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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 10  |  Issue : 3  |  Page : 131-136

Comparative analysis of nerve conduction study methods in patients with carpal tunnel syndrome


Department of Neurology, S.M.S. Medical College, Jaipur, Rajasthan, India

Date of Submission04-Apr-2019
Date of Decision14-May-2019
Date of Acceptance15-May-2019
Date of Web Publication06-Jun-2019

Correspondence Address:
Dr. Pankaj Kumar Saini
F 40, R.D. Hostel, S.M.S. Medical College, Jaipur, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/INJMS.INJMS_34_19

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  Abstract 

Background: Patients with mild-to-moderate carpal tunnel syndrome (CTS) may not be picked up by routine nerve conduction methods. Hence, this study was performed to identify the most sensitive way to detect mild-to-moderate CTS and to evaluate the sensitivity of different methods for the diagnosis of CTS. Subjects and Methods: We included 60 clinically confirmed CTS patients in our study. We recorded the clinical characteristics and laboratory features in a prescribed proforma. We also included 60 healthy age- and sex-matched asymptomatic individuals as controls in our study. We excluded patients with underlying peripheral neuropathy. We included median distal motor latency, median distal sensory latency, median-versus-ulnar second lumbrical-interossei comparison study, median-versus-ulnar wrist-to-digit four comparison study, median-versus-radial thumb sensory study, median-versus-ulnar motor distal latency difference, and median-versus-ulnar sensory latency difference tests in our study. Results: Of 60 patients, female: male ratio was 2.3:1, and the mean age was 44.28 ± 11.41 years. Mean symptom duration was 0.76 ± 0.03 years. Of 42 females, 38 (90.4%) were engaged in daily household activities. In patients group, median nerve distal motor latency was 5.024 ± 2.05 ms, whereas sensory latency was 3.53 ± 0.75 ms. Sensitivity was the highest in median-versus-ulnar wrist-to-digit four comparison study (90.19%), followed by median-versus-radial thumb sensory study (88.23%), and median-versus-ulnar second lumbrical-interossei comparison study (86.27%). Median distal motor latency test had the lowest sensitivity (72.55%). Conclusions: In patients with mild CTS, electrophysiological tests including median-versus-ulnar wrist-to-digit four comparison study, median-versus-radial thumb sensory study, and median-versus-ulnar second lumbrical-interossei comparison study should be incorporated to improve the sensitivity for the diagnosis of CTS.

Keywords: Carpal tunnel syndrome, electrophysiological tests, median nerve


How to cite this article:
Jain D, Saini PK, Sharma CM, Kumawat BL. Comparative analysis of nerve conduction study methods in patients with carpal tunnel syndrome. Indian J Med Spec 2019;10:131-6

How to cite this URL:
Jain D, Saini PK, Sharma CM, Kumawat BL. Comparative analysis of nerve conduction study methods in patients with carpal tunnel syndrome. Indian J Med Spec [serial online] 2019 [cited 2019 Nov 12];10:131-6. Available from: http://www.ijms.in/text.asp?2019/10/3/131/264530


  Introduction Top


Carpal tunnel syndrome (CTS) is by far the most common focal entrapment mononeuropathy. The median nerve usually gets entrapped at the wrist, as it passes through the carpal tunnel. Women are more often affected as compared to men, and it usually involves dominant hand first.[1]

CTS is clinically characterized by numbness, burning, tingling, and pain over the lateral palmar surface in the affected hand and the fingers (predominantly involving the thumb, index, and middle fingers). Patients may have frequent night awakenings due to paresthesias in hand and usually, get relieved by shaking of hands. The diagnosis of CTS is unlikely if symptoms are absent in thumb, index, and middle finger.[2]

Patients may exhibit signs such as Tinel's sign, i.e., paresthesia in the distribution of median nerve when the median nerve percussion is done at the wrist, and Phalen's sign, i.e., paresthesia after passively flexing the hand at the wrist for 1 min can aid in the diagnosis, but these are neither very sensitive nor specific tests.[3]

Higher prevalence of CTS has been observed in certain professions which involve repetitive hand movements, especially wrist flexion, or repetitive forceful grasping or pinching. CTS is diagnosed clinically and confirmed by various electrophysiological tests, including conventional methods, i.e., median distal motor latency and median distal sensory latency. In addition to conventional tests, various comparison tests including median-versus-ulnar second lumbrical-interossei comparison study, median-versus-ulnar wrist-to-digit four comparison study, median-versus-radial thumb sensory study, median-versus-ulnar motor distal latency difference, median-ulnar palmar mixed comparison study, inching study, and median-versus-ulnar sensory latency difference tests are carried out to confirm a diagnosis of CTS.[4]

