Multifocal neural conduction impairment in forestry workers exposed and not exposed to vibration.

OBJECTIVE: The aim of the study was to assess peripheral neural involvement induced by exposure to hand-arm vibration. METHODS: Twenty lumberjacks, working regularly with chain-saws and exposed to hand-arm vibration (group E) and 20 forestry workers performing heavy manual work and not exposed to vibration (group NE) were matched with a control group of 20 healthy non-manual workers (group C). The subjects of groups E and NE, all symptomatic, and of group C underwent extensive bilateral neurophysiological examination consisting of: sensory conduction (velocity and amplitude) of radial, median and ulnar nerves in digit-wrist segments; sensory conduction (velocity) of median nerve in wrist-elbow segment; mixed conduction (velocity and amplitude) of median and ulnar nerves in palm-wrist segments; motor conduction velocity, including distal motor latencies, and amplitude of median (elbow-wrist) and ulnar (elbow-wrist and across the elbow) nerves. RESULTS: Electrophysiological abnormalities were found in 85% of group E's limbs, versus 62.5% of group NE's limbs. The most frequent pathological pattern in group E was a 'multifocal' impairment (multiple sites of several nerve segments), with a prevalent involvement of sensory rather than motor fibres in the hand, seldom extending to the forearm. Multivariate analysis showed that the neurographic parameters which better characterized workers exposed to hand-arm vibration had a pattern different from that usually found in idiopathic carpal tunnel syndrome (CTS). CONCLUSION: These results suggest that vibration-induced neural involvement can be considered neither pure digital neuropathy, nor definite CTS, as previously described.     

Natural history of median nerve sensory conduction in industry: Relationship to symptoms and carpal tunnel syndrome in 558 hands over 11 years

We evaluated the natural history of median nerve sensory conduction, hand/wrist symptoms, and carpal tunnel syndrome (CTS) in an 11-year longitudinal study of 289 workers from four industries. Twenty hands which had carpal tunnel release surgery were excluded, leaving 558 hands for the primary study group. Overall, the trend was for mean sensory latencies and prevalence of slowing to increase, the prevalence of symptoms to decrease, and the prevalence of CTS to remain unchanged. Among individual hands, nerve conduction abnormalities tended to persist (82% 11-year persistence), while symptoms fluctuated widely (13% 11-year persistence). There was a strong, direct linear correlation between initial severity of slowing and subsequent development of CTS; however, most workers who developed de novo slowing did not develop symptoms or CTS. We conclude that changes in conduction status of the median nerve occur naturally with increasing age and do not necessarily lead to symptoms and CTS. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:711–721, 1998.     

The median palmar cutaneous nerve in normal subjects and CTS.

OBJECTIVE: The neurophysiological confirmation of carpal tunnel syndrome (CTS) relies on detecting abnormal median nerve transcarpal conduction in the presence of unaffected comparator nerves. We compare the palmar cutaneous median branch (PCBm) with the ulnar sensory nerve conduction to digit 5 (US(5)) as comparator nerves for diagnosing CTS. METHODS: In a prospective case control study of patients with clinically defined carpal tunnel syndrome and normal subjects, we determined and compared the PCBm and US(5) conduction velocity. RESULTS: We examined 57 hands with clinically defined CTS and 59 control hands. Comparison showed highly significantly slowed PCBm conduction (p<0.0001) but not for US(5) conduction (p=0.488). Using a 3 percentile cut-off for abnormality derived from controls, PCBm conduction velocity was abnormal in 46% of CTS hands. CONCLUSIONS: The high frequency of PCBm nerve conduction abnormality in CTS suggests that this nerve should not be used as a comparator nerve for the neurophysiological diagnosis of CTS. This finding may help explain some of the extension of sensory symptoms outside the median nerve distribution in CTS. SIGNIFICANCE: In CTS frequent abnormality of PCBm conduction makes this a poor comparator nerve and may explain extension of sensory symptoms beyond the median nerve.     

