Evoked potentials in patients with Huntington's disease and their offspring. I. Somatosensory evoked potentials

Spinal and cortical somatosensory evoked potentials (SEPs) were recorded in a large sample of patients with Huntington's disease (n = 37) and subjects at risk (first order offspring, n = 43). The SEPs were elicited by stimulation of the median and tibial nerves and recorded at Erb's point, the cervical level (C2) and at the corresponding scalp areas.The most striking finding in patients with Huntington's disease was a drastic diminution of the amplitude of the early cortical components, especially N20/P25 for the median nerve and N33/P40 for the tibial nerve. The latencies (Erb's point, C2, cortical) were only slightly prolonged in comparison to the normal values.Forty-three per cent of the persons at risk exhibited pathological results with a clear reduction in amplitude of the early cortical responses or with a pathological side difference between the amplitudes. Fifty-three per cent of the persons at risk exhibited a normal result. Two persons at risk (=6%) could not be classified unambiguously. Some patients with benign and symptomatic chorea were investigated. These showed normal results with one exception.The diagnostic and predictive value of the investigation of SEPS in Huntington's disease is discussed.     

Neurological dysfunction in asymptomatic HIV-1 infected men: evidence from evoked potentials

Neurological function in 159 subjects infected by the human immunodeficiency virus (HIV) who had no neurological symptoms or signs (129 asymptomatic, 30 with ARC/AIDS) was compared to that of 62 controls by means of pattern-reversal evoked potentials (PREPs), brain-stem auditory evoked potentials (BAEPs), median nerve somatosensory evoked potentials (MSEPs), tibial nerve somatosensory evoked potentials (TSEPs) and nerve conduction studies (NCSs). Central nervous system somatosensory conduction from lumbar cord to cortex was prolonged in both asymptomatic seropositive and ARC/AIDS groups, while peripheral somatosensory conduction, NCSs and PREP delays occurred only in the ARC/AIDS group. BAEPs did not show significant differences among groups. TSEPs were abnormal in 8% of asymptomatic carriers and 43% of patients with ARC/AIDS, MSEPs in 7% and 20%, PREPs in 4% and 0%, and BAEPs in 1% and 0% respectively. One or more evoked potentials were abnormal in 18 of 129 (14%) asymptomatic carriers and 13 of 30 (43%) subjects with ARC/AIDS as compared with 1 of 62 (2%) seronegative controls. We conclude that asymptomatic HIV carriers have subclinical neurological impairment of central somatosensory function and that the neurological impairment increases with disease progression to involve peripheral nerves and visual system.     

Nerve,spinal cord and brain somatosensory evoked responses: a comparative study during electrical and magnetic peripheral nerve stimulation

Somatosensory evoked potentials (SEPs) and compound nerve action potentials (cNAPs) have been recorded in 15 subjects during electrical and magnetic nerve stimulation. Peripheral records were gathered at Erb's point and on nerve trunks at the elbow during median and ulnar nerve stimulation at the wrist. Erb responses to electrical stimulation were larger in amplitude and shorter in duration than the magnetic ones when ‘electrical’ and ‘magnetic’ compound muscle action potentials (cMAPs) of comparable amplitudes were elicited. SEPs were recorded respectively at Cv7 and on the somatosensory scalp areas contra- and ipsilateral to the stimulated side. SEPs showed a statistically significant difference in amplitude only for the brachial plexus response and for the ‘cortical’ N20-P25 complex; differences were not found between the magnetic and electrical central conduction times (CCTs) or for the peripheral nerve response latencies. Magnetic stimulation preferentially excited the motor and proprioceptive fibres when the nerve trunks were stimulated at motor threshold intensities.     

Somatosensory evoked potentials after stimulation of digital nerves in upper limbs: Normative data

Normative data for somatosensory evoked potentials (SEPs) after stimulation of digital nervesfrom the first, third and fifth digits, which reach the spinal cord through C6, C7 and C8 roots are presented in 20 normal adults. SEP peak latencies and amplitudes are indicated for Erb's point, the level of the seventh and second cervical vertebrae and contralateral cortical hand area.     

Parameters of somatosensory evoked potentials in normal subjects in relation to age and height

Cortical SEPs by stimulation of median nerve at wrist (159 measurements; 144 subjects, 63 M - 81 F; mean age 39.7, range 11-70; mean height 162.5, range 134-190) and cortical SEPs by stimulation of posterior tibial nerve at ankle (100 measurements; 81 subjects, 37 M - 44 F; mean age 34.7, range 11-60; mean height 161.1, range 134-180 cm) have been performed. The latencies of N1 of median SEPs and of N1 and P1 of tibial SEPs significantly increase with the height of subjects. The statistical evaluation of latency values of each subject normalized at a height of 165 cm show a little increase of latency according to the age of the subjects; this increase is quite evident for the latency of P1 of tibial SEP.     

