Diagnostic utility of somatosensory and motor evoked potentials in a patient with thoracic outlet syndrome

OBJECTIVE: To evaluate the utility of somatosensory and motor evoked potentials in the diagnosis of neurogenic thoracic outlet syndrome (TOS). MATERIALS AND METHODS: In a female patient with progressive weakness and sensory disturbance, ulnar nerve somatosensory evoked potentials (SSEP), and intraoperative motor evoked potential (MEP) were performed. RESULTS: The SSEPs demonstrated no significant change in latency of major peaks at rest and after abduction of the shoulder. Diminishment of amplitude was noted after dynamic position of the arm. The MEPs demonstrated no significant change in latency after dynamic position. Diminishment of amplitude was noted after the dynamic position. The amplitude returned to normal after repositioning the arm. CONCLUSIONS: Electrophysiologic study is helpful in the diagnosis of neurogenic TOS. Reduced amplitude of cortical SSEP and myogenic MEP is expected during dynamic position of the affected arm.     

Abnormal brainstem evoked potentials in diabetes mellitus. Evoked potential testings and magnetic resonance imaging

Brainstem auditory evoked potentials (BAEPs) and median nerve somatosensory evoked potentials (MN-SEPs) were measured in 53 diabetic patients. Magnetic resonance imaging (MRI) was performed 12 patients with abnormal BAEPs and/or MN-SEPs in order to confirm the existence of lesions in the central nervous system. Twenty-six percent of the diabetic patients had abnormal BAEPs and three had a prolongation of the central conduction time in the MN-SEPs. MRI findings of ten of the 12 patients with abnormal BAEPs or MN-SEPs showed multiple small lesions in the pons, thalamus, and centrum semiovale etc. Two of them showed small lesion in the pontine basis which could induce prolonged interpeak latencies of BAEPs. Our MRI study might suggest that abnormal brainstem evoked potentials in diabetic patients were induced by diabetic macroangiopathy or microangiopathy.     

Cortical somatosensory evoked potentials. I. Recordings in the monkey Macaca fascicularis

1. The anatomic generators of somatosensory evoked potentials (SEPs) to median nerve stimulation in the 10- to 30-ms latency range were investigated in monkeys (Macaca fascicularis) by means of cortical-surface and laminar recordings. 2. Three groups of SEPs evoked by stimulation of the contralateral median nerve were recorded from the hand representation area of sensorimotor cortex: P10-N20, recorded anterior to the central sulcus (CS); N10-P20, recorded posterior to the CS; and P12-N25, recorded near the CS. These potentials were similar in morphology and surface distribution whether the animal was awake or anesthetized. 3. P10-N20 exhibited a polarity inversion to N10-P20 across the CS, both in cortical-surface recordings and in laminar recordings within cortex and white matter of motor and somatosensory cortex. In contrast, P10-N20 and N10-P20 did not exhibit polarity inversion in recordings from the surface and white matter of the crowns of motor and somatosensory cortex, respectively. These results strongly suggest that these potentials are produced by a tangential generator located in the posterior wall of the CS, primarily in area 3b of somatosensory cortex. 4. P12-N25 was largest over the hand area of somatosensory cortex and showed polarity inversion across the crown of somatosensory cortex but not across the crown of motor cortex or across the walls of the CS, suggesting that P12-N25 is due to a radially oriented generator located in areas 1 and 2 of somatosensory cortex. 5. P10-N20 and P12-N25 are thought to be equivalent to the "primary evoked response" recorded from somatosensory cortex of other mammals. 6. These results are very similar to those obtained in human cortical-surface recordings and demonstrate that the monkey P10-N20, N10-P20, and P12-N25 potentials correspond to the human P20-N30, N20-P30, and P25-N35 potentials, respectively. The only appreciable difference in human and monkey SEPs is that the monkey P12-N25 appears to be generated in areas 1 and 2, whereas the human P25-N35 appears to be generated only in area 1. 7. There was no evidence of locally generated activity in areas 3a and 4.     

