Median Motor Nerve Conduction Velocity Research Articles

A neurological and neurophysiological study of chloralkali workers previously exposed to mercury vapour

Neurological and neurophysiological examinations were conducted in 77 former chloralkali workers previously exposed to mercury vapour and 53 referents. The exposure had ceased on average 12.3 years prior to the study. There was a higher prevalence of reduced distal sensation (13.0% vs 1.9%), postural tremor (18.2% vs 7.5%) and impaired coordination (10.4% vs 1.9%) among the exposed subjects as compared to the referents. Abnormal Romberg's test (6.5% vs 0%) and line walking (7.8% vs 0%) were also more prevalent. The first negative peak in visual evoked response (N75) was bilaterally prolonged, and the median motor (55.9 m/s vs 58.0 m/s) and sensory nerve conduction velocity (55.6 m/s vs 59.0 m/s) were slightly reduced among the highly exposed subjects. The results indicate that slight neurological abnormalities, which in most cases could not be classified as disease, may persist many years after exposure cessation.

Autosomal recessive form of hereditary motor and sensory neuropathy type I.

We studied pathologic changes in sural nerve biopsies from four patients with probable autosomal recessive (AR) hereditary motor and sensory neuropathy (HMSN) type I with a median motor nerve conduction velocity greater than 10 m/sec, comparing them with the pathologic features in autosomal dominant (AD) HMSN type I. The four recessive and two sporadic cases showed segmental demyelination. However, the classic onion bulbs of concentric Schwann cell processes, which occur in AD type I, were rare; many axons, also of a smaller size, were surrounded by onion bulbs of basal laminae. Schwann cells of the myelinated and unmyelinated types were involved in these onion bulb formations. Patients with HMSN type I who have many basal lamina onion bulbs should be considered as having AR inheritance.

The Effect of γ‐Linolenic Acid on Human Diabetic Peripheral Neuropathy: A Double‐blind Placebo‐controlled Trial

Twenty-two patients with distal diabetic polyneuropathy confirmed both clinically and by objective nerve function studies, completed a double-blind, placebo-controlled study to assess the effect of dietary supplementation with gamma-linolenic acid on their neuropathy. Patients received either 360 mg gamma-linolenic acid (12 patients) or indistinguishable placebo capsules (10 patients) for 6 months. All patients were assessed at the beginning and end of the study period by neuropathy symptom and sign scoring, motor and sensory nerve conduction studies, and thermal threshold measurements. When compared with the placebo group, patients on gamma-linolenic acid showed statistically significant improvement in neuropathy symptom scores (p less than 0.001), median nerve motor conduction velocity (p less than 0.01) and compound muscle action potential amplitude (p less than 0.01), peroneal nerve motor conduction velocity (p less than 0.05) and compound muscle action potential amplitude (p less than 0.05), median (p less than 0.01) and sural (p less than 0.001) sensory nerve action potential amplitude and ankle heat threshold (p less than 0.001) and cold threshold (p less than 0.01) values. gamma-Linolenic acid therapy might have a useful role in the prevention and treatment of distal diabetic polyneuropathy.

Syndrome digital des vibrations et syndrome du canal carpien: Deux entites electrophysiologiques differentes?

Workers using vibrating tools are exposed to vascular and nervous symptoms called vibration syndrome (VS); moreover, the same subjects show increased prevalence of possible carpal tunnel syndrome (CTS). To determine the diagnostic criteria of both syndromes, we studied clinical and neurophysiological signs and differences in 18 patients with VS and in 18 with CTS; neither group had any other pathologic symptoms. Clinical symptoms clearly distinguished the 2 groups of patients: Raynaud's phenomena were mainly observed in patients with VS (83% of cases), whereas Tinel's sign was found exclusively in patients with CTS (56% of cases). Neurophysiological results were qualitatively similar in both patients groups compared to control group results, showing a significant decrease in median motor and sensory nerve conduction velocities (NCV), a significantly higher motor distal latency and a lower nerve action potential amplitude. These group results and the scattering of interindividual results did not allow us to classify any given patient in one group or the other. Nevertheless, statistical analysis showed differences between the 2 patient groups: median abnormalities were more severe, especially as revealed by the abductor pollicis brevis electromyogram, in patients with CTS, whereas ulnar motor distal latency and motor and sensory NCV were abnormal, exclusively in 50% of patients with VS. These results lend support to the assumption that the mechanical and vascular mechanisms responsible for lesions in both groups of patients may differ in nature or occur in a different sequence.

