Electrodiagnosis of Carpal Tunnel Syndrome: Which Transcarpal Conduction Technique Is Best?

Comparison of the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome

OBJECTIVES

This study aimed to compare the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome.

METHODS

The study recruited the electromyography results of 105 hands of 60 patients who had a complaint of carpal tunnel syndrome (CTS) on the hand diagram. The average sensory-ulnar motor delay difference (MSUMLD) was determined by simple subtraction, and the modified method was calculated based on the results of the classic method. The modified method and the MSUMLD were compared according to their sensitivity and specificity in the diagnosis of CTS.

RESULTS

In this study, 54 hands were evaluated with a unilateral nerve conduction study (45 right; 9 left). A total of 23 hands with CTS and 31 hands without CTS were diagnosed electrophysiologically. The MSUMLD had 91.3% sensitivity and 93.5% specificity; however, the modified method showed 95.7% sensitivity and 96.8% specificity in the diagnosis of CTS. Moreover, the modified method had 100% sensitivity and specificity in the diagnosis of moderate CTS.

CONCLUSIONS

The modified method may have higher diagnostic accuracy than the MSUMLD for diagnosing CTS.

The Sensitivity and Specificity of Nerve Conduction Studies for Diagnosis of Carpal Tunnel Syndrome: A Systematic Review

Background: The utility of nerve conduction studies (NCS) for diagnosis of carpal tunnel syndrome (CTS) has continued to be a subject of debate. Proponents of NCS assume a high sensitivity and specificity; however, many are unaware of the actual literature on this topic and the cutoff values commonly used for diagnosis. The purpose of this systematic review of the literature is to report the sensitivity and specificity of NCS for diagnosis of CTS in various studies. Methods: A literature review of PubMed and EMBASE databases was performed for all articles on NCS for diagnosis of CTS. The outcome of interest was the sensitivity and/or specificity of the NCS distal motor latency (DML) or distal sensory latency (DSL) cutoff value used to diagnose CTS in each study. Results: A total of 3066 total articles were screened and 21 were included in the review after assessment by two independent reviewers. The mean cut-off value for DSL was 3.37 ms (range 2.8-4 ms) and the mean cutoff value for DML was 4.28 ms (range 3.8-4.6 ms). Weighted mean DSL sensitivity was 73.4% and weighted mean DSL specificity was 93.6%. Weighted mean DML sensitivity was 56.2% and weighted mean DML specificity was 95.8%. Conclusions: There is significant variation in the cutoff values used for both DSL and DML. The wide range of cut-off values makes it difficult to interpret the literature, and there is a lack of high-quality studies with control groups using a priori cut-off values for diagnosis.

Role of concentric needle Single Fiber Electromyography in detection of subclinical motor involvement in carpal tunnel syndrome

Background

Conventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS). Single-fiber electromyography (SFEMG) measures the mean consecutive difference (MCD) as an expression of the variability in impulse transmission over the motor endplates and along the nerve fibers distally to the last branching point and along the muscle fibers.

Application of concentric needle SFEMG in a group of CTS patients who showed pure sensory abnormalities in nerve conduction studies to examine for subclinical motor involvement.

Methods

Thirty CTS patients having only sensory involvement proved clinically and by conventional electrophysiological studies were included in addition to 30 control subjects. Concentric needle SFEMG was performed to the abductor pollicis brevis (APB), abductor digiti minimi (ADM), and extensor digitorum communis (EDC) muscles.

Results

There was a statistically significant difference in the MCD between the patient and control groups in the APB only (p = 0.038).

Conclusions

The results suggest the presence of a subclinical motor median neuropathy at the wrist in patients with early and mild carpal tunnel syndrome and highlight the validity of the concentric needle SFEMG in early neuropathies.

Trial registration

PACTR201802002971380 registered 12 February 2018, retrospectively registered.

Low sensitivity of F-wave in the electrodiagnosis of carpal tunnel syndrome

OBJECTIVE

Previous studies showed "F-wave inversion" (F-INV) as a sensitive method in the electrodiagnosis of early stage of carpal tunnel syndrome (CTS). This study aimed at evaluating the sensitivity and specificity of F-wave and nerve conduction velocity (NCV) testing in CTS.

METHODS

We consecutively enrolled 244 cases and 108 controls. F-waves analysis included: Fwave minimum and mean latencies, F-wave persistence and chronodispersion, mean-F/CMAP amplitude ratio, F-INV. Specificity and sensitivity of F-waves parameters were calculated in the whole sample of CTS patients and by grouping the patients according to CTS severity. Multivariate logistic regression was also performed using F-INV as a dependent variable.

RESULTS

In the whole sample the sensitivity of F-mean-INV and of median-ulnar NCV comparative testing was 50.8% and 93.7%, respectively. F-INV sensitivity dropped to 8% in CTS early stage. F-INV could be predicted only by distal motor latency of the median nerve. The sensitivity of all F-wave parameters increased only in the most severe stages of CTS.

CONCLUSIONS

This study does not confirm the electrodiagnostic usefulness of F-INV in early stage of CTS. All F-wave parameters, including F-INV, are much less sensitive than conventional NCV in CTS electrodiagnosis. F-wave does not add further useful information specifically related to CTS.

[The arteriovenous fistula is an additional risk factor for developing carpal tunnel syndrome in hemodialysis patients]

INTRODUCTION

Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy reported in patients with renal failure undergoing periodic haemodialysis. The role of arteriovenous fistula was discussed. The aim of this study was to investigate this relationship.