A handheld nerve conduction measuring device in carpal tunnel syndrome

OBJECTIVES: The diagnostic utility and reliability of an easy-to-operate novel handheld nerve conduction tester in carpal tunnel syndrome (CTS) were evaluated. MATERIALS AND METHODS: Using the test device, the sensory nerve conductions (SNC) in the median and ulnar nerves were compared with each other in 194 patients with suspected CTS and 95 healthy controls. The test device results were compared with the results of nerve conduction studies (NCS) with traditional instrumentation. RESULTS: The new device correctly classified 145 of the 149 hands (97.3%) without median nerve lesion and 171 of the 200 hands (85.5%) with median nerve lesions in traditional NCS. The specificity of the new tester compared with traditional instrumentation was 98%. The correlation coefficient for different technicians in different studies was 0.87. CONCLUSIONS: The findings obtained with the new tester in CTS were reliable and reproducible. This tester may increase availability of NCS in CTS.     

A useful electrophysiologic parameter for diagnosis of carpal tunnel syndrome

In 43 patients (50 hands) with clinical manifestations of mild-moderate carpal tunnel syndrome (CTS) and 36 healthy volunteers (40 hands), orthodromic sensory nerve conduction velocity (SNCV) was measured with surface electrodes in the median nerve between the third digit and palm and between the palm and wrist. These figures were used to calculate the ratio of distal to proximal conduction (distoproximal ratio). All 90 hands were also subjected to other nerve conduction studies used for diagnosis of CTS. All control hands presented distoproximal ratios <1.0, reflecting higher conduction rates in the proximal segment. In contrast, 49 of 50 CTS hands (98%) presented reversed ratios (>1.0) indicating compromised proximal conduction. The sensitivity of this test was significantly greater than that of other methods evaluated, including comparative studies and segmental study of the palm-wrist portion of the median nerve. Segmental study of median SNCV with calculation of the distoproximal ratio is a sensitive technique for diagnosis of CTS in patients with normal findings in standard nerve conduction studies. © 1996 John Wiley & Sons, Inc.     

Predictive value of nerve conduction measurements at the carpal tunnel

We compared the predictive values of three measurements of sensory conduction of the median nerve at the carpal tunnel (maximum latency difference [MLD], 8-cm latency [S8], and 14-cm latency [S14]) in 2334 hands of industrial workers, workers' compensation patients, and students, The MLD was determined by the centimetric technique. The MLD was the most sensitive and efficient measurement for predicting carpal tunnel syndrome (CTS). An MLD ≥ 0.40 ms correctly identified 86.3% of 753 hands with CTS. The MLD correlated best with CTS and with the primary diagnostic category (CAT). MLD was the second factor selected in stepwise regression analysis for CAT (numbness was first and S8 was third). The MLD was the most important factor for predicting persistent or de novo CTS in a 5-year follow-up of 630 hands. Thus, the MLD was the most reliable nerve conduction study measurement for predicting current or future CTS in these subjects' hands.     

Anomalies of ulnar nerve conduction in different carpal tunnel syndrome stages

Impairment of ulnar sensory fibers at the wrist has recently been documented in moderate/severe carpal tunnel syndrome (CTS). This has been interpreted as a consequence of compressive forces transmitted to Guyon's canal by high pressure in the carpal tunnel or comorbidity between ulnar neuropathy and CTS. The main aim of the present study was to identify any ulnar nerve conduction impairment in the early stages of CTS. The relation between ulnar and median nerve conduction in all CTS severity stages was also assessed. Ulnar nerve sensory conduction at the wrist was investigated in 580 hands with CTS. Significant changes in ulnar nerve conduction were present even in the early stages of CTS. A significant, positive correlation was also found between CTS severity and conduction abnormalities of ulnar sensory fibers. These findings make the hypothesis of comorbidity weak. Based on the above results and on reports of high pressure in Guyon's canal in CTS, ulnar nerve conduction abnormalities may be caused in part by compressive forces progressively transmitted to the canal by increasing pressure in the carpal tunnel with increasing CTS severity. This does not exclude other causative factors such as subclinical traumatic damage acting on median and ulnar fibers.     

