Tibial SEPs Research Articles

Evoked potentials after autologous hematopoietic stem cell transplantation for multiple sclerosis

ObjectiveTo investigate the effect of autologous hematopoietic stem cell transplantation (AHSCT) on functional aspects of the nervous system assessed by visual (VEP), somatosensory (SEP), and motor (MEP) evoked potentials in patients with relapsing-remitting multiple sclerosis. BackgroundSeveral studies have demonstrated the efficacy of AHSCT on inflammatory activity and disability progression in patients with multiple sclerosis. However, the impact of AHSCT on evoked potentials has not been evaluated before. MethodsTwelve AHSCT-treated patients from Uppsala University Hospital were consecutively recruited. Evoked potentials (EP) were collected at baseline and two follow-up visits, 3 and 12 months post-AHSCT. We calculated a composite EP score for each participant and compared it between different time points. ResultsThe median total EP score decreased from 5 at baseline, to 2.5 at 12 months post-ASHCT (p = 0.008). A significant improvement in tibial SEP (tSEP) latencies was observed (42.7 vs 41.5 ms, p < 0.001), with a similar trend for MEP latencies 12 months post-ASHCT. No significant changes in median SEP or VEP latencies were observed. ConclusionsTreatment with AHSCT was associated with improved transmission in some central nervous system pathways in multiple sclerosis patients.

N°69 – N-Interval fourier transform analysis of cortical evoked responses – Median and tibial SEPs

N°69 – N-Interval fourier transform analysis of cortical evoked responses – Median and tibial SEPs

P45-S Optimisation of the recording parameters of tibial somatosensory evoked potentials (SEPs)

Background Tibial SEPs assess the function of the dorsal columns and supraspinal medial lemniscal somatosensory pathways. Lumbar N22 responses (T12/L1) and cervical P30 (Cv7) allow topographic localisation but are challenging to obtain in routine clinical practice. Here, we studied technical parameters that affect spinal and cortical (P40) responses. Materials and methods In a sample of consecutively referred patients, spinal response amplitudes and latencies were studied simultaneously with cup or subdermal needle and different reference electrode montages and correlated with BMI. P30 recordings were trialled and P40 amplitude optimisation was studied with three different montages (Cz’-Fz, Cz’-Cc, Ci-Cc). Results Responses with subdermal needles were of equal or smaller amplitude in 22/37 compared to cup electrodes. Contralateral iliac crest reference (0.74 ± 0.62 μV) gave larger amplitudes than ipsilateral (0.59 ± 0.61 μV; P = 0.017). Spinal N22 responses (cup electrode, contralateral reference) were present in 33/37patients with BMI 25(0.58 ± 0.54 μV) and were not strongly correlated with BMI (Spearman = −0.32). 30/136 recordings had absent spinal responses with recordable P40. A P30 response was not recordable in 115/140 when P40 was present. Amplitudes of Cz’-Cc (3.09 ± 2.01 μV) were significantly greater than Cz’-Fz (2.42 ± 1.83 μV) in 117/150 of recordings (P = 0.001) and Ci-Cc (2.48 ± 1.55 μV) in 97/150 (P = 0.008). There were no significant differences in latencies. Conclusions Subdermal needle and cup electrodes produce comparable N20 recordings and contralateral iliac crest reference provides largest amplitudes. Interestingly, BMI does not significantly influence N22 amplitude. The Cv7 response was often absent when N22 and P40 were normal. P40 amplitude is maximal at Cz’-Cc derivation.

T85. Sensory and motor evoked potentials in a multicenter setting: Definition of significant change in repeated measurements in healthy subjects on individual level