METHODS

Subjects for this study were hemodialysis patients who underwent systematic electroneuromyography between January 2003 and December 2010. Only patients with unilateral fistulae were included for the study.

RESULTS

One hundred and thirty-four out of 155 patients were examined. CTS was noted in 106 patients and was detectable only in ENMG in 42% of cases. It was more frequent (P<0.001) and more severe in the side of fistulae (P=0.08). Besides, development of CTS was only correlated with the longer duration of dialysis (P=0.005). This duration was significantly shorter in patients with CTS and diabetes.

CONCLUSION

The positive correlation between CTS and aretriovenous fistulae confirms the pathogenic role of this latter. The risk rises in these patients with the duration of hemodialysis and the presence of diabetes.

A study of interpolation method in diagnosis of carpal tunnel syndrome

Context:

The low correlation between the patients’ signs and symptoms of carpal tunnel syndrome (CTS) and results of electrodiagnostic tests makes the diagnosis challenging in mild cases. Interpolation is a mathematical method for finding median nerve conduction velocity (NCV) exactly at carpal tunnel site. Therefore, it may be helpful in diagnosis of CTS in patients with equivocal test results.

Aim:

The aim of this study is to evaluate interpolation method as a CTS diagnostic test.

Settings and Design:

Patients with two or more clinical symptoms and signs of CTS in a median nerve territory with 3.5 ms ≤ distal median sensory latency <4.6 ms from those who came to our electrodiagnostic clinics and also, age matched healthy control subjects were recruited in the study.

Materials and Methods:

Median compound motor action potential and median sensory nerve action potential latencies were measured by a MEDLEC SYNERGY VIASIS electromyography and conduction velocities were calculated by both routine method and interpolation technique.

Statistical Analysis Used:

Chi-square and Student's t-test were used for comparing group differences. Cut-off points were calculated using receiver operating characteristic curve.

Results:

A sensitivity of 88%, specificity of 67%, positive predictive value (PPV) and negative predictive value (NPV) of 70.8% and 84.7% were obtained for median motor NCV and a sensitivity of 98.3%, specificity of 91.7%, PPV and NPV of 91.9% and 98.2% were obtained for median sensory NCV with interpolation technique.

Conclusions:

Median motor interpolation method is a good technique, but it has less sensitivity and specificity than median sensory interpolation method.

Ultrasonography in the diagnosis of peripheral nerve disease

INTRODUCTION

High-resolution ultrasound (US) of the peripheral nerves is now a standard means of assessing neuromuscular disorders in many centers. Currently used in conjunction with electrodiagnostic (EDX) studies, nerve US is especially effective in the diagnosis of entrapment neuropathies.

AREAS COVERED

This article reviews the basic physics of peripheral nerve US, guidelines for its current use and future directions. Advantages of using nerve US alongside EDX studies are outlined along with current limitations of testing. The role of US in the diagnosis of entrapment neuropathy is emphasized, particularly in carpal tunnel syndrome (CTS). US assisted diagnosis of peripheral nerve tumors, hereditary neuropathy and dysimmune neuropathy and traumatic injuries is also described.

EXPERT OPINION

US is a powerful tool in the assessment of peripheral nerve disease. Nerve US is an evolving, young discipline. There is still much to learn, but current evidence supports US imaging of all patients presenting for evaluation of possible mononeuropathy. With improvements in resolution, the introduction of US contrast agents and objective measures of nerve echogenicity, there is promise for further expanding its role in the diagnosis of all peripheral neuropathies.

How to make electrodiagnosis of carpal tunnel syndrome with normal distal conductions?

The purpose of this study is to investigate which electrodiagnostic techniques are better in clinically diagnosed patients with carpal tunnel syndrome (CTS) and patients with CTS with normal distal conduction study. A total of 230 clinically diagnosed patients with CTS and 100 normal control subjects were enrolled. All subjects were evaluated by eight electrodiagnostic techniques, including conventional conduction studies: median distal sensory latency and distal motor latency; short distance conduction studies across wrist, including wrist-palm sensory conduction time and wrist-palm motor conduction velocity; comparison of median sensory conduction across the wrist with radial or ulnar nerves in the same limb (median-radial sensory latency difference [M-R] or median-ulnar sensory latency difference [M-U]); and comparison of median wrist-palm and palm-index conduction, including distoproximal conduction time difference and distoproximal conduction time ratio. Normal limits were derived by calculating the mean ± 2 standard deviations from the data of the controls. The sensitivity, specificity, positive predictive value, negative predictive value, and the area under the receiver operating characteristic curve with 95% confidence interval of each test were calculated. In clinically diagnosed patients with CTS, M-R is the best diagnostic technique with significant difference in area under the receiver operating characteristic curve (0.912) compared with other tests except that of M-U. The sensitivity, specificity, positive predictive value, and negative predictive value of M-R were 84.3%, 98%, 99%, and 73.1%, respectively. Further evaluation of patients with CTS with normal distal latencies also revealed the best diagnostic value of M-R and M-U with significance to other tests in area under the receiver operating characteristic curve. In clinical practice, after conventional median distal sensory latency and distal motor latency studies, the authors suggest performing M-R or M-U studies instead of segmental conduction or comparative studies of median nerves in the patients with CTS with normal distal latencies.