Somatosensory evoked potential recovery in myotonic dystrophy.

OBJECTIVE: To evaluate recovery functions of the sensory cortex using somatosensory evoked potentials (SEPs) elicited by paired stimuli of the median nerve in patients with myotonic dystrophy (MD). SUBJECTS/METHODS: Twelve MD patients were enrolled in the present investigation. Five patients with facioscapulohumeral muscular dystrophy (FSH) and 12 healthy volunteers were studied as control groups. SEP was recorded from the hand sensory area contralateral to the median nerve stimulated at the wrist. Single pulse or paired-pulse stimuli at various interstimulus intervals (ISIs) (10, 20, 40, 60, 80, 100, 150, 200 and 300 ms) were given. Recovery functions of N9, N20onset-N20peak, N20-P25 and P25-N33 components were studied. RESULTS: Conventional SEPs to a single stimulus were normal in the latency and amplitude in all the patients. Recovery functions of both N9 and N20o-N20p components were normal in the patients. In contrast, in MD patients, disinhibited or hyperexcitable recovery pattern was observed in recovery curves of the N20-P25 or P25-N33 components, whereas those were normal in FSH patients. CONCLUSIONS: Disinhibited cortical excitability (or hyperexcitability) is present in the sensory cortex in patients with myotonic dystrophy. This may reflect cortical pathology or functional alteration of the sensory cortex in MD.     

Cognitive impairment and diffuse white matter atrophy in alcoholics.

OBJECTIVE: Diffuse brain white matter atrophy is often seen in chronic alcoholics, but its relation with cognitive impairment remains to be solved. In order to address this issue, in alcoholics with cognitive impairment at different levels, we studied relations of the central sensory conduction time (CSCT) or brain magnetic resonance imaging (MRI) findings with the cognitive function. METHODS: Subjects were 35 alcoholics with mild cognitive impairment (mini-mental state examination score, MMSE, >/=24; mean+/-SD, 27.7+/-1.9), 12 with moderate to severe cognitive impairment (MMSE<24; 20.3+/-2.7), 15 with Alzheimer's disease (AD) (MMSE, 18.9+/-4.3) (disease control) and 20 healthy volunteers (MMSE, 28.5+/-1.6) (normal control). Median nerve SEPs were recorded in the all subjects, and the latencies and amplitudes of their N9, N11, P13/14, N20 and P25 components were measured. The ventriculocranial ratio (VCR) and the width of cortical sulci were measured on MRIs. These physiological parameters and MRI findings were compared between the 4 groups of the subject, and correlations between those all features were also analyzed. RESULTS: CSCT and VCR were significantly greater in alcoholics with moderate to severe cognitive impairment than those in the other 3 groups. Pearson's product-moment correlation analyses of the alcoholics disclosed that both the CSCT and VCR had significant negative correlations with the MMSE score. Moreover, the CSCT and VCR were positively correlated. CONCLUSIONS: Both physiological and morphological estimates of the white matter function (CSCT and VCR) had a significant correlation with the cognitive dysfunction. SIGNIFICANCE: The diffuse white matter atrophy may be one of the factors causing cognitive impairment in chronic alcoholics.     

Somatosensory evoked potential recovery in kii amyotrophic lateral sclerosis/parkinsonism-dementia complex (kii AlS/PDC).

OBJECTIVE: To evaluate the recovery function of the sensory cortex in patients with Kii amyotrophic lateral sclerosis/parkinsonism-dementia complex (Kii ALS/PDC) using somatosensory evoked potentials (SEPs) elicited by paired stimuli of the median nerve at the wrist. METHODS: Five patients with Kii ALS/PDC were compared with 5 patients with classical ALS, 5 with Parkinson's disease (PD), and 7 healthy normal volunteers. SEPs were recorded from the hand sensory area contralateral to the side of stimulation. Recovery functions of N20-P25 and P25-N33 components were evaluated by comparing the second SEPs elicited by paired pulse stimuli at various interstimulus intervals (ISIs, 20-300 ms) with the SEPs elicited by single stimuli. RESULTS: Conventional SEPs to a single stimulus had a normal latency and size in all patients. The recovery function of the N20-P25 and P25-N33 components showed significantly less suppression at short ISIs without any facilitation at long ISIs in Kii ALS/PDC patients than in normal subjects, classical ALS or PD patients. CONCLUSIONS: In Kii ALS/PDC, the sensory cortex is disinhibited or hyperexcitable. These abnormalities may reflect cortical pathology in the sensory cortex and may be partly due to a secondary effect on the sensory cortex from the primary parkinsonian pathological changes.     

