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ORIGINAL ARTICLE
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Neuroelectrophysiological Evaluation of Carpal Tunnel Syndrome before and after Surgical Intervention


1 Department of Physiology, M. J. N. Medical College and Hospital, Cooch Behar, West Bengal, India
2 Department of Physiology, I. P. G. M. E. and R. and, S. S. K. M. Hospital, Kolkata, West Bengal, India
3 Department of Plastic of Surgery, I. P. G. M. E. and R. and, S. S. K. M. Hospital, Kolkata, West Bengal, India

Date of Submission13-Dec-2021
Date of Acceptance17-Apr-2022
Date of Web Publication09-Jul-2022

Correspondence Address:
Debanjana Chowdhury,
Department of Physiology, M. J. N. Medical College and Hospital, Vivekananda Street, Pilkhana, Cooch Behar - 736 101, West Bengal
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/injr.injr_277_21

  Abstract 


Background: Carpal tunnel release operation (CTR) is required to alleviate the symptoms of carpal tunnel syndrome (CTS), the most common entrapment neuropathy.
Methods: Thirty-two patients (39 hands) of CTS were subdivided into Group I is moderate CTS (n = 9 hands), Group II is severe CTS (n = 14 hands), and Group III is extreme CTS (n = 16 hands) and underwent conventional electrophysiological evaluation and short segment transcarpal nerve conduction studies preoperatively and 1 and 3 months after open CTR operation.
Results: In the case of motor conduction parameter, distal motor latency showed statistically significant improvement after 1 month of CTR (P < 0.05) in all three groups of patients, and improvement consistently increased during 3rd month follow-up (P < 0.001). In Group III patients, preoperatively forearm motor conduction velocity (FMCV) and transcarpal motor conduction velocity (TMCV) were nonrecordable, FMCV became recordable in 6 hands, while TMCV in all 16 hands post CTR. In case sensory parameters, both distal sensory latency (DSL) and sensory nerve conduction velocity (SNCV) showed significant improvement in Group I, and no improvement was noted in Group III patients. Group II (6 of 14 hands) patients showed a reappearance of DSL and SNCV at 1-month follow-up and continued a steady improvement in 3rd month after CTR.
Conclusion: We found that TMCV is a more sensitive parameter in assessing improvement of median nerve function after CTR. It is possible to identify patients with a poor outcome by performing electrophysiological studies.

Keywords: Carpal tunnel syndrome, median nerve, nerve conduction studies, transcarpal motor conduction velocity



How to cite this URL:
Chowdhury D, Sen S, Banerjee T. Neuroelectrophysiological Evaluation of Carpal Tunnel Syndrome before and after Surgical Intervention. Indian J Rheumatol [Epub ahead of print] [cited 2022 Aug 20]. Available from: https://www.indianjrheumatol.com/preprintarticle.asp?id=350341




  Introduction Top


Carpal tunnel syndrome (CTS), the most common entrapment neuropathy, is due to the median nerve compression beneath the transverse carpal ligament in the wrist-to-palm segment.[1] Carpal tunnel release (CTR) is preferred over conservative therapies such as corticosteroid or splinting for moderate-to-severe patients having thenar weakness, atrophy, or long-standing nerve impairment documented in nerve conduction studies (NCS).[2],[3] Improvement of symptoms in post-CTR patients does not seem to corroborate with NCS, possibly because long segment NCS has been done which does not truly reflect the impairment distal to carpal block. Hence, we used transcarpal NCS (i.e. distal to carpal tunnel) to evaluate improvement in median nerve function after CTR.

Initially, the short segment transcarpal method was not widely accepted as routine examination because palmer stimulation of recurrent median motor thenar branch is difficult, and co-stimulation of the deep ulnar nerve and thenar muscle made it technically complicated. However, now, this short segment (palm wrist – 8 cm) NCS is considered as more useful and sensitive[4],[5],[6] than the long segment (wrist to digit 14 cm) because the effect of the focal pathology of CTS may be diluted in long segment studies.[7],[8],[9]

Various data are found regarding conventional NCS parameters such as distal sensory latency (DSL) and distal motor latency (DML)[10],[11] done on pre- and post-CTR patients, but no literature is available on transcarpal NCS method till date.[12],[13],[14]


  Methods Top


This longitudinal interventional study was carried out in the department of physiology, in collaboration with the department of plastic surgery, in a tertiary hospital in Kolkata from January 2013 to August 2014 on 32 female patients (39 hands as 7 patients underwent bilateral CTR release) between 30 and 60 years with features suggestive of CTS who attended department of plastic surgery.