An electroneurographic assessment of subclinical lead neurotoxicity.

While heavy exposure to inorganic lead is capable of inducing symptomatic neuropathy in man, the subclinical neuropathy due to low levels of occupational lead exposure remains to be proved. The reported results of electroneurographic studies on lead workers, however, have been controversial. In this study, 40 lead smeltery workers and 50 non-exposed referents were investigated. The air concentrations of lead at worksites were 0.25 to 42.5 mg/m3. The geometric means of PbB, PbU and delta-ALAU in lead exposed group were 40.03 micrograms/dl, 71 micrograms/l and 4.68 mg/l respectively, which were significantly higher (P less than 0.001) than those (7.01 micrograms/dl, 6.0 micrograms/l and 1.81 mg/l respectively) in the reference group. There were no clinical symptoms or signs of nerve damage in either group. Alcoholism and diabetes were excluded in both groups. Nerve conduction velocity was measured by a DISA 1500 electromyograph in both groups. Eleven electroneurographic parameters, including motor nerve conduction velocity (MCV) and distal latency (DML) of median, ulnar and peroneal nerves as well as sensory nerve conduction velocity (SCV) and distal latency (DSL) of median, ulnar and sural nerves, showed statistically significant differences between the two groups. However, the results of electroneurographic measurements of each individual in the lead-exposed group were all within the normal range. There was no correlation between the blood-lead levels and the neurophysiological measurements except for the median MCV. No correlation was seen between the median MCV and the exposure duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Peripheral nerve function in relation to quality of metabolic control in diabetes.

It has been proposed that increased polyol pathway activity resulting from hyperglycaemia induces neuropathy in diabetic patients. Recently, it has been demonstrated that erythrocyte sorbitol content is a reflection of polyol pathway activity in nerve. In the present study the relationship of erythrocyte sorbitol and glycosylated haemoglobin (HbA1) levels to peripheral nerve functions were investigated in 62 diabetic patients. Peroneal and median motor nerve conduction velocities, H-M intervals of the Hoffmann reflex, thermal discrimination thresholds and vibratory perception thresholds, either singly or in combination, were not significantly correlated with erythrocyte sorbitol or HbA1 levels. These findings show that a single measurement of erythrocyte sorbitol or HbA1 content cannot predict impairment of nerve function in diabetic subjects.

Multiple peaks in human nerve action potentials: [formula omitted], E. Stålberg and F. Zarola (Dept. of Clin. Neurophysiology, University Hospital, Uppsala, Sweden)