Neurogenic vestibular evoked potentials in the diagnosis of multiple sclerosis

OBJECTIVES: To determine the value of neurogenic vesibular evoked potential (NVESTEP) studies in comparison with other paraclinical tests in demonstrating dissemination in time and space in Multiple Sclerosis (MS) and in identifying clinically silent lesions. METHOD: All patients in whom MS was suspected but the diagnosis of MS was not possible based on the McDonald criteria were included in this study. We studied 14 patients and performed visual, brainstem auditory, somatosensory and neurogenic vestibular evoked potentials in all patients, together with MRI and CSF analysis of oligoclonal bands (OB). RESULTS: Two out of the thirteen patients could be movedfrom the category of "possible MS" to "MS" using the McDonald criteria based on an abnormal NVESTEP result. CONCLUSION: Neurogenic vestibular evoked potentials are potentially useful in identifying clinically silent lesions in patients with possible MS.     

Diagnostic criteria and genetics of the PEHO syndrome.

The PEHO syndrome (progressive encephalopathy with oedema, hypsarrhythmia, and optic atrophy) is a recently recognised disorder of unknown biochemical background. Diagnostic features have been found in neuroradiological and neuropathological studies, which show characteristic severe cerebellar atrophy. In combined neuroradiological and ophthalmological studies, 10 out of 21 possible PEHO patients fulfilled the criteria for true PEHO syndrome. All were abnormal at birth showing hypotonia, drowsiness, or poor feeding. Head circumference was normal, but usually dropped to 2 SD below average during the first year of life. Visual fixation was either absent from birth or lost during the first months of life. Nine patients had peripheral oedema in early childhood. The mean age of onset of infantile spasms was 4.9 months. All patients were extremely hypotonic and no motor milestones were reached. Patellar reflexes were brisk. Brain stem and somatosensory evoked potentials were abnormal in each case studied, cortical responses of somatosensory evoked potentials could not be elicited, and motor conduction velocities became delayed with age. Altogether 19 PEHO patients were found in 14 Finnish families. Autosomal recessive inheritance is likely.     

High frequency vibration induced gating of subcortical and cortical median nerve somatosensory evoked potentials: different effects on the cervical N13 and on the P13 and P14 far-field SEP components.

Subcortical and cortical somatosensory evoked potentials (SEP) to median nerve stimulation were recorded before, during and after high frequency (270 Hz) vibration of the fingers 1-3 in 8 healthy subjects. A marked decrease of the amplitude of all potentials was observed. The attenuation of the sensory nerve action potential (SNAP) of the median nerve and the attenuation of SEP components N9, N11 and N13 showed no differences, while the attenuation of the subcortical P14 component was significantly higher. This is in accordance with a generator of the cervical N13 in the interneurons beside the lemniscal pathway. The cortical N20 (post-rolandic) was significantly more decreased in amplitude than P14 while P22 (pre-rolandic) remained reduced in amplitude like P14. An increased latency of the far-field subcortical P14 was observed, while P13 recorded in the same montage remained unchanged in latency. These findings suggest different generators of these peaks. A generator of P14 above the nucleus cuneatus is confirmed. A presynaptic generator of P13 is suspected.     

P300等诱发电位对亚临床肝性脑病早期诊断的意义

目的:观察事件相关电位P_(300)、体感诱发电位、视觉诱发电位和脑干听觉诱发电位在亚临床肝性脑病诊断中的意义。方法:50例亚临床肝性脑病患者进行了心理测验,并做了头颅CT和视觉诱发电位、体感诱发电位、脑干听觉诱发电位和事件相关电位检查,30例正常人做为对照组。结果:亚临床肝性脑病的心理测验,韦氏法智力低下率为76％,视觉诱发电位异常率为13％,脑干听觉诱发电位异常率为20％,体感诱发电位异常率为40％,事件相关电位异常率为71％,正常对照组四种诱发电位的正常率是100％。头颅CT结果与亚临床肝性脑病无关。结论:视觉诱发电位、体感诱发电位、脑干听觉诱发电位和事件相关电位在亚临床肝性脑病中是异常的。事件相关电位更为敏感,对亚临床肝性脑病的早期诊断有重要意义。     

