ai-Cs7. Auditory stimulation was given by rarefaction clicks of 75dB intensity and 11.1 Hz frequency, and responses were recorded with surface electrodes.
Results: The amplitudes of peak I and V were larger with vertical recordings, that is the vertex-auricle (Cz-Ai) or vertex-7th cervical spine (Cz-Cs7) recordings, compared to horizontal recordings of both auricle (Ai-Ac) or extracephalic electrodes. The largest amplitude ratio of peak V/I was with vertex-7th cervical spine (Cz-Cs7) recording.
Conclusion: Changes in AEPs with respect to the sites of recording and reference electrodes are thought to be due to the vector of brain stem auditory nuclei and pathways. It might be helpful to consider these changes in the evaluation of brain stem lesions.
Objectives: To analyze the motor evoked potential (MEP) responses to a degree of voluntary contraction and stimulus intensity and to suggest the standardized optimal stimulation for MEP responses.
Methods: MEPs induced by a cortical stimulation were elicited at the thenar muscles in 15 normal subjects during the rest and gradual voluntary contraction, using the 10% of maximal voluntary contraction (MVC), 30%, 50%, and MVC. During rest and during each contraction, excitability threshold at rest (RET) and at contraction (CET) were determined. Consecutive stimuli were applied, according to the intensity of ratio increment (110% to 150% of excitation threshold).
Results: The RET showed a remarkable decrease (57.1⁑8.2% → 47.4⁑8.7%) after the voluntary contraction (P＜0.05). Shortening of latency reached the saturation level with 10% of MVC, irrespective of stimulus intensity. Amplitude reached a saturation level at 30% of MVC with 62.7% intensity of maximal output, which is equal to 140% intensity of its CET, and to 110% of RET. MEP amplitude at rest and at 10% of MVC were influenced by the excitation threshold (P＜0.05), but those at above 30% of MVC were not related.
Conclusion: The procedure for optimal facilitation for the MEPs is as follows; for minimal latency of MEPs, minimal contraction (10% of MVC) with RET intensity is enough. For maximal amplitude of MEPs, moderate contraction (30% MVC) with 110% intensity of RET is adequate.
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