Evoked potentials in HIV infection]

The study of the literature data on the multimodal evoked potentials in HIV infected patients shows many abnormalities as well in asymptomatic subjects without AIDS as in AIDS subjects with or without neurological signs. Visual evoked potentials (VEPs) reveal prolonged P100 wave latency in 22% of HIV asymptomatic subjects and in 26% of HIV symptomatic subjects; brainstem auditory evoked potentials (BAEPs) reveal an increase of the interpeak latency I-V in 16% of asymptomatic subjects and in 32% of symptomatic subjects; somatosensory evoked potentials (SEPs) by median nerve stimulation reveal prolonged central conduction time in 6% of asymptomatic subjects and in 11% of symptomatic subjects; somatosensory evoked potentials (SEPs) by tibial nerve stimulation reveal prolonged central conduction time in 4% of asymptomatic subjects and in 45% of symptomatic subjects; motor evoked potentials (MEPs) by magnetic stimulation reveal prolonged central motor conduction time in 46% of asymptomatic subjects.     

EEG and evoked potentials in HIV-infected children.

Forty-seven HIV-seropositive children were investigated by EEG and evoked potentials (BAEP, SEP). Twenty-three children were symptomatic (P2), 8 seropositive without symptoms (P1), and 16 children were less than 15 months of age (P0). Some of them were investigated at different stages of HIV infection. During the neonatal period, 7 newborns of drug-addicted mothers had seizures and frequent spikes and sharp waves in their EEGs. Among (P2) children 6/23 showed background slowing and 1 had rhythmic theta activity (6 with and 1 without neurological symptoms). In BAEP, bilateral prolonged interpeak latencies (IPL) were found in 1 child with severe AIDS encephalopathy. Side differences greater than or equal to 0.4 ms in IPL were seen in 2 (P2), 1 without and 1 with neurological symptoms. A late onset was seen in 2 (P1) and 4 (P2) children. Median SEPs were normal in 24/26 patients; N20/N13 amplitude ratio was reduced in 2 (P1) patients. EEG and BAEP revealed nonspecific abnormal features in HIV encephalopathy. The the progression of the disease. However, also in the symptomatic group, normal results of EEG and BAEP dominated. SEP in the symptomatic group revealed only normal values. For monitoring the effectiveness of AZT treatment in HIV encephalopathy, EEG seems to be a relevant investigation; for evoked potentials more data and experience are needed.     

Neurophysiological changes in Japanese encephalitis

Japanese encephalitis (JE) is an encephalomyelitis involving cortex, subcortex, brainstem and spinal cord. There is paucity of studies on the neurophysiological evaluation in JE. This study aims at comprehensive evaluation of EEG, sensory and motor evoked potentials, nerve conduction and electromyography; and correlate these with clinical findings. Sixty five patients with JE diagnosed on the basis of clinical, radiological and virological criteria were subjected to a detailed clinical evaluation during the acute stage of illness. Cranial CT scan or MRI was carried out in all the patients. All the patients underwent 10 or 18 channel EEG, motor and sensory evoked potentials to both upper and lower limbs bilaterally as well as peroneal and sural nerve conductions and concentric needle EMG. Outcome, was defined at the end of 3 months into poor, partial and complete recovery. The patient's age ranged between 2-65 years. There were 40 males and 25 female patients. Fifteen patients were less than 12 years of age. History of seizure was present in 31 patients. Quadriplegia was seen in 39 and hemiplegia in 8 patients. Muscle wasting was present in 16 patients and tendon reflexes were reduced in 12 and of mixed pattern in 14 patients. Cranial MRI revealed thalamic lesion in 38, basal ganglia in 21, substantia nigra in 30, pons in 5, cerebellum in 3 and cerebral cortex in 7 patients out of 57 patients. EEG revealed nonspecific theta to delta slowing in 45, alpha pattern coma in 5 and epileptiform discharges in 8 patients. EMG revealed fibrillations in 23 patients. Motor evoked potentials were abnormal in 34 out of 46 patients and revealed patchy and focal abnormalities comprising of unrecordable, prolonged and normal pattern. Somatosensory evoked potentials were abnormal in 8 patients only. At 3 month, 26 patients had complete, 13 partial and 15 had poor outcome. Eight patients died in acute stage and 3 were lost to followup. MEP correlated with weakness and 3 month outcome whereas EEG, SEP and EMG did not have any correlation. MEP changes were more frequent in JE and had prognostic significance.     