Electrophysiological studies in mild idiopathic carpal tunnel syndrome

Many techniques have been reported to improve the diagnosis of carpal tunnel syndrome (CTS), but there is no agreement on the diagnostic yield of these different methods. We used an electrophysiological protocol including the assessment of the orthodromic sensory conduction velocity of the median nerve along the carpal tunnel, comparison of median and ulnar sensory conduction between the ring finger and wrist, short segment incremental median sensory nerve conduction across the carpal tunnel recording from the III digit ('inching test'), the study of the refractory period of transmission (RPT) and calculation of the distoproximal ratio obtained by dividing the nerve conduction velocity in the median nerve between the third digit and the palm and between the palm and wrist in 41 patients with mild CTS (75 symptomatic hands) and in 45 control subjects. The distoproximal ratio calculation was the most sensitive technique (81%), but was also the least specific. The 'inching test', even though less sensitive, had the advantage of localising focal abnormalities of the median nerve along the carpal tunnel. RPT was abnormal in patients with recent symptoms. Combining the different techniques, an overall sensitivity of 92% was reached, 11% higher than the yield of the single best test suggesting that a multimodal approach could be useful. The best procedure for electrodiagnosis of mild CTS was to combine the median/ulnar comparison test with calculation of the disto-proximal ratio.     

The role of forearm mixed nerve conduction study in the evaluation of proximal conduction slowing in carpal tunnel syndrome

ObjectiveA decrease of forearm median motor conduction velocity (CV) is a common electrophysiological finding in carpal tunnel syndrome (CTS), ascribed to two possible mechanisms: either conduction block or slowing of the fastest myelinating fibers in the carpal tunnel, or retrograde axonal atrophy (RAA) with retrograde conduction slowing (RCS). We hope to utilize both direct and derived forearm median mixed nerve conduction studies to clarify the mechanism of the decrease of forearm median motor CV in CTS.MethodsSeventy-five CTS patients and 75 age-matched control subjects received conventional motor and sensory nerve conduction studies of median and ulnar nerves and forearm median mixed nerve conduction techniques. First, direct measurement of forearm median mixed conduction velocity (Forearm mixed CV) and nerve action potential amplitude (Forearm mixed amplitude) was determined with recording at elbow and stimulation at wrist. Then, stimulating electrode was placed over palm and recording at elbow and then at wrist to calculate the derived Forearm mixed CV. Electrophysiological parameters, including direct Forearm mixed CV and amplitude and derived Forearm mixed CV, were compared between CTS patients and controls.ResultsCTS patients had significantly prolonged wrist–palm sensory and motor conduction, significantly decreased forearm median motor CV, and normal ulnar nerve conduction. The direct Forearm mixed amplitude was significantly decreased in CTS patients. The direct Forearm mixed CV was similar in CTS patients and controls, but there was a significant decrease in derived Forearm mixed CV in CTS group. The difference between direct and derived Forearm mixed CV was significantly greater in the CTS, suggesting that direct and derived Forearm mixed CV represent CV from different nerve fibers, one passing outside carpal tunnel without undergoing RAA or the other through the carpal tunnel with occurrence of RAA.ConclusionA decrease of direct Forearm mixed amplitude really occurs in CTS, implying that RAA and RCS will develop over proximal median nerve at distal nerve injury and the decreased forearm median motor CV is best ascribed to RAA and RCS. Furthermore, in CTS, the direct Forearm mixed CV measures the CV from undamaged nerve fibers without passing through carpal tunnel, resulting in the misinterpretation of the cause of proximal conduction slowing secondary to conduction block or slowing over the wrist.SignificanceWe provide a direct evidence of the occurrence of RAA and RCS that would explain the cause of proximal median nerve conduction slowing. However, the clinical significance of RAA and RCS is uncertain.     

Does forearm mixed nerve conduction velocity reflect retrograde changes in carpal tunnel syndrome?

The mixed nerve conduction velocity of the median nerve in the forearm diverged from the motor and sensory nerve conduction velocities and correlated poorly with the severity of carpal tunnel syndrome (CTS) in 61 hands. In contrast, the motor and sensory nerve conduction velocities in the forearm correlated well with CTS severity. The mixed nerve conduction velocity in the forearm is probably determined by nonlesioned fibers such as those from the cutaneous palmar branch of the median nerve. The motor and sensory, but not the mixed nerve conduction velocities in the forearm may be used to estimate possible retrograde impairment in CTS. © 1994 John Wiley & Sons, Inc.     

