Median Nerve Function Research Articles

Time course and predictors of median nerve conduction after carpal tunnel release

Purpose To identify predictors of outcome and of electrophysiologic recovery in patients with carpal tunnel syndrome (CTS) treated by endoscopic carpal tunnel release using a nerve conduction testing system (NC-Stat; NEUROMetrix, Inc, Waltham, MA). Methods Validity of the automated nerve conduction testing system was shown by comparing presurgical distal motor latencies (DMLs) against a reference obtained by referral to an electromyography laboratory. The DML was evaluated in 48 patients with CTS. Measurements were obtained within 1 hour of surgery and at 2 weeks, 6 weeks, 3 months, and 6 months after carpal tunnel release. Presurgical and postsurgical DMLs were then compared and correlated with variables and possible predictors of outcome including age, body mass index, gender, and presurgical DMLs. Results The automated nerve conduction testing system DMLs matched those of reference electromyography/nerve conduction study values with high correlation. Sensitivity of the automated nerve conduction testing system when compared with a standardized CTS case definition was 89%, with a specificity of 95%. A significant correlation was found between the DML before release and the DML 1 hour after release. Moreover, maximal postsurgical DML improvement was highly dependent on the presurgical DML, with no improvement shown for the <4-ms group, mild improvement for the 4-to-6-ms group, and maximal improvement in the >6-ms group. Among the clinical variables of age, gender, and body mass index only age was mildly predictive of postrelease DML changes at 6 months. No other correlations between clinical variables and postsurgical DMLs were significant. In addition the predictive value of age was lost when combined with the presurgical DML in a multivariate analysis. Conclusions Postsurgical changes in the median nerve DML were highly dependent on the prerelease latency. The sensitivity and specificity of a nerve conduction monitoring system in detecting and aiding in the diagnosis of CTS is useful in the long-term management of patients with CTS and can aid in determining the level of improvement in median nerve function after endoscopic carpal tunnel release.

Quantitative vibration threshold testing in carpal tunnel syndrome: analysis strategies for optimizing reliability

Tuning forks and electronic vibrometers have been used to quantify vibration sensation thresholds, which are thought to be affected early in carpal tunnel syndrome (CTS). The purpose of this study was to identify a reliable testing procedure for a newly designed, computer-controlled vibrometer (PCV50; Ztech, Salt Lake City, UT). Fifty-two patients (mean age 48±8 years) with electromyographically confirmed CTS were tested on one occasion. The computer-controlled vibrometer, with a fixed frequency of 50 Hz, used stepwise changes in amplitude to determine vibration sensation threshold. Each patient had three vibrometer measures (trials) taken on the pulp of the third digit of their right and left hands during the first test session and were retested by a single repetition 40 to 60 minutes later (retest). Intraclass correlation coefficients (ICCs) were used to examine several data analysis strategies. The strategy that generated the highest ICCs for both the right and left hands assumed that the first trial was a learning or practice attempt, and compared the average of the second and third trials with the score from the second session (ICC = 0.86 and 0.89, respectively). The computer-controlled vibrometer offered an easily administered, quantitative, and comfortable means to assess median nerve function. Using this reliable testing procedure will allow for additional investigations to determine its usefulness in the early detection and accurate quantification of CTS-related impairment.

Bifid median nerve as a determinant of carpal tunnel syndrome recurrence after endoscopic procedures. A case report

A number of complications have been associated with endoscopic technique in treating carpal tunnel syndrome (CTS). We observed a female patient who had previously undergone endoscopic surgery for CTS. Shortly after surgery, this patient complained of pain, numbness and strength deficiency, as severe as it was before the operation. A new, open, surgical procedure was performed. During this second-look surgery, we found a bifid median nerve, which divided into two branches at the second third of the forearm, proximal to the flexor retinaculum. We strongly suggest a careful exploration of the median nerve in the carpal tunnel. Moreover, we believe that an extensive preoperative assessment of median nerve morphology and function is mandatory prior to endoscopic approach in treating CTS.

Carpal tunnel syndrome among apprentice construction workers.