脑白质疏松症与Binswanger病认知功能障碍的对比研究

目的探讨轻度认知功能障碍与痴呆在单纯脑白质疏松症(LA)、Binswanger病(BD)及脑白质疏松症合并脑梗死(LA CI)中的临床诊断价值.方法单纯LA组27例,BD组33例,LA CI组31例,对照组30例,行简易精神状态量表(MMSE)、临床记忆量表测验(CMS)、轻度认知功能障碍的认知评定并对比分析.结果单纯LA组、BD组、LA CI组MMSE及CMS成绩均明显低于对照组,差异有显著意义(P＜0.05);单纯LA组MMSE及CMS成绩明显高于BD组、LA CI组,差异有显著意义(P＜0.05);单纯LA组认知损害以轻度认知功能障碍为主(77.8%),无1例痴呆;BD组中度认知功能障碍占24.2%,痴呆占75.8%;LA CI组以中度认知功能障碍(19.4%)和痴呆(77.4%)为主.结论轻度认知功能障碍是诊断单纯LA的临床参考指标.中度认知功能障碍和痴呆是诊断BD和LA CI的临床参考指标.     

Abnormality of N30 somatosensory evoked potentials in Parkinson's disease: a multidisciplinary approach.

PURPOSE OF THE STUDY: Assess the N30 component of median nerve somatosensory evoked potentials (SEPs) in patients with Parkinson's disease (PD) and correlate its parameters with the severity of the disease, general cognitive ability and regional cerebral blood flow (rCBF). PATIENTS AND METHODS: Twenty-three non-demented, non-depressed PD patients (at stage II and III of the disease) and 23 age- and education-matched normal controls were enrolled in the study. SEPs were elicited by median nerve stimulation. PD patients' cognitive ability was assessed by means of: 1) Raven's Colored Progressive Matrices (RCPM); 2) the Test of Non-Verbal Intelligence (TONI-2); and 3) the Wisconsin Card Sorting Test (WCST). The patients' rCBF was evaluated by HMPAO SPECT. RESULTS: There was no difference between SEP N30 latency in PD patients and controls (P > 0.05). The P20-N30 peak-to-peak amplitude was lower in PD patients bilaterally (P < 0.05), and the amplitude of N30-P40 was lower on the right side only (P < 0.05). A significant increase in the amplitude ratio P14-N20/P20-N30 was observed in PD patients (P < 0.05). The correlation of these findings with the clinical parameters of the disease, and notably motor signs, was not significant. Of the three neuropsychological tests only the RCPM showed a positive relation to right P20-N30 amplitude. Regression analysis between SEP parameters and rCBF showed a correlation of N30 amplitude with blood flow in parietal cortical areas, but not in frontal regions.     

Portal-systemic encephalopathy: alterations in somatosensory and brainstem auditory evoked potentials

Median somatosensory and brainstem auditory evoked potentials (SEP and BAEP) were studied in 40 patients with liver cirrhosis consequent to chronic viral hepatitis. The patients were divided into 4 groups: group 1 with liver cirrhosis only, group 2 with hepatic failure (HF), group 3 with grade 1 or 2 hepatic encephalopathy (HE), and group 4 with grade 3 or 4 HE. The control group consisted of 10 age-matched normal subjects. The major changes occurred in the median cortical SEP late components (peaks after N20 and P25). From group 1 to group 4, there were progressive prolongation and sequential disappearance of the late components. Those changes in the cortical SEPs were reversible. The subcortical somatosensory and brainstem auditory conductions (SEP N13-N20 and BAEP I-V interpeak latencies) were slightly prolonged in all groups of patients. The present data indicate that SEP may be useful in detecting subclinical HE and in monitoring the clinical course of HE. The present data further indicate that chronic portal-systemic shunting in liver cirrhosis may result in a minimal impairment of cerebral function and sensory conduction in the CNS.     