Sensory and motor evoked potentials (SEP; MEP) can be used to measure quantitatively the extent of delayed signal conduction in multiple sclerosis (MS). They may be useful to monitor disease course and even serve as biomarkers in clinical trials (Hardmeier et al., 2017). Here we evaluate physiological and rater-related variability to determine the minimal significant change between two measurements intra-individually. 15 healthy subjects were evaluated twice within 30 days with median and tibial SEP and upper (UL) and lower limb (LL) MEP in three centers1–3 according to a common standardized protocol in keeping with IFCN recommendations. Four neurophysiologists (FJ, MH, PA, PF) independently marked all curves blinded to their previous ratings using a web-based tool (EPMark; HB, MH, PF). In SEP, N13, N20 and N22, P40, in MEP, cortico-muscular- (CML) and spinal-muscular-latencies were marked. N20, P40, shortest and mean CML, and central (motor) conduction times (CCT; CMCT) were analyzed. Mixed effect models were calculated using results of (a) 1st and 2nd rating of identical baseline curves (model 1), and (b) 1st baseline and follow-up rating (model 2) as combined outcomes. Based on model 2, confidence intervals (CI) were calculated for the difference of a repeated measurement of the same curve. Intra-class-correlation coefficient (ICC) for intra-and inter-rater reliability (model 1) was very high in median SEP (N20: 0.97; CCT: 0.85) and tibial SEP (P40: 0.95; CCT: 0.89). In MEP, ICC was higher when mean CML (UL: 0.94; LL: 0.90) or mean CMCT (UL: 0.88; LL: 0.91) was used instead of shortest CML (UL: 0.80; LL: 0.78) or shortest CMCT (UL: 0.65; LL: 0.81). As CCT and CMCT showed lower ICC, only CML, N20 and P40 were further analyzed. Total variance in model 2 ranged from 0.9 to 6.4 ms (N20: 0.9, P40: 6.4; CML-UL [shortest/mean]: 4.8/4.1; CML-LL: 5.8/3.7), mainly accounted for by inter-subject variability (64–79%); estimation of center effects was unreliable. 80%-CI ranged from 0.4 to 1.5 ms (N20: 0.4, P40: 1.3; CML-UL: 1.5/1.1; CML-LL: 1.1/0.9), 95%-CI from 0.7 to 3.0 ms (N20: 0.7, P40: 2.6; CML-UL: 3.0/2.2; CML-LL: 2.2/1.7). Main SEP components (N20, P40) and MEP cortico-muscular latencies show higher reliability than central conduction times. Mean instead of shortest CML further improves reliability. Intra-subject differences in individual tracts exceeding 0.4 to 3.0 ms (depending on test and CI level) most likely reflect true underlying changes. These numbers may be used to define responders to remyelinating therapies in MS. However, these confidence intervals may be higher in patients and have to be validated in a larger sample. In group level analyses, variability is much less important as over- and underestimation counterbalance each other. Supported by an unconditional research grant from Biogen Inc. MA, USA, which had no influence in planning the study or data analysis.

F107. Sensory and motor evoked potentials in a multicenter setting: Estimation of detectable group differences at varying sample sizes

Introduction Sensory and motor evoked potentials (SEP; MEP) can be used to measure quantitatively the extent of delayed signal conduction in multiple sclerosis (MS). They may be useful to monitor disease course and even serve as biomarkers in clinical trials (Hardmeier et al., 2017). Here we estimate the detectable differences in group means and in longitudinal group changes for different sample sizes accounting for physiological and rater-related variability. Methods 15 healthy subjects were evaluated twice within 30 days with median and tibial SEP and upper (UL) and lower limb (LL) MEP in three centers 1-3 according to a common standardized protocol in keeping with IFCN recommendations. Four neurophysiologists (FJ, MH, PA, PF) independently marked all curves blinded to their previous ratings using a web-based tool (EPMark; HB, MH, PF). N20, P40, shortest and mean cortico-muscular-latencies (CML) were analyzed; central (motor) conduction times were omitted due to lower test-retest-reliability. In addition, the sum of the z-transformed results from each test was divided by number of tests to yield a quantitative EP-score (qEPS). Mixed effect models using results of time-points 1 and 2 as combined outcomes were employed to calculate the standard error (SE) of a group mean of cross-sectional measurements or longitudinal changes. The respective SE formulas were used to calculate the difference d detectable with a power of 90% [d = (1.96 + 1.28) ∗ sqrt( SE 1 2 + SE 2 2 ) -2CoV] as a function of group size assuming a central reading center. Covariance between group means by common influence of raters on both groups was ignored for a more conservative estimate. Results For a sample size of n = 60, cross-sectional group mean difference (d1) is estimated to range from 0.6 to 2.1 ms (N20: 0.6, P40: 1.5; CML-UL [shortest/ mean]: 1.4/1.2; CML-LL: 1.7/2.1), and longitudinal mean group difference (d2) from 0.4 to 2.7 ms (N20: 0.4, P40: 1.0; CML-UL: 1.1/0.8; CML-LL: 1.6/2.7). For a sample size of n = 100, d1 ranged from 0.5 to 2.0 ms (N20: 0.5, P40: 1.2; CML-UL: 1.1/1.0; CML-LL: 1.4/2.0), and d2 from 0.4 to 2.6 ms (N20: 0.4, P40: 0.8; CML-UL: 0.9/0.7; CML-LL: 1.5/2.6). For qEPS [including shortest or mean CML], d1 was 0.5/0.4 ms for n = 60, and 0.4/0.3 ms for n = 100; d2 was 0.3/0.2 ms for n = 60 and 0.2/0.2 for n = 100. Conclusion Quantitative evaluation of combined SEP and MEP is possible in a multicenter setting with an independent reading center and allows reliable detection of significant differences in small groups of subjects. When evaluating an intervention, significant changes of EP results at an individual level help to identify responders, while significant changes at a group level may help to determine the biological effectiveness of an intervention. However, variability may be higher in patients and thus, consecutively, estimates of sample size. Supported by an unconditional research grant from Biogen Inc. MA, USA, which had no influence in planning the study or data analysis.

