Reduction In Motor Conduction Velocity Research Articles

Risk factors of asymptomatic reduction of motor conduction velocity of the ulnar nerve across the elbow.

The aim of the study was to check the risk factors for subjects with motor conduction velocity (MCV) reduction of the ulnar nerve across the elbow without symptoms/signs of ulnar neuropathy at the elbow (UNE) using a database of a previous multicenter case-control study on UNE patients. From the previous database, we extracted all asymptomatic UNE (A-UNE) and matched for age and sex with a control and UNE groups with a ratio of 1:2. Anthropometric factors were measured and all participants filled in a questionnaire on demographic, lifestyle factors, and medical history. One-sample proportion test and univariate and multivariate logistic regression analyses were performed. We enrolled 64 A-UNE, 124 UNE, and 124 controls (mean age 53years). There were more males with A-UNE than females (74.2%). The predominantly or exclusively concerned side of A-UNE was the right. Logistic regression showed that A-UNE was associated with diabetes (OR = 2.99, 95% CI = 1.21-7.39) and width of cubital groove (CGW) (OR = 0.89, 95% CI = 0.81-0.97). Risk factors for A-UNE are different from UNE. The prevalence of right side in A-UNE was not due to particular elbow postures. Diabetes is a risk factor, probably because MCV reduction of the ulnar nerve across the elbow was an early manifestation of asymptomatic polyneuropathy in diabetes. A-UNE is associated with narrow CGW as already demonstrated in UNE, even if the OR was higher in UNE than in A-UNE. Only future longitudinal studies will be able to check whether the A-UNE subjects develop symptoms and signs of true mononeuropathy with time.

Electrophysiological Study of the Tibial Nerve Across the Tarsal Tunnel in Distal Symmetric Diabetic Polyneuropathy.

The aim of the study was to demonstrate abnormalities of motor conduction of the tibial nerve across the tarsal tunnel in type 2 diabetes. One hundred twenty-four consecutive patients (mean age = 66.6 yrs, 62.1% male) with distal symmetric diabetic polyneuropathy clinically diagnosed were prospectively enrolled. Nerve conduction studies of deep peroneal, tibial, superficial peroneal, medial plantar, and sural nerves and standard needle electromyography in the lower limbs were performed. Demographic, anthropometric, and clinical findings were collected. Motor conduction velocity of the tibial nerve across tarsal tunnel was slowed in 60.5% of patients; another 4% showed conduction block across tarsal tunnel without reduction of motor conduction velocity. Overall percentage of abnormalities across tarsal tunnel (64.5%) exceeds that of the sensory conduction velocities of proximal sural and superficial peroneal nerves. Abnormal tibial motor conduction velocity across tarsal tunnel represents the most common abnormality among all motor nerve conduction study parameters and significantly correlates with hemoglobin level, diabetic neuropathic index score, and diabetic complications frequency. Tibial conduction abnormalities across tarsal tunnel are the most sensitive motor parameter in distal symmetric diabetic polyneuropathy, second only to conduction abnormalities of sensory/mixed distal nerves of the feet. The use of nerve conduction studies across tarsal tunnel of the tibial nerve may be useful in the electrophysiological protocol to confirm the diagnosis of distal symmetric diabetic polyneuropathy.

Electrophysiological demyelinating features in hereditary ATTR amyloidosis

Objective: To elucidate the electrophysiological demyelinating features in patients with hereditary ATTR amyloidosis that may lead to a misdiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP).Methods: In 102 patients with hereditary ATTR amyloidosis (85 Val30Met and 17 non-Val30Met; 37 and 65 from endemic and non-endemic areas, respectively), results of motor nerve conduction studies (MNCSs) with a 2-Hz low-cut filter in the unilateral ulnar and tibial nerves were retrospectively investigated to assess whether each MNCS parameter demonstrated demyelinating features that fulfil the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic (EFNS/PNS EDX) criteria for CIDP.Results: Thirteen patients with low compound muscle action potential (CMAP) amplitude in the tibial nerve (0.7 ± 0.7 mV) and prolonged distal CMAP duration in the ulnar nerve satisfied the definite EFNS/PNS EDX criteria for CIDP. Abnormal temporal dispersion and prolongation of distal latency in the tibial nerve were observed in 5 of 13 patients. However, only one of the 13 patients presented with the reduction of motor conduction velocity in each nerve. No patient exhibited conduction block in any nerve.Conclusion: Patients with hereditary ATTR amyloidosis occasionally show electrophysiological demyelinating features without conduction block following severe axonal degeneration.

