Median Motor Conduction Research Articles

Dropping Objects in Carpal Tunnel Syndrome: Clinical and Electrophysiological Features.

Background Dysfunction in both afferent sensory and efferent motor components of the median nerve may contribute to the manifestation of the symptom of dropping objects (DO) in carpal tunnel syndrome (CTS). The objective of this study was to compare the clinical and electrophysiological characteristics of CTS patients with dropping objects (wDO) and those without dropping objects (w/oDO). The study evaluated the correlation between DO symptoms and median partial conduction block, as well as the reduction in median motor conduction velocity at the wrist. Methodology An examination for CTSand the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) were performed. Median and ulnar sensory and motor nerve conduction studies were conducted in both upper extremities, and the percentage decrease in the median compound motor action potential amplitude at the wrist level was calculated. Results The study included 201 female participants aged between 22 and 88 years, comprising 57 patients withCTSwDO, 78 patients with CTSw/oDO, and 66 healthy controls. In the CTSwDO group, compared to the CTSw/oDO group, BCTQscores were significantly higher, the prevalence of sensory deficits was more pronounced, and a larger number of hands, both dominant and non-dominant, were classified as stage 3 or higher in the clinical CTS classification. However, no correlation was found between the presence of DO symptoms and any neurophysiological findings. Conclusions DO may be a symptom of clinical severity in CTS, as previously reported.No neurophysiological parameter that could be associated with DO was identified.

Body mass index and carpal tunnel syndrome: A case-control study.

To investigate the electrophysiological characteristics of carpal tunnel syndrome (CTS) and to evaluate the relationship between electrophysiological indexes and body mass index (BMI). In the analysis of 153 hospitalized patients with CTS, the median motor conduction velocity, motor conduction amplitude, motor conduction latency, sensor conduction velocity, sensor conduction amplitude and median sensory latency were analyzed. BMI was calculated. Total 171 healthy individuals were selected as control group. According to Guidelines for Prevention and Control of Overweight and Obesity in Chinese Adults, patients were divided into groups A, B and C. Patients with BMI (kg/m2) <24 were classified into group A; those with 24 ≤ BMI < 28 were regarded as overweight and classified into group B; and those with BMI ≥ 28 were regarded as obese and classified into group C. The BMI of CTS patients was significantly higher than that of healthy individuals (P < .05). For the sensory nerve, with the increase of BMI, the incubation period was gradually prolonged and the conduction velocity gradually decreases (P < .05). In terms of motor latency, with an increase in BMI, the latency showed a trend of first decreasing and then increasing, while the conduction velocity showed a trend of first increasing and then decreasing (P < .05). Electrophysiological examination plays an important supporting role in the diagnosis of CTS. BMI is positively correlated with the degree of CTS injury to a certain extent. Weight loss can effectively prevent the occurrence of CTS and slow the progression of nerve damage in CTS patients.

AĞIR KARPAL TÜNEL SENDROMU İÇİN RİSK FAKTÖRLERİNİN İNCELENMESİ - EV HANIMLIĞI BİR RİSK Mİ?

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. In this study, risk factors of severe CTS were examined. This study was conducted on 227 patients diagnosed with CTS in EMG laboratuary. The criteria of American Academy of Electrodiagnostic Medicine was used as the diagnosis for CTS. All patients were examined for bilateral median and ulnar motor and sensory peak latency, amplitude and conduction velocities. The patients were classified into 4 groups electrophysiologically; Normal, Light, Medium, Severe. Electrophysiological classification was compared with the identified risk factors. The mean age of the patients was 51.04±13.37 (min=18-max=83). Severe CTS cases in both hands were higher in housewives. Housewifery increased the risk of severe CTS in the right and left hand by 2.74 and 2.23 times, respectively. In addition, obesity increased the risk of severe CTS in the right and left hand by 5.10-4.40, presence of lateral epicondylitis was 2.73-4.19 and medial epicondylitis was 4.39-4.93, respectively. Hand dominancy was increased the risk of severe CTS by 6.88 times for the left hand and 1.15 times for the right hand. Otherwise in multivariate analyse of left hand results, obesity increase the risk of severe CTS by 3.34, left hand dominancy 7.83 times, chronic disease 2.62 times, and for the right hand being a housewife increases the risk by 2.14, obesity 4.68 times and medial epicondylitis 6.40 times. This study put forth that being a housewife, obesity, dominant hand, presence of lateral or medial epicondylitis are the risk factors of severe CTS.