3-2-06. Somatosensory Evoked Potentials (SEPs) in Vitamin B12 deficiency

Abstract Vitamin B12 deficiency mainly affects the dorsal column. In this study, we investigated which part of the sensory pathway is affected in vitamin B12 deficiency using NCS and SEPs. We retrospectively reviewed EMG database of Teikyo University and Mitsui Memorial Hospital from 2008 to 2016, and enrolled patients who presented with sensory symptoms and/or gait disturbance, and whose serum B12 level was below 170 ng/ml. Enrolled were 17 patients. Spinal MRI demonstrated abnormalities in 4/17. NCS was abnormal in 3/15 patients for the sural nerve and in 5/12 patients for the median nerve. When NCS and peripheral segments of the SEPs were combined, conduction delay was detected in 12/15 patients for the lower limb and 8/13 patients for the upper limb. Delay of the central conduction was rarer, 3/15 patients in tibial SEPs. N9o to P13/14o segment in median SEPs was abnormal in 4/8 patients, although this is a mixture of the peripheral and central conductions. Vitamin B12 deficiency patients showed abnormalities of the peripheral nerve conduction more frequently than those of the central conduction. SEPs are useful in localizing the lesion along the sensory pathway, not only for CCT but for peripheral conduction.

Longitudinal assessment of brainstem reflexes in Multiple Sclerosis compared to multimodal evoked potentials, MRI and clinical evaluations

Background We have previously shown in patients with relapsing-remitting Multiple Sclerosis (MS) that: ( i ) the vestibulomasseteric (VMR), acousticmasseteric (AMR), trigeminocollic (TCR) and vestibulocollic (VCR) reflexes are able to spot brainstem (BS) dysfunctions undetected by clinical and MRI examinations; (ii) the combined use of these Brainstem Reflexes (BSRs) with multimodal Evoked Potentials (EPs) is more valuable than each single test in the early years after onset. Our aim was to document BS changes over time by BSRs, EPs, MRI and BS signs/symptoms (CLIN) before and after at least one year follow up, in MS. Methods Forty-five MS patients (34.8 ± 8.6 yrs old; disease duration 8.9 ± 6.6 yrs) underwent BSRs, EPs (namely Brainstem Auditory Evoked Potentials – BAEPs, median and tibial Somatosensory Evoked Potentials-mSEPs and tSEPs), MRI and CLIN examination. BSR and EP data were ranked and summed up to obtain a cumulative score expressing severity of neurophysiological impairment. Before-after changes were tested with Wilcoxon test. Results After 15.1 ± 4.2 months from initial evaluation, no relapses had been reported by any patient. This was in line with the stability of the frequency of CLIN and MRI abnormalities (37.3% and 71.1%, respectively) at the follow up. Despite this, BSRs and EPs revealed a worsening of BS function. In particular, although the proportion of altered BSRs did not change significantly (80.6% vs 90.3%; p = 0.180), a significant worsening of scores was observed for VMR ( p = 0.001), AMR (0.018) and TCR ( p = 0.013). Similarly to BSRs, the incidence rate of EP abnormalities did not increased significantly (84.4% vs 86.7%, p = 0.564), but the analysis of cumulative score showed a significant worsening for the whole EP set ( p = 0.03) as well as for median SEP (68.9% vs 75.6%, p = 0.03), P14 mSEP (33.3% vs 51.1%, p = 0.005), tibial SEP (60% vs 66.7%, p = 0.03). Conclusions BSRs and EPs were able to reveal a significant worsening of BS functions in spite of any variation of both BS signs/symptoms and of MRI BS lesion load. This is in agreement with previous reports on BSR/EP ability to detect clinically and radiologically silent BS lesions. Further studies are needed in a larger cohort of patient to assess BSR clinical usefulness in a longitudinal perspective. FISM GRANT 2011/R/17.