Three clinical trials to evaluate the efficacy of the aldose reductase inhibitor sorbinil in improving or preventing diabetic neural function have either been completed or are currently in progress. In the first study from Seattle and Chicago, motor and sensory nerve conduction velocities (NCV) were evaluated in 39 insulin- and noninsulin-dependent, glycemic-stable diabetic patients in a randomized, double-blind, crossover trial. During the 9 weeks of treatment with 250 mg/d of sorbinil, there was a faster nerve conduction velocity of all 3 nerves tested when compared with the placebo period: peroneal motor NCV (+0.70 ± 0.24 m/s; x ± SEM; P < 0.008), median motor NCV (+0.66 ± 0.27 m/s; P < 0.005), and median sensory NCV (+1.16 ± 0.50 m/s; P < 0.035). Conduction velocity for all 3 nerves declined significantly within 3 weeks following cessation of the drug. These effects of sorbinil were unrelated to glycemic control, which was constant during the study. Although the effects of sorbinil in improving nerve conduction velocity were small, the findings suggest that the polyol-pathway activity contributes to slowed nerve conduction velocity in diabetics. The second study is a seven-center, double-blind, randomized, 12-month trial of 210 to 280 diabetic patients with clinical signs, symptoms, and objective measurements of neuropathy. The trial has a common-core protocol with end-point evaluations of scored neural signs, symptoms, and neural measurements. Two unique neural tests were designed and validated for use in this trial: thermal and tactile perception thresholds of the fingers and toes. Thresholds were determined using a two-alternative, forced-choice procedure on the Opticon Tactile Tester and Thermal Sensitivity Tester. Data analysis showed that there was no significant difference as a result of gender, dominant v nondominant side, age, digit temperature, room temperature, presence of heavy callouses, or technologists. In validation studies, diabetics without clinical evidence (history and examination) of diabetic neuropathy were not significantly different from normals, but diabetics with clinical evidence of diabetic neuropathy had elevated finger and toe thermal and tactile perception thresholds (all P < 0.001). There was no significant difference in the test results from normals from each of the seven centers. Thus, these tests were well suited for multicenter trials. Special protocols in each of the seven centers allowed for a broad spectrum of ancillary studies including the following: evaluation of autonomic nervous system integrity, white blood cell sorbitol and myo-inositol levels, impotence evaluation, single-fiber electromyography, sural nerve biopsy, and sensory evoked potentials. This trial is designed to address the question of whether sorbinil could improve diabetic neuropathy. Using the core protocol and the special studies for each center, a wide spectrum of neurologic end-points are evaluated in a bouble-blind fashion. The third protocol is a 12-center, double-blind, randomized, 212-year study of 600 to 720 diabetic patients with minimal or no diabetic complications. There is a common-core protocol with end-point measures of retinopathy, nephropathy, and neuropathy. This trial is unique in that (1) the placebo data adds valuable information into the natural history of diabetic complications, and (2) there is a unique collaborative arrangement between the national Institutes of Health and a pharmaceutical company, representing a first of its kind. This trial is designed to address the question of whether sorbinil could prevent diabetic complications (the primary end-point is retinopathy; the secondary end-points are nephropathy and neuropathy). In summary, these three trials are landmark trials representing advances in the basic pathophysiology of diabetic neuropathy, resulting in the development of new clinical tools and establishing a precedence for collaboration in important clinical trials.

Increased nerve conduction in diabetics after a year of improved glucoregulation

We studied median, ulnar and peroneal motor nerve conduction velocity (NCV) and median sensory action potential (SAP) latency and amplitude in 18 insulin-dependent diabetic patients who were begun on a continuous subcutaneous insulin infusion (CSII) program. With institution of this therapy, significant decreases in mean blood glucose and glycosylated hemoglobin occurred. After 12 months of CSII treatment, median, peroneal, and ulnar motor NCVs all increased significantly. The average NCV increase was 2.5 m/s. Median SAP amplitude and latency did not significantly change. In a second group of 12 diabetic patients with the same mean age and comparable initial NCV and SAP measures, no significant changes in motor NCVs or SAPs occurred after 12 months of conventional insulin treatment. These results indicated the need for further long-term studies of the role of strict glucose control in the prevention of diabetic neuropathy.