Hence, it is crucial to diagnose CTS at an early stage to exclude other causes and also to prevent further damage to the median nerve, as more severe manifestations are associated with a worse prognosis.[5] Various electrodiagnostic tests are available to establish the diagnosis of CTS.[6]

In a review by the American Association of Neuromuscular and Electrodiagnostic Medicine Quality Assurance Committee, they found that sensory conduction studies were more sensitive as compared to motor studies, and sensory or mixed nerve studies across the wrist and comparison of radial or ulnar sensory nerve conduction study to the median sensory conduction in the same limb were most sensitive. It was found that median sensory study recording median distal sensory latency had a sensitivity of 49%–66% and 97.5%–100% specificity. Whereas, median distal motor latency had a sensitivity of 60%–74% and specificity of 95%–99%.[7]

Hence, this study was aimed to evaluate the sensitivity of various nerve conduction methods for the diagnosis of CTS and to evaluate the most sensitive method in patients with mild CTS. We also evaluated the association of CTS with household activities and its severity according to the body mass index (BMI).


  Subjects and Methods Top


We included 60 clinically confirmed CTS patients in our study. Patients were diagnosed clinically by criteria given by Vogt et al.,[8] which included

  1. Pain or paresthesia in hand (nocturnal or activity related)
  2. Reduced two-point discrimination or sensory impairment in the distribution of the median nerve
  3. Isolated atrophied abductor pollicis brevis muscle
  4. Positive Tinel's or Phalen's sign.


Patients were suspected of having CTS if they had (a) along with one criterion from b to d.

We recorded clinical characteristics and laboratory features in a prescribed proforma. We also included 60 healthy, age- and sex-matched asymptomatic individuals as controls in our study. We excluded patients with underlying peripheral polyneuropathy. Recorders and medicath sciences machine were used to perform nerve conduction studies. Skin temperature was maintained >32°C.

Following electrodiagnostic tests were carried out in all patients:

  1. Median distal motor latency [9] [Table 1]
  2. Median distal sensory latency [9] [Table 2]
  3. Median-versus-ulnar second lumbrical-interossei comparison study [9],[10][Table 3]. Median distal motor latency recorded over the second lumbrical muscle was compared to the ulnar motor latency, which was recorded over the second interossei muscle
  4. Median-versus-ulnar wrist-to-digit four comparison study [9],[10][Table 4]
  5. Median-versus-radial thumb sensory study [9],[10][Table 5]
  6. Median-versus-ulnar motor distal latency difference [9][Table 6]
  7. Median-versus-ulnar sensory latency difference [9][Table 7].
Table 1: Median distal motor latency

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Table 2: Median distal sensory latency

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Table 3: Median-versus-ulnar second lumbrical-interossei comparison study

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Table 4: Median-versus-ulnar wrist-to-digit four comparison study

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Table 5: Median-versus-radial thumb sensory study

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Table 6: Median-versus-ulnar motor distal latency difference

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Table 7: Median-versus-ulnar sensory latency difference

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We used disc recording electrodes of 1 cm for mixed nerve studies, and sensory studies were done using ring electrodes. A ground electrode was kept between recording and stimulating electrodes. The same machine was used for all the tests with a percutaneous supramaximal response. Pulse duration was kept as 0.05/0.1 ms for mixed nerve and sensory stimulation. For stimulation of the motor nerve, a pulse duration of 0.2/0.5 ms was used. A 20 Hz and 2 kHz filter was used. Specifics of the methodologies of respective tests are outlined in [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]. Patients were graded according to the severity in the mild, moderate, and severe category according to the criteria given by Herrmann and Logigian.[11]

  1. Mild – prolonged median motor and sensory distal latencies only
  2. Moderate – latency prolongation with a mild reduction of sensory nerve action potential (SNAP) or compound muscle action potential (CMAP)
  3. Severe – unrecordable median SNAP or severe reduction of CMAP with active denervation or severe chronic denervation/reinnervation.


Statistics

Statistical analysis was performed using descriptive analysis. Mean and the standard deviation were calculated, which were applied to all nerve conduction tests. Student's t-test (two-tailed) was used for comparative analysis. We calculated the sensitivity of each test. We could not calculate the false-positive values, as we do not have any standard gold test for comparison.