Assessment of brainstem reflexes improves the diagnostic sensitivity of multimodal evoked potentials, MRI and clinical testing in the investigation of brainstem function in multiple sclerosis

Background Brainstem (BS) functions are conventionally studied by multimodal evoked potential (EP) recordings, MRI and clinical examination (CLIN). In Multiple Sclerosis (MS), increasing evidence accounts for a BS involvement, often undetected by standard testing. Recently, brainstem reflexes (BSRs) have drawn attention in evaluating BS dysfunction in MS especially the vestibulocollic (VCR) and vestibuloocular reflexes. In contrast, the vestibulomasseteric (VMR), acousticmasseteric (AMR) and trigeminocollic (TCR) reflexes have never been studied systematically in MS. Aims: to investigate whether the diagnostic sensitivity of CLIN, EPs and MRI can be improved adding the assessment of VMR, AMR, TCR and VCR either as single reflexes or in a 4-BSR battery. Methods The 4-BSR battery was recorded in 60 patients (33.3 ± 8.3 yrs) with relapsing-remitting MS (illness duration 8.2 ± 6.4 yrs). EP set included standard BAEPs, median and tibial SEPs Conventional MRI scans were focused on the BS lesion load. Group differences and correlations between variables were analysed with Mann–Whitney U test and Mc Nemar test. Results Distribution of BSR and EP abnormality frequencies in MS was: VMR 62.1%, AMR 55.1%, TCR 58.6%, VCR 25.9%; BAEPs 37.3%, median SEPs 60.3% and tibial SEPs 58.6%. Overall, BS dysfunction was detected as follows: BSRs 86.9%, EPs 82.7%, MRI 71.7%, CLIN 37.7%. While the performance of BSRs and EPs, taken separately, was not significantly higher than that of combined MRI/CLIN testing (70%), the paired use of BSRs/EPs had a sensitivity of 93.3%, which was significantly superior (p = 0.007), in a subset of patients with a disease duration ⩽6.4 yrs. Conclusions BSRs revealed brainstem lesions otherwise undetected by CLIN and MRI, thus providing additional evidence of BS dysfunction in MS. Noteworthy, BSRs could effectively complement the usual EP testing in early detection of clinically and radiologically silent lesions. This may encourage EPs/BSRs paired use in newly diagnosed. FISM GRANTS 2008/R/9 and 2011/R/17.

LP11: Post-chirurgic preserved motor and sensory function in spite of transitory tibial SEP and MEP flattening during lumbar distraction in total disk replacement

LP11: Post-chirurgic preserved motor and sensory function in spite of transitory tibial SEP and MEP flattening during lumbar distraction in total disk replacement

Somatosensory Evoked Potentials Study in Cervical Spondylotic Myelopathy Patients

Background: Cervical spondylotic myelopathy (CSM) is considered the most serious consequence of cervical spondylosis and accounts for the majority of non_traumatic paraparesis and/or quadriparesis. The electrical property of the spinal cord and its susceptibility to injuries renders electrophysiology relevant to the management of CSM. Somatosensory evoked potentials study (SEPs) is an objective assessment of the functional integrity of the neural pathway.Objective: Utilizing both of the median and the posterior tibial SEPs in evaluating the functional integrity of the cervical spinal cord in patients with CSM and to correlate the SEPs findings with the clinical and MRI findings.Patients and methods: Twenty two patients with CSM (11 male and 11 female) ranging in age from 29 to 77 years with a mean age of (56 ±11) years and matched with 25 healthy subjects of the control group were enrolled in this study.Results: In this study, 86.36% of patients had abnormal SEPs study (either tibial or median or both tests abnormal), with 68.2% abnormal tibial and 63.6% abnormal median. There was no difference between right and left side study of neither median nor tibial SEPs studies (P&gt;0.05). Loss of N13, loss or delayed N20 and loss or delayed N13-N20 were the most frequent abnormalities for median SEPs and loss or delayed P37 and LP-P37 were most frequent abnormalities in tibial SEPs. Results showed that normal SEPs findings mostly correlated with mild and early myelopathy (grade-1 and grade-2 Nurick). Abnormal SEPs findings are useful in prediction the progression of myelopathy in patients with mild clinical neurological deficits in the early stages of the disease.Conclusion: This study concluded that both median and tibial SEPs montages are useful important objective assessment of the spinal cord function to evaluate patients with CSM since MRI and SEPs may evaluate different aspects of the disease process.

