Multiple point electrical stimulation of ulnar and median nerves.
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A computer-assisted method of isolating single motor units (MUs) by multiple point stimulation (MPS) of peripheral nerves is described. MPS was used to isolate 10-30 single MUs from thenar and hypothenar muscles of normal subjects and patients with entrapment neuropathies, with the original purpose of obtaining a more representative mean motor unit potential for estimating the number of MUs in a muscle. The two important results that evolved from MPS however, were: (1) in the absence of 'alternation' MUs were recruited in an orderly pattern from small to large, and from longer to shorter latencies by graded electrical stimulation in both normal and pathological cases, (2) a comparison of the sizes of MUs recruited by stimulation proximal and distal to the elbow suggested that axonal branching can occur in the forearm 200 mm or more proximal to the motor point in intrinsic hand muscles. (+info)
In vivo finger flexor tendon force while tapping on a keyswitch.
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Force may be a risk factor for musculoskeletal disorders of the upper extremity associated with typing and keying. However, the internal finger flexor tendon forces and their relationship to fingertip forces during rapid tapping on a keyswitch have not yet been measured in vivo. During the open carpal tunnel release surgery of five human subjects, a tendon-force transducer was inserted on the flexor digitorum superficialis of the long finger. During surgery, subjects tapped with the long finger on a computer keyswitch, instrumented with a keycap load cell. The average tendon maximum forces during a keystroke ranged from 8.3 to 16.6 N (mean = 12.9 N, SD = 3.3 N) for the subjects, four to seven times larger than the maximum forces observed at the fingertip. Tendon forces estimated from an isometric tendon-force model were only one to two times larger than tip force, significantly less than the observed tendon forces (p = 0.001). The force histories of the tendon during a keystroke were not proportional to fingertip force. First, the tendon-force histories did not contain the high-frequency fingertip force components observed as the tip impacts with the end of key travel. Instead, tendon tension during a keystroke continued to increase throughout the impact. Second, following the maximum keycap force, tendon tension during a keystroke decreased more slowly than fingertip force, remaining elevated approximately twice as long as the fingertip force. The prolonged elevation of tendon forces may be the result of residual eccentric muscle contraction or passive muscle forces, or both, which are additive to increasing extensor activity during the release phase of the keystroke. (+info)
Nonoccupational risk factors for carpal tunnel syndrome.
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OBJECTIVE: To examine the relation between selected nonoccupational risk factors and surgery for carpal tunnel syndrome. DESIGN: Case-control study using an administrative database. PARTICIPANTS: Enrollees of New Jersey Medicare or Medicaid programs during 1989 to 1991. MEASUREMENTS: The outcome of interest was open or endoscopic carpal tunnel release. We examined the relation between carpal tunnel release and diabetes mellitus, thyroid disease, inflammatory arthritis, hemodialysis, pregnancy, use of corticosteroids, and hormone replacement therapy. MAIN RESULTS: In multivariate models, inflammatory arthritis was strongly associated with carpal tunnel release (odds ratio [OR] 2.9; 95% confidence interval [CI] 2.2, 3.8). However, corticosteroid use also appeared to be associated with a greater likelihood of undergoing carpal tunnel release, even in the absence of inflammatory arthritis (OR 1.6; 95% CI 1.2, 2.1). Diabetes had a weak but significant association with carpal tunnel release (OR 1.4; 95% CI 1.2, 1.8), as did hypothyroidism (OR 1.7; 95% CI 1.1, 2.8), although patients with hyperthyroidism did not have any change in risk. Women who underwent carpal tunnel release were almost twice as likely to be users of estrogen replacement therapy as controls (OR 1.8; 95% CI 1.0, 3.2). CONCLUSIONS: Although inflammatory arthritis is the most important nonoccupational risk factor for carpal tunnel release, these data substantiate the increase in risk associated with diabetes and untreated hypothyroidism. Further investigation in detailed clinical studies will be necessary to confirm whether changes in corticosteroid use and hormone replacement therapy offer additional means of risk reduction for this common condition. (+info)
Conduction block in carpal tunnel syndrome.
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Wrist extension was performed in six healthy subjects to establish, first, whether it would be sufficient to produce conduction block and, secondly, whether the excitability changes associated with this manoeuvre are similar to those produced by focal nerve compression. During maintained wrist extension to 90 degrees, all subjects developed conduction block in cutaneous afferents distal to the wrist, with a marked reduction in amplitude of the maximal potential by >50%. This was associated with changes in axonal excitability at the wrist: a prolongation in latency, a decrease in supernormality and an increase in refractoriness. These changes indicate axonal depolarization. Similar studies were then performed in seven patients with carpal tunnel syndrome. The patients developed conduction block, again with evidence of axonal depolarization prior to block. Mild paraesthesiae were reported by all subjects (normals and patients) during wrist extension, and more intense paraesthesiae were reported following the release of wrist extension. In separate experiments, conduction block was produced by ischaemic compression, but its development could not be altered by hyperpolarizing currents. It is concluded that wrist extension produces a 'depolarization' block in both normal subjects and patients with carpal tunnel syndrome, much as occurs with ischaemic compression, but that this block cannot be altered merely by compensating for the axonal depolarization. It is argued that conduction slowing need not always be attributed to disturbed myelination, and that ischaemic compression may be sufficient to explain some of the intermittent symptoms and electrodiagnostic findings in patients with carpal tunnel syndrome, particularly when it is of mild or moderate severity. (+info)
Agreement between symptom surveys, physical examination procedures and electrodiagnostic findings for the carpal tunnel syndrome.