Comparison of second lumbrical interosseous median and ulnar motor conduction study in population of subjects with idiopathic carpal tunnel syndrome and non-CTS hands-a cross-sectional study

Background: Second lumbrical interosseous (2L-I) median-ulnar motor conduction study across wrist is pivotal in electrodiagnosis of carpal tunnel syndrome (CTS) in different grades of severity. 2L-I Median versus ulnar distal motor latency (DML) difference more than 0.5 milliseconds is used to diagnose median neuropathy at wrist. Other variables of study, namely, 2L DML, compound muscle action potential (CMAP) amplitude, CMAP duration, and conduction velocity (CV) remain less explored with few studies pressing for its role to substantiate CTS diagnosis. Aims and Objectives: Current cross-sectional study aimed to explore role of 2L-I DML, amplitude, duration, and CV in diagnosis of median neuropathy at wrist. Materials and Methods: Total 70, 37 clinically suspected CTS hands and 33 age, height, and weight matched non-CTS hands underwent 2L-I Median Ulnar motor conduction study. Results: Statistically significant difference (P &lt; 0.05) in 2L median DML, CMAP amplitude, duration and CV between CTS and non-CTS hands along with 2L-I Median versus Ulnar DML difference. 2L DML and 2L-I DML difference variables showed better specificity and sensitivity: 83.78 and 93.91, respectively, in diagnosing CTS. Conclusion: We concluded that apart from 2L-I DML difference other variables such as DML, amplitude, duration, and CV may also play substantial role in evaluation of CTS and may be included as part of electrodiagnostic protocol.

Temporal evolution of nerve conduction study abnormalities in anti‐myelin‐associated glycoprotein neuropathy

A distal-predominant demyelinating symmetric pattern is most frequent in patients with neuropathy associated with anti-myelin-associated glycoprotein (MAG) antibodies. The literature however lacks longitudinal data to describe whether this is consistent over time. From the Ottawa Neuromuscular Center database, we identified 23 patients with both immunoglobulin M gammopathy and anti-MAG antibodies. For median, ulnar and fibular motor conduction studies, we analyzed distal latency and amplitude, negative peak duration, terminal latency index (TLI), and conduction velocity. For median, ulnar, sural, and superficial fibular sensory conduction studies, we analyzed distal latency and amplitude. Results were compared for the earliest and the latest data sets. The mean time interval between the two assessment points was 6.5 years. Median and ulnar motor nerve conduction studies did not show a significant change for any of the parameters tested. There was disproportionate prolongation of median distal motor latency and reduction in TLI, compared to the ulnar nerve. Deep fibular motor conduction studies showed a marked reduction in amplitudes over time. Sensory potentials were recordable in the upper limb in less than 50% at the first study and less than 25% on the most recent study. There was an even larger attrition of recordable sural and superficial fibular sensory potentials. Our results highlight the stability of median and ulnar motor conduction study results over a mean observation period of 6.5 years. In contrast, lower limb motor and all sensory potentials show a marked trend toward becoming unrecordable.

Systematic prospective electrophysiological studies of the median nerve after simple distal radius fracture

PurposeTo assess whether there is a measurable impairment of median nerve conduction study parameters with uncomplicated distal radius fracture.MethodsPatients were assessed prospectively at the time of cast removal (visit 1) after a standard 6–8 week immobilization for uncomplicated distal radius fracture. Patients with prior entrapment neuropathy or polyneuropathy were excluded. Patients were asked to report sensory symptoms. Median and ulnar motor and sensory conduction studies were performed bilaterally, as well as transcarpal stimulation. All electrophysiologic studies were repeated at a follow-up visit 2, on average 7.8 weeks later.Results39 patients were assessed at visit 1 and 30 (77%) were available for follow-up visit 2. Paresthesia in the median territory on the fractured side were reported in 20% at visit 1 and 26% at visit 2. Electrophysiological evidence of only mild carpal tunnel syndrome was found on the fractured side in 4/39 at visit 1 and 6/30 at visit 2. There were only 2 cases of moderate-marked median neuropathy, both asymptomatic and on the unfractured side. Median motor and sensory latencies and amplitudes did not show statistically significant differences between fractured and unfractured sides with the single exception of median distal motor latency at visit 1.ConclusionsMedian territory paresthesia at the time of cast removal following distal radius fracture are often not associated with electrophysiologic evidence of median neuropathy. Most median nerve electrophysiologic parameters do not significantly differ between the fractured and uninjured sides. Significant traumatic median neuropathy is not likely to be a frequent manifestation of uncomplicated distal radius fracture.Level of evidenceDiagnostic analysis, Level III

Hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1A

The aim of this study was to investigate hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1 A (CMT1A), a common inherited demyelinating neuropathy. By using pure-tone audiometry, 43 patients with CMT1A and 60 healthy controls with normal sound detection abilities were enrolled. Speech perception in quiet and noisy backgrounds, spectral ripple discrimination (SRD), and temporal modulation detection (TMD) were measured. Although CMT1A patients and healthy controls had similar pure-tone thresholds and speech perception scores in a quiet background, CMT1A patients had significantly (p < 0.05) decreased speech perception ability in a noisy background compared to controls. CMT1A patients showed significantly decreased temporal and spectral resolution (both p < 0.05). Also, auditory temporal processing of CMT1A patients was correlated with speech perception in a noisy background (r = 0.447, p < 0.01) and median motor conduction velocity (r = 0.335, p < 0.05). Therefore, we assumed that demyelination of auditory nerve in CMT1A causes defective cochlear neurotransmission, which reduces temporal resolution and speech perception in a noisy background. Because the temporal resolution test was well correlated with the degree of demyelination in auditory and peripheral motor nerves, temporal resolution testing could be performed as an additional marker for CMT1A.

S37. A surprising diagnosis of a longstanding leg weakness

Multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy is an asymmetric variant of chronic inflammatory demyelinating polyradiculoneuropathy. It presents with multifocal motor and sensory deficits, typically affecting the arms initially and the legs subsequently. Tinel’s sign is frequently elicited at the sites of disease. Nerve conduction studies (NCS) are characterized by evidence of focal demyelination. Spinal fluid often reveals mild to moderate increase of protein. Anti-GM1 antibodies can be present but never in a high titer. Sural nerve biopsy may reveal demyelinating changes. MADSAM responds to intravenous immunoglobulin and in 40% of cases to steroids. Chart review. 52-year-old woman presented with a 10-year history of progressive right leg weakness. She had frequent muscle cramps in the right leg and numbness up to the knee. She denied low back pain, left leg weakness, urinary or bowel symptoms. The neurological examination revealed muscle atrophy of the left forearm and hand, as well as the right posterior thigh and calf. She had no fasciculations. Muscle strength testing of the left hand revealed the following: wrist flexors 4+/5, wrist extensors 4/5, distal finger flexors 4+/5, finger abductors 4−/5, thumb flexor 3/5 and thumb abductor 4/5; and that of the right leg showed: right hip extensor 3/5, knee flexor 4−/5, ankle plantar flexion 2/5, dorsiflexion 5/5, inversion 4−/5, eversion 5/5 and toes extension 5/5. The right arm and left leg examination was unremarkable. Deep tendon reflexes were preserved except for the right ankle jerk which was absent. Sensory examination disclosed only a right-sided pinprick gradient from the toes to the mid-foot. Serum protein electrophoresis with immunofixation was normal and anti-GM1 antibodies were absent. Lumbar spine MRI was unremarkable. MRI of the right leg showed atrophy of the posterior compartment of the thigh and proximal calf. Nerve conduction studies revealed partial conduction block and temporal dispersion of left ulnar and bilateral median motor responses in the forearm, mild median motor conduction slowing through the forearms, an absent right tibial motor response, and absent sural sensory responses. The abnormal sensory responses argue against multifocal motor neuropathy. These findings were interpreted as being consistent with MADSAM with secondary axonal loss particularly in the leg where motor and sensory responses were unevocable. MADSAM typically presents with upper limbs weakness. The striking feature in this patient was the longstanding right leg weakness which overshadowed the left hand weakness. The importance of more extensive clinical and electrodiagnostic evaluation in patients presenting with focal neurological complaints is born out in this patient in whom diagnostic demyelinative findings were evident only in the less affected upper limbs.

Evolution of clinical, electrophysiological, and radiological aspects of the carpal tunnel syndrome before and after surgery.