A longitudinal study of short latency somatosensory evoked responses in healthy newborns and infants

Maturational changes in short latency somatosensory evoked responses (SERs) were studied in 18 healthy full-term newborns in the first week of life and consequently repeated at 2–3 and 6–7 months of age. Both median nerves were electrically stimulated individually and evoked responses were recorded at 3 levels: Erb's point (EP), second cervical vertebra (CII), and contralateral parietal scalp (C′c). In the neonatal period, results of 32 stimulated nerves were obtained in all cases at the EP and CII levels. At the parietal level, potentials were present in 85% of cases, absent in 9% and questionable in 6%. Parietal potentials were occasionally noted on one side only. Repeat examinations at 2–3 and 6–7 months of age demonstrated significant maturational changes in the SERs. These changes were most prominent in the neonatal period and 2 months of age. They included decreased interpeak latencies, increased amplitude and markedly diminished dispersion of parietal potentials. Minimal changes in wave form configuration and latency were noted at the EP and CII level. These findings most likely reflect myelination and increased synaptic efficiency predominantly in the central sensory pathway. The purpose of this investigation was to delineate a reliable technique for SERs in newborbs and infants that could be applied both to research and clinical settings. Normative data were established in newborns and infants as this will help us in accurately differentiating a nomal from an abnormal group of neonates and infants.     

正常小儿胫神经诱发脊髓电位特征和脑瘫小儿该电位的变化

采取刺激后胫神经(PTN)诱发叠加技术,利用体表无创伤性双极记录方法观察了16例正常小儿和43例脑瘫小儿的脊髓诱发电位(SCEP)。正常小儿的SCEP自下而上潜伏时逐渐延长、电压减小。从椎体C6到T10表现为Pa-Na-Pb三相波,T10～T12为Pa-Na1-Na2-Pb波,T12～L4为多相复合波。左右侧SCEP波形相似,潜伏时、电压相同,它们之间无统计学显著差别;但不同节段之间SCEP差异显著;脊髓传导速度为57.14m/s。脑瘫小儿SCEP正常者占14％;全髓反应低下者占20％;左右侧反应不对称者占46％;节段性反应低下者占15％;其它异常约占5％。不但节段间存在显著差异,而且全脊髓左右侧电压间以及颈、腰骶髓的潜伏时间出现显著差异。脊髓传导速度减低(患侧46.22m/s,对侧53.48m/s)。结果提示:(1)正常小儿脊髓活动左右对称,不同脊髓节段对PTN刺激反应不同。(2)脑瘫小儿脊髓活动左右不对称,一侧功能下降时对侧有一定代偿力,脊髓传导速度减慢。     

Results of decompression of peripheral nerves in diabetics: a prospective, blinded study

Diabetic neuropathy traditionally is considered progressive and irreversible and will result in lower extremity ulceration and amputation in a segment of the diabetic population, despite the best efforts to control serum glucose levels. Restoration of sensation to the diabetic may prevent these complications of neuropathy. The present study was designed to evaluate whether decompression of a peripheral nerve at a known site of anatomic narrowing can restore sensibility to that nerve in the diabetic. Twenty diabetic patients ( 14 type I, 6 type II, with a mean duration of diabetes of 14.8 years) had surgical decompression of a median nerve at the wrist and an ulnar nerve at the elbow, or a decompression of the posterior tibial nerve at the ankle (total of 31 nerves). A therapist, in a manner blind to the operative site, evaluated two-point discrimination in the pulp of the appropriate digit. The postoperative sensibility was compared with that of the nontreated, contralateral extremity. At a mean of 23.3 months, 69 percent of the lower-extremity nerves and 88 percent of the upper-extremity nerves (79 percent overall) had improvement in sensibility. In comparison, 32 percent of the control (not decompressed) contralateral nerves had measurable progression of neuropathy. The hypothesis that decompression of a peripheral nerve in the diabetic will improve sensibility was confirmed at the p < 0.001 level.     

Spinal and cortical potentials evoked by tibial nerve stimulation in humans: effects of sex, age and height.

