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.
Citations
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.
Citations
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.
Citations
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.
Citations
To investigate the predictive index of functional recovery after primary pontine hemorrhage (PPH) using the combined motor evoked potential (MEP) and somatosensory evoked potential (SEP) in comparison to the hematoma volume and transverse diameter measured with computerized tomography.
Patients (n=14) with PPH were divided into good- and poor-outcome groups according to the modified Rankin Score (mRS). We evaluated clinical manifestations, radiological characteristics, and the combined MEP and SEP responses. The summed MEP and SEP (EP sum) was compared to the hematoma volume and transverse diameter predictive index of global disability, gait ability, and trunk stability in sitting posture.
All measures of functional status and radiological parameters of the good-outcome group were significantly better than those of the poor-outcome group. The EP sum showed the highest value for the mRS and functional ambulatory category, and transverse diameter showed the highest value for "sitting-unsupported" of Berg Balance Scale.
The combined MEP and SEP is a reliable and useful tool for functional recovery after PPH.
Citations
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.
Citations
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: Retrospective chart review was performed in 561 patients. Among 561 stroke patients, 116 subjects were recruited and classified into two groups: patient group, 43 cases with RSD; control group, 73 cases without RSD. Upper extremity function was assessed based on feeding, dressing and personal hygiene scores of the modified Barthel index at the beginning of rehabilitation treatment and at the time of discharge. Causes of stroke and length of stay were recorded. Median nerve-somatosensory evoked
potential studies were performed and assessed.
Results: The incidence of RSD was 7.7% and the time to development of RSD was 62.3±34.1 days after the onset of stroke. There was no significant difference in functional status between two groups at initial and final evaluation. The upper extremity function had improved in both groups although the length of stay was longer in patient group. SSEP abnormalities were more frequent in the patient group.
Conclusion: The presence of well-managed RSD affected neither the functional status nor the functional recovery of upper extremity in stroke patients. (J Korean Acad Rehab Med 2003; 27: 480-484)
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)
Method: The subjects were 65 patients with neurogenic bladder. The causes of neurogenic bladder were consist of seven brain lesions; 39 spinal cord injuries; 15 cauda equina syndromes; and four peripheral polyneuropathies. PSEP and EBCR were done.
Results: Of the patients with hyperreflexic bladder (43.1%), PSEP latency was normal in 21.4%, delayed in 21.4%, and not obtainable in 57.2%. Of the patients with areflexic bladder (56.9%), PSEP latency was normal in 24.3%, delayed in 21.6%, and not obtainable in 54.1%. Of the patients with hyperreflexic bladder, EBCR latency was normal in 82.1%, delayed in 14.3%, and not obtainable in 3.6%. Of the patients with areflexic bladder, EBCR latency was normal in 16.2%, delayed in 37.8%, and not obtainable in 46.0% (p＜0.01).
Conclusion: There was significant correlation between EBCR and type of neurogenic bladder, but not with PSEP. These results seem to be reflected from the neuro-anatomical lesion of the neurogenic bladder. (J Korean Acad Rehab Med 2003; 27: 70-74)
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.
This 32 year-old man sustained crush injury and resultant in paraplegia. Lumbar MRI was taken and revealed fracture and dislocation between L2 and L3 vertebrae bodies. On the day of the injury, he underwent a surgical intervention of posterolateral fixation and bone graft from L1 to L4 vertebrae. He was transferred to Rehabilitation Medicine Department of Asan Medical Center where patient was subsequently found to have an unexpected neurologic finding of decreased sensation below T5 dermatome on right and below T6 on left. Accordingly we took a thoracic MRI which showed features consistent with arachnoiditis at thoracic and lumbar cord segment. A dermatomal somatosensory evoked potential study was performed with finding of abnormal somatosensory pathway below mid thoracic dermatome. We reported an unusual case of thoracic arachnoiditis occurred after the surgical fixation of the lumbar vertebral fracture and dislocation.
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 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: Intraoperative somatosensory evoked potentials (SEPs) are widely used for the early detections of cerebral ischemia during temporary occlusive procedures of the parent vessels in aneurysm surgery. This study intended to evaluate the usefulness of median nerve SEPs during intracranial aneurysm surgery.
Method: Between September 1995 and June 1997, we monitored 42 aneurysm patients in Uijongbu St. Mary's hospital. Median nerve SEPs were detected on scalp and cervical spine during surgery. We measured latencies, amplitudes of N20 and N13 waveforms and central conduction time (CCT, N20-N13). We analyzed pre- and post-surgical radiologic findings and changes of neurologic signs.
Results: The delayed latencies, CCT, and reduced amplitudes of median nerve SEPs during intraoperative monitoring were closely related to neurological deficits after surgery.
Conclusion: Intraoperative SEPs are useful in preventing clinical neurological injury during surgery of intracranial aneurysm and in predicting which patients will have unfavourable outcomes.
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: 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: To evaluate the changes of dermatomal SEP (DSEP) in children with a spastic cerebral palsy (CP) after the selective posterior rhizotomy (SPR).
Method: The subjects were 14 spastic CP children, with the age from 3 to 6 years old, who underwent SPR. DSEPs were studied at the L2-3, L4, L5, S1 dermatomes bilaterally, pre and postoperatively. Postoperative DSEPs were interpreted by the changes of latency, amplitude and waveforms.
Results: 1) All children were spastic diplegia except one who was a spastic hemiplegia. 2) Preoperative DSEPs were flat or severely distorted in 40 of 112 waveforms (34.5%). 3) Postoperative DSEP latencies were no change in 39.3%, improved in 17.9%, and worsened in 25.6% respectively. Amplitudes were no change in 30.8%, improved in 38.5%, and worsened in 13.7% respectively. Waveforms were no change in 64.1%, improved in 22.2%, and worsened in 8.5% respectively. There was no statistical difference of postoperative changes of the 3 categories according to the root levels.
Conclusion: The results showed that the preoperative DSEPs were abnormal in 34.5% suggestive the lesions of CP being more widespread than strictly involving the motor system. This study confirmed that the most SEPs unchanged by the SPR. A further study for the relationship of postoperative DSEP changes and clinical findings such as functional impairment would be needed.
Objective: To evaluate the diagnostic values of segmental somatosensory evoked potentials (SEPs) in the unilevel/unilateral lumbosacral radiculopathies.
Method: Thirty-nine radiculopathy patients of whom diagnosis was confirmed by the surgery or selective nerve root injection and 20 subjects with no evidence of radiculopathy were included in the study. Before the treatment, superficial peroneal nerve segmental SEPs and sural nerve segmental SEPs were performed. Sensitivities and specificities were delineated from the several diagnostic criteria.
Results: The analysis of side-to-side mean cortical P1 latency difference (＞2.0 SD) reveals a segmental SEPs sensitivity for L5 radiculopathies of 12.1% and sensitivity for S1 radiculopathies of 0%. The analysis of side-to-side mean percent amplitude difference (2.0 SD) reveals a segmental SEPs sensitivity for L5 radiculopathies of 9.1% and sensitivity for S1 radiculopathies of 0%. The analysis of side-to-side mean cortical P1 latency difference (＞3 ms) and the side-to-side mean amplitude reduction (＞50%) show the similar results. The specificities of L5 radiculopathies and S1 radiculopathies are variable from 40.0% to 93.3%. Sensitivities of segmental SEPs are lower than needle EMG. It is not root specific, even the SEP is not obtainable unilaterally.
Conclusion: The diagnostic values of segmental somatosensory SEPs are questionable in the unilevel/unilateral lumbosacral radiculopathies which are confirmed by the surgery or selective nerve root injection.
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