The serial use of two provocative tests in the clinical diagnosis of carpal tunnel syndrome

Objectives - 1) To examine the diagnostic value of the newly proposed manual carpal compression test (mCCT). 2) To evaluate the test efficacy of a serial use of mCCT and Phalen's test (PT) in the clinical diagnosis of carpal tunnel syndrome (CTS) in comparison with standard nerve conduction studies. Materials and methods - Prospective, controlled study of 47 patients with 63 symptomatic CTS hands according to clinical as well as electrophysiological criteria. In the control group, 39 hands of 20 healthy volunteers were examined. Clinical neurological examination including mCCT and PT and standard nerve conduction studies were always performed: sensory nerve conduction velocity third and fifth digit to wrist, median distal motor latency. Calculation of sensitivity, specificity, positive and negative predictive value for the mCCT, PT and mCCT + PT, i.e. at least one of both tests positive after sequential application. Results - Sensitivity 83% for mCCT, 79% for PT and 92% for mCCT + PT. Specificity 92% for all three conditions. Excellent positive predictive value of 95% and good negative predictive value of 88% for mCCT + PT. Conclusion - The serial application of mCCT and PT is very useful in the clinical diagnosis of CTS. This finding facilitates the clinical diagnosis by the primary physician, it helps to improve referral decisions to electrophysiological departments and other ancillary examinations and may reduce costs.     

Al-hijamah (wet cupping therapy of prophetic medicine) as a novel alternative to surgery for carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common neuropathy of median nerve causing decreased physical and work performance. Herein, a 37-year-old male manual worker diagnosed with severe CTS exhibited severe pain with frequent awakening from night sleep to put hands in ice. Patient’s consent and ethical guidelines were carried out. As a novel approach, Al-hijamah was performed to both hands at the anterior and posterior carpal regions (using scarification safety technique) and at the back region. Immediately after Al-hijamah, a dramatic decrease in pain, numbness and parathesia occurred. Nerve conduction velocity and electromyography carried out few days after Al-hijamah confirmed improved voluntary motor unit morphologies in both hands. The severe degree of bilateral CTS improved electrophysiologically to be moderate. Scheduled surgical intervention was cancelled. This did better than a German report treating CTS using traditional Chinese wet cupping therapy at the trapezius muscle without applying sucking cups at the carpal region.

Carpal tunnel syndrome is the most common neuropathy affecting the median nerve (causing approximately 90% of all neuropathies). Carpal tunnel syndrome incidence may reach approximately 3.8% among the general population with females more affected than males.1 Carpal tunnel syndrome is a significant cause of morbidity manifested as decreased physical capabilities, decreased work performance and decreased financial outcomes due to decreased employment productivity particularly in manual workers.2-4 Dentists, dental hygienists and dental assistants, soldiers, laboratory workers, and secretaries are some of those at risk due to their occupation.5 In this report, Al-hijamah (Arabic wet cupping therapy) is investigated as a promising novel treatment for CTS.     

拇指感觉神经传导速度诊断轻度腕管综合征的临床应用价值

目的:探讨拇指感觉神经传导速度(sensory nerve conduction velocity,SCV)诊断轻度腕管综合征的临床应用价值。方法:对18例(26只手)轻度腕管综合征的患者和15例(30只手)年龄性别相匹配的正常人,测定了腕部正中神经和桡神经的感觉神经传导速度,并进行对比研究。结果:中指正中神经SCV的异常率为50%,腕部正中神经/桡神经(刺激拇指)SCV差值的异常率为84.6%,明显大于用常规检查方法组(刺激中指),有8例12只手腕部正中神经感觉动作电位(刺激拇指)中出现双峰电位,而对照组则无。结论:在腕管综合征肌电图的诊断中,比较正中神经和桡神经SCV的差值是早期诊断腕管综合征的敏感指标之一。     