The aim of the study was to analyze the evolution of the clinical, electrophysiological, and ultrasound aspects of carpal tunnel syndrome (CTS) before and 4 and 8weeks after surgery. A Boston Carpal Tunnel Questionnaire, an ultrasound scan, and an electrophysiological exam were performed in 14 patients the day of surgery, 4 and 8weeks after. The nerve conduction study included: median nerve sensory conduction stimulating digit 3 and 4, median motor conduction from the abductor pollicis brevis, ulnar nerve sensory, and motor conduction. A significant improvement of the symptoms and a significant decrease of the median nerve proximal cross-sectional area on the ultrasound scan were observed 4weeks after surgery. Distal motor latency (DML) was >4.2ms in six patients and decreased along the three visits. DML was ≤4.2ms in the eight others and stayed stable after surgery. We observed a significant increase of the sensory median nerve amplitude response at the wrist stimulating the third digit 8weeks after surgery. When operated patients are referred for control, we recommend to perform: (1) 4weeks after surgery, an ultrasonography, and a measure of the DML of the median nerve; (2) 8weeks after surgery, a measure of the sensory conduction velocity of the median nerve.

Change in peripheral nervous conduction velocity in patients with occupational chronic mercury poisoning and related influencing factors

Objective: To investigate the change in peripheral nervous conduction velocity in patients with occupational chronic mercury poisoning and related influencing factors. Methods: From February 2011 to December 2014, urinary mercury examination and neural electromyography were performed for 104 patients with occupational chronic mercury poisoning. The data on age, type of work, working years of mercury exposure, and past medical history were collected, and peripheral nervous conduction velocity and its correlation with age, working years of mercury exposure, and urinary mercury concentration were analyzed. Results: All the 104 patients with occupational chronic mercury poisoning had a mean of 45.37±9.82 years, median (P(25), P(75)) working years of 7 (3, 11) , and a median (P(25), P(75)) urinary mercury concentration of 88.50 (56.25, 163.03) μg/g Cr. The major clinical manifestations of peripheral nerve injuries were numbness of extremities (20.2%) , hypopselaphesia/hypalgesia or hyperpselaphesia/hyperalgesia (9.6%) , and bone/muscle pain in the extremities (6.7%) . Neural electromyography showed an increase in denervation potential (fibrillation potential or positive sharp wave) and a detection rate of abnormal peripheral nervous conduction velocity as high as 65.4%. The patients with an older age and more working years had a higher incidence rate of abnormal sensory conduction velocity of the ulnar nerve. There were significant reductions in motor and sensory conduction velocities of the median nerve, motor and sensory conduction velocities of the ulnar nerve, motor conduction velocity of the common peroneal nerve, and the sensory conduction velocity of the superficial peroneal nerve (P<0.05) , with the increase in urinary mercury concentration. Conclusion: Patients with occupational mercury poisoning have a high rate of abnormal neural electromyographic findings, which can be used as an important method for early identification of chronic peripheral nerve injuries induced by mercury poisoning. The degree of peripheral nerve injuries increases with the increasing time of mercury exposure and urinary mercury concentration.

Electrophysiological evaluation of peripheral nerve in patients with impaired glucose tolerance

This study retrospectively reviewed 75 patients with impaired glucose tolerance(IGT)admitted in our hospital from March 2015 to October 2015. All patients underwent Toronto clinical scoring system(TCSS) evaluation. Patients with IGT were further divided into normal score group(TCSS-N, n=50)and abnormal score group(TCSS-A, n=25)according to their scoring results, and 30 healthy volunteers were served as control group. All patients and controls underwent motor and sensory nerve conduction studies, as well as sympathetic skin response(SSR)test using the Keypoint.Net(Medoc Ltd)electromyogram device. The results showed that the SSR amplitude of lower limbs was reduced [(0.61±0.44 vs 1.00±0.33)mv, P<0.05] and latency of lower limbs was extended [(1 880±282 vs 1 642±256)ms, P<0.05]in IGT group compared with control group. But median, ulnar, tibial, and peroneal nerve sensory and motor conduction revealed no difference between two groups. In TCSS-A group, the SSR amplitude of lower limbs was reduced [(0.47±0.39)mv, P<0.05], latency of lower limbs was extended [(2 062±291)ms, P<0.05]and the sensory nerve action potential(SNAP)amplitude of the tibial nerve was significantly lower compared with control group [(1.83±0.37 vs 2.07±0.30)μv, P<0.05]. Compared to TCSS-N group, latency of lower limbs was extended [(2 062±291 vs 1 808±246)ms, P<0.05]in TCSS-A group. The SSR amplitude of lower limbs were reduced[(0.66±0.44)mv, P<0.05]and latency were prolonged(P<0.05)in TCSS-N group compared with control group. Pearson correlation analysis showed that the SSR amplitude and latency of the lower limbs were correlated with the postprandial blood glucose, blood glucose fluctuation, body weight, as well as body mass index. These results suggest that there exists peripheral nerve damage in the patients with IGT, mainly involving the small fiber nerve of the lower limbs. Large fibers may also be mildly affected as the disease progresses. (Chin J Endocrinol Metab, 2017, 33: 574-577) Key words: Peripheral nerve; Impaired glucose tolerance; Nerve conduction; Sympathetic skin response