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OBJECTIVES: The goal of this study was to evaluate the concordance between various clinical screening procedures for carpal tunnel syndrome. METHODS: The subject population consisted of 824 workers from 6 facilities. The evaluated procedures included bilateral sensory nerve conduction testing, physical examinations, and symptom surveys, including hand diagrams. The agreement between the outcomes of various combinations of these procedures was assessed by determining the kappa coefficient. RESULTS: There was relatively poor overlap between the reported symptoms, the physical examination findings, and the electrodiagnostic results consistent with carpal tunnel syndrome. Overall, only 23 out of 449 subjects (5%) with at least 1 positive finding met all 3 criteria (symptoms, physical examination findings, and electrophysiological results consistent with carpal tunnel syndrome) for the dominant hand. The screening procedures showed poor or no agreement with kappa values ranging between 0.00 and 0.18 for all the case definitions evaluated for carpal tunnel syndrome. CONCLUSIONS: The poor overlap between the various screening procedures warns against the use of electrodiagnostic findings alone without the symptom presentation being considered. The results of this study also point to a need for the further development and evaluation of methods for detecting carpal tunnel syndrome. (+info)
Musculoskeletal manifestations in a population-based cohort of patients with giant cell arteritis.
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OBJECTIVE: To define musculoskeletal manifestations occurring in a population-based cohort of patients with giant cell (temporal) arteritis (GCA). METHODS: The records of 128 patients with GCA diagnosed over a 42-year-period (1950-1991) in Olmsted County, MN, were reviewed for the presence and type of musculoskeletal manifestations, their relationship to the onset and course of GCA, and their response to treatment. RESULTS: Fifty-three patients (41%) developed polymyalgia rheumatica: 23 before, 17 concurrently with, and 13 after the diagnosis of GCA. Thirty patients (23%) developed 1 or more peripheral musculoskeletal manifestations. These included peripheral synovitis in 23 patients (6 of whom fulfilled criteria for rheumatoid arthritis), distal extremity swelling with pitting edema in 13, distal swelling without pitting in 5, tenosynovitis in 6, and carpal tunnel syndrome in 2. Fifty-seven episodes of peripheral manifestations occurred in the 30 patients at different times during the course of GCA. In most, the onset of PMR and peripheral manifestations was within 2 years of the diagnosis of GCA. CONCLUSION: Musculoskeletal symptoms in GCA are common and varied. Most appear linked temporally to the underlying GCA, indicating that the nature of this illness and its clinical expression are broader than often considered. (+info)
Beta2-microglobulin and renal bone disease.
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Dialysis-related amyloidosis (DRA) is characterized by amyloid deposition mainly in bone and joint structures, presenting as carpal tunnel syndrome, destructive arthropathy, and subchondral bone erosions and cysts. Beta2-microglobulin has been demonstrated to be a major constituent of amyloid fibrils. DRA occurs not only in patients undergoing long-term hemodialysis, but also in patients undergoing continuous ambulatory peritoneal dialysis. The incidence of this complication increases with the duration of dialytic therapy and the age of the patient. While a definitive diagnosis of DRA can be made only by histological findings, various imaging techniques often support diagnosis. The molecular pathogenesis of this complication remains unknown. Recent studies have, however, suggested a pathogenic role of a new modification of beta2-microglobulin in amyloid fibrils--that is, the advanced glycation end-products (AGEs) formed with carbonyl compounds derived from autoxidation of both carbohydrates and lipids ("carbonyl stress"). Therapy for DRA is limited to symptomatic approaches and surgical removal of amyloid deposits. High-flux biocompatible dialysis membranes could be used to delay DRA development. (+info)
The wrist of the formula 1 driver.
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OBJECTIVES: During formula 1 driving, repetitive cumulative trauma may provoke nerve disorders such as nerve compression syndrome as well as osteoligament injuries. A study based on interrogatory and clinical examination of 22 drivers was carried out during the 1998 formula 1 World Championship in order to better define the type and frequency of these lesions. METHODS: The questions investigated nervous symptoms, such as paraesthesia and diminishment of sensitivity, and osteoligamentous symptoms, such as pain, specifying the localisation (ulnar side, dorsal aspect of the wrist, snuff box) and the effect of the wrist position on the intensity of the pain. Clinical examination was carried out bilaterally and symmetrically. RESULTS: Fourteen of the 22 drivers reported symptoms. One suffered cramp in his hands at the end of each race and one described a typical forearm effort compartment syndrome. Six drivers had effort "osteoligamentous" symptoms: three scapholunate pain; one medial hypercompression of the wrist; two sequellae of a distal radius fracture. Seven reported nerve disorders: two effort carpal tunnel syndromes; one typical carpal tunnel syndrome; one effort cubital tunnel syndrome; three paraesthesia in all fingers at the end of a race, without any objective signs. CONCLUSIONS: This appears to be the first report of upper extremity disorders in competition drivers. The use of a wrist pad to reduce the effects of vibration may help to prevent trauma to the wrist in formula 1 drivers. (+info)