Methyl bromide myoclonus: an electrophysiological study

We report a case of myoclonus from overnight exposure to methyl bromide. Myoclonus was either spontaneous or induced by somatosensory stimulation or voluntary movements, multifocal and sometimes generalized. Median SEP showed normal size P14-N20, but giant parietal P25, N33 and frontal P22-N30 waves. Back-averaging showed a biphasic EEG spike of maximal amplitude at the central region contralateral to the corresponding myoclonic jerk recorded from abductor pollicis brevis and preceding it by a short interval consistent with conduction in corticospinal pathways. Long latency reflexes from cutaneous and mixed nerve stimulation were enhanced. The above electrophysiological findings suggest that myoclonus following methyl bromide poisoning belongs to the cortical reflex myoclonus category.     

Parkinson's disease and lower limb somatosensory evoked potentials: apomorphine-induced relief of the akinetic-rigid syndrome and vertex P37-N50 potentials.

We evaluated brainstem P30, vertex-central P37-N50 and contralateral frontal N37 somatosensory evoked potentials (SEPs) from the tibial nerve in 14 patients affected by Parkinson's disease (PD) with akinetic-rigid syndrome. In seven patients SEPs were recorded after administration of apomorphine. The cortical P37-N50 complex was either absent (five patients, eight tested sides) or significantly smaller in patients as compared to the control group (n = 18). There was a relationship between abnormalities of early vertex potentials and degree of motor impairment. Administration of apomorphine was followed by an increase in amplitude of P37-N50 response, which was maximal after 15-30 min and then progressively returned to basal values in parallel with clinical improvement. Amplitude of brainstem P30 and frontal N37 responses was within normal values and did not vary following drug administration. These results suggest that the P37-N50 complex arises from independent cortical generators, probably located in the pre-rolandic cortex, which may be selectively affected by basal ganglia dysfunction. Amplitude decrease of the P37-50 complex may reflect an abnormal processing of somatosensory inputs within the pre-central cortex due to defective modulation exerted by basal ganglia circuitry on cortical excitability. SEP potentiation following apomorphine, besides indicating that this dysfunction is partly reversible, might suggest objective method to measure therapeutic efficacy.     

Topography and intracranial sources of somatosensory evoked potentials in the monkey. II. Cortical components

Averaged somatosensory evoked potentials (SEPs) and associated multiple unit activity (MUA) were recorded from a series of epidural and intracortical locations following stimulation of the contralateral median nerve in the monkey. Cortical components were differentiated from the earlier subcortical activity and the intracerebral distribution and sources of each cortical potential were determined. Under barbiturate anesthesia the SEP wave form is simplified and can be wholly attributed to two sources. The earliest cortical activity consists of a biphasic P10-N20 wave which is generated in the posterior bank of the central sulcus. A second wave form, P12-N25, originates in the crown of the postcentral gyrus. No other cortical areas are active. In the alert state the morphology of the surface SEP is complex and reflects the interaction of volume conducted activity from several adjacent cortical sources. The wave form overlying the hand area of the postcentral gyrus consists of P12, P20, P40, N45 and P110. Precentral recordings exhibit P10, P13, N13, N20, P24, N45 and P110. Six anatomical sources have been identified. P10 and N20 originate in the posterior bank of the central sulcus including areas 3a and 3b and are volume conducted in an anteroposterior direction. P12 originates in area 1 as well as the anterior portion of area 2. P20 is generated in the medial portion of the postcentral gyrus including area 5. The source of P40 lies within the lateral portion of the parietal lobe including area 7b. Two components were generated in precentral cortex: P13/N13 originates principally in area 4 within the anterior bank of the central sulcus and P24 reflects activity in the anteromedial portion of the precentral gyrus including area 6. The long latency SEP components, N45 and P110, are generated widely within the somesthetic areas of postcentral cortex. The early cortical SEP components recorded in the monkey closely resemble in configuration and topography those recorded from man although the latter are longer in latency, reflecting interspecies differences in the length of conduction pathways as well as in cortical processing time.     

Abnormalities of parietal and prerolandic somatosensory evoked potentials in Huntington's disease.