Do Electrodiagnostic Variables Correlate with Functional Outcomes in Carpal Tunnel Syndrome?

Background: The most common entrapment neuropathy seen in electrodiagnostic (EDX) laboratories is carpal tunnel syndrome (CTS). The diagnostic value of EDX with regard to CTS is well-established, but EDX’s predictive value is unclear. To date, only one study has attempted to establish a relationship between EDX findings and a patient’s clinical status pre- and post-treatment, and there was no significant relationship found. Objective: To establish a relationship between EDX variables and clinical severity assessment with Disabilities of the Arm, Shoulder, and Hand (DASH) scores at a single point in time and over a period of time. Methods: The study was a prospective single group cohort. 41 patients referred to an EDX clinic with suspected diagnoses of CTS were enrolled. Patients underwent EDX studies and completed DASH questionnaires at initial and follow-up visits at 8-month to 12-month intervals. Data collected included median sensory, mixed, and motor latencies, amplitudes, conduction velocities, and needle electromyography (EMG). Correlation coefficients were determined between EDX data variables and severity assessment (independent variables) and patients’ DASH questionnaire measures (dependent variables) at initial and follow-up assessments. Results: Change in DASH score over time positively correlated with left distal median motor latency (DMML) decrement and right transcarpal median sensory conduction block and negatively correlated with left median sensory nerve action potential (SNAP) amplitude decrement percentage, right needle EMG motor unit morphology abnormality, and right median forearm motor conduction velocity increment. The correlations observed are of unclear significance since the DASH scores themselves did not change significantly over time. Conclusions: Objective EDX data coupled with patient-reported outcome (PRO) measures such as the DASH score may be more meaningful in directing clinical care than either of them alone.

Electrophysiological and clinical comparison of local steroid injection by means of proximal versus distal approach in patients with mild and moderate carpal tunnel syndrome

Local corticosteroid injection is one of the treatment modalities for carpal tunnel syndrome. Symptomatic and electrophysiological improvement following local corticosteroid injection has been documented. The aim of the present study was to compare the effects of proximal and distal approaches of local steroid injection in patients with mild and moderate carpal tunnel syndrome on clinical scores and electrophysiological parameters at the end of 1 month following injection. A total of 30 patients were included and randomly assigned into one of the two groups based on the local steroid injection approach either by means of distal (group I) or by mean of proximal approach (group II). Clinical and electrophysiological examinations were carried out before and 1 month following the injection. There was a significant reduction in the pain and disability scores of the Boston Carpal Tunnel Questionnaire between the baseline and follow-up in both groups. Median motor nerve distal latency was statistically significantly reduced in both groups 1 month after the injection. Median motor conduction velocity and amplitude (amp) showed a statistically nonsignificant difference 1 month following the injection. Median sensory distal latency, amp, and conduction velocity showed statistically significant difference between the two groups. The average duration of the procedure in group I was 9.29 ± 0.76 s compared with 47.91 ± 9.66 s in group II. The average grade of pain expressed by the patients in group I was 1.97 ± 0.82 compared with 5.11 ± 0.67 in group II. Local corticosteroid injection at the carpal tunnel using the distal approach is associated with favorable clinical and electrophysiological results similar to those reported using the proximal approach. The distal approach is much less time consuming and more comfortable compared with the proximal approach.