In terms of lost-work time and restricted workdays, surgery, and rehabilitation, one of the most costly occupational musculoskeletal disorders is carpal tunnel syndrome (CTS). The purpose of this study was to determine the prevalence of CTS among apprentice construction workers. This cross-sectional study included apprentices from four construction trades. Apprentices completed a self-administered questionnaire and received electrophysiologic studies assessing median nerve function across the carpal tunnel. A surveillance case definition for CTS was based on characteristic hand symptoms and the presence of median mononeuropathy across the carpal tunnel. Of the 1,325 eligible apprentices, 1,142 (86.2%) participated in the study. The prevalence of CTS among apprentices was 8.2%; sheet metal workers had the highest rate (9.2%). In operating engineers, the prevalence of CTS was significantly higher (OR = 6.9; 95% CI = 2.6-18.2) among the heavy equipment mechanics than the drivers of those vehicles. Body mass index, age, and self-reports of working overhead were associated with prevalent CTS. Less than 15% of the apprentices with CTS sought medical attention for their disorder. Many construction workers begin developing CTS before or during their apprenticeship. Few apprentices seek medical attention for hand symptoms characteristic of CTS. The results of this study indicate a public health need for the implementation of prevention strategies for CTS in the construction industry.

Predictors of carpal tunnel syndrome: an 11-year study of industrial workers.

In 1984 we initiated a study of factors associated with carpal tunnel syndrome (CTS) in industrial workers by using a case definition based on both symptoms and electrophysiologic findings. Medical history, lifestyle factors, and symptoms were assessed by interview, and electrodiagnostic studies were used to measure median nerve function. Job tasks were classified by both interview and direct observation of work activities. Follow-up evaluations were conducted in 1989 and 1994-1995. The analytic sample consisted of 111 women and 145 men free of CTS in 1984 who were examined at both subsequent contact points. In logistic regression analyses, greater age, female gender, relative overweight, cigarette smoking, and vibrations associated with job tasks were found to significantly increase risk for dominant-hand CTS, whereas presence of an endocrine disorder was marginally related to reduced risk for CTS. These findings were generally similar when analyzed separately for men and women. Similar to other chronic noninfectious diseases, personal factors may play an important role in determining risk for CTS.

Measurement System for Evaluating Dynamic Wrist Workloads and CTS Risk

This study presents an evaluation of measurement system investigating the relationship between dynamic wrist workloads including posture, force and repetition, and median nerve function, hence, CTS risk. The performance of a biaxial electrogoniometer and force sensor for generating dynamic wrist workloads were evaluated with custom made calibration fixtures. The results for electrogoniometer measurement showed that non-repeatability and non-linearity were 4.0% and 1.6%, respectively, in the flexion/extension plane, and 3.3% and 0.9%, respectively, in the radial/ulnar plane. The non-repeatability and non-linearity for the force sensors were 14.3% and 1.6%, respectively. These results demonstrated that the electrogoniometer and force sensors are useful for future study. The performance of EMG machine for measuring nerve conduction was also examined and the results was consistent across day and trial. Further research is quantifying the relationship between dynamic wrist workloads with resultant changes in motor and sensory conduction function in the median nerve.

Effects of an aerobic exercise program on median nerve conduction and symptoms associated with carpal tunnel syndrome.

Carpal tunnel syndrome is associated with greater body mass index and less physical activity. To determine the effect of aerobic exercise on median nerve conduction and symptoms suggestive of carpal tunnel syndrome, 30 symptomatic volunteers (30 to 64 years old) with abnormal median nerve conduction studies participated in a 10-month program of supervised aerobic exercise. Changes in percentage of body fat, body mass index, peak oxygen consumption, 14-cm median sensory latency, and hand/wrist symptoms were assessed. A decrease in 14-cm sensory median latency correlated with a decrease in percentage of body fat (R = 0.52, P = 0.004) and was predicted by an increase in peak oxygen utilization (partial R = 0.52, P = 0.005) and a decrease in body mass index (partial R = 0.47, P = 0.014). There was also a tendency for a set of symptoms sometimes associated with carpal tunnel syndrome (pain, tightness, and clumsiness) to be relieved by the exercise program. These results suggest that an aerobic exercise program can be beneficial to median nerve function and may be associated with a reduction in hand symptoms.

Carpal tunnel syndrome surgery: identification of a neurophysiological high-risk category

Surgical decompression of the median nerve is a standardized treatment for carpal tunnel syndrome. After surgery a clinical and neurophysiological improvement is observed also on severe cases. We report 4 cases of carpal tunnel syndrome (CTS) in the hands of 3 patients with prolonged median wrist-thenar distal motor latency (longer than 10 ms, normal values < 4.0 ms) and absence of digit-wrist sensory responses. In these patients surgery caused complete loss of median nerve function. Such a marked increase of median distal motor latency (DML) is rare (0.6% in 500 CTS hands consecutively examined in our laboratory) and suggests the presence of a chronic condition with severe disruption of the myelin. On the basis of these anecdotal observations, we suggest that patients with median DML of 10 ms or more be considered at high risk for CTS surgery failure.