Cervical, parietal and prerolandic somatosensory evoked potentials (SEPs) to median nerve stimulation at the wrist were recorded with an earlobe reference in 24 patients with Huntington's disease (HD) and in 24 age-matched normal controls. Cortical responses of abnormal wave form and reduced amplitude were constantly observed in HD patients. SEP changes affected more severely the prerolandic (P22/N30) pattern, which could not be recognized in two-thirds of patients, than the parietal (N20/P27) pattern, which could be identified in all cases. The N20 latency and the central conduction time (N13-N20 interval) were significantly increased. The occurrence of abnormalities of central conduction and of a predominant involvement of the prerolandic SEP pattern suggests an impairment of impulse transmission along the somatosensory lemniscal pathway at subcortical, possibly thalamic, level in HD.     

Somatosensory evoked potentials in comatose patients: correlation with outcome and neuropathological findings

Summary Subcortical and early cortical somatosensory evoked potentials (SEPs) were recorded in 63 comatose patients and classified into five salient SEP grades, which were defined as follows: grade 1, normal SEP; grade 2, SEPs with a clearly recognizable scalp component N20, normal central conduction time but clearly distorted wave N20–P25; grade 3, SEPs with a still recognizable N20 but delayed central conduction time and severely altered wave N20–P25; grade 4, SEPs with absence of N20 but with a more or less recognizable P15; grade 5, SEPs with absence of both N20 and P15. When these five patterns were compared with outcome, it was found that bilaterally normal SEPs or only unilaterally distorted SEPs were generally followed by good outcomes. Bilaterally altered SEPs (grade 2 or 3) were indicative of reduced chances of full recovery. The great majority of patients showing either grade 4 or 5 SEPs died within a few days after the recording session. In 31 patients, it was found post mortem that grade-2 SEPs reflected cortical brain damage, whereas grade-3 SEPs correlated well with subcortical lesions. In post-traumatic patients, this SEP pattern coresponded to diffuse subcortical shearing lesions. Patients with grade 4 or 5 SEPs were found to have severe brain oedema giving rise to transtentorial herniation, which was combined with secondary midbrain haemorrhage and tonsillar herniation in all patients with bilateral grade-5 SEPs.     

Effects of age and body height on somatosensory evoked potentials]

The influence of age and height on somatosensory evoked potentials (SEP) following median and tibial nerve stimulation was studied. Age correlated with increase of latencies and decrease of amplitudes; exceptionally the amplitude of cortical N20 component increased with age. The central conduction time P31-P40 (tibial nerve stimulation) was longer in elderly subjects, whereas the time N13-N20 (median nerve stimulation) was independent of age. Height showed a positive correlation with latencies and peripheral conduction times; central conduction times (N13-N20 and P31-P40) were independent on height. The correlations of SEP parameters with age and height were expressed quantitatively by regression equations. The presented equations should be treated as a valuable complement to normative data in interpretation of SEP testing results.     

Somatosensory evoked potentials: correlations with height

Somatosensory evoked potentials (SEPs) to median and posterior tibial nerve stimulation were studied in 160 subjects aged 20-90 years. Height was highly correlated with latencies of spinal and cortical SEPs (N13, N20, N22, and P40). Although tibial central conduction (N22-P40) was also highly correlated with height, median conduction (N13-N22) was not correlated with the latter. Multiple correlation and regression analysis showed that except for the median N13-N20 latency, height provided the best prediction of the remaining SEP latencies. Age alone was not correlated with SEP latencies, but its significance was observed when age and height were considered together as the predictors. Effects of age and height on SEP latencies were independent of gender. The present data indicate that except for the N13-N20 conduction, height is the most important parameter for SEP latencies and can be used for construction of normograms.     

Mapping of early and late human somatosensory evoked brain potentials to phasic galvanic painful stimulation

In the present study, we modeled the spatiotemporal evolution of human somatosensory evoked cortical potentials (SEPs) to brief median-nerve galvanic painful stimulation. SEPs were recorded (-50 to +250 ms) from 12 healthy subjects following nonpainful (reference), slight painful, and moderate painful stimulations (subjective scale). Laplacian transformation of scalp SEPs reduced head volume conduction effects and annulled electric reference influence. Typical SEP components to the galvanic nonpainful stimulation were contralateral frontal P20-N30-N60-N120-P170, central P22-P40, and parietal N20-P30-P60-P120 (N = negativity, P = positivity, number = latency in ms). These components were observed also with the painful stimulations, the N60, N120, P170 having a longer latency with the painful than nonpainful stimulations. Additional SEP components elicited by the painful stimulations were parietomedian P80 as well as central N125, P170 (cP170), and P200. These additional SEP components included the typical vertex negative-positive complex following transient painful stimulations. Latency of the SEP components exclusively elicited by painful stimulation is highly compatible with the involvement of A delta myelinated fibers/spinothalamic pathway. The topography of these components is in line with the response of both nociceptive medial and lateral systems including bilateral primary sensorimotor and anterior cingulate cortical areas. The role of attentive, affective, and motor aspects in the modulation of the reported SEP components merits investigation in future experiments.     