Cases included in the study were presented with complaints of numbness, paresthesia, nocturnal and/or activity-induced exacerbation, subjective weakness of the hand, and poorly localized upper limb pain in the median nerve distribution for at least 2 months supported by positive Phalen's test and Tinel's sign.

According to the American Association of the Electrodiagnostic Medicine criteria, the patients (39 hands) are subdivided into three groups:

  • Group I is moderate CTS (n = 9 hands)
  • Group II is severe CTS (n = 14 hands)
  • Group III is extreme CTS (n = 16 hands).


Patients having conditions or medications that cause neuropathy such as diabetes, hypothyroidism, end-stage renal disease, and autoimmune diseases, taking drugs such as INH, antiepileptics, chemotherapy, exposure of heavy metals, and history of past medical or surgical treatment of CTS were excluded from the study.

After obtaining clearance from I P G M E R Research Oversight Committee (Institutional Ethics Committee) of I. P. G. M. E and R and S. S. K. M Hospital, Kolkata, West Bengal, on 05/02/2013 having Memo No. Inst/IEC/80 and with proper written consent, all the patients underwent NCS during presurgical and 1 and 3 months post operation.

NCS was done using RMS NCV EMG EP MARK II with Aleron 201 Electromyograph with RMS Stimulator by standard protocol.

In the case of wrist-to-palm motor conduction study, wrist stimulation was done by a conventional method. To stimulate median motor fibers in the palm, the cathode was placed toward the wrist on a line drawn from the wrist to first metacarpal space.[4],[5] Anode was directed distally toward the base of 5th digit to prevent recording short latency leading to error in the calculation of wrist-to-palm median motor conduction velocity (W-P MCV), as shown in [Figure 1] and [Photograph 1].
Figure 1: Arrangement of the stimulating and recording electrodes for measuring transcarpal motor conduction velocity (wrist to palm median motor conduction velocity). Cathode of the stimulator was placed toward the wrist, on a line drawn from the wrist to first metacarpal space, and anode was directed distally toward the base of 5th digit to stimulate the median nerve in palm. The placement of the electrode at wrist is same as in conventional nerve conduction studies

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In our study, the distance between the stimulation site at the wrist (S2) and palm (S3) varied from 60 to 70 cm due to the variable course of the recurrent motor branch of the median nerve. Stimulus intensity was gradually increased to stimulate the recurrent median motor nerve without co-activation of the deep branch of the ulnar nerve. Change in thenar twitch (abduction to adduction of thumb) and compound muscle action potential waveform configuration was considered to be due to co-stimulation of deep branch of the ulnar nerve. Differences in latency at palm and wrist were used to calculate W-P MCV [Figure 2].
Figure 2: Transcarpal (wrist-to-palm) median nerve motor conduction study

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Electrophysiological data: Parameters analyzed

  1. DML
  2. Forearm motor conduction velocity (FMCV)
  3. Transcarpal motor conduction velocity (TMCV) (W-P MCV)
  4. DSL
  5. Wrist-to-digit 2 sensory nerve conduction velocity (SNCV).


Calculations of the mean, standard deviation, standard deviation of the mean, etc., were done as per the standard statistical method. Thereafter, MS-Office Excel 2007 and GraphPad Prism version 5.01 (San Diego; CA, USA: Graph Pad Software Inc., 2007) were used for statistical analysis and graphical representation. P < 0.05 was considered statistically significant.


  Results Top


All the patients were female and aged between 45 and 55 years, with a mean weight of 55.14 ± 5.76 kg and a mean height of 150.7 ± 1.52 cm.

In all three groups, there is a statistically significant improvement of DML in 1 month follow up period (P < 0.05) as derived from [Table 1]. It consistently improved in 3rd month follow-up period (P < 0.001) when compared preoperatively.
Table 1: A comparative study of distal motor latency between Group I, Group II, and Group III preoperative and postoperative follow-up in 1 and 3 months

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There is a significant improvement in FMCV after 3 month follow up (P < 0.001) in Group I and Group II patients as obtained from [Table 2]. However, in cases of extreme CTS (Group III), only six patients of 16 patients have a recordable FMCV after 1 month of CTR, and they showed a consistent improvement of FMCV in 3-month follow-up. However, the remaining ten patients still had NR FMCV even after 3 months of CTR. For this reason, in this group, we failed to show a significant improvement of FMCV after CTR.
Table 2: A comparative study of forearm conduction velocity between Group I, Group II, and Group III preoperative and postoperative follow-up in 1 and 3 months