Reversible conduction failure is distinct from neurophysiological patterns of recovery in mild demyelinating Guillain–Barré syndrome

Axonal Guillain–Barré syndrome (GBS) can present with rapid resolution of nerve conduction failure also referred to as early reversible conduction failure. It is unclear if this reversible conduction failure represents successful immunotherapy or part of the natural evolution of mild axonal disease, or whether it is in fact recovery from mild demyelination. Here we describe two patients with axonal and demyelinating GBS with favorable outcomes without immunotherapy. One was a 32-year-old pregnant woman with axonal GBS. She presented with acute limb weakness, areflexia and mild sensory symptoms. Serial neurophysiology revealed reversible conduction block across elbow segment of the ulnar nerve without remyelinating features in the recovery stage. The second patient was a 38year-old pregnant woman with demyelinating GBS presenting with acute limb weakness, reduced lower limb reflexes and sensory disturbance in a glove and stocking distribution. Although nadir was reached on Day 8, nerve conduction studies revealed progressive prolongation of median distal motor latency and conduction slowing across the elbow segment of the ulnar nerve over 2weeks. Conduction failure in axonal GBS can spontaneously recover, and is distinct from the recovery pattern seen in mild demyelinating GBS. Serial nerve conduction studies can help distinguish between the two pathophysiologies.

HAND WEAKNESS IN CHARCOT-MARIE-TOOTH DISEASE 1X

There have been suggestions from previous studies that patients with Charcot-Marie-Tooth disease (CMT) have weaker dominant hand muscles. Since all studies to date have included a heterogeneous group of CMT...

Nerve conduction studies in Charcot–Marie–Tooth disease in a cohort from Turkey

In the demyelinating form of Charcot-Marie-Tooth disease, median motor conduction velocity (MCV) was noted to be around 20 m/s in peripheral myelin protein 22 (PMP22) duplications, in contrast to higher MCVs in connexin 32 gene (Cx32) mutations and lower MCVs in the demyelinating form of myelin protein zero gene (MPZ) mutations.Nerve conduction studies were performed in 64 families with both common and rare mutations.Mean MCV of the median nerve was 20 ± 5 m/s in PMP22 duplications, 34 ± 6 m/s in Cx32 mutations, 20 ± 9 m/s in KIAA1985 (SH3TC2) mutations, and 11 ± 8 m/s in MPZ mutations. Conduction was generally uniform; however, conduction blocks were present in 1 patient each with the MPZ mutation and PMP22 duplication, both with unusual phenotypes.Our results confirm those of the other investigators. Electrophysiological results of the rare KIAA1985 (SH3TC2) mutation reveal that their MCVs span a broad range and that conduction is uniform.

Effects of Topiramate on Peripheral Nerve Excitability

Antiepileptic drugs are generally used to control the cortical hyperexcitable states. But some of them are also effective on the peripheral nervous system, so they may be used in some states like neuropathic pain. Several recent reports suggest the possible effects of antiepileptic drugs on peripheral nerve excitability. Strength duration time properties gives an indirect idea about the persistent, paranodal sodium (Na) channels and may indirectly reflect the peripheral nerve excitability. Topiramate suppresses the cortical hyperexcitability, but previous studies could not prove a significant effect of topiramate on peripheral nerves. The aim of this study is to investigate the probable nerve excitability changes caused by topiramate. Forty migraine patients and 40 controls were included in the study. Median motor and sensory conduction parameters were recorded. Strength duration properties were also recorded from abductor pollicis longus muscle, with the stimulation of median nerve. The electrophysiological studies were repeated 4 weeks after the initiation of topiramate in the treatment group. Nerve conduction parameters were not significantly affected by 4-week topiramate treatment. But the strength duration time constant decreased significantly, reflecting a reduction in the excitability. This decrement seemed to be more obvious in those in whom topiramate was also clinically useful. The method used demonstrated a probable effect of topiramate on the peripheral nerve excitability.

Hand weakness in Charcot-Marie-Tooth disease 1X

There have been suggestions from previous studies that patients with Charcot–Marie–Tooth disease (CMT) have weaker dominant hand muscles. Since all studies to date have included a heterogeneous group of CMT patients we decided to analyse hand strength in 43 patients with CMT1X. We recorded handedness and the MRC scores for the first dorsal interosseous and abductor pollicis brevis muscles, median and ulnar nerve compound motor action potentials and conduction velocities in dominant and non-dominant hands. Twenty-two CMT1X patients (51%) had a weaker dominant hand; none had a stronger dominant hand. Mean MRC scores were significantly higher for first dorsal interosseous and abductor pollicis brevis in non-dominant hands compared to dominant hands. Median nerve compound motor action potentials were significantly reduced in dominant compared to non-dominant hands. We conclude that the dominant hand is weaker than the non-dominant hand in patients with CMT1X.