  Results Top


The patient's group had a mean age of 44.28 ± 11.41 years. Female: male ratio was 2.3:1. Bilateral symptoms were present in 46 (76.6%) patients. The mean symptom duration was 0.76 ± 0.03 years. Fourteen (23.3%) patients had hypothyroidism. Of 42 females, 38 (90.4%) were engaged in daily household activities. In our study, of 60 patients, 24 (40%) patients were in the 31–40 years age group (36.75 ± 2.60), and hence, this age group was more prone to CTS in our study [Table 8].
Table 8: Clinical characteristics of the cases

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The comparison between different nerve conduction studies of the cases and asymptomatic control groups is shown in [Table 9]. In mild CTS patient's group, median nerve distal motor latency was 4.29 ± 0.82 ms, whereas median distal sensory latency was 3.45 ± 0.63 ms. The latency difference in median-versus-ulnar second lumbrical-interossei comparison study was 1.33 ± 0.69 ms. Median-versus-ulnar wrist-to-digit four comparison study showed a latency difference of 1.08 ± 0.69 ms. In median-versus-radial thumb sensory study, latency difference was 0.94 ± 0.29 ms. Median-versus-ulnar motor distal latency difference was 1.62 ± 0.76 ms. Median-versus-ulnar sensory latency difference was 1.12 ± 0.77 ms. Of 120 hands (60 patients) examined, 102 were symptomatic. Of 102 hands, 68 had mild, 13 had moderate, and 21 had severe CTS [Table 10].
Table 9: Results of different nerve conduction tests in cases and controls

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Table 10: Results of different nerve conduction tests in cases according to the severity

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Of 102 hands, median motor distal latency test was positive in 74 hands. Median distal sensory latency test was positive in 80 hands, and median-versus-ulnar second lumbrical-interossei comparison study was positive in 88 hands. Median-versus-ulnar wrist-to-digit four comparison study was positive in 92 hands, median-versus-radial thumb sensory study was positive in 90 hands, median-versus-ulnar motor distal latency difference test was positive in 82 hands, and median-versus-ulnar sensory latency difference test was positive in 84 hands [Table 10].

Sensitivity was the highest in median-versus-ulnar wrist-to-digit four comparison study (90.19%), followed by median-versus-radial thumb sensory study (88.23%) followed by median-versus-ulnar second lumbrical-interossei comparison study (86.27%). Median-versus-ulnar sensory latency difference test had a sensitivity of 82.35%. Median-versus-ulnar motor distal latency difference test had a sensitivity of 80.4% followed by median distal sensory latency test with a sensitivity of 78.43%. Median distal motor latency test had the lowest sensitivity (72.55%) [Table 10].

Patients with mild CTS had a low BMI of 26.47 ± 1.34. Patients with moderate CTS had a mean BMI of 29.56 ± 2.12. BMI was the highest (32.28 ± 2.86) in severe CTS patients. The difference in BMI with an increase in the severity of CTS was found to be statistically significant (P < 0.05).


  Discussion Top


The most accurate diagnosis of CTS can be established by a combined approach, including detailed clinical history, examination, and electrodiagnostic tests. Although we do not have any gold standard diagnostic test for CTS, objective diagnosis of CTS is commonly established by various electrodiagnostic tests.[2]

The median distal motor latency and median sensory latency test are the basic electrodiagnostic tests used in the diagnosis of CTS. However, these tests cannot confirm mild CTS. They have a sensitivity ranging from 60% to 74% for median distal motor latency and a sensitivity of 50%–66% for median distal sensory latency.[7] In our study, the sensitivities of these tests were 72.55% and 78.43%, respectively. Hence, more sensitive tests are further required to detect mild CTS patients.

According to the guidelines proposed by the American Association of Electrodiagnostic Medicine, nerve conduction tests in patients suspected of CTS should include (1) median nerve sensory conduction study across the wrist, keeping the conduction distance of 13–14 cm, (2) if the initial test is normal, median-versus-ulnar sensory latency difference, or median-versus-radial thumb sensory study, or mixed nerve conduction studies across the wrist should be done, and (3) comparison of median nerve motor distal latency with the recording of distal latency in one another nerve in the affected limb.[12]

Studies conducted by Uncini et al.[13],[14] and Cioni et al.[15] have shown that median-versus-ulnar wrist-to-digit four comparison study is highly sensitive in detecting CTS. This test had a sensitivity of 90.19% in our study, and it also detected maximum patients with mild CTS.

Previous studies have shown that median-versus-radial thumb sensory study and median-versus-ulnar sensory latency difference test have a sensitivity of 82%–86% in diagnosing CTS.[7],[16] This is in accordance with our study results.

Median-versus-ulnar second lumbrical-interossei comparison study had a sensitivity of 86.27% in our study, which is in accordance with the previous study done by Moon et al.,[17] in which they found a sensitivity of 85%. However, this test had a sensitivity of 97.5% in a study done by Löscher et al.,[18] which may be due to the different epidemiological profile of the patients. We also observed the superiority of median-versus-ulnar sensory latency difference test as compared to the median distal sensory latency test.