Motor and somatosensory evoked potentials in tuberculous meningitis: a clinico-radiological correlation

OBJECTIVE: The sensory and motor functions in severe tuberculous meningitis (TBM) may be difficult to assess clinically and may be helped by evoked potential studies. Lack of motor and somatosensory evoked potential studies in TBM prompted the present study. METHODS: All the patients with TBM underwent detailed neurological evaluation and cranial CT scan study. Motor and somatosensory evoked potentials to both upper and lower limbs were carried out bilaterally. The outcome was defined on the basis of 3 month Barthel Index (BI) score into good (BI > 12) and poor (BI < 12). RESULTS: Forty-one highly probable patients with TBM whose ages ranged between 8 and 64 years and 14 of whom were females were included in this study. Twenty-three patients were in stage III (meningitis, neurological signs and altered sensorium), 12 in stage II (meningitis with neurological sign) and the remaining patients were in stage I (meningitis only). Cranial CT scan was carried out in all and MRI in 18 patients. On CT scan hydrocephalus was present in 21, infarction in 14 and tuberculoma in 4 patients. Motor evoked potential (MEP) was abnormal in 18 patients (36 limbs) and SEP in 9 patients (23 limbs). Upper limb central motor conduction time to abductor digiti minimi (CMCT-ADM) was abnormal in 15 and that to tibialis anterior (TA) in 21 limbs. CMCT abnormality was lateralized in 6 and only upper or lower limbs were involved in 11 patients. The SEP abnormalities were lateralized in 2 patients and only upper or lower limbs were involved in 3. The MEP changes correlated with stage of TBM and outcome whereas SEP with outcome only. CONCLUSION: Motor and somatosensory evoked potentials may be helpful in objective documentation of respective motor and sensory functions in TBM patients with altered sensorium.     

Electroencephalography in AIDS and AIDS-related complex

EEG records from 47 patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) were reviewed retrospectively to correlate EEG findings with neurologic abnormalities. Abnormal EEGs were found in 22 of 33 (67%) patients with AIDS and 5 of 14 (36%) patients with ARC. Among 27 patients with abnormal EEGs, there were 9 patients with dementia, 10 with opportunistic infections of the CNS, and 6 with no apparent neurologic disease. AIDS dementia was associated with intermittent or continuous slowing, often most prominent anteriorly. Focal slowing or sharp activity was usually found in patients who had focal CNS processes, such as cerebral toxoplasmosis and CNS lymphoma. These findings suggest the EEG can be a useful diagnostic test for evaluating patients with AIDS and ARC, particularly when these patients present with seizures, psychiatric symptoms, or cognitive dysfunction. The significance of abnormal EEGs in patients who are neurologically asymptomatic is unknown.     

Neurophysiological features in relation to clinical signs in clinically diagnosed corticobasal degeneration