Isolated motor conduction block associated with infliximab

TNF-alpha antagonists have been associated with various types of peripheral neuropathies, including multifocal motor neuropathy with conduction block and mononeuropathies [1]. We present two patients treated with infliximab who developed unifocal motor neuropathy with conduction block. A 34-year-old female with Crohn’s disease developed painless weakness of right-hand pincer grip of insidious onset. She had previously received five courses of infliximab infusions (5 mg/kg) and a further dose 3 days after symptom onset. Infliximab partially controlled gastrointestinal symptoms and she was otherwise well. Regular medication included the oral contraceptive pill, levothyroxine, folate, omeprazole, B12 injections, and iron infusions. Examination revealed MRC grade 4 power of the right abductor pollicis brevis, flexor pollicis longus, flexor digitorum profundus (median), and opponens pollicis. Flexor carpi radialis was mildly weak (4?) but forearm pronation remained strong. There were no sensory signs and systemic examination was unremarkable. A detailed four-limb neurophysiological examination 6 weeks after symptom onset revealed isolated severe right median motor conduction block 2.5–6.5 cm proximal to the antecubital fossa skin crease (Fig. 1). Median and other sensory conduction responses were normal. EMG of median innervated forearm muscles including abductor pollicis brevis and flexor pollicis longus was consistent with conduction block, with reduced recruitment of motor units but no spontaneous activity or other evidence of motor axon loss. Right median sympathetic skin response, somatosensory evoked potentials, and thenar thermal threshold testing were all normal. There was evidence for systemic active inflammation with mild leukocytosis, thrombocytosis, and normocytic anemia; ESR 102 mm/h and CRP 51 mg/l. Anti-DNA antibodies, ANCA, ANA, RA latex, glycolipid and antiGAD antibodies, anti-GM1, and anti-GQ1b antibodies were either normal or negative. An MRI with gadolinium showed hyperintensity of the right median nerve in the lower third of the right arm on TIRM and T2-weighted images, with subtle enhancement but no enlargement. This corresponded to the site of conduction block. No specific treatment was given, but there was significant improvement of power in weak muscles within 4 weeks of presentation, and complete recovery at 1 year. Patient 2, a 41-year-old female with ankylosing spondylitis, had been treated with regular infliximab infusions since 2003. In April 2009, she awoke with painless weakness of left finger and wrist extension 3 days after an infliximab infusion (270 mg). Examination revealed MRC grade 0 finger extension and 4wrist extension with radial deviation and no sensory loss. Initial neurophysiological examination 1 week after symptom onset showed profound A. W. Michell (&) Department of Clinical Neurophysiology, Box 124 Addenbrooke’s Hospital, Cambridge CB2 0QQ, UK e-mail: andrew.michell@addenbrookes.nhs.uk

Influence of Age and the Severity of Median Nerve Compression on Forearm Median Motor Conduction Velocity in Carpal Tunnel Syndrome

Forearm median motor conduction velocity (FMCV) is reduced in carpal tunnel syndrome (CTS). The aim of this study was to investigate the association of FMCV with age and severity of median nerve compression. Forearm median motor conduction velocity and median nerve motor distal latencies were measured in 312 CTS hands. Forearm median motor conduction velocity correlated negatively with age. This correlation persisted in the subgroups of hands with severe and less severe CTS. Forearm median motor conduction velocity correlated negatively with the degree of compression (as measured by median nerve motor distal latencies). This correlation persisted in subgroup of hands with severe CTS but not in less severe ones. Multiple regression analysis comparing the influence of age and median nerve motor distal latencies on FMCV showed higher standardized coefficients (beta) value for age than for median nerve motor distal latencies, suggesting a greater influence for age. The beta value for age is higher in severe group than in less severe group, suggesting that age has higher influence on FMCV in severe group. The degree of compression influences FMCV in hands with severe CTS but not in hands with less severe CTS. This difference in severe and less severe CTS may be because of the differences in the underlying pathophysiological processes in the 2 entities.