Guillain–Barré syndrome related to pandemic influenza A (H1N1) infection

Dear Editor, Since April 2009, the world has been experiencing a pandemic influenza caused by the reasserting virus A (H1N1). Little information about neurological complications induced by this virus is available in the literature. We report the case of a 37-year-old woman who was admitted to our intensive care unit for respiratory distress associated with flaccid tetraplegia. Two weeks ago, she had fever, asthenia, and cough. A nasopharyngeal swab was performed, and reverse-transcription polymerase chain reaction (RT-PCR) confirmed infection with pandemic flu virus A (H1N1). Ten days later, she suffered muscular weakness of the lower limb, then the upper limb. At admission, she had normal consciousness, flaccid tetraplegia with complete areflexia, and symmetric paresthesia of the lower limb. A few hours later, she developed severe dyspnea with impaired coughing, accumulation of airway secretions, nasal voice, swallowing difficulties, and severe hypoxemia (SpO2 at 85% under 10 l oxygen/min) requiring mechanical ventilation. During the first 2 days, episodes of bradycardia and hypertension were recorded on hemodynamic monitoring. Diagnosis of Guillain–Barre syndrome was considered and confirmed by electromyography showing reduction in motor conduction velocity and prolonged distal latencies, which were more severe in the lower limb. On analysis of cerebrospinal fluid, there was no albuminocytologic dissociation. Investigations performed in order to identify another triggering factor were negative. Five consecutive plasma exchanges were performed, and the patient improved progressively. Repeated and prolonged weaning tests were successful, and the patient had a vigorous cough. She was free from mechanical ventilation within 2 weeks, and neither swallowing problems nor dysautonomia abnormalities were reported. The patient was discharged from our intensive care unit within 45 days. Guillain–Barre syndrome is an acute, immune-mediated polyradiculoneuropathy. In 66% of patients, history of respiratory or gastrointestinal infection within 6 weeks preceding onset of the disease is found [1]. Some infectious agents are particularly known as triggering factors of Guillain–Barre syndrome [2]. Sivadon-Tardy et al. [3] reported that influenza virus can also induce Guillain–Barre syndrome, but the majority of infections were due to virus A (H3N2), and clinical course was less severe compared with other infectious agents. For our patient, acute respiratory failure and bulbar dysfunction were the main causes leading to intensive care admission. Bulbar dysfunction can be responsible for autonomic instability and aspiration that worsens respiratory distress [4]. Determining the best time for mechanical ventilation is crucial, and up to 25% of patients with Guillain–Barre syndrome may need mechanical ventilation [1]. Delayed intubation, especially when bulbar dysfunction is considered, may increase the risk of early-onset pneumonia related to aspiration [4]. In adults, plasmapheresis is considered the gold standard for treatment of the most severe cases of Guillain– Barre syndrome. In five randomized trials, plasma exchange reduced the need for prolonged ventilation from 27% to 4% [2]. To the best of our knowledge, there are no available data concerning clinical severity and prognosis of Guillain–Barre syndrome related to pandemic flu virus A (H1N1). Further studies are needed to clarify the incidence of this complication and its prognostic impact.