Postoperative relieve of abnormal vasoregulation in carpal tunnel syndrome

OBJECTIVE: To study the skin temperature changes as a sign of altered blood flow regulation due to abnormal sympathetic nerve function in carpal tunnel syndrome (CTS) and the efficacy of carpal tunnel release (CTR) operation in the alleviation of those signs and other symptoms of CTS. SUBJECTS AND METHODS: Forty-one healthy hands (n=41) of 22 volunteers and 22 hands (n=22) with clinically diagnosed carpal tunnel syndrome of 16 patients were examined. A series of infrared photos of the hands of each subject were taken and stored by using digital infrared thermography (DIRT) before and 6 months after the CTR. The temperatures of the finger tips from digit 1 (D1) to digit 5 (D5), the center point of thenar (Th) and hypothenar (Ht) eminences were measured, the median nerve index (MI=(D1-D2)+(D1-D3)+(D2-D3)) and the temperature differences between the median and the ulnar nerve distribution area (MED.ULN=(D1-D5)+(D2-D5)+(D3-D5)+(Th-Ht)) were calculated. Absolute values were used when calculating the temperature differences between different points. RESULTS: All the CTS patients were released from the CTS symptoms, i.e. numbness and pain after the operation, and the results of nerve conduction studies (NCS) were all back to normal. The MI and MED.ULN in CTS hands were significantly smaller before CTR compared to those of healthy control subjects (MI: p<0.001, MED.ULN: p<0.005), and those after CTR (p<0.005 for both parameters). The results also showed that all finger tips of the affected hand including those innervated by the ulnar nerve were cooler before but warmer after the operation. Before the operation, the non-CTS hands of the CTS patients, were also colder (although the difference was not significant) than the healthy control subjects but approached the same level after the CTR operation of the CTS hands. CONCLUSION: The results of DIRT measurements suggest that the blood flow regulation in CTS is abnormal possibly because of disturbed sympathetic vasomotor regulation and that the circulation gets normal together with the alleviation of the other symptoms of CTS as recorded 6 months after CTR operation.     

Comparison of median and radial nerve sensory latencies in the electrophysiological diagnosis of carpal tunnel syndrome

An electrophysiological diagnosis of carpal tunnel syndrome (CTS) was made on the basis of the median sensory nerve action potential (SNAP) alone in 79 of 161 (49.1%) symptomatic hands without electrophysiological evidence of a generalised peripheral neuropathy. Comparison of distal sensory latencies (DSLs) for the median and radial nerves yielded abnormal results in 17 of the remaining hands with normal median nerve DSLs, increasing the electrodiagnostic yield to 59.6%. Carpal tunnel decompression has been performed in seven of these hands, with abnormal intraoperative findings reported in two, while all improved clinically following surgery, substantiating the diagnosis of CTS. Although the technique described here would not appear to increase the electrodiagnostic yield more than comparison of DSLs for the median and ulnar nerves, which has been reported previously, it remains an effective, quick and simple procedure for increasing the sensitivity of the nerve conduction studies.     

Relationship of age and sex to sensory conduction of the median nerve at the carpal tunnel and association of slowed conduction with symptoms

A cross-sectional study of 471 randomly selected employees from 4 industries was performed to assess the prevalence of slowing of sensory conduction of the median nerve at the carpal tunnel as well as the effect of age and sex on slowing. The association between slowed conduction and symptoms of carpal tunnel syndrome (CTS) was also evaluated. Slowing was identified in 17% of the subjects and in 11% of the hands. The prevalence and the severity of slowing increased with increasing age of the subjects. Slowed conduction occurred more often among the women in the study, but this was shown to be an effect of age and not of sex. Slowing occurred six times more often in hands with symptoms of CTS than in those not reporting symptoms.     