Somatosensory evoked potentials by posterior tibial nerve stimulation at the ankle were performed in 74 healthy volunteers (36 females and 38 males) aged 14-76 years. Cortical potentials were obtained in all subjects and spinal potentials (N22) in 71 subjects. All parameters were related to subject's age, height and sex. Sex influenced only P40-N50 amplitude, which was greater in females. All latencies of spinal and cortical components increased in a similar manner with subject's height (about 0.16-0.18 ms per cm), whereas the N22-P40 interpeak latency was independent from height, but related to T12-Cz distance. Absolute latencies of the spinal and of most cortical components, but not interpeak latencies, increased with subject's age (about 0.06-0.09 ms per year). The parameters to compute normative data (according to univariate or bivariate regression models) are furnished. Limits of right-left differences are reported.     

The effect of temperature on conduction velocity in human muscle fibers

The effects of variation of intramuscular temperature (T) on conduction velocity (CV) of the action potential along single human muscle fibers of the biceps brachii was studied in situ in 15 normal volunteers (mean age 39 years, range 21–62 years). Cooling was obtained by direct application of ice over a rectangular skin region including the stimulating and recording area. The intramuscular T was monitored by a needle thermocouple (copperconstantane). In all the 24 muscle fibers studied, a linear relationship was observed between CV and T. The slopes of the regression lines, ranging between 0.190 and 0.079 m/s, were positively correlated with the starting CV at 36°C ranging between 2.2 and 5.2 m/s. If conduction changes are expressed as a percentage of the basal CV at 36°C, the CV/T coefficient is the same for all the fibers and independent of the individual CV: 3.4% of CV/°C.     

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.     

CMV+ Serostatus Associates Negatively with CD4:CD8 Ratio Normalization in Controlled HIV-Infected Patients on cART

Cytomegalovirus (CMV) infection is common among HIV-infected patients but its repercussion on the course of CD4+ and CD8+ T cells after cART initiation remains elusive. The French Dat''AIDS cohort enrolled 5,688 patients on first-line cART, from which we selected patients who achieved HIV suppression for at least 12 months without modification of cART, and for whom CMV serostatus was available. Five hundred and three patients fulfilled the selection criteria (74% male, median age 43 yrs, 15.5% CDC stage C), of whom 444 (88.3%) were seropositive for CMV (CMV+). Multivariate analyses using mixed-linear models adjusted for the time from HIV suppression, sex, age, transmission risk group, duration of HIV follow-up, the interaction between time from HIV suppression and CMV+ serology, and the nadir CD4 count revealed a negative correlation between CMV+ and CD4:CD8 ratio (coeff. = -0.16; p = 0.001). This correlation was also observed among patients displaying optimal CD4 recovery (≥500 cells/mm3 at M12; coeff. = -0.24; p = 0.002). Hence, CMV+ serostatus antagonizes normalization of the CD4:CD8 ratio, although further analyses of the impact of co-morbidities that associate with CMV serostatus, like HCV infection, are needed to elucidate this antagonism formally. However, this might reflect a premature T cell senescence, thus advocating for a close monitoring of T cells in CMV co-infected patients. In addition, our results raise the question of the benefit of treatment for asymptomatic CMV co-infection in HIV-infected patients.     

Epidural recordings of electrical events produced in the spinal cord by segmental, ascending and descending volleys

Epidural electrodes implanted for a percutaneous trial of therapeutic spinal cord stimulation were used to record electrical events evoked by the stimulation of peripheral nerves or of the spinal cord itself. The data collected in patients with no neurological deficit were analyzed in order (1) to check the consistency between epidural and surface recordings, (2) to get information on the genesis of such potentials, and (3) to demonstrate the feasibility of complex neurophysiological studies by means of epidural electrodes. Spinal cord potentials evoked by segmental volleys were recorded at cervical levels with the recording electrodes anterior, lateral and posterior to the spinal cord. The refractory period of the evoked potentials has been studied as well. Responses to stimulation of the tibial nerve were obtained at T11-12 vertebral level with posterior epidural electrodes. Segmental cervical potentials were characterized by a P10, N11, N13/P13 followed by a slow positivity/negativity. A response of similar waveform, but with different peak latencies, was recorded at segmental levels following tibial nerve stimulation. Such a response showed an increasing number of spikes while ascending along the spinal cord. Maximum conduction velocities in the cord were between 65 and 85 m/s. Our epidural recordings are similar to those obtained from the skin, but with a greater amplitude and waveform resolution. Furthermore, the use of epidural electrodes made it feasible to perform complex examinations of sensory function (i.e., the study of orthodromic and antidromic conduction along the dorsal cord and of the influence of a single dorsal cord volley on the segmental cervical potential). Finally, the genesis of the potentials recorded is discussed.     

Risk of AIDS related complex and AIDS in homosexual men with persistent HIV antigenaemia.