Cold Exposure Exacerbates the Development of Diabetic Polyneuropathy in the Rat

Diabetic polyneuropathy (DPN) and cold-induced nerve injury share several pathogenic mechanisms. This study explores whether cold exposure contributes to the development of DPN. Streptozotocin-induced diabetic rats and controls were exposed to a room temperature (23°C) or cold environment (10°C). H-reflex, tail and sciatic motor, and sensory nerve conduction studies were performed. Analyses of sural nerve, intraepidermal nerve fibers, and skin and nerve nitrotyrosine ELISAs were performed. Diabetic animals exposed to a cold environment had an increased H-reflex four weeks earlier than diabetic room temperature animals (P = .03). Cold-exposed diabetic animals also had greater reduction in motor conduction velocities at 20 weeks (P = .017), decreased skin nerve fiber density (P = .037), and increased skin nitrotyrosine levels (P = .047). Cold exposure appears to hasten the development of DPN in the rat STZ model of diabetes. These findings support that further study into the relationship between ambient temperature and DPN is warranted.

P13.1 Conduction block in Charcot–Marie–Tooth type 1B (CMT1B) neuropathy

Background: On neurophysiological studies the hereditary demyelinating motor and sensory neuropathies (CMT1) usually show uniform reduction in motor conduction velocities. On the other hand, conduction block (CB) far from compression sites is typical of acquired demyelinating neuropathies. Aims: To describe a patient with CMT1 in whom neurophysiological studies disclosed marked CB outside entrapment sites. Case report:A34-year-oldwomanwith afive-year history ofmuscle cramps, right hand and distal lower limbweakness after longstanding efforts. She only startedwalking at the age of 30months but had no other motor development problem. Her father had a history of disabling demyelinating motor– sensory neuropathy. On neurological examination, she had bilateral pes cavus, slight weakness on right thumb abduction, bilateral foot dorsiflexion and hallux extension weakness (4/5); there was a generalized areflexia and distal lower limb light touch and pinprick hypostesia and few errors on postural sense testing; walking on heels was impaired. Motor conduction studies showed low velocities with prolonged latencies, with absent motor responses in feet. Partial conduction blocks were present in the median and ulnar nerves at the forearm (below elbow), more severe aftermuscular fatigue. Sensory potentialswere absent (lower limbs) or small. Laboratorial evaluation includingCSFanalysis was unremarkable. The genetic study was positive for the 233C > T mutation at the MPZ gene. Conclusion: This case illustrates the electrophysiological heterogeneity of CMT1B and adds this entity to conduction block differential diagnosis.

888. Characterization of New Murine Models of Globoid Cell Leukodystrophy: Relevance for Gene Therapy Applications and Studies on Disease Pathogenesis

The Twitcher mouse (twi) is well known as a naturally occurring authentic mouse model of human globoid cell leukodystrophy (GLD), characterized by a stop mutation leading to complete deficiency of galactocerebrosidase (GALC) activity. The most commonly used twi mouse is on the C57BL/6J genetic background. Two novel murine models of GLD are currently available beside the original twi: i) the twi crossed into a different genetic background (FVB-Twi), that we generated based on previous indications on the effects of the genetic background in modulating GLD severity (Tominaga K. et al., J. Neurosci. Res. 2004; Biswas S. et al., Neurobiol. of Disease 2002); ii) a mouse with low GALC activity, recently generated in D. Wenger's laboratory by introducing in the murine GALC gene a polymorphism that was found in individuals having some not otherwise explainable neurological abnormalities in the presence of 10|[ndash]|20% residual GALC activity, the trs mouse (Luzi P. et al., Mol. Genetics and Metab. 2001). These three models showed some substantial differences in their phenotype and overall survival, and represent a unique opportunity not only to evaluate gene therapy efficacy in a wider therapeutic window, but also to better investigate disease pathogenesis. We characterized these new models in comparison with the C57BL/6J twi by longitudinal clinical, neurophysiological, neuroradiological and pathological evaluations. FVB-Twi and trs mice have a slightly milder phenotype as compared to original twi, with higher body weight, later onset of twitching, a delayed decline in walking ability, as measured by footprint analysis, longer life span (38|[plusmn]|2, 43|[plusmn]|2 and 56|[plusmn]|4 days in twi, FVB-Twi and trs, respectively), and better general health conditions. Despite the slower progression of the disease, neurophysiological studies showed a severe impairment of motor conduction along both central and peripheral nervous system, with profound reduction of motor conduction velocity (below 8m/sec) and un-evocable MEPs by 30 post-natal days of age in all examined models. Conventional brain MR imaging and histopathology showed lower grade demyelination in FVB-Twi and trs as compared to C57Bl/6 twi, and on going MR diffusion studies will provide quantification of the brain myelin content in the 3 different models. Overall, our data demonstrate the availability of new murine models of GLD characterized by a delayed demyelination as compared to the original twi mutants, that will constitute a precious tool for identifying the best timing of intervention to achieve correction of the GLD phenotype with gene therapy.