We investigated the association between clinical and neurophysiological characteristics in patients with a clinical diagnosis of probable corticobasal degeneration (CBD), and searched for neurophysiological features supporting the diagnosis in life. Ten patients with clinically probable CBD underwent comprehensive neurological evaluation and brain MRI. Long latency reflexes (LLR), upper limb somatosensory (SEP) and motor evoked (MEP) potentials were recorded. The mini-mental state examination (MMSE), the phonemic verbal fluency test (PVFT) and the De Renzi ideomotor apraxia test were also performed. Polygraphic EEG was performed in the six patients with myoclonus. The SEP N30 frontal component was absent bilaterally in four patients, was absent on the left side in one, and had increased latency in other three. MEPs were abnormal in four patients (three had prolonged central motor conduction time, one of whom also had increased MEP threshold, and one had increased MEP threshold). All six patients with myoclonus had enhanced LLRs at rest, which were also of abnormally increased amplitude during motor activation; latencies were generally shorter than in classic cortical reflex myoclonus. On back-averaging, no EEG spikes time-locked to EMG activity were found in any myoclonus patient. Five patients were demented by MMSE, eight had ideomotor apraxia scores in the ideomotor apraxia range and five had defective verbal fluency. Brain MRI revealed asymmetric cortical atrophy in all patients, particularly evident frontoparietally. Neurophysiological techniques, particularly LLR, can assist CBD diagnosis especially in patients with myoclonus. Patients with evident parkinsonism had greater SEP N30 (frontal) abnormalities, while most patients with marked paresis had slower MEP times. Received: 29 June 2002 / Accepted in revised form: 31 January 2003 Correspondence to: F. Girotti     

皮层电极在颅内动脉瘤术中监测中的应用研究

目的 研究颅内动脉瘤术中应用皮层电极进行皮层脑电图(EEG)和皮层运动诱发电位(MEP)监测的价值和意义.方法 42例颅内动脉瘤患者,翼点开颅夹闭动脉瘤术中常规行头皮EEG、体感诱发电位(SEP)、MEP和皮层EEG、MEP监测,将监测变化结果与术后神经功能做前瞻性研究.结果 36例可诱发出皮层MEP,8例监测出现了变化,其中SEP 4例、皮层EEG 6例、头皮EEG 2例、皮层MEP 7例、头皮MEP 5例.皮层MEP出现变化的6例非大脑前动脉系统动脉瘤中仅3例头皮MEP出现了变化.结论 皮层MEP所需刺激量小,较适合于非大脑前动脉动脉瘤的术中监测,其敏感性高于头皮MEP.皮层EEG监测的敏感性明显高于头皮EEG.     

颅内动脉瘤术中诱发电位监测的初步探讨

目的 初步探讨颅内动脉瘤手术中躯体感觉诱发电位、脑干听觉诱发电位及运动诱发电位的临床应用价值.方法 在16例动脉瘤手术中开展诱发电位监测,观察术中电生理信号改变与术后神经功能状态的关系.结果 11例术中未出现电生理信号异常改变,5例术中出现了异常信号,其中信号未能恢复正常的4例术后均出现新发神经功能障碍.结论 诱发电位监测可实时了解颅内动脉瘤手术中有无脑缺血所致的神经功能障碍,对指导手术及评估预后均有重要意义.

Abstract：

Objective To explore the application of intraoperative neuroelectrophysiological monitoring on somatosensory evoked potentials (SEP), brainstem auditory evoked potentials (BAEP) and motor evoked potentials (MEP) during intracranial aneurysm surgery.Methods SEP, BAEP or MEPs were monitored during operations on 16 patients with intracranial aneurysms.The relationship between the intraoperative changes of electrophysiological signals and the postoperative outcomes of neurological deficits was evaluated.Results 11 patients without abnormal intraoperative electrophysiological signal changes demonstrated no new neurological deficits after surgery.However, in the left 5 patients, abnormal changes of intraoperative electrophysiological signals were detected.Among these 5 patients, 4 with abnormal electrophysiological signals which were not recovered intraoperatively demonstrated new developed functional deficits immediately after surgery.Conclusion During intracranial aneurysm surgery, the monitoring on SEP, MEP and BAEP is beneficial not only to timely detecting neurological functional deficits resulted from intraoperative cerebral ischemia, but also to properly guiding surgical manipulation, and to reliably predicting postoperative outcome as well.     