Subdermal needle electrode facilitates recording of lumbar N22 tibial SEP responses

Subdermal needle electrode facilitates recording of lumbar N22 tibial SEP responses

Isolated degeneration of the posterior column as a distinct entity—A clinical and electrophysiologic follow-up study

Objective The aim of the study was to better describe the long term clinical course and electrophysiologic and radiologic findings in isolated degeneration of the posterior column. Methods Four patients with the presenting symptoms of a progressive tabetic ataxia were followed up clinically and electrophysiologically over up to 15 years between 1997 and 2008. They received standardized neurological examinations, electrophysiologic testing with SEP, MEP, NCV, EMG, autonomic testing and cardiac evaluation, head and spine MRI, laboratory evaluation including CSF analysis. Results Progressive gait ataxia due to pallhypasthesia and loss of position sense with areflexia remained the only symptoms. Pes cavus deformity was a notable clinical feature in all cases. There was no involvement of other systems and all patients remained fully ambulatory. There was no cardiac involvement. Electrophysiology was characterized by absent cortical tibial SEP with normal lumbar complexes and normal nerve conduction studies and transcortical magnetic stimulation as well as sympathetic skin response. MRI of the cord was normal. Laboratory analysis and CSF were unrevealing. Conclusion Isolated degeneration of the posterior column is a rare condition with a clinically benign course without progression involving other systems and characteristic electrophysiologic findings (isolated loss of cortical tibial-SEP with normal lumbar leads). Pes cavus deformity seems to be an unusual but typical clinical feature. The etiology is most likely a sporadic degenerative disease of the cord.

A study of clinical, MRI and multimodality evoked potentials in neurologic Wilson disease

The aims of this study were evaluate motor, somatosensory, visual and auditory brainstem evoked potential (MEP, SEP, VEP, ABER) changes in Wilson disease (WD) and correlate these with magnetic resonance imaging (MRI) and clinical findings. Neurologic WD diagnosed on the basis of clinical, ceruloplasmin and Kayser-Fleischer ring were evaluated including pedigree charting, hepatic, renal, hematologic and osteoarticular manifestations. Blood counts, serum chemistry, MRI, MEP to tibialis anterior, tibial SEP, VEP and ABER were performed. Evoked potential (EP) changes were correlated with clinical and MRI findings. Eighteen WD patients were recruited from 17 families whose mean age was 16 years. Movement disorders were present in 14, cognitive decline in 12 and pyramidal signs in 12 patients. MRI revealed involvement of basal ganglia in 80%, thalamus in 40%, brain stem in 46.7% and subcortical white matter in 53.3%. MEP was abnormal in 35.7%, SEP in 30.8%, VEP in 57% and ABER in 61.5% patients; the latter three EP changes were subclinical. Frequency and number of EP abnormalities were higher with increasing severity of illness. SEP, VEP and ABER reveals subclinical abnormality and MEP helps in documenting both clinical and subclinical abnormalities. Number of EP abnormalities increases with increasing clinical severity of WD.

Abnormalities of somatosensory evoked potentials in konzo – an upper motor neuron disorder

Objective: To determine whether the somatosensory pathways are involved or not in konzo.Methods: In 1998, 21 konzo subjects (15 females and 6 males; mean age 21 years) underwent a SEP study with a two-channel-equipment (Medtronic Keypoint, Denmark) whereas in 2000, 15 subjects (7 females and 8 males; mean age 21 years) participated in a study with a 4-channel-equipment.Results: Most subjects (19/21 in 1998 and 12/15 in 2000) showed normal median SEPs. The remainders had no median cortical responses. All 21 subjects in 1998 and 9 out of 15 in 2000 showed abnormalities of tibial SEPs mainly consisting of absence of cortical responses, prolonged cortical latencies, and central sensory delay to the lumbar spine. Most subjects showed normal absolute latencies both at peripheral and spinal levels. The SEP findings did not correlate with the severity, neither the duration of konzo, nor the experience or not of sensory symptoms at the onset of the disease.Conclusion: Our findings are not specific of konzo. However, they suggest involvement of intracranial somatosensory pathways and point to similarities with other motor neuron diseases.