Dynamica van de rolstoelhoepel: lichaamsgewicht en functie van de N. medianus

Wheelchair pushrim kinetics: Body weight and median nerve function [Archives of Physical Medicine and Rehabilitation 1999;80(8):910-5]

Letter to the Editor: The Continuing Challenge of Evaluating Carpal Tunnel Syndrome Impairment

Abstract The author responds to The Continuing Challenge of Evaluating Carpal Tunnel Syndrome Impairment in the March/April 2000 issue of The Guides Newsletter. Carpal Tunnel Syndrome (CTS) is a clinical diagnosis based on the patient's history and objective findings on examination. Patients present with dull, aching discomfort of the hand, forearm, or upper arm; paresthesias and tingling of the hand; subjective weakness or numbness; and, occasionally, autonomic changes. Nerve conduction velocity studies are highly accurate in documenting median nerve entrapment at the level of the wrists, but this is an anatomic finding and does not mean that the entrapment produces any symptoms. An electrophysiologic study does not predict if or when the median nerve entrapment will become symptomatic, which is based on the patient's history. Electromyography (EMG) and nerve conduction velocity (NCV) studies do not help distinguish among the many etiologies of CTS. EMG/NCV testing can provide significant, highly accurate information regarding the physiologic function of the median nerve at the level of the wrist, but physicians must know how to interpret this information in the clinical setting. [The Editor responds: Several traditional findings of CTS have little or no diagnostic value, and electrodiagnosis is the diagnostic test of choice, although reported sensitivities range from 49% to 84% with specificities of 95% to 97%.]

Pre- and post-employment median nerve latency in pork processing employees.

There is some controversy regarding the relationship between development of median nerve dysfunction and employment activities. We performed nerve conduction studies of median nerve function on individuals before and after starting employment in the pork processing industry. After working an average of 64 days, employees (n = 45) showed significant prolongation of median motor and sensory nerve latency when comparing initial and final testing results in both dominant and non-dominant hands (P = < 0.01 to 0.03). A similar trend was found when testing a smaller group of employees (n = 17) who were already working (mean of 3 days), though this did not generally reach statistical significance. This study supports the conclusion that prolongation of median motor and sensory nerve latency can occur within as little as 2 months after beginning employment in the pork processing industry.

Wheelchair pushrim kinetics: Body weight and median nerve function

Objectives: Individuals who use manual wheelchairs are at high risk for median nerve injury and subsequent carpal tunnel syndrome (CTS). To gain a better understanding of the mechanism behind CTS in manual wheelchair users, this study examined the relation between (1) pushrim biomechanics and function of the median nerve, (2) pushrim biomechanics and subject characteristics, and (3) median nerve function and subject characteristics. Design: Case series. Setting: Biomechanics laboratory and an electromyography laboratory. Participants: Thirty-four randomly recruited individuals with paraplegia who use a manual wheelchair for mobility. Intervention: Subjects propelled their own wheelchair on a dynamometer at 0.9m/sec and 1.8m/sec. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. Bilateral nerve conduction studies focusing on the median nerve were also completed. Main Outcome Measures: Pearson's correlation coefficients between subject characteristics, median nerve conduction studies, and propulsion biomechanics; a regression model of nerve conduction studies incorporating subject characteristics and pushrim biomechanics. Results: Subject weight was significantly related to median nerve latency ( r = .36, p = .03) and median sensory amplitude ( r = −.43, p = .01). Height was also significantly related to median sensory amplitude ( r = −.58, p = .01). Subject weight was significantly related to the peak resultant force applied to the pushrim ( r = .59, p < .001). Height, weight, and weight-normalized pushrim forces were successfully incorporated into a linear regression model predicting median sensory amplitude ( r = .63, p < .05) and mean median latency ( r = .54, p < .05). Conclusion: This study found subject weight to be related to pushrim forces and median nerve function. Independent of subject weight, pushrim biomechanics were also related to median nerve function. Through weight loss and changes in pushrim biomechanics, it may be possible to prevent median nerve injury in manual wheelchair users.