Multimodal electroneurophysiological studies of systemic lupus erythematosus

The purpose of this study was to obtain electrophysiological documentation of possible involvement of central and peripheral nervous system (CNS and PNS) in systemic lupus erythematosus (SLE) patients even in the absence of neurological manifestations. The study included 30 consecutive patients with SLE and 25 age- and sex-matched volunteers as a control group. They were subjected to neurological and rheumatological tests and an extensive battery of neurophysiological tests, besides Wechsler adult intelligence scale. Overt neurological manifestations were observed in 14 patients (46.7%). Neurophysiological data revealed that 25 patients (83%) had at least 2 abnormal tests; 11 (68.8%) patients of the asymptomatic group and 14 patients (100%) of the symptomatic group with no significant differences between them. Seventeen patients (56.7%) had evidence of PNS dysfunction either in nerves (46.7%) or muscles (10%); 7 of them in the asymptomatic group. Twenty-four patients (80%) had evidence of CNS dysfunction. Twenty-two patients (73%) had abnormalities recorded on electroencephalography; 9 patients in the asymptomatic group and 13 patients in the symptomatic group. Eleven patients (37%) had abnormal values of P100 of visual evoked potential; 5 patients in the asymptomatic group and 6 in the symptomatic group. Eight patients (26.7%) had abnormal latency of wave I of brain stem response; 3 of them in the asymptomatic group. Abnormal prolongation of the P300 component of event-related potentials was recorded in 2 patients (12.5%) of the asymptomatic group, while low IQ was observed in 8 patients of each group. Neurophysiological abnormalities are fairly common in SLE patients whether symptomatic or asymptomatic. The use of such tests favors a true incidence of nervous system involvement, more accurate diagnosis, and may lead to better clinical care before the development of debilitating CNS and PNS changes.     

Somatosensory evoked responses in the diagnosis of thoracic outlet syndrome.

A study was made of 11 patients with cervical rib, and one patient with Klippel-Fiel syndrome and enlarged transverse processes to determine whether evoked potentials recorded from both Erb's points and the cervical spine in response to median and ulnar nerve stimulation provided information additional to that obtained by EMG and peripheral conduction studies. It was found that in seven patients who had pain and paraesthesias but no objective neurological signs both the peripheral and central conduction studies were within normal limits. By contrast, of five patients who had objective signs, conventional EMG and conduction studies were abnormal in three patients, but abnormalities of the evoked potentials obtained from ulnar nerve stimulation were obtained in all five patients. It is suggested that this application of evoked potential estimation is a useful addition to the more conventional peripheral investigations.     

The nervous system in early HIV infection: a prospective study through 7 years

In this study 28 patients with early stage HIV infection (CD4 >280 x 10(6)/l) were subjected to yearly examinations of the nervous system up to 7 years in order to detect any deterioration. Clinical neurological as well as neuropsychological performance was evaluated. The patients also underwent yearly neurophysiological tests (digital EEG, visual evoked potentials, somatosensory evoked potentials, auditory evoked potentials P300 and electroneurography). Every other year, SPECT with (99m)Tc-D,L-hexamethylpropylene amine oxime and brain MRI were performed. Originally, 38 patients were included in the study but only the results of 28 patients who complied with three of more yearly check-ups are presented. The results of yearly investigations of cerebrospinal fluid (CSF) have been presented earlier [Eur J Neurol4 (1997) 1]. All the patients showed signs of HIV in the CSF. Yet, no major deterioration in the neurological, psychological performance, neurophysiological or neuroimaging examinations could be discerned.     

CNS involvement in Japanese patients with chronic inflammatory demyelinating polyradiculoneuropathy

Thirteen consecutive Japanese patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) were studied by MRI, evoked potentials, and EEG. We found 3 of these patients exhibited symptoms of CNS disorders. Of these 3, 2 with abnormal MRI and visual evoked potentials, and one with abnormal brainstem auditory evoked potentials were detected. Another case without clinical CNS signs showed abnormal EEG findings. The subclinical CNS abnormalities found in the Japanese patients were considered to be less frequent than in cases from Western countries reported previously.     