Quantitative MRI of the wrist and nerve conduction studies in patients with idiopathic carpal tunnel syndrome

OBJECTIVE: To correlate morphological findings of idiopathic carpal tunnel syndrome (CTS) with the function of the median nerve. METHODS: In this study, 105 wrists of 105 women patients with idiopathic CTS, and 36 wrists of 36 female volunteers were subjected to nerve conduction studies and MRI. Cross sectional area, signal intensity ratio, and the flattening ratio of the median nerve, carpal tunnel area, flexor tendon area, synovial area, and intersynovial space, and the palmar bowing of the transverse carpal ligament (TCL) were quantified by MRI and correlated with the severity of the disease determined by nerve conduction studies. RESULTS: Cross sectional areas of the median nerve, flexor tendons, and carpal tunnel, and the palmar bowing of the TCL of the CTS groups were greater than in the control group, but differences were not detected among the CTS groups for the area of the flexor tendons and the carpal tunnel. Enlargement, flattening, and high signal intensity of the median nerve at the distal radioulnar joint level were more significant in the advanced than in the earlier stages of the disease. Increase in palmar bowing of the TCL was less prominent in the most advanced group. Linear correlation between the area of the carpal tunnel and palmar bowing of the TCL was noted. CONCLUSION: Severity of the disease could be judged by evaluating not only longitudinal changes of signal intensity and configuration of the median nerve, but also palmar bowing of the TCL. Increased palmar bowing of the TCL was found to be associated with an increase in the area of the carpal tunnel.     

Correlation between two-point discrimination and median nerve sensory response.

Static two-point discrimination (2PD) has been relied upon clinically to gauge the extent of median neuropathy in patients with carpal tunnel syndrome (CTS). Correlation with median nerve sensory conduction findings has not been well-established. We determined the median sensory nerve action potential parameters from the first and third digits of 83 hands referred primarily for suspected CTS. These results were compared to 2PD carried out in a standardized fashion by a group of hand surgeons. A lack of correlation was found in most electrodiagnostic parameters, with the exception of peak and onset latencies to the thumb; on further analysis, 2PD to the thumb was found to be useful if abnormal, but contributed nothing if negative. We conclude that static 2PD results may correlate with latency, but do not overall adequately predict the findings on sensory nerve conduction examination of the median nerve.     

环指感觉神经感觉传导速度在轻度腕管综合征诊断中的应用

目的 寻找诊断轻度腕管综合征(CTS)敏感的电生理检查方法。方法 临床症状、体征符合CTS,正中神经运动末端潜伏期正常的患者19例(29侧)和年龄性别相匹配的健康对照组23名(25侧),采用顺向性感觉神经传导速度(SCV)测定法分别测定环指(指4)正中神经和尺神经SCV,中指(指3)正中神经SCV。结果 环指尺神经SCV>45.2 m/s,正中神经SCV<44.1 m/s,和(或)尺神经SCV与正中神经SCV差值>8.1 m/s(x+σx),考虑符合CTS诊断。CTS组中指正中神经SCV测定异常率为66％,环指为76％,环指正中神经与尺神经SCV差值异常率为93％。环指刺激在8例(14侧)患者腕部正中神经处记录到双峰电位,但对照组均未见。结论 比较环指正中神经和尺神经SCV在鉴别轻度CTS方面是敏感的方法之一,在怀疑CTS时,该项检查可作为常规的电生理检查方法。     

Ulnar nerve conduction abnormalities in carpal tunnel syndrome

Introduction: The aim of this study was to verify the involvement of ulnar nerve fibers in cases of carpal tunnel syndrome (CTS) and investigate the correlation between ulnar nerve conduction parameters and extra‐median spread of symptoms. Methods: Electrophysiological studies were conducted in 93 CTS and 76 control hands. Patients were analyzed with regard to symptoms in the fifth finger. Results: In the CTS cases, ulnar distal motor latency (DML) and distal sensory latency (DSL) were significantly longer, and amplitudes were lower than in controls. Increased median nerve DML correlated with increased ulnar nerve DSL and decreased sensory amplitudes and conduction velocities (SCVs). In cases with symptoms in the fifth finger, ulnar nerve SCVs and amplitudes were lower than in patients without symptoms. Conclusions: Pathological processes leading to median neuropathy in CTS may affect ulnar nerve motor and sensory fibers in the Guyon canal. This may explain the extra‐median spread of sensory symptoms in CTS patients. Muscle Nerve 44: 352–357, 2011