Sensitivity of three median-to-ulnar comparative tests in diagnosis of mild carpal tunnel syndrome

Neuropathy 10-15 years after Roux-en-Y gastric bypass for severe obesity: A community-controlled nerve conduction study

Objective

We searched for long-term peripheral nerve complications 10-15 years after Roux-en-Y gastric bypass surgery (RYGB), using a comprehensive nerve conduction study (NCS) protocol.

Methods

Patients (n = 175, mean age 52.0, BMI 35.2) and 86 community-controls (mean age 56.8, BMI 27.2) had NCS of one upper and lower limb. New abnormality scores from 27 polyneuropathy-relevant (PNP27s) and four carpal tunnel syndrome-relevant NCS-measures (CTS4s) were compared between groups with non-parametric statistics. Estimated prevalences were compared by 95 % confidence limits. The clinical neurophysiologist's diagnosis was retrieved from hospital records (PNP-ncs, CTS-ncs, other).

Results

Abnormality score did not differ between RYGB and control groups (PNP27s: 1.9 vs 1.7, CTS4s: 0.7 vs 0.6, p > 0.29). BMI correlated weakly with CTS4s in patients (rho = 0.19, p = 0.01), and less with PNP27s (rho = 0.12, p = 0.12). Polyneuropathy (PNP-ncs) prevalence was 12 % in patients and 8 % in controls. CTS-ncs prevalence was 21 % in patients and 10 % in controls (p = 0.04).

Conclusions

NCS-based abnormality scores did not differ between patients 10-15 years after RYGB and community-recruited controls, neither for PNP nor CTS.

Significance

Long-term polyneuropathic complications from RYGB have probably been avoided by modern treatment guidelines. NCS-diagnosed CTS is common in overweight RYGB patients. RYGB-patients with significant neuropathic symptoms need clinical evaluation.

Liverpool carpal tunnel scoring system to predict nerve conduction study results: A prospective correlation study

BACKGROUND

Carpal tunnel syndrome (CTS) is one of the most common peripheral nerve compressive neuropathies. The clinical symptoms and physical examinations of CTS are widely recognised, however, there is still debate around what is the best approach for assessment of CTS. Clinical assessment is still considered the gold standard, however, controversies do exist regarding the need for investigations such nerve conduction studies (NCS) to aid with management decisions.

AIM

To correlate the severity of NCS results to a scoring system which included symptoms, signs and risk factors.

METHODS

This was a prospective correlation study. We scored patients’ signs and symptoms using our CTS scoring system. This was then correlated with the findings of the NCS. The scoring system included - four symptoms (2 Katz hand diagrams – one for tingling and one for numbness; nocturnal paresthesia and bilateral symptoms) and four clinical signs (weak thumb abduction test; Tinel’s sign; Phalen sign and hypoalgesia in median nerve territory) and two risk factors (age more than 40 years and female sex). We classified the NCS results to normal, mild, moderate and severe.

RESULTS

There were 61 scores in 59 patients. The mean scores for the categories were as follows: 6.75 for normal NCS; 5.50 for mild NCS; 9.17 for moderate NCS and 9 for severe NCS. All scores of 8 or more matched with NCS results of moderate and severe intensity apart from three scores which were greater than seven that had normal NCS. Eta score was 0.822 for the CTS score being the dependent value and the NCS category being the independent variable showing a strong association between the scoring system and the NCS group.

CONCLUSION

We feel that this simple scoring system can be used to predict and correlate the severity of NCS in patients with CTS.

Prolonged median distal sensory nerve action potential duration in carpal tunnel syndrome

OBJECTIVE

Routine nerve conduction study (NCS) parameters are less sensitive in the early stage of carpal tunnel syndrome (CTS). Recently, some studies have shown that prolonged distal sensory nerve action potential (DSNAP) duration may be a more sensitive technique for the diagnosis of demyelinating peripheral neuropathies. We aimed to evaluate the sensitivity of median DSNAP duration in patients with CTS.

METHODS

DSNAP duration and routine NCS data of the median nerve were retrospectively collected in 173 CTS patients, 73 controls, and 78 cervical radiculopathy patients.

RESULTS

Prolonged median DSNAP durations were found in 22 patients (22/35, 63%) and 36 patients (36/54, 67%) in the minimal and mild CTS groups respectively, which was more sensitive than routine NCS parameters. The percentage of patients demonstrating abnormalities in median NCS was significantly increased from 80% to 92% with the addition of DSNAP duration.

CONCLUSION

Our results demonstrate the electrodiagnostic value of median DSNAP duration for the diagnosis of CTS, especially in early cases.

Role of Biomechanical Factors in Resolution of Carpal Tunnel Syndrome Among a Population of Workers

OBJECTIVES

Identify if Carpal tunnel syndrome (CTS) symptoms vary by measured biomechanical exposures.

METHODS

A nested prospective cohort within a large, multicenter, 8-year cohort study. The CTS case definition was tingling/numbness in 2+ median nerve-served digits plus a nerve conduction study consistent with CTS. Workers were assigned to: (1) low (strain index [SI] less than or equal to 6.1), and (2) high (SI more than 6.1) job groups.