Somatosensory evoked potentials/fields--exploration of brain function

We have summarized the history of electroencephalography(EEG) since 1875, when a paper by Richard Caton was published describing the first EEG recordings in animals. Somatosensory evoked potentials (SEPs) were recorded by George Dawson in 1951. Thereafter, SEPs were developed for clinical use with other evoked potentials such as auditory evoked potentials(VEPs). To understand evoked potentials, related mechanism of induction of far-fields-potentials(FFP) following stimulation of the median nerve has been discussed. SEPs consisted of P9, N9, N10, P11, N11, N13, P13, P14, N18, N20 and P20/P22. Scalp recorded P9 FFP arises from the distal portion of the branchial plexus as reflected by N9 stationary negative potential recorded over the stimulated arm. Cervical N11 and N13 arise from the root entry zone and dorsal horn, respectively. Scalp recorded P13, P14 and N18 FFP originate from the brainstem. In this communication, magnetoencephalography(MEG) and results of one of our recent studies on somatosensory evoked fields(SEFs) are also discussed. One of the important features of MEG is that magnetic signals detected outside the head arise mainly from cortical currents tangential to the skull. Since the net postsynaptic current follows the orientation of cortical pyramidal cells, the MEG signals mainly reflect activity of the fissural cortex, whereas radial current may remain undetected. In our study, we demonstrated SEFs elicited by compression and decompression of a subject's glabrous skin by a human operator. Their dipoles were tangentially oriented from the frontal lobe to parietal lobe.     

Sensory and motor evoked potentials findings in patients with thoracic outlet syndrome

OBJECTIVE: Diagnostic utility of somatosensory and motor evoked potentials in two patients with neurogenic and vascular thoracic outlet syndrome (TOS) were investigated. MATERIALS AND METHODS: In two female patients with progressive weakness and sensory disturbance of the arms, mixed nerve somatosensory evoked potentials (SSEP), and motor evoked potentials (MEP) were tested before and after dynamic position of the affected arm. RESULTS: The cortical and cervical (C7) ulnar SSEPs demonstrated no change in latency of major peaks at rest and after abduction of the shoulder. A slight diminishment of cortical amplitude was noted in the first patient after the dynamic position of the arm. The MEPs demonstrated significant drop in amplitude after dynamic position of the arm in both cases signifying neurovascular compression during elevation of the affected arm. No change in MEP latency was noted. The MEP amplitude completely returned to normal after repositioning the arm. CONCLUSIONS: Evoked potential studies are helpful in the diagnosis of neurogenic or vascular TOS. Reduced amplitude of MEP occurs after elevation of the arm above the head which improves after normal position of the arm.     

抑郁症患者感觉诱发电位变化与自杀行为的相关研究

目的:探讨抑郁症患者感觉诱发电位(SEP)变化与自杀行为的关系。方法:应用国产脑诱发电位仪,记录了48例抑郁症患者和40名正常对照者的SEP。结果:(1)与正常对照组相比,抑郁症组均出现P2主成分波幅降低(正常对照组(6.1±2.5)μV,自杀史阳性组(2.7±1.9)μV,自杀史阴性组(3.8±2.7)μV,P0.01)。(2)抑郁症患者的SEP改变主要与有无自杀行为史可能相关。结论:自杀行为相关的生物学指标与SEP的关系有待下一步随访。     

Effect of anti-epileptic drug monotherapy and polypharmacy on visual and auditory evoked potentials

Previous reports have suggested that some anticonvulsants may prolong somatosensory and auditory evoked potential latencies. We compared pattern-reversal visual and brainstem auditory evoked potentials in normal controls, patients on monotherapy, and patients taking polypharmacy. Visual evoked potential amplitudes were less in seizure patients, and P1 latencies were longer in epileptics on polypharmacy than controls. Absolute latencies of brainstem auditory evoked potentials were longer in polypharmacy patients than in controls or monotherapy patients. I-III, III-V, and I-V interpeak latencies were greater in polypharmacy patients than in those on monotherapy or controls. These findings suggest that anticonvulsants may affect conduction along visual and auditory pathways, and that antiepileptic drug polypharmacy and monotherapy may differ in their effects.     