Unusual distal radial epiphyseal injury in a child

An eleven-year old boy presented to the accident and emergency department after falling o€ a roof from a height of about 10 feet. His only signi®cant injury was to the left wrist. Physical examination revealed a swollen dorsally angulated left wrist. He initially had no neurovascular de®cit in the hand and radiographs showed a double Salter Harris type II fracture [1] of the distal radial and ulnar metaphyses (Fig. 1). Two hours after admission he developed signs of median nerve compression and manipulative reduction and POP application under a general anaesthetic was undertaken. After manipulation median nerve function returned. Further X-rays showed a large volar metaphyseal fragment, which was rotated through 908 (Fig. 2). This, was not reducible by closed manipulation and surgical exploration was therefore undertaken. This revealed a large metaphyseal fragment which presented it's cancellous surface volarly and was compressing the median nerve. When this fragment was reduced a stable reduction was achieved and a forearm cast was only required (Fig. 3). The fracture subsequently went on to unite satisfactorily. At 6/52 follow-up the growth plate showed no signs of damage. Injury, Int. J. Care Injured 30 (1999) 149±150

Surgical prognosis in carpal tunnel syndrome: usefulness of a preoperative neurophysiological assessment.

In this study 37 CTS hands underwent pre- and post-operative (15 days 2 and 6 months) evaluation of median nerve distal motor latency (DML) and sensory nerve conduction velocities (SNCV: I digit and III digit-wrist). Pre-operatively, CTS hands were classified as mild (decreased SNCV, normal DML), moderate (decreased SNCV, increased DML) or severe (absent sensory nerve action potentials, increased DML). Post-operatively, all hands presented clinical and neurophysiological improvement. The three groups of patient showed different clinical and neurophysiological responses to nerve decompression: we observed a rapid restitutio ad integrum in mild group, an improvement with normalisation in about 50% of the hands in moderate group, and a high percentage of restore of the sensory responses with no normalisation in severe group. A marked improvement of sensory symptoms was observed in all cases, but some degree of motor and/or sensory deficit was still present six months after surgery in more advanced cases. Preoperative electrophysiological assessment of median nerve function in CTS hands have an important role in predicting the outcome of surgical decompression.

Surgical Principles and Planning for the Rheumatoid Hand and Wrist

Each surgical procedure available for the rheumatoid hand has a score card. The most indicated and necessary procedures include: extensor tenosynovectomy and Darrach for the impending or already ruptured extensor tendons; flexor tenosynovectomy and carpal tunnel release for the patient with impaired median nerve function; stabilization of the deformed unstable thumb with MP or IP arthrodesis; and flexor tenosynovectomy in the palm and finger of a motivated patient with significant disparity between active and passive motion. Relative indications for surgery include arthrodesis for the unstable wrist; MP arthroplasty for the fixed MP volar and ulnar subluxation with inability to open the hand; synovectomy for the occasional patient with painful boggy synovitis of the MP or PIP joint; and reconstruction of the fixed swan neck deformity with relatively good PIP joints. Both MP and PIP joints can and should be operated on at the same time. Extensive wrist surgery, that is, tenosynovectomy and Darrach or arthrodesis, should not be performed at the same time as MP arthroplasty. Try to do the "winner operations" first.

The relationship of vitamin B6 status to median nerve function and carpal tunnel syndrome among active industrial workers.

Case reports and small case series suggest that vitamin B6 deficiency is an important etiologic factor in carpal tunnel syndrome (CTS). This hypothesis has never examined in a randomly selected study population, particularly among active workers. We examined 125 randomly selected active workers from two industrial plants. Each worker completed a self-administered symptom questionnaire and underwent electrodiagnostic testing of the median and ulnar sensory nerves. Laboratory biochemical analyses of vitamin B6 status were also performed using the erythrocyte glutamic pyruvic transaminase assay, and quantification of plasma pyridoxal-5'-phosphate. Measurements of vitamin B6 status were unrelated to self-reported symptoms potentially consistent with CTS, electrophysiologically determined median or ulnar nerve function, and CTS defined on the basis of self-reported symptoms and electrophysiologic measurements. These results suggest that CTS among active industrial workers is unrelated to vitamin B6 status. Furthermore, in our opinion, empiric prescription of vitamin B6 to patients with CTS is unwarranted and potentially hazardous.

重度手根管症候群の手術例の検討 神経内剥離術例と手根管開放術単独例の比較

Adjunctive internal neurolysis of the median nerve followed by release of the transverse carpal ligament is widely performed for treating carpal tunnel syndrome. However, the efficacy of internal neurolysis is still controversial. In this series, eleven hands in eleven patients had internal neurolysis of the median nerve and carpal tunnel release, twelve hands in eleven patients had standard ligament release alone.Thenar muscle strength and bulk were recorded in all hands. Median nerve function was evaluated using the two-point discrimination test and electromyography. Preoperatively, all hands had severe thenar muscle atrophy with no motor response to stimulation.Analysing the postoperative data, the majority of hands in both groups achieved satisfactory results and there was no significant difference between the results of the two groups. Results of this study indicate that standard surgical release of the transverse carpal ligament is equally effective in patients with severe carpal tunnel syndrome. Therefore, it can be suggested that internal neurolysis is not necessary in the treatment of carpal tunnel syndrome.