RESULTS

Among 1201 workers, 106 had CTS. Those in the high SI group became and remained symptom-free for at least 3 months, faster than the low SI group, adjusted hazard ratio (HR) = 2.07 (95% confidence interval [CI] = 1.21 to 3.56, P = 0.008). Only surgical release trended towards resolving CTS. Light duty had no impact, and job change was associated with delayed symptoms resolution.

CONCLUSIONS

High biomechanical exposures paradoxically predicted faster improvement in CTS and light duty did not result in symptom resolution.

A new method to define cutoff values in nerve conduction studies for carpal tunnel syndrome considering the presence of false-positive cases

BACKGROUND

Nerve conduction studies (NCS) are useful tools for diagnosing carpal tunnel syndrome (CTS). Establishing the normal values is the first step required for utilizing NCS for diagnosis. Previous epidemiological studies demonstrated the presence of fairly large number of false-positive subjects regarding NCS among control population, which has not been properly considered in past studies. This study proposed a new method to address this issue.

METHODS

Non-diabetic 144 CTS patients were retrospectively enrolled using clinically defined inclusion criteria. Controls consisted of 73 age-matched volunteers without hand symptoms. Six NCS parameters were evaluated including peak-latency difference by the thumb method (thumbdif) and that by the ring-finger method (ringdif). The Youden index of the receiver operator characteristic curve was used both to judge the sensitivity of a parameter and to identify false-positive cases that were thought to have subclinical median neuropathy at the wrist. The linear function of six parameters was constructed, and the coefficient for each parameter was variously changed.

RESULTS

When the Youden index took on the maximum value, seven control subjects (10%) were identified as false-positive and were excluded from the calculation of normal values. The most sensitive parameter before exclusion was thumbdif, whereas ringdif became the most sensitive after exclusion. The cut-off value for ringdif was 1.15 ms before exclusion, but was 0.37 ms after exclusion.

CONCLUSION

This method can be widely applied to solve the statistical problem when the gold standard is lacking, and the outside reference standard is not completely reliable.

Clinical and electrophysiological evaluation of carpal tunnel syndrome: approach and pitfalls

One of the most common referrals to the electrodiagnostic (EDX) laboratory is to confirm a clinical impression of carpal tunnel syndrome (CTS). The EDX studies are valuable in localizing median nerve abnormalities to the wrist, grading its severity, and excluding other condition that can mimic or coexist with CTS. However, there are many clinical and EDX pitfalls that can lead to misdiagnosis. Careful clinical assessment and attention to technical factors and details of the EDX techniques are fundamental for the quality and accurate interpretation of the study. This review aims to discuss the clinical and the EDX approaches to the diagnosis of CTS with emphasis on the commonly encountered pitfalls.

Ring finger sensorial conduction studies in grading carpal tunnel syndrome: Part II

BACKGROUND

Comparison of sensory conduction of median nerve (MN) with the one of ulnar nerve (UN) over writs-to-ring finger (RF) segment is useful in electrodiagnosis of carpal tunnel syndrome (CTS). However, there is not any consensus regarding the usage of this technique in grading of CTS.

OBJECTIVES

To determine whether the hands of CTS with elicitable MN sensory responses on index finger, but not on RF (non-respondings) compose a more severe electrophysiologic grade than the hands with elicitable responses on both fingers (respondings).

MATERIAL AND METHODS

The patients with bilateral moderate grade of CTS in whom one hand was responding and the contralateral hand was non-responding were included. Conduction study results of MN and UN were compared between respondings and non-respondings.

RESULTS

A total of 19 patients were included. Mean distal sensory onset latency (DSOL) of MN over index finger was longer (4.26 ± 0.49 msec versus 3.44 ± 0.39 msec; p< 0.001), sensory conduction velocity (SCV) was slower (33.7 ± 4.3 m/sec versus 40.2 ± 3.0 m/sec; p< 0.001), SNAP amplitude was smaller (10.3 ± 3.3 μV versus 19.1 ± 7.7 μV; p< 0.001), distal motor latency was longer (5.69 ± 0.60 msec versus 4.63 ± 0.32 msec; p< 0.001), and minimum F wave latency was longer (29.3 ± 1.7 msec versus 26.8 ± 1.4 msec; p< 0.001) in non-respondings than respondings. The nonresponding hand had a longer MN DSOL and slower SCV on index finger compared with contralateral responding hand in all of 19 patients.

CONCLUSION

Non-responding hands have more progressed median neuropathies, and represent a more severe electrophysiologic grade than responding hands. Further studies are warranted to determine whether the absence of MN sensory responses on ring finger is related with forthcoming NCS worsening and a preferable hallmark for deciding surgical intervention or not.

Expression of vitamin D receptor in the subsynovial connective tissue in women with carpal tunnel syndrome

Studies suggest that low vitamin D levels are associated with carpal tunnel syndrome. We aimed to evaluate whether level of vitamin D receptor expression in the endothelial cells of the subsynovial connective tissue is associated with clinical features of carpal tunnel syndrome. We obtained the subsynovial connective tissue from 52 women with carpal tunnel syndrome during surgery and performed immunohistochemical analysis of vitamin D receptors in the endothelial cells of the subsynovial connective tissue. We explored correlation of vitamin D receptor expression with clinical features of carpal tunnel syndrome, such as age, symptom duration, symptom severity and electrophysiological severity. Diverse range of vitamin D receptor expression was observed. Vitamin D receptor expression was independently associated with distal motor latency. This suggests that vitamin D receptor expression may be associated with disease progression, as prolonged distal motor latency reflects severity of the disease. Further studies are necessary to explore the role of vitamin D and vitamin D receptors in patients with carpal tunnel syndrome.