One hundred and ninety eight men seropositive for human immunodeficiency virus (HIV) antibody and 58 HIV antibody seroconverters were studied for an average of 19.3 (SEM 0.5) months to assess the relation between HIV antigenaemia and the risk of developing the acquired immune deficiency syndrome (AIDS) and AIDS related complex. Forty (20.2%) of the 198 HIV antibody seropositive men were antigen positive at entry and remained so during follow up. Eight (13.8%) of the 58 HIV antibody seroconverters and 20 (12.7%) of the remaining 158 HIV antibody seropositive men became antigen positive during follow up, resulting in an end point attack rate for HIV antigenaemia of 14.3%. AIDS related complex was diagnosed in 25 (15.8%) of the HIV antigen negative men and in 14 (20.7%) of the HIV antigen positive men. AIDS was diagnosed in 15 men, resulting in an end point attack rate for AIDS of 23.9% in the HIV antigen positive group and 1.3% in the antigen negative group. HIV antibody seropositive men without symptoms but with persistent HIV antigenaemia are at increased risk of developing AIDS and AIDS related complex.     

Seroprevalence of Toxoplasma gondii Infection among HIV/AIDS Patients in Eastern China

Toxoplasmosis, a neglected tropical disease caused by the protozoan parasite Toxoplasma gondii, occurs throughout the world. Human T. gondii infection is asymptomatic in 80% of the population; however, the infection is life-threatening and causes substantial neurologic damage in immunocompromised patients such as HIV-infected persons. The major purpose of this study was to investigate the seroprevalence of T. gondii infection in subjects infected with HIV/AIDS in eastern China. Our findings showed 9.7% prevalence of anti-T. gondii IgG antibody in HIV/AIDS patients, which was higher than in intravenous drug users (2.2%) and healthy controls (4.7%), while no significant difference was observed in the seroprevalence of anti-Toxoplasma IgM antibody among all participants (P>0.05). Among all HIV/AIDS patients, 15 men (7.7%) and 10 women (15.9%) were positive for anti-T. gondii IgG antibody; however, no significant difference was detected in the seroprevalence of anti-Toxoplasma IgG antibody between males and females. The frequency of anti-Toxoplasma IgG antibody was 8.0%, 13.2%, 5.5%, and 0% in patients with normal immune function (CD4⁺ T-lymphocyte count ≥500 cells/ml), immunocompromised patients (cell count ≥200 and <500 cells/ml), severely immunocompromised patients (cell count ≥50 and <200 cells/ml), and advanced AIDS patients, respectively (cell count <50 cells/ml), while only 3 immunocompromised patients were positive for anti-T. gondii IgM antibody. The results indicate a high seroprevalence of T. gondii infection in HIV/AIDS patients in eastern China, and a preventive therapy for toxoplasmosis may be given to HIV/AIDS patients based on CD4⁺ T lymphocyte count.     

Seropositivity for HIV and the development of AIDS or AIDS related condition: three year follow up of the San Francisco General Hospital cohort

The three year actuarial progression rate to the acquired immune deficiency syndrome (AIDS) in a cohort of men in San Francisco who were seropositive for the human immuno-deficiency virus (HIV) was 22%. An additional 26 (19%) developed AIDS related conditions. β₂ Microglobulin concentration, packed cell volume, HIV p24 antigenaemia, and the proportion and number of T4 lymphocytes each independently predicted progression to AIDS. β₂ Microglobulin was the most powerful predictor. The 111 subjects tested who were normal by all predictors (40%) had a three year progression rate of 7%, and the 68 subjects who were abnormal by two or more predictors (24%) had a progression rate of 57%. Two thirds of all men who progressed to AIDS were in the last group. The median T4 lymphocyte count in subjects who did not progress to AIDS fell from 626 × 10⁶ to 327 × 10⁶/1. HIV p24 antigenaemia developed in 7% of the subjects per year. The proportion who were abnormal by two or more predictive variables rose to 41%. At three years an estimated two thirds of the seropositive subjects showed clinical AIDS, an AIDS related condition, or laboratory results that were highly predictive of AIDS.It is concluded from the observed rates and the distribution of predictive variables at three years that half of the men who were seropositive for HIV will develop AIDS by six years after the start of the study, and three quarters will develop AIDS or an AIDS related condition.     