Clinical trials of sorbinil on nerve function

Three clinical trials to evaluate the efficacy of the aldose reductase inhibitor sorbinil in improving or preventing diabetic neural function have either been completed or are currently in progress. In the first study from Seattle and Chicago, motor and sensory nerve conduction velocities (NCV) were evaluated in 39 insulin- and noninsulin-dependent, glycemic-stable diabetic patients in a randomized, double-blind, crossover trial. During the 9 weeks of treatment with 250 mg/d of sorbinil, there was a faster nerve conduction velocity of all 3 nerves tested when compared with the placebo period: peroneal motor NCV (+0.70 ± 0.24 m/s; x ± SEM; P < 0.008), median motor NCV (+0.66 ± 0.27 m/s; P < 0.005), and median sensory NCV (+1.16 ± 0.50 m/s; P < 0.035). Conduction velocity for all 3 nerves declined significantly within 3 weeks following cessation of the drug. These effects of sorbinil were unrelated to glycemic control, which was constant during the study. Although the effects of sorbinil in improving nerve conduction velocity were small, the findings suggest that the polyol-pathway activity contributes to slowed nerve conduction velocity in diabetics. The second study is a seven-center, double-blind, randomized, 12-month trial of 210 to 280 diabetic patients with clinical signs, symptoms, and objective measurements of neuropathy. The trial has a common-core protocol with end-point evaluations of scored neural signs, symptoms, and neural measurements. Two unique neural tests were designed and validated for use in this trial: thermal and tactile perception thresholds of the fingers and toes. Thresholds were determined using a two-alternative, forced-choice procedure on the Opticon Tactile Tester and Thermal Sensitivity Tester. Data analysis showed that there was no significant difference as a result of gender, dominant v nondominant side, age, digit temperature, room temperature, presence of heavy callouses, or technologists. In validation studies, diabetics without clinical evidence (history and examination) of diabetic neuropathy were not significantly different from normals, but diabetics with clinical evidence of diabetic neuropathy had elevated finger and toe thermal and tactile perception thresholds (all P < 0.001). There was no significant difference in the test results from normals from each of the seven centers. Thus, these tests were well suited for multicenter trials. Special protocols in each of the seven centers allowed for a broad spectrum of ancillary studies including the following: evaluation of autonomic nervous system integrity, white blood cell sorbitol and myo-inositol levels, impotence evaluation, single-fiber electromyography, sural nerve biopsy, and sensory evoked potentials. This trial is designed to address the question of whether sorbinil could improve diabetic neuropathy. Using the core protocol and the special studies for each center, a wide spectrum of neurologic end-points are evaluated in a bouble-blind fashion. The third protocol is a 12-center, double-blind, randomized, 2 1 2 - year study of 600 to 720 diabetic patients with minimal or no diabetic complications. There is a common-core protocol with end-point measures of retinopathy, nephropathy, and neuropathy. This trial is unique in that (1) the placebo data adds valuable information into the natural history of diabetic complications, and (2) there is a unique collaborative arrangement between the national Institutes of Health and a pharmaceutical company, representing a first of its kind. This trial is designed to address the question of whether sorbinil could prevent diabetic complications (the primary end-point is retinopathy; the secondary end-points are nephropathy and neuropathy). In summary, these three trials are landmark trials representing advances in the basic pathophysiology of diabetic neuropathy, resulting in the development of new clinical tools and establishing a precedence for collaboration in important clinical trials.

Syndrome digital des vibrations: etude neuro-physiologique chez 17 patients

Studies were carried out on 17 male workers with clinical vibration disease who had been working with different vibrating tools (compressed-air hammers, chain-saws, rock drills, grinders) for 2 to 39 years. Their neurophysiological results were compared with those of 20 healthy men (control group). Median motor nerve conduction velocity (NCV) between elbow and wrist was significantly reduced and motor distal latency (DL) significantly longer in 43% cases. A distinct decrease of the conduction velocity of distal (finger-wrist) median sensory fibers (in 56% of cases) as well as reduced amplitude of the sensory evoked potential (62% of cases) were found. EMG showed alterations only in patients with NCV abnormalities. These electrophysiological findings point to distal axonal as well as to demyelination damage. The results, which are discussed in relation to previously published work in this field and according to a pathogenetic hypothesis of this syndrome, allowed us to draw practical conclusions for the neurophysiological examination of patients with vibration disease.

Effects of glycemic control and aldose reductase inhibition on nerve conduction velocity

In two studies of patients with diabetes who did not have neurologic symptoms, nerve conduction velocity was increased either by an improvement in glucose control or by the administration of the aldose reductase inhibitor sorbinil. In a 1981 study by Graf et al, glycemic control and motor and sensory nerve conduction velocities were evaluated in 18 patients with non-insulin-dependent diabetes before and after one, three, six, and 12 months of antihyperglycemic therapy. There was an improvement in motor nerve conduction velocity (median motor, p <0.01; peroneal motor, p <0.05; and tibial motor, p <0.05), which was associated with the improvement in fasting plasma glucose levels after three months for some motor nerves (median motor: r = −0.62, p <0.01; peroneal motor: r = −0.50, p <0.05). A direct linear relationship between the change in fasting glucose and glycosylated hemoglobin levels and the change in median motor nerve conduction velocity after 12 months of anti-hyperglycemic therapy was also found. Thus, there was a tendency for those patients who had the greatest improvement in glycemic control to have the greatest improvement in motor nerve conduction velocity. The findings in the first study are consistent with the hypothesis that hyperglycemia contributes to slowed nerve conduction velocity. In a 1983 randomized, double-blind, crossover study by Judzewitsch et al, motor and sensory nerve conduction velocities were evaluated in 39 patients with insulin-dependent or non-insulin-dependent diabetes in whom glycemic control was stable. During nine weeks of treatment with 250 mg per day of sorbinil, nerve conduction velocity was faster in the three tested nerves when compared with the velocities during the placebo period (peroneal motor nerve conduction velocity: +0.70 ± 0.24 m per second, mean ± SEM, p <0.008; median motor nerve conduction velocity: +0.66 ± 0.27 m per second, p <0.005; median sensory nerve conduction velocity: +1.16 ± 0.50 m per second, p <0.035). Although the effect of an improvement in glycemic control and administration of sorbinil in increasing nerve conduction velocity in two groups of neurologically asymptomatic patients with diabetes was small, the findings are consistent with the hypothesis that polyol pathway activity contributes to slowed large-fiber nerve conduction velocity in these patients.