LEVEL OF EVIDENCE

IV.

Lumbrical-interosseous recording technique versus routine electrodiagnostic methods in the diagnosis of carpal tunnel syndrome

Objectives

We aimed to evaluate the sensitivity of second lumbrical-interosseous (L-I) technique and to compare the results with other electrophysiological methods in patients with carpal tunnel syndrome (CTS).

Patients and methods

This cross-sectional study was conducted in an electrophysiology laboratory of a university hospital between January 2003 and January 2004. A total of 102 patients with CTS (174 hands) and 40 healthy controls (80 hands) were included. Median motor nerve conduction studies were obtained with recordings from the abductor pollicis brevis (APB), median sensory nerve conduction studies from digits I-III and at palm-wrist segment (P-W), median-ulnar sensory comparison at digit IV (M-U), and median-radial sensory comparison at digit I (M-R) were along with L-I technique.

Results

The highest sensitivities were found in the median sensory conduction velocity across the palm-wrist (88%), and digit I-wrist segments (80%), median motor distal latency over the APB (77%), and L-I study (76%). The specificities of conventional tests were higher than the sensitivity of L-I method (63%).

Conclusion

L-I method has a good diagnostic sensitivity in CTS; however, P-W, median sensory nerve conduction velocity at digit I and median distal motor latency are more sensitive than L-I method. Therefore, L-I method can be applied as a supportive technique in the evaluation of patients with CTS.

Confiabilidad de los estudios de neuroconducción en el síndrome de túnel carpiano

Objetivo Determinar la confiabilidad entre dos observadores y el cambio mínimo detectable de los estudios de neuroconducción para diagnosticar el síndrome de túnel carpiano.Métodos Se estudiaron 69 pacientes remitidos para estudio electrofisiológico por sospecha de síndrome de túnel carpiano. A los pacientes, se les realizaron dos exámenes,dos días diferentes, por dos evaluadores. Se evaluaron las latencias sensitivas y motoras de los nervios mediano y cubital; todos fueron clasificados como negativos, incipientes, leves, moderados, severos o extremos. Se calculó la variación relativa entre ensayos, el coeficiente de correlación intraclase, el índice de kappa, el límite de acuerdo y el cambio mínimo detectable.Resultados La variación relativa entre ensayos de la latencia motora del nervio mediano fue de -6,8 % a 15,9 % con coeficiente de correlación intraclase de 0,98 para la diferencia con la latencia del nervio cubital. El cambio mínimo detectable fue de 0,4ms. La variación relativa entre ensayos de la latencia sensitiva del nervio mediano fue -5,0 % a 11 % con coeficiente de correlación intraclase de 0,95 para la diferencia con el nervio cubital. El cambio mínimo detectable fue de 0,2ms. La clasificación ele trofisiológica coincidió en 93 % de los casos, índice de kappa de 0,89.Conclusiones Las latencias sensitivas y motoras del nervio mediano así como la diferencia de estas con el nervio cubital son medidas confiables. El cambio mínimo detectable obtenido en nuestro estudio le sirve al clínico para establecer si los cambios de las latencias en estudios consecutivos o después del tratamiento son significativos.

Double peak sensory nerve action potentials to single stimuli in nerve conduction studies

INTRODUCTION

In humans, sensory nerve action potentials (SNAPs) can show 2 separate deflections, i.e., double peak potentials (DPp), which necessarily means that 1 peak is delayed with respect to the other. DPps may have various origins and be due to either physical or physiological properties.

METHODS

We review the nature of commonly encountered DPps in clinical practice, provide the most likely interpretations for their physiological origin, and assess their reproducibility and clinical utility.

RESULTS

We classified the DPps into 3 categories: (1) simultaneous anodal and cathodal stimulation. (2) simultaneous recording from 2 different nerves at the same site, and (3) SNAP desynchronization.

CONCLUSIONS

Although the recording of DPps is not a standardized neurophysiological method, their study brings interesting cues about the physiology of nerve stimulation and paves the way for clinical application of such an observation. Muscle Nerve 55: 619-625, 2017.

Comparison of high-resolution sonography and electrophysiology in the diagnosis of carpal tunnel syndrome

Background:

The diagnostic accuracy of high-resolution ultrasonography (HRUS) in comparison to electro-diagnostic testing (EDX) in carpal tunnel syndrome (CTS) is debatable.

Objective:

The aim of this study was to compare the diagnostic accuracy of HRUS with EDX in patients with various grades of CTS and CTS associated with peripheral neuropathy (CTS + PNP).

Materials and Methods:

A prospective cohort of 57 patients with possible CTS was studied along with matched controls. The cross-sectional area (CSA) of the median nerve at the inlet of carpal tunnel was assessed by a sonologist blinded to the clinical and EDX data. Palm wrist distal sensory latency difference (PWDSLD), second lumbrical-interosseus distal motor latency difference (2LIDMLD) and CSA were compared in patients with different grades of severity of CTS and CTS+PNP.