Long latency event-related potentials in patients infected with human immunodeficiency virus

Long latency auditory evoked potentials were recorded in 55 homosexual men infected with human immunodeficiency virus (HIV). Forty-one of these patients were asymptomatic from the infection and 14 had clinical signs of illness. Nine of the symptomatic patients were demented and 8 (6 of whom were demented) met other diagnostic criteria for acquired immunodeficiency syndrome (AIDS). Cerebral responses were recorded from Fz, Cz, and Pz electrode placements referred to linked mastoids and averaged separately to rare (2,000 Hz) and frequent (1,000 Hz) tones presented in a pseudorandom sequence. Electroencephalography (EEG) was performed in 54 of the patients and magnetic resonance imaging (MRI) or computed tomography (CT) was done in 14 (13 of whom were symptomatic from the infection). The latency of N1, P2, N2, and P3 components was delayed in HIV-positive patients compared to normal and this was particularly so for the N1, N2, and P3 components. These changes were more marked in those patients who were symptomatic from their infection, especially in those who were demented. They were, however, present to a lesser degree even in asymptomatic (Class II) patients. Thus, 78% of the demented patients and 28% of nondemented patients had a delay in latency of at least one of the evoked potential components beyond the upper limit of our normal population. By contrast, the EEG was normal in all patients with asymptomatic HIV infection and most symptomatic patients, although 5 patients in this latter group had mild generalized slowing. MRI and CT findings were similarly nonspecific, particularly in the nondemented group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anorectal functions in patients with spinal cord injury

We wished to establish anorectal functions in patients with spinal cord lesions, related to the level of lesion and its completeness. We also wished to determine the value of neurophysiological tests for completeness of transsections in comparison with manometry and visceral sensory testing. In 32 patients (31.5 +/- 14.1 years, 25 males) with spinal trauma, completeness of transsection was assessed clinically. In 16 of these patients (30 +/- 15.6 years, nine males), a neurological work-up included recording of somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) from the pudendal nerve within the first week after trauma. Also, anal sphincter EMG and pudendal nerve terminal motor latency (PNTML) were assessed. All patients also underwent conventional anorectal manometry and visceral sensory testing. Of all 32 patients, 15 were judged as 'complete' based on their clinical signs. Of those 16 tested neurologically, seven were labelled 'complete' since no MEP or SEP were detectable; one had pudendal SEP and MEP present, while SEP were present but delayed (47.0 +/- 8.8 msec) in the remaining patients. In four of these patients, also MEP were recorded (27.9 +/- 5.2 msec) and normal. PNTML was present in 12/16 patients independent of the completeness of lesion, and was rated normal in nine and delayed in three patients. EMG was normal in five, and pathological in 11 cases. In 5/15 cases of those judged as 'complete' (in 3/7 evaluated neurologically), visceral sensory testing revealed a minimal threshold for rectal perception of distension of 44 mL (range: 10-130), which sometimes was also perceived as urge to defecate. In a further case, manometry showed major voluntary action of the anal sphincter. These patients had lesions at all levels of the spinal column, ranging from cervical (C4,C6,C7) via thoratical (2 x T7,T8,T12) to lumbar segments. Anorectal function testing, and specifically visceral sensory testing may be superior to neurological assessment of 'completeness' of spinal cord lesions. It may be that visceral afferent pathways others than spinothalamic tract are involved in rectal perception that are less accessible to conventional neurophysiological diagnostic work-up.     

Abnormal somatosensory evoked potentials in two patients with conversion disorder

On clinical grounds, somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) are currently used to discriminate between hysterical and neurological conditions. The present paper reports on two patients with severe gait disturbance who had the near-total absence of SEP responses on the scalp during the symptomatic period, which normalized after recovery. These findings, along with others, may shed light on the brain correlates of conversion phenomena.     

Motor evoked potential studies in Creutzfeldt-Jakob disease.