Effect of Ankle Joint Inversion Trauma on Common Peroneal Nerve MCV

This study has been conducted to determine effect of ankle joint inversion trauma on common peroneal nerve motor conduction velocity (MCV). Twenty patients (8 males and 12 females) who were 30 to 45 years of age (X=33.75+1.15) participated in this study. They received the same medical care and manual tests for the inversion trauma. The involved lower limbs were considered the experimental group, while the normal contralateral lower limbs were considered the control group for all the twenty patients. Measurements of the MCV were carried out 10 days post trauma as a first record and one month post trauma as a second record for the both groups. Data collected for the first record showed that averages of MCV (m/sec), were 29.50+2.14 and 42.45+3.08 for the experimental and control groups respectively. While data collected for the second record showed that averages of MCV (m/sec), were 31.02+2.25 and 42.80+3.11 for the experimental and control groups respectively. Results showed a highly significant reduction in MCV for the first record in the experimental group, and in the second record for the experimental group, MCV was still significantly reduced. Results of this study support the hypothesis that inversion ankle trauma is frequently accompanied by peroneal nerve lesions. Also suggest that MCV measurements can be a valuable tool in evaluating more objectively the functional instability of the ankle joint.

CLINICAL AND IMMUNOLOGICAL FEATURES AND RESPONSE TO IVIg IN PATIENTS WITH CLINICALLY TYPICAL MULTIFOCAL MOTOR NEUROPATHY BUT NO OVERT CONDUCTION BLOCK

Multifocal motor neuropathy (MMN) is characterized by progressive asymmetric limb weakness usually predominant in the upper limbs associated with conduction block (CB) in motor but not sensory nerves. There are, however, occasional patients with clinically typical MMN in whom no CB can be detected. Whether these patients differ from patients with MMN and CB remains unclear. Since 1991, we have observed 24 patients with the typical clinical features of MMN. In 20 of them (14 men and 6 women), electrophysiological studies disclosed the presence of CB in at least one motor nerve. In four (all women), no evidence of CB could be detected in examined nerves even if three had some features of demyelination, including asymmetric reduction of motor conduction velocities (1 patient) or prolonged or absent F wave latencies (3 patients). Three of them had markedly reduced or absent proximal and distal CMAP amplitudes in some nerves. The mean age of onset of MMN was similar in patients with (41.5 years, range 21–70) and without CB (41.5 years, range 24–57). The mean duration of the disease at the time of our first visit was longer in patients without CB (18.5 years, range 13–25) than in those with CB (6.3 years, 3 months–25 years); only 3 patients with CB had a duration of the disease longer than 10 years. All patients without CB had a predominant or exclusive impairment of upper limbs compared with 18 (90%) of those with CB. The mean Rankin score before therapy was slightly worse in patients without (2.5) than with (2.2) CB. Anti‐ganglioside antibodies were found in 1 patient without CB (25%) and in 8 (40%) with CB. All but 2 patients with CB (90%) consistently improved with IVIg. All patients without CB also improved with IVIg, but only one did so consistently. In conclusion, patients with the typical clinical presentation of MMN but no overt CB are clinically and immunologically indistinguishable from those with MMN and CB. The longer duration of the disease and frequent axonal impairment in patients without CB may explain the lower efficacy of IVIg in these patients than in those with CB.