Results:

Total 92 hands of 57 patients met the clinical criteria for CTS. Mean CSA at the inlet of carpal tunnel was 0.11 ± 0.0275 cm². It had the sensitivity, specificity, positive predictive value and negative predictive values of 76.43%, 72.72%, 89.47% and 68%, respectively (P < 0.0001). Overall, HRUS had good correlation with PWDSLD and 2LIDMLD electro-diagnostic studies in all grades of CTS and CTS + PNP.

Conclusion:

HRUS can be used as a complementary screening tool to EDX. However, EDX has been found to be more sensitive and specific in mild CTS.

Practical approach to electrodiagnosis of the carpal tunnel syndrome: A review

Despite being the most common entrapment neuropathy and the most common reason for referral to the electromyography (EMG) laboratory, the diagnosis of carpal tunnel syndrome (CTS) continues to be challenging due to a large number of electrodiagnostic (EDX) tests available. We present a flowchart and propose a practical approach to the diagnosis of CTS using the available literature and the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) guidelines and the Practice Parameter for Electrodiagnostic Studies in Carpal Tunnel Syndrome.

Effects of varying case definition on carpal tunnel syndrome prevalence estimates in a pooled cohort

OBJECTIVE

To analyze differences in carpal tunnel syndrome (CTS) prevalence using a combination of electrodiagnostic studies (EDSs) and symptoms using EDS criteria varied across a range of cutpoints and compared with symptoms in both ≥1 and ≥2 median nerve-served digits.

DESIGN

Pooled data from 5 prospective cohorts.

SETTING

Hand-intensive industrial settings, including manufacturing, assembly, production, service, construction, and health care.

PARTICIPANTS

Employed, working-age participants who are able to provide consent and undergo EDS testing (N=3130).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

CTS prevalence was estimated while varying the thresholds for median sensory latency, median motor latency, and transcarpal delta latency difference. EDS criteria examined included the following: median sensory latency of 3.3 to 4.1 milliseconds, median motor latency of 4.1 to 4.9 milliseconds, and median-ulnar sensory difference of 0.4 to 1.2 milliseconds. EDS criteria were combined with symptoms in ≥1 or ≥2 median nerve-served digits. EDS criteria from other published studies were applied to allow for comparison.

RESULTS

CTS prevalence ranged from 6.3% to 11.7%. CTS prevalence estimates changed most per millisecond of sensory latency compared with motor latency or transcarpal delta. CTS prevalence decreased by 0.9% to 2.0% if the criteria required symptoms in 2 digits instead of 1.

CONCLUSIONS

There are meaningful differences in CTS prevalence when different EDS criteria are applied. The digital sensory latency criteria result in the largest variance in prevalence.

Premotor potential study in carpal tunnel syndrome

INTRODUCTION

Premotor potentials (PMPs) precede compound muscle action potentials evoked from the second lumbrical muscle after median nerve stimulation. Although PMP has been identified as a median sensory nerve action potential, few reports have documented the significance of PMP parameters for diagnosing carpal tunnel syndrome (CTS).

METHODS

We investigated the relationships between PMP parameters and results of 6 standard median nerve conduction studies in 74 CTS hands.

RESULTS

Significant correlations were noted in all comparisons. PMP conduction velocity was strongly correlated with the sensory conduction velocity between wrist and digit 2 (r(2) = 0.91). Moreover, PMP parameters were significantly correlated with neurophysiological severity of CTS.

CONCLUSION

Measuring PMP parameters with a second lumbrical-interosseous study may be useful for diagnosing CTS.

Carpal tunnel syndrome and radiographically evident basal joint arthritis of the thumb in elderly Koreans

BACKGROUND

Previous studies have suggested a high prevalence of carpal tunnel syndrome in patients seeking treatment for basal joint arthritis of the thumb. The purpose of this study was to compare the prevalence of carpal tunnel syndrome between individuals with and those without radiographic evidence of basal joint arthritis of the thumb in the general elderly Korean population, and to determine if there is a correlation between the severity of carpal tunnel syndrome shown by electrophysiological studies and the severity of basal joint arthritis as seen on radiographs.

METHODS

We evaluated hand radiographs and nerve conduction studies of 192 men and 176 women (more than sixty-five years of age) who participated in the Korean Longitudinal Study on Health and Aging. The basal joint of the thumb was assigned a grade for osteoarthritis of 0 to 4 on radiographs with use of the Kellgren and Lawrence criteria. The diagnosis of carpal tunnel syndrome was based on the combination of a positive response to survey questions and a positive nerve conduction study. Motor distal latency and motor conduction velocity were measured to assess the electrophysiological severity of carpal tunnel syndrome.

RESULTS

The prevalence of carpal tunnel syndrome was 16.7% in the group with basal joint arthritis and 10.9% in the group without basal joint arthritis, a difference that was not significant (p = 0.249). Neither motor distal latency nor motor conduction velocity was significantly correlated with the severity of the basal joint arthritis in the entire group of 368 study subjects (p = 0.154 and p = 0.662, respectively) or in those with carpal tunnel syndrome (p = 0.603 and p = 0.998, respectively).

CONCLUSIONS

This study of Koreans who were more than sixty-five years of age showed that the prevalence of carpal tunnel syndrome is similar in patients with and those without radiographic findings of basal joint arthritis of the thumb. We found no correlation between the electrophysiological severity of carpal tunnel syndrome and the severity of basal joint arthritis.