Secondary surgery following brachial plexus injuries.

The favourable treatment of post-traumatic brachial plexus lesions based on our experience of 362 cases over a 12 year period is reported. Twenty-five percent of the patients needed secondary operations. The spectrum of the latter consisted of arthrodesis, tenodesis, and musculotendinous transfer, including free neurovascular tissue transfer partially innervated by nerve transposition. Functionally, secondary tendon transfer can help to improve the effect of nerve repair techniques. To restore shoulder function the trapezius transfer (n = 22) has been used mainly; elbow flexion has been regained by pedicled latissimus dorsi translocation (n = 22), triceps-to-biceps transfer (n = 18), bipolar latissimus muscle transfer, and free neurovascular tissue transfer (n = 8). The Steindler flexorplasty was performed in four plexopathies, and finally a pedicled serratus muscle transfer was used. A unipolar latissimus dorsi transfer results in an ability to lift 10-15 kg, whilst the bipolar latissimus transfer and the triceps-to-biceps transfer produced a maximal strength of 5-8 kg. Epitrochlear flexor-pronator mass transfer produced a strength of 2-5 kg, whereas free neurovascular latissimus dorsi transfer developed a maximal muscular strength of 2-4 kg in the unipolar variation and 1-2 kg for the bipolar LD. In 97 secondary procedures to the lower arm and hand the following secondary operations were indicated: in 29 cases of radial nerve palsy transfers according to Merle d'Aubigne, a further 21 wrist tenodeses and 8 wrist arthrodeses were performed. To restore median nerve function, coupling tendon transfer (n = 4) and free neurovascular gracilis transfer (n = 3) were selected.(ABSTRACT TRUNCATED AT 250 WORDS)

Feasibility of Using the Gap Detection Tactility Test for Monitoring Cutaneous Sensory Deficits

Periodic worker monitoring methods are needed for detecting cumulative trauma disorders, such as carpal tunnel syndrome (CTS), in the early stages. An experiment was conducted for studying the feasibility of using a new aesthesiometer for periodically measuring functional tactile sensitivity. It was conducted to investigate gap detection sensory threshold differences between five normal subjects and seven subjects diagnosed having CTS. The gap detection test was used because of its functional resemblance to many work-related activities. Average gap detection sensory threshold using the index finger was 0.21 mm (SD = 0.14 mm) for the normal subjects and increased 114% to 0.45 mm (SD = 0.16 mm) for the CTS subjects when finger probing was allowed. Average gap detection sensory threshold using the index finger was 1.57 mm (SD = 0.56 mm) for the normal subjects and increased 61% to 2.53 mm (SD = 0.82 mm) for the CTS subjects when finger probing was not allowed. The results suggest that people suffering from CTS may experience similar functional deficits in daily living and work activities. A strong relationship was also observed between electrophysiologic variables and the gap detection sensory thresholds when both the CTS and normal hands were pooled. This suggests that performance in the gap detection test might measure the level of median nerve function in CTS.

Effects of 830 nm continuous wave laser diode irradiation on median nerve function in normal subjects

The presence, magnitude, and nature of the effect that low intensity laser irradiation has on nerve function, growth, and repair constitute a contentious area of research. We have addressed one aspect of this controversy by systematically examining the influence of 830 nm laser radiation on median nerve function. In particular, we investigated median nerve motor and sensory distal latencies, action potential amplitudes, action potential areas, and conduction velocities as well as dorsal hand skin temperatures in 33 normal subjects in a double-blinded, randomized controlled study. All subjects received identical treatment: 30 seconds of "irradiation" at 10 points over the course of the right median nerve (five sites on the forearm and five sites distal to the wrist crease) with either an active (1.2 J/point) or inactive (0 J/point) 40 mW 830 nm continuous wave IR laser diode. Latencies, conduction velocities, amplitudes, areas, and skin temperatures were collected bilaterally at a baseline immediately prior to irradiation and at intervals of 1, 5, 10, 15, 20, and 30 minutes following treatment. Analysis of the results reveals that motor and sensory distal latencies were decreased in the treated limbs of the laser-treated group relative to the control group by 3-4% (P < .016 and .046, respectively, rank sum test). No significant differences in these quantities were found between the limbs within either group. Similarly, no alterations of action potential amplitudes, action potential areas, forearm conduction velocities, or skin temperatures were detected within or between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)