Alcohol consumption and transition of mild cognitive impairment to dementia

Aim:  Mild cognitive impairment (MCI) is a prodrome for dementia. Alcohol drinking patterns may affect cognitive functions and the effects may accumulate to a significant level at an advanced age. This study investigated the relationship between alcohol consumption and risks for dementia in a cohort of elderly patients with MCI.
Methods:  Patients with suspected cognitive impairment were screened. One hundred and seventy-six patients who met the MCI criteria were enrolled. Lifetime and daily alcohol consumptions were assessed at baseline using a self-report questionnaire answered by patients and their caregivers. Patients were classified according to alcohol consumptions as abstainers, light–moderate and heavy drinkers. Global cognitive functions were assessed periodically with Mini-Mental State Examination (MMSE). Enrolled patients were followed for 2 years.
Results:  Of the 176 patients diagnosed as having MCI, 15 (8.5%) died, 13 (7.4%) were lost to follow up, and 66 (37.5%) developed dementia during follow up. Light–moderate alcohol drinkers had better MMSE performance than abstainers ( P  < 0.05) and heavy drinkers ( P  < 0.01) 2 years after MCI diagnosis. Patients who consumed a total of ≤300 kg alcohol prior to MCI diagnosis had less cognitive decline than patients who consumed no ( P  < 0.05) or >300 kg alcohol ( P  < 0.01). Heavy drinkers had a higher risk for dementia than abstainers ( P  < 0.05) and light–moderate drinkers ( P  < 0.05) 2 years after MCI diagnosis.
Conclusions:  A J-shaped relationship may exist between alcohol consumption and cognitive decline in MCI patients. Light–moderate alcohol drinking may be associated with decreased risks for dementia in elderly patients with MCI.     

Effects of alcohol on myoclonus and somatosensory evoked potentials in dyssynergia cerebellaris myoclonica.

Three brothers with dyssynergia cerebellaris myoclonica received alcohol to study the correlation between improvement of myoclonus and alteration in somatosensory evoked potentials (SEPs). Alcohol considerably improved myoclonus for about six hours in two patients (cases 1 and 2) but had only a mild effect in one (case 3). All three patients had giant cortical SEPs. The amplitudes of median N20-P25 and P25-N35 components and tibial N30-P40 and P40-N50 components were considerably decreased after alcohol ingestion in two patients (cases 1 and 2) but unchanged or slightly decreased in one (case 3). The peak latencies of those components were not affected by alcohol. There was thus a good correlation between the suppression of myoclonus and the decrease in giant SEP amplitude.     

Posterior cortical brain dysfunction in cognitively impaired patients with Parkinson's disease--a rCBF scintigraphy study

Objectives –  The aim of the study was to visualize cortical function in Parkinson's patients with various degrees of cognitive impairment.
Materials and methods –  Thirty-seven patients with Parkinson's disease and three with Parkinson plus syndromes underwent cognitive assessment and rCBF using ^99mTC-HMPAO-SPECT.
Results –  Almost no regional reductions in cerebral blood flow were seen in patients without cognitive impairment ( n  = 16). Limited, mainly posterior, blood flow reductions were seen in patients with mild cognitive impairment ( n  = 14), whereas the reductions were extensive and bilaterally symmetric, involving both anterior and posterior brain regions in patients with dementia ( n  = 10).
Conclusions –  The findings suggest a widespread cortical, mainly posterior type of dysfunction and a relationship between the degree of cognitive impairment and the magnitude of the dysfunction.     