多种诱发电位和MRI检查在多发性硬化诊断中的价值

目的：探讨诱发电位和磁共振成像（MRI）检查在多发性硬化（MS）诊断中的价值。方法：收集65例MS患者的临床资料、磁刺激运动诱发电位（MEP）、脑干听觉诱发电位（BAEP）、视觉诱发电位（VEP）、体感诱发电位（SEP）以及MRI结果,比较不同检测方法对其临床诊断的价值。结果：MS患者的磁刺激MEP、BAEP、VEP、SEP以及MRI的异常检出率分别为78％（51／65）、51％（33／05）、80％（52／65）、71％（46／65）和85％（55／65）。4项诱发电位检查总异常检出率为88％（57／65）,与MRI检查结果比较差异无统计学意义（P〉0．05）。各种诱发电位和MRI检查均能发现临床下病灶：6例患者经MRI检查发现病灶但无相应临床症状;8例患者有临床症状而MRI检查未见相应病灶,但诱发电位检查可见异常。结论：MRI和各种诱发电位检查具有相互补充作用,结合临床合理选择使用此两种检查有助于提高MS诊断的敏感性。     

Timing and characteristics of perceptual attenuation by transcranial stimulation: a study using magnetic cortical stimulation and somatosensory-evoked potentials.

Transcranial cortical magnetic stimulation (CMS) is a noninvasive, non-noxious procedure to induce perceptual attenuation when applied concomitant to sensory stimuli. To investigate the perceptual timing of simple stimulus features in the somatosensory modality, we applied right hemisphere CMS at different intervals following a stimulus delivered to the left hand. Different intervals between peripheral stimuli and CMS were defined according to the components of the somatosensory-evoked potentials (SEP), previously obtained in response to the same stimulus. Perceptual attenuation was maximal when CMS coincided with the primary cortical response (parietal N20 potential); conversely, perception of stimulus intensity was not modified when CMS was concomitant with the N200 and P300 potentials. Using small CMS intensities, a "perceptual dip" was observed when CMS arrived in coincidence with the N120 potential, a SEP response thought to be originated in part in the second somatic area. Our results support the view that both N200 and P300 are post-perceptual responses. The results also suggest that the cortical processes active during the N20 and N120 potentials may be essential for the conscious perception of somatosensory stimuli delivered to the hand.     

体感诱发电位提取方法的研究与分析

目的:为了更好地研究体感诱发电位的提取方法。方法:将基于自参考自相关自适应干扰对消技术(AAA-ICT)单次提取体感诱发电位的方法与传统的叠加平均提取方法作比较。结果:通过80例神经系统正常的受试者体感诱发电位的深入研究与分析,表明传统的叠加平均方法在提取体感诱发电位上有其合理内涵,但却存在着无法避免的缺陷。结论:AAA-ICT方法避免了其缺陷,实现了体感诱发电位提取方法上的又一大飞跃,具有很好的临床应用价值。     

Topography and dipole analysis of reafferent electrical brain activity following the Bereitschaftspotential

 The cerebral events related to limb movements can be studied noninvasively with the method of evoked potentials. In this study, a brain potential is analysed that follows the onset of a simple finger movement. Because this potential occurred after active as well as after passive movements, its previously alleged reafferent somatosensory nature is confirmed in this study. Detailed topographic analysis revealed that this potential has the same polarity and merges with the preceeding Bereitschaftspotential (BP; in the active movement) at central electrodes, whereas at parietal electrodes polarity is opposite to the BP. In individual subjects, the maximum of the BP and the peak of the reafferent potential are separated by a small gap, previously described as pre-motion positivity. A comparison with the N20 potential of the electrically evoked somatosensory potential showed similar potential topography, albeit opposite polarity. The dipole analysis supported the view that the reafferent and the electrically evoked potentials are likely to arise from the same cortical area, namely the primary somatosensory cortex. Received: 18 April 1996 / Accepted: 18 October 1996     

Scalp topography of somatosensory evoked potentials following median and posterior tibial nerve stimulation in Down's syndrome