Is methyl prednisolone useful in acute transverse myelitis?

Hospital based observational study. To evaluate the role of methyl prednisolone (MPS) in the management of acute transverse myelitis (ATM). Twenty-one patients with ATM were included in a prospective hospital based study during 1992-1997. All the patients underwent neurological examination, spinal MRI, somatosensory and motor evoked potentials of both upper and lower limbs and concentric needle EMG study. Twelve consecutive patients did not receive MPS therapy who were managed during 1992-1994 and nine consecutive patients during 1995-1997 received MPS therapy in a dose of 500 mg i.v. for 5 days. The clinical and neurophysiological studies were repeated 3 months later. The outcome was defined on the basis of Barthel index (BI) score at the end of 3 months into good (BI> or =12) and poor (BI<12). The age of MPS group was 25.5 years (range 12-42) and three were females. The age of non MPS group was 33.5 years (range 16-70) and two were females. In the MPS group 33% had poor outcome compared to 67% in the non MPS group. In the MPS group mean admission BI score was 7.3 which improved to 14.6 after MPS therapy. In the non MPS group, the admission BI score was 3.2 which improved to 9.6 at 3 month follow-up. In patients with complete paraplegia, evidence of denervation on EMG and unrecordable central motor conduction time to lower limb and tibial SEP were associated with poor outcome irrespective of MPS treatment. Global test statistics did not suggest a beneficial role of MPS therapy in the outcome of ATM. Our results do not suggest a beneficial role of methyl prednisolone on the 3 month outcome of ATM.

Neurophysiological studies in acute transverse myelitis.

A systematic evaluation of anterior horn cell, motor and sensory pathways is possible by electromyography (EMG), motor (MEPs) and somatosensory (SEPs) evoked potentials, respectively, which may provide valuable information on acute transverse myelitis (ATM). In a prospective hospital-based study, EMG, MEP and SEP studies were carried out on admission and after 3 months in 39 patients with ATM. All the patients also underwent detailed clinical evaluation, and spinal magnetic resonance imaging (MRI) was performed in 28. Outcome was defined at the end of 3 months as poor, partial or complete recovery on the basis of functional status. Spinal MRI revealed hyperintense signal changes in T2 extending for two segments to the entire spinal cord. Central motor conduction time to tibialis anterior (CMCT-TA) was more frequently abnormal (90%), followed by tibial SEP (77%). CMCT to abductor digiti minimi (ADM) was abnormal in 30% and median SEP in 15% of patients. Evidence of denervation on EMG was present in 51% of patients. The CMCT-TA improved in 48% patients and tibial SEP in 32%. Median SEP improved in all patients, and CMCT-ADM remained prolonged in two. At 3 months 2 patients had died, and 18 had poor, 10 partial and 9 complete recovery. CMCT was correlated with muscle power, tone, reflex and MRI changes. Patients' outcome of was correlated with CMCT, SEP and EMG. These results are consistent with pronounced involvement of dorsal region of spinal cord in ATM. MEP is more frequently abnormal than SEP.

Guamanian neurodegenerative disease: electrophysiologic findings.

Amyotrophic lateral sclerosis (ALS), parkinsonism and/or dementia are highly prevalent among the Chamorro population of Guam. The incidence of Guamanian ALS has markedly declined in recent years, but these incidence figures may reflect underascertainment of subclinical disease. Guamanian Chamorro patients have not been systematically studied using modern clinical neurophysiological techniques. Electromyography (EMG: needle exam and nerve conduction studies) was used to study 29 patients with the major subtypes of Guamanian neurodegenerative disease, as well as 11 neurologically normal Guamanian Chamorro subjects. Central conduction was assessed by somatosensory evoked potentials (SEP's) in 16 patients. EMG evidence of peripheral neuropathy, (often subclinical) was found in 45% of Guamanian patients but no Chamorro control subjects. Diabetes mellitus, which is highly prevalent in this population, was present in some, but not all of these cases. Clinically unsuspected motor neuron disease was identified by EMG in only one of the 23 Guamanian patients with parkinsonism and/or dementia and in none of the 11 Chamorro control subjects. Two of seven patients with the clinical phenotype of Guamanian ALS had a more benign EMG pattern on the needle electrode exam with absence of fibrillation and fasciculation potentials. Three of 16 patients (all with parkinsonism and dementia) had mildly abnormal tibial SEP's. No patient had EMG evidence of myopathy or a defect of neuromuscular transmission. We conclude: (1) peripheral neuropathy may be a manifestation of Guamanian neurodegenerative disease; (2) the declining prevalence of ALS on Guam is not associated with the development of a subclinical form of motor neuron disease; (3) the substantial overlap of Guamanian ALS with parkinsonism-dementia reported in prior decades is no longer apparent; (4) abnormal central conduction, as assessed by tibial SEP's, is present in some patients with Guamanian parkinsonism-dementia.