Multifocal motor neuropathy with conduction block: a study of 24 patients.

Twenty four patients with pure motor neuropathy are reported. The chronic motor involvement associated with fasciculations and cramps, mainly in the arms, led, in most patients, to an initial diagnosis of motor neuron disease. In some patients (nine of 24), there was no appreciable muscle atrophy. Tendon reflexes were often absent or weak. The finding of persistent multifocal conduction block confined to motor nerve fibres raises questions about the nature and the importance of this syndrome. Segmental reduction of motor conduction velocity occurred at the site of the block, but significant slowing of motor nerve conduction was not found outside this site. The response to intravenous IVIg treatment seems to be correlated with the absence of amyotrophy. Patients with little or no amyotrophy had an initial and sustained response to IVIg, and did not develop amyotrophy during the follow up study. They could be considered to have a variant of chronic inflammatory demyelinating polyneuropathy. Patients with pronounced amyotrophy independent of the disease duration did not respond as well to IVIg treatment, suggesting the existence of a distinct entity. Among the patients treated about two thirds who had an initial good response to IVIg had high or significant antiganglioside GM1 (anti-GM1) antibody titres, but there was no correlation between the high titres before treatment and long lasting response to IVIg treatment.

Anti-oxidant and pro-oxidant effects on nerve conduction velocity, endoneurial blood flow and oxygen tension in non-diabetic and streptozotocin-diabetic rats

Increased oxygen free radical activity, coupled with reduced protection against oxidative stress, could play a role in the aetiology of neurovascular abnormalities in experimental diabetes mellitus. To test this hypothesis, non-diabetic and streptozotocin-diabetic rats were treated with the anti-oxidant probucol or the pro-oxidant primaquine. One-month diabetes caused 21.4% and 13.6% reduction in sciatic motor and saphenous sensory conduction velocity (p < 0.001). These deficits were prevented by probucol treatment (p < 0.001). After 1-month untreated diabetes, conduction velocity deficits were reversed by a further month of probucol treatment (p < 0.001). For non-diabetic rats, primaquine treatment caused a 12.9% reduction in motor conduction velocity (p < 0.001), which was prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect diabetic rats. Sciatic nerve nutritive endoneurial blood flow, measured using microelectrode polarography and hydrogen clearance, was 48.0% reduced by 2-month diabetes (p < 0.001). This was completely prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect blood flow in diabetic rats. However, in non-diabetic rats it caused a 30.0% reduction (p < 0.01) which was prevented by probucol treatment (p < 0.05). Sciatic endoneurial oxygen tensions were also measured by microelectrode polarography. Mean tension was 38.8% reduced by diabetes (p < 0.001). This was prevented by probucol treatment. Non-diabetic rats given primaquine treatment showed a 21.7% reduction in endoneurial oxygen tension (p < 0.01). The data suggest that vascular-mediated nerve dysfunction in diabetes depends on oxidative stress, and that similar effects in non-diabetic rats may be produced by pro-oxidant treatment. This provides evidence for the potentially important role of oxygen free radical activity in diabetic neuropathy.

N-hexane neuropathy in offset printers.

In an offset printing factory with 56 workers, 20 (36%) developed symptomatic peripheral neuropathy due to exposure to n-hexane. Another 26 workers (46%) were found to have subclinical neuropathy. The initial change in the nerve conduction study was reduced amplitude of the sensory action potentials, followed by reduced amplitude of the motor action potentials, reduction in motor conduction velocities and increase in distal latencies. These changes indicate primary axonal degeneration with secondary demyelination. Sural nerve biopsy in a severe case showed giant axonal swellings due to accumulation of 10nm neurofilaments, myelin sheath attenuation and widening of nodal gaps. The development of neuropathy bore no direct relationship to the duration of exposure, hence factors such as individual susceptibility may be important. Optic neuropathy and CNS involvement were uncommon and autonomic neuropathy was not encountered.

The effect of the calcium antagonist nifedipine on peripheral nerve function in streptozotocin-diabetic rats.