Cerebral responses elicited by stimulation of the vesico-urethral junction (VUJ) in diabetics

To investigate the involvement of the visceral afferent nerves in diabetes mellitus, we enrolled 46 male patients in a study, examining the cerebral potentials evoked by stimulation of the vesico-urethral junction (VUJ CEP) and the pudendal (penile CEP) and posterior tibial nerves (tibial CEP). The age range was 23–67 (mean 45.8) years. The epithelial surface of the vesico-urethral junction was stimulated bipolarly with an electrode attached to a specially produced Foley catheter. Cerebral responses were recorded bipolarly at vertex.VUJ CEPs were absent (27 patients) or protracted and/ or of low amplitude (4 patients) (total 31 patients; 67.8%). Penile CEP and/or tibial CEP could be obtained in all cases; however, protracted P1 peak latencies were detected in 15 (32.8%). The abnormalities of VUJ CEP did not correlate with the presence of peripheral neuropathy, while the abnormalities of penile CEP and/or tibial CEP invariably coincided with the presence of peripheral neuropathy. Although neither age nor the duration of diabetes correlated with abnormal CEPs as determined by any of the tests, insulin dependence correlated with abnormal penile CEP and to a lesser extent with VUJ CEP.We conclude that VUJ CEP is informative in evaluating the physiological condition of visceral afferents, and can be used in diagnosis of the early involvement of visceral afferents in diabetes mellitus.     

Evoked potential findings in Behçet's disease. Brain-stem auditory,visual, and somatosensory evoked potentials in 44 patients

We studied 54 patients with Behçet's disease, 41 males and 13 females, mean age 28 years. Forty-four patients had auditory brain-stem evoked potential (BAEP) recordings, 39 had pattern reversal visual evoked potentials (VEP), 27 had median nerve somatosensory evoked potential (SEP) recordings, and 25 tibial nerve SEPs. BAEPs were abnormal in 16 patients (52%) with neurological manifestations and in 4 (31%) without, because of decreased amplitude of wave V, prolonged I–III or III–V interpeak latencies, or uncertain/absent waves III and/or V. Eleven patients (40%) with neurological symptoms and 3 patients (25%) without, had abnormal VEPs. Absent potentials, decreased amplitude, with or without prolonged P100 latency, were found in 75% of the cases, the rest had prolonged P100 latency only. Median SEPs were abnormal in 8 patients (38%) with neurological manifestations. Four patients (21%) had abnormal tibial SEPs. Decreased amplitude with or without mild slowing in central conduction was the predominant SEP abnormality. SEPs were normal in all patients without neurological symptoms. In total, 84% of patients with, and 38% of patients without, neurological symptoms had abnormalities of one or more EP modality.When used cautiously, EP studies in Behçet's disease might be helpful to separate neuro-Behçet from other disorders with similar symptomatology, to disclose subclinical CNS involvement, to evaluate and monitor CNS disease activity, and to provide objective measures of treatment response.     

The diabetic polyneuropathy. I. Relation between impaired function in peripheral nerves and clinical findings

789 patients with diabetes mellitus were studied by clinical and electroneurographical investigation. Motor and sensory conduction velocities of the median nerve and motor conduction velocity of the tibial nerve were determined. 86.1% of the patients suffered from juvenile diabetes, and 13.9% from maturity onset diabetes. Average duration of the disease was 9.5 years, average age of the patients was 26.7 years. Clinical signs of polyneuropathy were found in 19.1%. In 40.9% of the patients at least one of 3 conduction velocities was found to be delayed. Patients with clinical signs of polyneuropathy exhibited delayed nerve conduction velocities and delayed distal latencies. Diagnosis of polyneuropathy almost with certainty is possible by determining the three nerve conduction velocities and the three corresponding distal latencies. 22% of patients without clinical signs of polyneuropathy exhibited electroneurographical signs of impaired peripheral nerve function. Heredity, body weight, lipid metabolism, actual metabolic balance, and treatment were found to be without any significant influence on nerve conduction velocity.     

Changes in sexual behaviour and the fall in incidence of HIV infection among homosexual men.

To investigate the epidemiology and normal course of infection with HIV the prevalence and incidence of the infection were studied among two cohorts of homosexual men in Amsterdam in 1980-7. The cumulative incidence of infection increased from a weighted 2.2% in 1980 to 39.0% in 1987. The estimated yearly incidence of HIV was 3.0% in 1981, rose to 8.8% in 1984, and fell gradually to 0% in 1987. During the study the sexual behaviour of the cohorts was examined. The number of men with whom anopenetrative intercourse was practised fell from a mean of 10.6 to 1.4 for those positive for HIV antibody, whereas the number with whom anoreceptive intercourse was practised fell from a mean of 3.7 to 0.5 for those negative for the antibody. In addition, there was a reduction in the number of cases of hepatitis B and syphilis among men in general. The decline in infection with HIV was assumed to be linked to changes in sexual behaviour. Such changes practised early in the course of the epidemic probably had a strong effect on the number of cases of AIDS among homosexual men in Amsterdam.