Correlations among autonomic, sensory, and motor neural function tests in untreated non-insulin-dependent diabetic individuals.

A well-defined group of untreated non-insulin-dependent (NIDD) subjects were evaluated to determine whether involvement of neural function measurements is generalized and symmetrical and to compare the autonomic, sensory, and motor neural measurements. After age adjustment, the sensory and motor neural function measurements were significantly slower in the diabetic group than in normal subjects (P less than 0.01). Similarly, the autonomic nervous system function measurements were also abnormal in the NIDD group (P less than 0.01). Further analysis revealed that each of the specific measurements--median motor nerve conduction velocity (NCV,P less than 0.005), peroneal motor NCV (P less than 0.005), median sensory NCV (P less than 0.005), dark-adapted pupil size after muscarinic blockade (P less than 0.02), pupillary latency time (P less than 0.02), and RR-variation after beta adrenergic blockade (P less than 0.001)--was significantly less by analysis of covariance after age adjustment in the NIDD group than in normal subjects. Thus, there was evidence of motor and sensory neural impairment in the upper and lower extremities as well as evidence of impairment of the reflex arcs involving the parasympathetic nerves to the heart and eye and the sympathetic nerves to the iris. Further analysis revealed that right and left NCV were correlated (P less than 0.01), as were the median motor and median sensory NCV (P less than 0.01), the median motor and peroneal motor NCV (P less than 0.001), and the peroneal motor and median sensory NCV (P less than 0.001). Thus, there was evidence of symmetrical upper and lower limb, as well as motor and sensory proportional involvement of large nerve fiber NCV in this group of NIDD subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Phrenic nerve conduction time in Guillain-Barré syndrome.

Phrenic nerve conduction was studied in 28 patients with Guillain-Barré syndrome. Conduction time was prolonged in 18 (64.3%) patients and serial studies showed progressive improvement with restoration of normal values in the majority by 12 weeks. The conduction abnormalities had a positive correlation with the extent of the disease, morbidity and mortality. Phrenic nerve conduction time was found to be a more sensitive parameter than vital capacity or median nerve motor conduction velocity in assessing the severity of the disease and predicting impending ventilatory failure.

Anticonvulsant therapy and its possible consequences on peripheral nervous system: a neurographic study.

We studied 80 epileptic patients receiving antiepileptic drugs in mono- or polytherapy. For every patient, peroneal and median nerve motor conduction velocities and median nerve sensory conduction velocity were calculated. The average conduction velocity values were remarkably slower than those of a group of 55 normal subjects. We found at least one abnormal conduction velocity value in patients treated with carbamazepine (CBZ), phenobarbital, and phenytoin. There was no specific prevalence of one of these drugs. We found a noticeable relationship between conduction velocity slowing and daily dosage for CBZ only. There was no relationship between conduction velocity slowing and drug blood levels or duration of treatment.