Recent data suggests that reduced nerve blood flow is implicated in the aetiology of experimental diabetic neuropathy, which may be prevented by manipulations that reduce receptor-mediated vasoconstrictor activity. This investigation examines the effects of nifedipine, a voltage-sensitive calcium channel antagonist which has a direct vasodilatory effect on vessels, on nerve conduction, hypoxic resistance and capillary density in streptozotocin-induced diabetic rats. Treated and non-treated non-diabetic and diabetic groups were employed. Diabetes duration was 2 months. Treatment was preventive, groups received a nifedipine dietary supplement (40 mg.kg-1.day-1) for 2 months from the start of the study. Conduction was measured in sciatic motor branches supplying tibialis anterior and gastrocnemius muscles, and sensory saphenous nerve. Diabetes resulted in a 23-28% reduction in motor conduction velocity (p < 0.001), and a 15% deficit for sensory saphenous nerve (p < 0.001). In the nifedipine-treated diabetic group, motor and sensory conduction deficits were minimal compared with non-treated diabetes (p < 0.001). Nifedipine treatment had no significant effect on conduction velocity in non-diabetic rats. In vitro measurement of sciatic nerve hypoxic resistance revealed a 60% increase in the time taken for compound action potential amplitude to reach half its initial value with diabetes (p < 0.001). This was not significantly affected by nifedipine treatment. Experimental diabetes or nifedipine treatment did not significantly alter sciatic nerve endoneurial capillary density. We conclude that nifedipine, a vasodilator which acts directly on vascular smooth muscle, prevents nerve conduction deficits in experimental diabetes.

Peripheral neuropathy in children on long-term phenytoin therapy

Nerve conduction studies of the ulnar, median, posterior tibial, peroneal and sural nerves were performed in 21 epileptic children aged 6 to 17 years on long-term phenytoin therapy. Auditory brain stem evoked responses were obtained in 16 patients to evaluate the effect of phenytoin on central nervous system synapses. Of the 21 patients examined, 15 (71.4%) showed abnormal findings. The most frequent abnormality was slowed motor conduction velocity of the ulnar nerve (33.3%) and posterior tibial nerve (23.8%), followed by slowed sensory conduction velocity of the sural nerve (20%), lowered H/M ratio (14.3%), slowed motor conduction velocity of the peroneal nerve (14.3%) and of the median nerve (14.2%). A significant correlation was noted between the total dosage and duration of therapy with PHT and the reduction of motor conduction velocity in the posterior tibial nerve. Auditory brain stem evoked responses showed no significant differences in each peak latency between the patients and the normal control group. The study indicates that long-term phenytoin therapy can cause latent impairment of peripheral nerve function in children with no clinical evidence of peripheral neuropathy.

Neurophysiological studies of autogenous sural nerve grafts.

Sixteen autogenous sural nerve grafts used for ulnar and median injuries in the forearm have been studied neurophysiologically up to two and a half years after operation. Motor and sensory nerve conduction studies revealed a slow but sustained improvement during the follow-up period. By two years, motor conduction velocity across the graft itself reached in most cases 40 to 85% of the conduction velocity in the contralateral normal limb. Some reduction of motor conduction velocity was observed in the uninjured nerve proximal to the graft but this was less marked. Sensory nerve action potentials were obtained in 44% of nerves after 18 months although in all cases the amplitude of the potentials and in most cases their velocity, was greatly reduced.

Peripheral neuropathy following a single exposure to arsenic: Clinical course in four patients with electrophysiological and histological studies

Four patients are described who developed a peripheral neuropathy 10 days to 3 weeks after ingestion of a single dose of arsenic. All improved slowly, but after 6 to 8 years 3 of them still had abnormal neurological symptoms and signs. Electrophysiological studies showed reduction of motor conduction velocity and marked abnormalities of sensory nerve action potentials. The findings suggest that conduction is abnormal in at least some surviving nerve fibres. Sural nerve biopsies from 2 patients showed axonal degeneration, which was at an early stage in some fibres, even 10 weeks after intoxication.