OBJECTIVES: Motor evoked potentials (MEPs) were recorded in 7 cases of Creutzfeldt-Jakob disease (CJD) to asses the involvement of pyramidal motor pathways in these cases. The diagnosis of CJD was confirmed by autopsy in 5 cases and based on clinical data in two cases. METHODS: Transcranial (MEP-cortex), root magnetic (MEP-root) and electrical stimulation of peripheral nerves (F-wave, direct M-response) were performed. The cortical excitability threshold, F-wave frequency, MEP amplitudes, peripheral motor conduction velocity, standardized distal latencies and central, root, and F-wave conduction times were evaluated. RESULTS: The results of MEP testing were markedly abnormal. Cortical excitability thresholds were elevated, MEP amplitudes were reduced while the conduction function was rather preserved. The features of functional disturbances and/or loss of upper and lower motor neurons were revealed. They correlated with the advancement of key clinical CJD symptoms (progressive dementia, extrapyramidal and cerebellar signs, myoclonic jerks, mutism and typical periodic EEG changes), while motor lesion signs might only be slight or absent. CONCLUSIONS: Conduction slowing, if present, seemed to be secondary to axonal lesion.     

Peripheral neuropathies in human immunodeficiency virus infection. A prospective study of 56 patients

Neurologic disorders are common in patients infected with HIV1. Judging from reported cases, the central nervous system would be more frequently involved than the peripheral nervous system (PNS). The purpose of the present prospective study was to ascertain the incidence and the nature of PNS disorders in patients infected with HIV1. Fifty-six patients [asymptomatic carriers: 5; persistent generalized lymphadenopathy (PGL): 13; AIDS related complex (ARC): 9 and acquired immunodeficiency syndrome (AIDS): 29] were submitted to clinical and laboratory investigations and 52 underwent electromyogram and nerve conduction velocity tests. CSF was examined in 29 and nerve biopsies in 28. Our findings showed that a PNS impairment was present in 50/56 patients i.e. 89 p. 100. It was mainly a moderate sensory polyneuropathy, more often at the subclinical (29/50: 58 p. 100) than at the clinical (21/50: 42 p. 100) level. It concerned asymptomatic carriers (2/5) as well as PGL (11/13), ARC (8/9) and AIDS (29/29) patients. These data show that peripheral nerves are a target for HIV1.     

The role of sensory and motor evoked potentials in the prognosis of Pott's paraplegia.

OBJECTIVE: In view of paucity of evoked potential changes in Pott's paraplegia, it is proposed to evaluate the role of motor and somatosensory evoked potentials in predicting the outcome. METHODS: Consecutive patients with Pott's paraplegia during 1993-2003 were subjected to detailed clinical, radiological and evoked potential study. The latter comprised of tibial somatosensory evoked potential (SEP) and motor evoked potential (MEP) study to tibialis anterior. The patients were clinically evaluated at 6 and 12 months and the outcome was defined into poor (bed ridden), partial (dependent for activities of daily living) and complete recovery (independent). The evoked potential findings were correlated with clinical and radiological findings and outcome. RESULTS: There were 39 patients whose age ranged between 16 and 70 (mean 42.1) years and 22 were females. The mean duration of symptoms was 8.2 months. Sensory motor deficit was present in 18 and pure motor signs in 21 patients. Five patients had quadriplegia and remaining had paraplegia. The muscle weakness was severe in 12 and moderate in 15 patients. In 12 patients, lower limb power was normal but they had lower limb hyper-reflexia with or without spasticity suggesting pyramidal dysfunction. Pinprick and joint position sensations were abnormal in 18 patients. MRI was abnormal in all and revealed cervical involvement in 7, thoracic in 22 and lumbar in 10 patients. Paravertebral soft tissue shadow was present in 36 and cord compression in 30 patients. Motor evoked potential was abnormal in 19 patients (unrecordable in 11 patients, 21 sides and prolonged in 8 patients, 14 sides). SEP was abnormal in 18 patients (unrecordable in 15 patients, 25 sides and prolonged central conduction in 8 patients, 9 sides). Both MEP and SEP were abnormal in 16, normal in 18, and only MEP was abnormal in 3 and only SEP in 2 patients. At 6 month 25 patients had complete, 9 partial and 5 poor recovery. At 1 year 33 had complete and 4 partial recovery. SEP and MEP abnormalities correlated with respective sensory and motor functions, vertebral level and outcome at 6 and 12 months. CONCLUSIONS: MEP and SEP both are helpful in predicting 6-month outcome. Combining SEP and MEP gives stronger correlation with 6-month outcome compared to only MEP or SEP. The potential role of evoked potentials in deciding different therapeutic strategies needs further studies.     