The effect of local corticosteroid injection on F-wave conduction velocity and sympathetic skin response in carpal tunnel syndrome

The aim of this study was to evaluate the efficacy of steroid injection for the treatment of the carpal tunnel syndrome (CTS), with F-wave parameters and sympathetic skin response (SSR). Seventeen hands of 10 women patients were treated with local steroid injection with 2-month follow-up. All patients underwent single injection into the carpal tunnel. Response to injection was measured nerve conduction studies (NCSs), median nerve F waves, and SSR before and after treatment. To determine the normal values, 42 hands of 21 healthy women were also studied. There was a significant improvement of sensory and motor nerve conduction values when compared to baseline values (P < 0.01). At the end of follow-up period, the median sensory distal latency and the sensory latency differences between the median and the ulnar nerve were improved 35 and 65%, respectively. The maximum, mean F-wave amplitudes and chronodispersion showed a slight improvement with respect to baseline values and controls, but statistical significance was not achieved after treatment. Although no statistically significant improvements were observed in SSR parameters, slightly decreased amplitudes and increased habituation of SSR were noted at the end of the treatment. The present study shows that the local steroid injection results in improvement in NCSs values, but the F-wave parameters were not effectual in short-term outcome of CTS treatment. These findings suggest that the sensory latency differences between the median and the ulnar wrist-to-digit 4 are better parameters in the median nerve recovery after treatment than the median sensory distal latency. Furthermore, the SSR does not seem to be a sensitive method in follow-up of CTS treatment.

A new median motor test: comparison with conventional motor studies in carpal tunnel syndrome

INTRODUCTION

Carpal tunnel syndrome (CTS) is the most commonly operated of entrapment peripheral neuropathies, and its surgical outcome largely depends on the underlying mechanism involved. Early identification of CTS is essential because it is associated with a better prognosis.

AIM

To identify CTS at an earlier stage and hence improve the potential future outcome, the authors propose incorporating a new method of using the second lumbricalis (2L-MC) to register the nerve conduction.

METHODS

We prospectively evaluated 121 of 216 patients with confirmed carpal tunnel syndrome and 49 cases from 25 healthy subjects. According to the accepted criteria of Stevens, we divided our study into two groups of mild CTS and moderate CTS, respectively. Following our proposed method, we stimulated the palm, distal forearm, and elbow and measuring the difference in latency between the second lumbricalis and the second interosseous, in addition to the conventional neurophysiologic assessments.

RESULTS

Seventeen of 109 (15.6%) hands showed a significant difference in latency using 2L-MC within the mild CTS group, while only 4 of 107 (3.7%) within the moderate CTS group remained undiagnosed using this method. In the mild CTS group, motor involvement was only shown to be slightly more sensitive when compared with 2LI-DML.

DISCUSSION

Adding the proposed test to the conventional studies of CTS in our cases presented showed a 14% increased sensitivity in detecting motor dysfunction when compared with conventional studies alone. Therefore, this new 2L-MC study represents a useful technique for assessing early motor involvement in CTS and would only add a few extra minutes to the standard diagnostic procedures. To conclude, we propose that incorporating this study as part of the standard assessment of CTS is given further consideration.

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.

Diurnal variation in clinical and electrophysiologic parameters associated with carpal tunnel syndrome

OBJECTIVE

Patients with carpal tunnel syndrome (CTS) often report aggravated symptoms in the early morning. In this study, we aimed to identify diurnal variations in clinical and electrophysiologic parameters of patients with CTS.

DESIGN

A cross-sectional clinical and electrophysiologic study was designed. First, electrophysiologic examinations were performed at 2 p.m. to confirm the diagnosis of patients who had been clinically labeled with CTS. Patients who were electrophysiologically and clinically diagnosed with CTS were included in the study, and electrophysiologic examinations were repeated at 7 p.m. and 7 a.m. A total of 64 hands with CTS (27 bilateral, 10 unilateral) and 40 control hands were studied. Grip and pinch strength of all the patients included in the study were measured using a hand dynamometer. Finally, a CTS clinical symptom severity scale and functional status scale were used to measure the symptoms and functional impairment, respectively.

RESULTS

The median motor nerve distal latency and median F-minimum latency were found to be prolonged in the CTS group in the morning, and the grip strength was also markedly reduced at this time. Similar results were obtained for the median palm mixed nerve conduction velocity and amplitude.

CONCLUSIONS

This study demonstrated that the clinical and electrophysiologic parameters of CTS patients were clearly different in the morning hours, with the symptoms of CTS manifesting at that time.

The significance of second lumbrical-interosseous latency comparison in the diagnosis of carpal tunnel syndrome

AIM

To assess the significance of the second lumbrical-interosseous latency (2LI-DML) comparison in the diagnosis of carpal tunnel syndrome (CTS).

PATIENTS AND METHODS

We examined 150 consecutive hands of patients referred with suspected CTS, using the 2LI-DML test and other standard measures of median nerve function. Correlations of the 2LI-DML test with standard tests were computed.

RESULTS

Hundred and four hands were electrophysiologically confirmed to have CTS. The 2LI-DML test was abnormal in 99/104 (95.2%) hands with CTS with a mean value of 1.54 +/- 1.12 ms. Among the other measures, the orthodromic median-ulnar palmar velocity comparison was the most frequently abnormal test (95/104 hands, 91.3%), followed by the double-peak morphology of orthodromic sensory action potential from digit 4 (94/104, 90.4%). The 2LI-DML test significantly correlated, either positively or negatively, with all other standard tests.