Giant SEPs and SEP-recovery function in Unverricht–Lundborg disease

ObjectiveTo evaluate the relationship between sensory hyperexcitability as revealed by giant SEPs and the SEP recovery function (SEP-R) in a series of patient with progressive myoclonic epilepsy of Unverricht–Lundborg type, identified as epilepsy, progressive myoclonic 1A (EPM1A), MIM #254800.MethodsWe evaluated SEPs by applying median nerve stimuli and SEP-R using paired stimuli at inter-stimulus intervals (ISIs) of between 20 and 600 ms in 25 patients and 20 controls. The SEPs were considered “giant” if the N20P25 and P25N33 amplitudes exceeded normal mean values by +3SD.ResultsDuring the paired-stimulus protocol, the SEPs elicited by the second stimulus (S2) were detectable at all ISIs but consistently suppressed in the 13 patients with giant SEPs reflecting a significantly delayed SEP-R. Maximal suppression roughly corresponded to the plateau of a broad middle latency (>100 ms) wave pertaining to the S1 response.ConclusionsThe cortical processing dysfunction generating giant SEPs in EPM1A patients consistently combines with a long-lasting suppression of hyperexcitability that leads to a delayed giant SEP-R without obstructing the response to incoming stimuli.SignificanceThe delayed SEP-R is not due to true inhibition but the suppression of aberrant hyper-synchronisation sustaining giant SEPs. A broad middle latency SEP component adds a significantly suppressive effect. This suggests that cortico-subcortical circuitries contribute to both the gigantism and the delayed SEP-R.     

Alzheimer and vascular neuropathological changes associated with different cognitive States in a non-demented sample

The state between aging with no cognitive impairment and dementia has become a major focus for intervention. The neuropathological and neurobiological correlates of this intermediate state are therefore of considerable interest, particularly from population representative samples. Here we investigate the neuropathological profile associated with different cognitive ability levels measured using strata defined by Mini Mental State Examination (MMSE) scores. One hundred and fifty one individuals were stratified into three cognitive groups including: non-, mildly, and moderately impaired at death. Alzheimer's disease, atrophy, and vascular pathologies were investigated. Mild impairment was associated with an increased risk of vascular pathologies including small vessel disease and lacunes. In contrast, the moderately impaired group showed a more extensive pattern of pathology, including tangles and neuritic plaques (entorhinal/hippocampus), atrophy (cortical and hippocampal), and vascular disease (small vessel disease, lacunes, and infarcts). In a population-based sample of older people, MMSE score defined strata are associated with multiple pathologies. The profile of AD and vascular changes becomes more complex with increased cognitive impairment and these changes are likely to constitute a major substrate for age associated cognitive impairment. The results highlight the need for rigorous investigation of both neurodegenerative and vascular risks factors in old age.     

Three-dimensional gray matter atrophy mapping in mild cognitive impairment and mild Alzheimer disease

BACKGROUND: Alzheimer disease (AD) is the most common form of dementia worldwide. Mild cognitive impairment (MCI) is the recent terminology for patients with cognitive deficiencies in the absence of functional decline. Most patients with MCI harbor the pathologic changes of AD and demonstrate transition to dementia at a rate of 10% to 15% per year. Patients with AD and MCI experience progressive brain atrophy. OBJECTIVE: To analyze the structural magnetic resonance imaging data for 24 patients with amnestic MCI and 25 patients with mild AD using an advanced 3-dimensional cortical mapping technique. DESIGN: Cross-sectional cohort design. Patients/ METHODS: We analyzed the structural magnetic resonance imaging data of 24 amnestic MCI (mean MMSE, 28.1; SD, 1.7) and 25 mild AD patients (all MMSE scores, >18; mean MMSE, 23.7; SD, 2.9) using an advanced 3-dimensional cortical mapping technique. RESULTS: We observed significantly greater cortical atrophy in patients with mild AD. The entorhinal cortex, right more than left lateral temporal cortex, right parietal cortex, and bilateral precuneus showed 15% more atrophy and the remainder of the cortex primarily exhibited 10% to 15% more atrophy in patients with mild AD than in patients with amnestic MCI. CONCLUSION: There are striking cortical differences between mild AD and the immediately preceding cognitive state of amnestic MCI. Cortical areas affected earlier in the disease process are more severely affected than those that are affected late. Our method may prove to be a reliable in vivo disease-tracking technique that can also be used for evaluating disease-modifying therapies in the future.