We also observed that the severity of CTS increases with increase in BMI; this result was as per the study done by Werner et al.[19] Female patients predominated in our study, and 90.4% of them were engaged in household activities. Hence, this may be hypothesized that repeated exposure of hands in household activities is also a predisposing factor for CTS. A study by Farioli et al.[20] also found similar results.

Limitations of the study

Our study population was small, and hence, the results of the study may not be applicable to the whole population. We did not include median-ulnar palmar mixed comparison study and inching method in our study. However, we have incorporated more sensitive tests, including digit four comparison study, median-versus-radial thumb sensory study, and second lumbrical-interossei comparison test in our study.


  Conclusions Top


Standard nerve conduction tests, including median distal motor latency and median distal sensory latency tests, are less sensitive in detecting mild CTS. Highly sensitive electrophysiological tests including median-versus-ulnar wrist-to-digit four comparison study, median-versus-radial thumb sensory study, and median-versus ulnar second lumbrical-interossei comparison study should be incorporated in the evaluation of patients with CTS, especially patients with mild CTS to increase the diagnostic yield of CTS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Phalen GS. The carpal tunnel syndrome: Seventeen years' experience in diagnosis and treatment of six hundred fifty-four hands. J Bone Joint Surg Am 1966;48:211-28.  Back to cited text no. 3
    
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Chang CW, Wang YC, Chang KF. A practical electrophysiological guide for non-surgical and surgical treatment of carpal tunnel syndrome. J Hand Surg Eur Vol 2008;33:32-7.  Back to cited text no. 5
    
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Stevens JC. AAEM minimonograph #26: The electrodiagnosis of carpal tunnel syndrome. American Association of Electrodiagnostic Medicine. Muscle Nerve 1997;20:1477-86.  Back to cited text no. 6
    
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Vogt T, Mika A, Thömke F, Hopf HC. Evaluation of carpal tunnel syndrome in patients with polyneuropathy. Muscle Nerve 1997;20:153-7.  Back to cited text no. 8
    
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Herrmann DN, Logigian EL. Electrodiagnostic approach to the patient with suspected mononeuropathy of the upper extremity. Neurol Clin 2002;20:451-78, vii.  Back to cited text no. 11
    
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American Association of Electrodiagnostic Medicine, American Academy of Neurology, and American Academy of Physical Medicine and Rehabilitation. Practice parameter for electrodiagnostic studies in carpal tunnel syndrome: Summary statement. Muscle Nerve 2002;25:918-22.  Back to cited text no. 12
    
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Uncini A, Lange DJ, Solomon M, Soliven B, Meer J, Lovelace RE. Ring finger testing in carpal tunnel syndrome: A comparative study of diagnostic utility. Muscle Nerve 1989;12:735-41.  Back to cited text no. 13
    
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Uncini A, Di Muzio A, Awad J, Manente G, Tafuro M, Gambi D. Sensitivity of three median-to-ulnar comparative tests in diagnosis of mild carpal tunnel syndrome. Muscle Nerve 1993;16:1366-73.  Back to cited text no. 14
    
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Cioni R, Passero S, Paradiso C, Giannini F, Battistini N, Rushworth G. Diagnostic specificity of sensory and motor nerve conduction variables in early detection of carpal tunnel syndrome. J Neurol 1989;236:208-13.  Back to cited text no. 15
    
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Lee WJ, Liao YC, Wei SJ, Tsai CW, Chang MH. How to make electrodiagnosis of carpal tunnel syndrome with normal distal conductions? J Clin Neurophysiol 2011;28:45-50.  Back to cited text no. 16
    
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Moon PP, Maheshwari D, Sardana V, Bhushan B, Mohan S. Characteristics of nerve conduction studies in carpal tunnel syndrome. Neurol India 2017;65:1013-6.  Back to cited text no. 17
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Löscher WN, Auer-Grumbach M, Trinka E, Ladurner G, Hartung HP. Comparison of second lumbrical and interosseus latencies with standard measures of median nerve function across the carpal tunnel: A prospective study of 450 hands J Neurol 2000;247:530-4.  Back to cited text no. 18
    
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Werner RA, Albers JW, Franzblau A, Armstrong TJ. The relationship between body mass index and the diagnosis of carpal tunnel syndrome. Muscle Nerve 1994;17:632-6.  Back to cited text no. 19
    
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Farioli A, Curti S, Bonfiglioli R, Baldasseroni A, Spatari G, Mattioli S, et al. Observed differences between males and females in surgically treated carpal tunnel syndrome among non-manual workers: A sensitivity analysis of findings from a large population study. Ann Work Expo Health 2018;62:505-15.  Back to cited text no. 20
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]



 

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