CONCLUSION

The 2LI-DML comparison is highly sensitive in diagnosing CTS, even in mild cases in which standard tests fail to detect abnormalities.

Sensitivities of conventional and new electrophysiological techniques in carpal tunnel syndrome and their relationship to body mass index

The purpose of this study is to evaluate prospectively the sensitivities of conventional and new electrophysiological techniques and to investigate their relationship with the body mass index (BMI) in a population of patients suspected of having carpal tunnel syndrome (CTS). In this study, 165 hands of 92 consecutive patients (81 female, 11 male) with clinical diagnosis of CTS were compared to reference population of 60 hands of 30 healthy subjects (26 female and 4 male). Extensive sensory and motor nerve conduction studies (NCSs) were performed in the diagnosis of subtle CTS patients. Also, the patients were divided into subgroups and sensitivities were determined according to BMI. The mean BMI was found to be significantly higher in the CTS than in the control group (p < 0.001). The sensitivity of the median sensory nerve latency (mSDL) and median motor distal latency (mMDL) were 75.8% and 68.5%, respectively. The most sensitive parameters of sensory and motor NCSs were the difference between median and ulnar sensory distal latencies to the fourth digit [(D4M-D4U), (77%)] and the median motor terminal latency index [(mTLI), (70.3%)], while the median-to-ulnar sensory action potential amplitude ratio (27%) and the median-thenar to ulnar-hypothenar motor action potential amplitude ratio (15%) were least sensitive tests. Sensory tests were more sensitive than motor NCSs. Combining mSDL with D4M-D4U, and mMDL with mTLI allowed for the detection of abnormalities in 150 (91%) and 132 (80%) hands, respectively. Measurements of all NCSs parameters were abnormal in obese than in non-obese patients when compared to the BMI. The newer nerve conduction techniques and combining different NCSs tests are more sensitive than single conventional NCS test for the diagnosis of suspected CTS. Meanwhile, CTS is associated with increasing BMI.

Effects of bias on the results of diagnostic studies of carpal tunnel syndrome

PURPOSE

Design weaknesses in studies of diagnostic tests can lead to biases that produce misleading results. The extent to which such biases exist in studies of diagnostic tests for carpal tunnel syndrome (CTS) is unknown, and no studies address whether these biases influence published estimates of the performance of CTS diagnostic tests. The present study investigates these issues.

METHODS

We conducted a systematic review of studies of tests used to diagnose CTS in adults. Whether a study had design-related biases was determined using the Quality Assessment of Diagnostic Accuracy Studies instrument, by determining whether a study had a case control design, and by considering each study's level of evidence. We used meta-regression to determine whether any of these factors influenced estimates of the sensitivity, specificity, and diagnostic odds ratio of diagnostic tests.

RESULTS

A total of 23 studies of 129 diagnostic test evaluations met our inclusion criteria. Of those, 87% (20 of 23 studies) contained at least 1 bias and, on average, each study contained 2 biases. The most common design-related bias was spectrum bias (61% of studies [14 of 23 studies]), which was perfectly correlated with use of a case control design. Spectrum bias was associated with a statistically significant overestimation of sensitivity, specificity, and the diagnostic odds ratio. Test review bias (which was clearly present in 35% of studies [8 of 23 studies]) was associated with statistically significant overestimation of sensitivity and the diagnostic odds ratio. These results were not influenced by whether the diagnostic test under study was a clinical or an electrodiagnostic test.

CONCLUSIONS

Well-designed studies of diagnostics for CTS are uncommon, and shortcomings in the design of studies of clinical and electrodiagnostic tests are associated with overestimates of the performance of these tests. Consequently, most articles on diagnostic tests for CTS are unlikely to report results that are applicable to actual clinical practice.

Short-term electrophysiological conduction change in median nerve fibres after carpal tunnel release

Standard electrophysiological techniques and analysis of the stimulus-response relationship (i.e., the input-output (I-O) curves) of the median nerve were performed in 16 patients with carpal tunnel syndrome (CTS) both prior to and 1 and 6 months after surgical decompression at the wrist. One month after carpal tunnel release (CTR), conduction in cutaneous and motor axons (i.e., sensory conduction velocity and distal motor latency) was found to be improved with respect to pre-surgical values, whereas motor action potentials and the motor I-O curve showed a decrease with respect to control values. This suggested reduced efficiency of axon recruitment following CTR. Six months after surgery, all parameters were significantly improved with respect to control values. The sensory and motor I-O curves suggested that the reduced motor fibre recruitment efficiency observed 1 month after CTR was due to changes in current density distributions under the surface stimulating electrode on the median nerve at the wrist. Slight transient compression (such as that due to post-surgical oedema) acting on median fibres located superficially within the nerve cannot be excluded, however. Since electrophysiological studies are an important, objective method of evaluating the outcome of surgical CTR, electrophysiologists must be aware of the possibility of reduced compound motor action potential (CMAP) in the first few months after surgery.