Motor and somatosensory evoked potentials in cervical spondylotic myelopathy

We recorded upper and lower limb MEPs and SEPs in 55 patients with clinically suggestive and myelography-documented cervical cord compression due to spondylotic changes. MEPs were abnormal in biceps brachii of 21 patients (38%), in first dorsal interosseous muscle of the hand of 49 patients (89%) and in tibialis anterior of 47 patients (85%). Overall, MEP abnormalities were present in at least one muscle of 51/55 patients (93%). Median SEPs were abnormal in 20 cases (36%), ulnar SEPs in 24 (44%) and posterior tibial SEPs in 40 (73%). Overall incidence of SEP alterations was 73% (40/55) and SEPs detected clinically silent sensory dysfunction in 10 patients (18%). Among the 43 patients who underwent surgical decompression, first dorsal interosseous (FDI) MEPs and tibial SEPs remained abnormal in most cases 1 year after surgery, independently of clinical outcome. On the other hand, serial EP studies seemed useful to confirm and monitor the clinical evolution of unoperated patients.

73-Year-Old Man With Gait Disturbance and Imbalance

A 73-year·old right-handed man with a history of diabetes, hyperlipidem ia, co ronary artery disease, and asthmatic obstructive lung disease came to our institution beca use of a 2year history of gradual worseoiog of gait aod balaoce. One year previously, he had undergone coronary artery bypass grafting without perioperative complica tions. Subsequently, h is gait worsened, and his fee l felt "glued to the floor." During the 2 years before the curre nt examination, he also noticed urinary urgency, occasional incont inence, and irnpotcnce. His wife noti ced that he had had some mental slo wing and forgetfulness during the precediog 18 months. Review of systems revealed no history of tremo r. speech change, diffi culty with use of his arms, or wea kness . Five months before the current assessment, a neu rol ogist had noted parkin son ism; amantadi oe hydrochlori de and carbidopaIcvodopa were prescribed separate ly but yielded no benefi t. On initi al consultation , the patient had norm al mental status and cranial nerve func tions. Motor examina tion showed generally preserved strength, red uced aokle jerks, and flexor plantar responses bilaterally. Muscle tone was mildly spastic in the legs. Sensory examinat ion showed mild hypoe sthesia 10 pinprick in bot h hands (fingertips) and feet (up 10 the ankles); other sensory modalit ies were normal. His ga it was wide-based , and externa l anal sphincte r tone was mildly reduced . Parkinsoni an signs included shuffl ing gait, slowed walking, and postural instability.

Neurophysiologic Assessment in the Management of Spinal Dysraphism

Neurophysiologic techniques provide a valuable addition to the armamentarium of tools for the evaluation of sensory and motor function in the pediatric spinal cord. These techniques include median, radial, and ulnar nerve evoked potentials from the upper extremity; common peroneal and tibial nerve evoked potentials from the lower extremity; dermatomal potentials; and compound muscle action potentials and compound nerve action potentials. The techniques that evaluate the sensory system have been used extensively and effectively as research tools, as adjuncts to diagnostic evaluation, and for intraoperative monitoring. There is a considerable literature that describes the properties of SEPs in the infant and young child. Techniques for assessing the descending pathways have been developed in the last 10 years. These techniques hold great promise as both diagnostic and intraoperative monitoring tools. Many questions, however, still exist concerning their value and use. The rapidly increasing capability available in computer systems is also providing enhanced capability in the acquisition, display, and analysis of neurophysiologic data. It is now common to acquire multiple responses simultaneously, e.g. tibial SEPs, pudendal SEPs, and motor potentials. It is also possible to apply computationally intensive numerical algorithms in real time to enhance signal quality and reduce the time required to produce an interpretable display. Finally, it is possible to monitor multiple cases simultaneously from remote locations. These enhanced computational capabilities are helping to optimize the contribution of neurophysiologic monitoring to patient care.