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In all three groups, there is a statistically significant (P < 0.001) improvement in TMCV when compared preoperatively with postoperative 3 month follow up as derived from [Table 3].
Table 3: A comparative study of transcarpal motor conduction velocity between Group I, Group II, and Group III preoperative and postoperative follow-up in 1 and 3 months

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There is a remarkable improvement in sensory conduction parameters (DSL and SNCV) which is highly statistically significant (P < 0.001) when preoperative data are compared with 3 month postoperative data in Gr I patients as derived from [Table 4].
Table 4: A comparative study of sensory conduction parameters in Group I during preoperative and postoperative follow-up in 1 and 3 months

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Group II (n = 14 hands) patients with severe CTS had NR sensory parameters before operation. Only six patients (denoted by Group IIa; n = 6 hands) showed recordable sensory parameters (DSL and SNCV) after CTR, hence having statistically significant improvement (P < 0.001) from preoperative period to 3 month follow-up as obtained from [Table 5].
Table 5: A comparative study of sensory conduction parameters in Group IIa during preoperative and postoperative follow-up in 1 and 3 months

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  Discussion Top


In our study, DML (motor conduction parameter) showed statistically significant improvement after CTR than sensory parameters, which is in corroboration with the prevalent literature.[12],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24] Our study is further substantiated by intraoperational electrophysiological study where DML is showed to improve as early as 1 h of release.[13]

In moderate (Group I) and severe (Group II) CTS patients, FMCV and TMCV are equally sensitive in detecting postoperative improvement. In extreme cases of CTS (Group III) of preoperative NR FMCV and TMCV in 16 hands, only in 6 hands (37.5%) FMCV returned, but TMCV reappeared in 100% cases showing highly significant (P < 0.001) improvement after 3 months of CTR. Therefore, we conclude that TMCV is more sensitive parameter as compared to FMCV in assessing the improvement of median nerve function after CTR operation. This is supported by several studies showing that short segment NCS has better diagnostic sensitivity to long segment studies because the effect of focal pathology of CTS may be diluted in long segment studies.[4],[6],[9],[25],[26],[27]

The lack of return of FMCV in extreme cases is due to incomplete and inefficient remyelination, residual alteration in axonal morphology, and permanent loss of fast conducting nerve fibers.

The sensory parameters may have a slower improvement in extreme CTS patients, but the return of sensory parameters in 1 month postoperatively in Group II patients (6 of 14 hands; 42.86%) has some prognostic significance. Hence, it is possible to identify patients with a poor outcome by performing electrophysiological studies as predicted in other studies.[15],[18],[20],[21],[28],[29],[30],[31]

Although significant improvement has occurred in all the NCS parameters after CTR, they did not return to the normal baseline values which is well-documented in the literature.[12],[32],[33] After CTR, it becomes extremely difficult to determine the subjective symptoms and physical findings because the patients cannot differentiate between the pain of CTS itself and pain caused by the surgical procedure, so the only way to assess improvement is by NCS. NCS can be used as an objective tool to study the correct status of the median nerve in patients complaining of no improvement or recurrence of symptoms after CTR. Postoperative NCS provides additional information about inadequate decompression of median nerve or recurrence of entrapment overtime. It also helps to differentiate between CTS or other diseases which involve median nerve like cervical radiculopathy, spondylotic myelopathy, trapezeometatarsal disease mimicking CTS. Hence, we can conclude that postoperative NCS, especially TMCV, should be routinely performed in clinical practice to evaluate neurological improvement after CTR.

Limitations

  1. In the Indian population, a moderate group of patients are more reluctant for undergoing surgery, so we had to work with less number of hands
  2. All the patients being female, we have no data of male CTS patients
  3. As the follow-up period was short, the return of NCS parameters to normal baseline values after CTR could not be documented.



  Conclusion Top


We found that conventional NCS parameters (FMCV, DSL and SNCV) were NR in extreme CTS patients even after 3 months of operation but TMCV became recordable as early as 1 month post CTR. Therefore we conclude that TMCV is a more sensitive parameter in assessing improvement in all three subsets (moderate, severe and extreme) of CTS patients.

Acknowledgments

The authors are thankful to the study subjects who gave consent for the research work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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