Sonography and electrodiagnosis in carpal tunnel syndrome diagnosis, an analysis of the literature

We present a review of the international literature concerning sonography for the diagnosis of carpal tunnel syndrome (CTS). Analysis of the results and comparison with electrodiagnostic data provide a sensible albeit personal view on the relevance of sonography and whether it competes or is complementary to electrodiagnosis (EDX). Although EDX is considered as the gold standard for CTS diagnosis, one author chose surgical results to define CTS. The normal and threshold mean values for sonography are particularly variable from one study to another. The standard deviation (S.D.), when compared to mean values, makes normal and abnormal data overlap considerably and produces many false negatives when the specificity is high, and many false positives when the sensitivity is high. In fact, sonography is non-interpretable in only 10 to 15% of the population, and it affirms the median nerve lesion at the wrist in 55% of cases when EDX does it in more than 90% with common tests. Further more the specificity of sonography leads to a false positive diagnosis in 1 case out of 5 versus 1 out of 40 with EDX. The main conclusion is that there is no competition but rather a complementarity between sonography and EDX: sonography is certainly an efficient imaging technique but cannot replace proper EDX performed for upper limb paresthesiae. Namely, sonography can answer only one out of the 8 questions a complete EDX answer: Are sonographic images compatible with a median nerve lesion at the wrist? The answer to this solely question can be obtain with a partial EDX using a single conduction test (motor or sensitive), then duration and cost will be comparable to sonography but will be both more sensitive and specific. Finally, one must kept in mind that the final aim of all examinations in CTS is to determine the cause(s) of upper limb paresthesiae, not simply if there is a median nerve lesion at wrist or not.

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.

Factors influencing F-wave latency detection of lumbosacral root lesions using a detection theory based model

OBJECTIVE

To evaluate the F-wave dilution hypothesis; which implies that absolute F-wave latencies obscure the much smaller delay associated with slow intra-lesion conduction, such is caused by nerve root compression in lumbosacral radiculopathy. A corollary objective is to determine how F-wave measurement and pathological factors influence diagnostic accuracy.

METHODS

An analytical model is developed based on signal detection theory and a number of simplifying assumptions. Diagnostic accuracy, quantified by the area under the receiver operating characteristic (ROC) curve, is determined for various model realizations derived from the clinical and experimental neurophysiology literature. A preliminary experimental validation of model predictions is also performed.

RESULTS

Absolute F-wave latency does not influence the accuracy of focal lesion detection. F-wave latency variance and lesion pathology are the determinant factors. F-wave latencies and distal latencies are estimated to have qualitatively similar detection characteristics, although distal latencies have quantitatively better diagnostic efficacy for comparable focal pathology. Preliminary experimental results support the modeled dependence of diagnostic accuracy on latency variance and lesion severity.

CONCLUSIONS

Absolute F-wave latency does not dilute slow conduction within focal lesions, such as in lumbosacral radiculopathy. The dominant measurement factor is F-wave latency variance.

SIGNIFICANCE

To maximize the diagnostic utility of F-wave latencies, focus must be placed on reducing latency variance, such as through correction for demographic covariates. This model calls into question the F-wave dilution hypothesis.

Segmental study of the median nerve versus comparative tests in the diagnosis of mild carpal tunnel syndrome

OBJECTIVE

The aims of this study were to analyze normative data of nerve conduction studies (NCS) by optimal transformations, and compare the utility of electrodiagnostic tests in detecting mild carpal tunnel syndrome (CTS).

METHODS

In 131 hands of patients with mild CTS and 136 hands of controls, the segmental study of the median nerve between the digit-palm and palm-wrist segments, and the median-to-ulnar and median-to-radial comparative tests were performed. Normal limits were derived by calculating the mean+/-2 standard deviations of the optimally transformed data of the controls. The specificity, sensitivity, and misclassification rate were calculated to evaluate the utility of each test.

RESULTS

All tests had high specificities, ranging from 98.5 to 100%. The distoproximal latency ratio (DPLR) of the median nerve showed the highest sensitivity and the difference between the median and radial sensory latencies (D1M-D1R) the second highest, but there was no statistical difference between them. The difference between the median and ulnar mixed nerve latencies in the palm-to-wrist segment (PM-PU) showed the lowest sensitivity. Misclassification rates of the DPLR, D1M-D1R, and PM-PU were 6.9, 3.8, and 6.1%, respectively.

CONCLUSIONS

Optimal transformation of NCS data is mandatory to diminish the effect of skewness and enhance the diagnostic accuracy. As compared to the comparative tests, the segmental study of the median nerve is more easily applied and yields higher sensitivity in detecting mild CTS.

SIGNIFICANCE

With a high diagnostic yield and easy application, the segmental study of the median nerve may routinely be used to evaluate patients with mild CTS.

The significance of intact sympathetic skin responses in carpal tunnel syndrome

The current study aimed to investigate the impact of carpal tunnel syndrome (CTS) on sympathetic skin response (SSR) recorded from the median and ulnar territory. Thirty patients were studied and idiopathic CTS was documented in a total of 46 hands. These were classified, according to electrophysiological criteria, into two groups; a group of 31 hands with severe CTS and a group of 15 hands with mild/moderate CTS, and were compared with a group of 30 hands of age-matched controls. SSR was recorded simultaneously from the median and ulnar side of the palm following electrical stimulation at the wrist, in a mid-point between median and ulnar nerve. Latency, amplitude, habituation and the median-to-ulnar ratio were estimated. In all controls clear recordings of SSR were obtained. In the patient groups, absence of SSR was never observed either in mild/moderate or in the severe CTS hands. The mean SSR latency and amplitude values recorded from both the median and ulnar nerves did not significantly differ between mild/moderate or severe CTS hands and controls. Likewise, the median-to-ulnar ratio and habituation of SSR latencies and amplitudes did not significantly differ between groups. SSR does not seem to be a sensitive method for evidence of autonomic involvement in CTS, even in patients manifesting sudomotor or other autonomic symptoms. In the present setting, SSR appeared to be independent of somatic afferent function and the corresponding sensory action potentials.