Cortical motor neuron excitability during cutaneous silent period

Objective: To investigate cortical motor neuron excitability during cutaneous silent period (CSP), motor evoked potentials (MEPs) from abductor pollicis brevis following transcranial magnetic stimulation (TCM) were recorded with and without a conditioning of ipsilateral painful digital nerve electric stimulation.Methods: MEPs following TCM were recorded with and without a conditioning stimulation at an interstimulus interval (ISI) from 0 ms to 100ms in 6 controls and four patients who had reduced pain sensation in unilateral upper limbs associated with cervical syringomyelia. In addition MEPs and evoked spinal cord potentials (ESCPs) from cervical epidural space following TCM with and without a conditioning stimulation were recorded in four patients with thoracic myelopathy.Results: MEP amplitude was clearly attenuated by a conditioning stimulation at an ISI from 40 ms to 80 ms in controls (statistically significant at 60 ms). In patients with cervical syringomyelia, MEP amplitude was attenuated by a conditioning stimulation in asymptomatic hands similarly in controls but that was unchanged by a conditioning stimulation in the symptomatic hand with reduced pain sensation. In patients with thoracic myelopathy MEP amplitude was attenuated by conditioning stimulation similarly in controls, but ESCP amplitude was unchanged.Conclusions: We demonstrated that noxious cutaneous nerve stimulation suppressed spinal motor neurons but cortical motor neuron excitability was unchanged during CSP. In clinical practice, measurement of MEP suppression after noxious cutaneous nerve stimulation may provide useful information in patients with damaged pain related nerve fibers.     

Neurophysiological assessment of the motor and sensory spinal pathways in chronic spinal cord injury

Introduction of transcranial magnetic stimulation (TMS) has provided means to study non-invasively corticospinal functions in humans. The purpose of the present study was to obtain an objective evaluation of spinal cord functions in spinal cord injury (SCI) subjects using TMS, multichannel surface EMG and somatosensory-evoked potentials (SSEP). Multichannel surface EMG recording was performed during reinforcement manoeuvres and during vibratory tonic reflex. Twenty-five post-traumatic clinically incomplete (ambulatory, AMB, and non-ambulatory, nAMB) SCI subjects were studied and compared to a control group of seven subjects. After preliminary analysis of neurophysiological studies they were divided into four groups according to presence or absence of motor-evoked potentials (MEP) in response to TMS in muscles below the level of the lesion and according to their ability to ambulate. TMS was delivered at vertex at 100% intensity and recorded from the large muscles of the upper and lower limbs. Surface EMG was recorded during reinforcement manoeuvres (RM) in the leg muscles and EMG activity was scored. SSEP were recorded at T12, L2, L4 and SI spinous processes and at Cz' on the scalp following tibial nerve stimulation at popliteal fossa. The prevalence of EMG responses during RM was higher in group with present MEPs (AMB/MEP+ and nAMB/MEP+) than in the group without MEPs. The group with present MEPs also showed better preserved functions of the ascending tracts compared to subjects without MEPs. Groups with present MEPs had 5/10 normal, 2/10 abnormal and 3/10 absent cortical SSEPs, whereas groups without MEPs showed 1/11 normal, 4/11 abnormal and 6/11 absent cortical SSEPs. Sustained function of ascending tracts was also positively correlated with preserved ability to ambulate. It was concluded that TMS in combination with multichannel surface EMG monitoring and sensory evoked potentials may prove feasible in assessing the functional capacity of the spinal cord after spinal cord lesion.