Neuromuscular function in weight-trainers

Electrophysiologic measurements were made on the median-innervated thenar muscles and triceps surae in 17 weight-trainers (bodybuilders and weight-lifters) and in control subjects. In the median-innervated thenar muscles, the weight-trainers presented normal values for motor unit counts, reflex potentiation, and twitch contractile properties; however, the weight-trainers possessed a significantly greater (8%) median motor nerve conduction velocity. In the triceps surae, the weight-trainers exhibited significantly greater reflex potentiation (70%), which was interpreted as an increased ability to activate motor units during maximal voluntary contractions. Peak twitch tension (16%) and twitch contraction time (20%) of the triceps surae were significantly greater in the weight-trainers, whereas their twitch half-relaxation time and soleus motor unit counts were not significantly different from control values. The observed difference may reflect a combination of genetic endowment and the effects of training.

The natural history of painful diabetic neuropathy--a 4-year study.

Thirty-nine patients with painful diabetic peripheral neuropathy were selected for a follow-up study to determine the natural history of this condition. Symptoms, motor conduction velocities (MCV) and ankle pressure indices were recorded at the initial assessment and after a mean study period of 4.7 years. Thirty-six patients completed the study and showed no significant changes in symptoms, but there was a significant fall in median nerve MCV. It is concluded that symptoms of established diabetic neuropathy persist for several years, and the changes in MCV may reflect continuing deterioration in nerve function.

Neurophysiological effects of long-term exposure to hydrocarbon mixtures.

Motor nerve conduction velocity (MCV) was measured on median, ulnar and peroneal nerves in a reference group of 52 workers and a group of 95 workers exposed to hydrocarbon mixtures in a shoe factory. Exposure-related changes were found in motor action potential (MAP) amplitudes of the three nerves and in median and peroneal MCVs. Electroneurographic abnormalities were also present in a subgroup of workers exposed to air concentrations near the current ACGIH (1979) recommended threshold limit value (TLV) for the mixture. Our results suggest the need for lowering the TLV for the main components n-hexane and cyclohexane. A synergistic effect of the two hexacarbon solvent might also be considered in the hygienic evaluation of the workplace.

Diabetic neuropathy and plasma glucose control

Diabetic neuropathy is defined, and theories of its pathogenesis are reviewed. Recent studies designed to investigate the influence of plasma glucose on nerve function in noninsulin-dependent diabetic patients are summarized. Motor nerve conduction velocities in the median and peroneal nerves were measured using a double-stimulus technique, and sensory conduction velocity was measured by conventional methods before and after therapy with oral agents or insulin. The degree of hyperglycemia was assessed by measurement of fasting plasma glucose and glycosylated hemoglobin concentrations. The degree of slowing in motor nerve conduction velocity in untreated patients was found to correlate with the fasting plasma glucose and glycosylated hemoglobin concentrations, but sensory nerve function, although abnormal, did not show such correlation. Reduction of hyperglycemia was associated with improvement in motor nerve conduction velocity in the peroneal and median motor nerves of these patients, but sensory nerve conduction velocity showed no such improvement. Improvement in median motor nerve conduction velocity was directly related to the degree of reduction in fasting plasma glucose concentration. These findings suggest that metabolic factors related to hyperglycemia are important in the impaired motor nerve function seen in noninsulin-dependent patients with maturity-onset diabetes.

Rapid improvement in nerve conduction velocity following renal transplantation

In 12 patients with chronic renal failure who received kidney transplants from either cadavers (6) or related living donors (6), rapid improvement in median sensory and motor nerve conduction velocities (NCVs) was observed within a few days after transplantation. The postoperative improvement in median sensory NCV was found to bear a statistically significant negative correlation with creatinine and myo-inositol concentrations. We suggest that metabolic phenomena are responsible for the rapid improvement in median sensory NCV following renal transplantation. The close relationship between myo-inositol and the median sensory NCV following transplantation suggests that elevated plasma myo-inositol concentrations may be related to nerve conduction abnormalities in uremic polyneuropathy.

Ulnar nerve lesions associated with the carpal tunnel syndrome.

Electrophysiological studies were performed on median and ulnar nerves in 234 cases of carpal tunnel syndrome. Abnormalities of the ulnar nerve sensory action potential were found in 39·3% of cases. The amplitude of the ulnar nerve sensory action potential was related to the amplitude of the median nerve sensory action potential, and to the median nerve motor conduction velocity in the forearm. The findings suggest that in a significant proportion of patients with carpal tunnel syndrome, a more generalized subclinical neuropathy may be present.