Summary The scalp topography of somatosensory evoked potentials (SEPs) following stimulation of the median and posterior tibial nerve of 39 patients with Down's syndrome was compared with that of age-matched normal controls using significance probability mapping (SPM). The maximal area of each potential in Down's syndrome was similar to that in normal controls, but the scalp distribution was wider. The amplitudes of all components, except the N45 and P59 potentials of the posterior tibial nerve SEPs, were greater in Down's syndrome, and the t values calculated by SPM were significantly greater. However, the difference of SEP maps between Down's patients and aged controls (over 65 years) was much smaller than that between Down's patients and age-matched controls. Therefore, we conclude that the generator sources and generating mechanisms of SEPs in Down's syndrome are not different from those of normal control, however SEP potentials in Down's syndrome are remarkably enhanced, resulting in a wider distribution, probably due to accelerated aging in Down's patients.The authors are very grateful to Ms. Junko Matsuda and Ms. Rieko Kakigi for their technical assistance. This study was supported by the Brain Science Foundation, the Kato Memorial Trust for Nambyou Research, the Ministry of Education, Science and Culture in Japan (Grant-In-Aid for New Program, Integrative Studies on Physiological Functions, Grant No. 03NP0101), and by the Ministry of Health and Welfare in Japan (Long Life Science General Project).     

Somatosensory evoked potentials in the diagnosis of cervical spondylotic myelopathy.

Median, ulnar, radial and common peroneal nerve somatosensory evoked potentials (SEPs) were studied in 17 patients suffering from cervical spondylotic myelopathy. Median, ulnar and common peroneal nerve SEPs were abnormal in 41%, 71% and 100% of cases respectively. Abnormalities of the scalp far-field P14 evoked by upper limb stimulation correlated with joint and touch sensation impairment, but not with radiological findings. Therefore, P14 may be a reliable marker of dorsal column impairment in cervical spondylotic myelopathy. The analysis of the cervical N13 response, which was recorded using a cephalic reference electrode, did not give any further information. Common peroneal nerve SEP abnormalities were found in all our patients, but they were obviously of no value in identifying the cervical spine as the site of lesion.     

Somatosensory and brainstem auditory evoked responses in sleep-related periodic leg movements

The pathophysiological mechanisms of sleep-related periodic leg movements (sPLM) and restless legs syndrome are unknown. Evoked potentials have been demonstrated to be abnormal in a variety of episodic movement disorders. In the present study, mixed nerve somatosensory and brainstem auditory evoked responses were examined in patients with polysomnographically documented sPLM who also had restless legs. Normal lower extremity (posterior tibial nerve stimulation) and upper extremity (median nerve stimulation) somatosensory evoked responses were recorded in a group of 10 patients with documented sPLM. Brainstem auditory evoked responses also were normal. These findings do not provide any evidence for a primary afferent sensory disturbance and indirectly support a recently forwarded hypothesis that sPLM is a reflection of suppression of descending inhibitory influences on pyramidal tract function.     

Correlation between temperature and vibration thresholds and somatosensory evoked potentials

The psychophysically assessed thermal specific, thermal pain and vibration sensitivities were correlated to somatosensory evoked potentials in eighteen patients with definite multiple sclerosis. In the psychophysical tests, modality specific stimuli were used. Somatosensory potentials were electrically evoked. The abnormalities of both the temperature and the vibration sensitivity were to same extent related to the somatosensory evoked potentials. Dorsal columns-medial lemnisc and anterolateral-spinothalamic demyelinating lesions were presumed. The psychophysical tests supplement the clinical, laboratory, neuroradiologic and electrophysiological tests. These should be included in the battery of diagnostic tests in multiple sclerosis.     

Interference of vibrations with input transmission in dorsal horn and cuneate nucleus in man: a study of somatosensory evoked potentials (SEPs) to electrical stimulation of median nerve and fingers

Summary The effects of 50 Hz palm vibrations on somatosensory potentials (SEPs) evoked by electrical stimulation of the median nerve at the wrist and of the 2nd and 3rd fingers were studied in 10 normal subjects. Vibrations were found to produce attenuation of the N13 spinal and P14 brainstem potentials and of the N20 contralateral parietal response. Brachial plexus (N9, P9) and dorsal column (P11) responses were not modified by vibrations. These SEP findings show: 1) that vibrations do not interfere at the periphery with the processing of brief ascending volleys triggered by an electrical stimulus and 2) that such an interference does occur in spinal dorsal horn and cuneate nucleus. Reduced input transmission in the cuneate nucleus is likely to be responsible for perceptual alterations induced by vibrations.