Optimal recording electrode placement in the lumbrical–interossei comparison study

The lumbrical-interossei comparison study is commonly employed in the electrodiagnosis of carpal tunnel syndrome. Placement of the recording electrodes relies on anatomic landmarks as the muscles being recorded cannot be seen or palpated. To determine the optimal active electrode location, 15 controls and 5 patients were studied using a grid of 12 electrodes placed over the lateral palm. Amplitudes, rise-times, and latencies of the responses at each location were measured. The lowest control latency difference was located in the lateral mid-proximal palm (mean 0 ms, upper range of 0.5 ms). This location also had the highest lumbrical amplitude and rise-time. More distal in the palm, the mean latency difference increased to 0.5 ms with an upper range of 0.9 ms. When performing the lumbrical-interossei comparison study, it is essential to place the active recording electrode in the optimal location. Failure to do so will result in an increased number of false-positive studies.

Cutaneous silent period in carpal tunnel syndrome

The cutaneous silent period (CuSP), a transient suppression of electromyographic activity that follows painful stimuli, allows an indirect study of the small-diameter A-delta fibers. To assess the function of these fibers in peripheral nerve disorders, we compared the CuSP of 40 controls to that of 40 patients with carpal tunnel syndrome (CTS) and one patient with a traumatic transection of the median nerve. Patients with CTS were divided into three severity groups, based on electrophysiological data. In CTS, digit 2 evoked CuSP onset latency was increased in all groups, and CuSP duration from abductor digiti minimi was reduced in all groups. In our series, although some parameters of the CuSP were altered, only transection of the nerve abolished it. A-delta fibers are robust, probably due to their less vulnerable small diameter. This characteristic may be useful to study various conditions and essential for patients to retain some sensation within the median nerve territory.

The relationship between symptoms and electrophysiological detected compression of the median nerve at the wrist

OBJECTIVE

The aim of this study was to evaluate the relationship between carpal tunnel syndrome symptoms and compression of the median nerve at the wrist in symptomatic patients.

METHODS

A total of 250 patients were selected among those referred for electrodiagnostic evaluation with complaints involving hand or wrist. Primary and secondary symptoms were extracted from the answers to the instrument proposed by Levine et al. [J Bone Joint Surg Am 1993;75:1585]. The association of symptoms and the presence of compression of the median nerve at the wrist were ascertained through a multiple logistic regression test.

RESULTS

Secondary symptoms (pain and weakness) were inversely associated with the presence of median nerve compression. Furthermore, primary symptoms (paresthesia, disability and nocturnal symptom) occurred similarly in patients with and without electrophysiologic findings of median nerve compression at the wrist.

Comparison of sensory conduction techniques in the diagnosis of mild idiopathic carpal tunnel syndrome: which finger, which test?

To compare the sensitivity of different electrodiagnostic tests on the same hand affected by mild carpal tunnel syndrome (CTS), 189 hands with the clinical diagnosis of CTS and 61 hands of healthy persons were evaluated prospectively. On all hands, median sensory studies from digits 1, 2, 3, 4, and the palm-to-wrist segment from digit 3 and medial motor latency were recorded. Sixty-two hands with delayed motor latency (>4.2 ms) were excluded to ensure that only mild cases were enrolled. Sensory median-radial latency differences from the thumb, median-ulnar latency difference between second and fifth digits, and median-ulnar latency difference from the fourth digit were calculated in each limb. Sensory studies of only one median innervated digit failed to diagnose 15-20% of hands. Conduction velocity at the palm-to-wrist segment was the most sensitive, diagnosing 99% of cases. In comparative tests, median radial sensory latency difference from the first digit was the most sensitive (94%), and median ulnar latency difference from the fourth digit was the least (85%) sensitive. Segmental measurement has the highest diagnostic yield and may be used first in the evaluation of CTS.

Diagnostic utility of waveform analysis of compound muscle action potentials for carpal tunnel syndrome

PURPOSE

To determine the diagnostic utility of waveform analysis of compound muscle action potentials (CMAP) for carpal tunnel syndrome (CTS).

METHODS

A total of 131 hands in 71 patients diagnosed with CTS (grouped according to severity) and 80 hands in 44 normal subjects were evaluated using nerve conduction test through the carpal tunnel combined with waveform analysis of CMAP.

RESULTS

Compared to normal subjects, the sensory nerve conduction velocity and mean frequency of the CMAP waveform were significantly reduced in patients with CTS. Compared with distal motor latency and sensory nerve conduction velocity, the mean frequency of the CMAP decreased significantly with increasing clinical severity.

CONCLUSION

This study suggests that waveform analysis of CMAP is of diagnostic value in CTS, and is also of value in objective evaluation of postoperative recovery of carpal median nerve dysfunction.