Meng S, Reissig L.F., Beikircher R, Tzou C. H., Grisold W, Weninger W.J. (2015). Longitudinal gliding of the median nerve in the carpal tunnel: Ultrasound cadaveric evaluation of conventional and novel concepts of nerve mobilization. Archives of physical medicine and rehabilitation 96 (12). doi: 10.1016/j.apmr.2015.08.415.
By: Kyle Turcott
Carpal tunnel syndrome is a common neuropathy causing pain, weakness, and tingling in the hands and fingers. A frequently used conservative treatment for carpal tunnel syndrome includes nerve gliding exercises. This is based on the assumption that an essential property of peripheral nerves is their ability to glide smoothly and that the lack of mobility leads to stress and neuropathy. There is much debate regarding the level of evidence and efficacy of nerve gliding to treat carpal tunnel syndrome. This article suggests that one reason there is insufficient evidence to support the efficacy of nerve gliding is that the current literature has primarily focused on median nerve movement proximal to the carpal tunnel. Using ultrasound scanning the researchers found that traditionally used nerve gliding exercises have a greater effect on the longitudinal movement of the median nerve proximal to the carpal tunnel and less effect on movement within the carpal tunnel. After collecting data on the findings, the researchers were unsatisfied with the results and created a nerve gliding exercise involving finger abduction and adduction.
In the Weeds
This study was broken into two parts. In the first part, researchers examined 9 upper extremities from fresh, nonembalmed whole-body cadavers (5 men, 4 women, median age 82 years). Bodies were initially examined using ultrasound to detect any anatomical anomalies. Using ultrasound guidance researchers implanted intraneural markers made of small wire along three sections of the median nerve. The first was within the carpal tunnel, the second was proximal to the carpal tunnel, and the third was between the two heads of the pronator teres. In addition, periosteal reference markers were placed into adjacent bones. After neural and periosteal markers were placed a physiotherapist simulated 6 movement traditionally believed to promote median nerve gliding (detailed below A-F).
The 6 movements were broken up and reorganized as AB, BC, CD, DE, and EF and in each position the distance between the median nerve and the periosteal markers was recorded. The second part of the study was identical to the first part with the exception of an additional nerve gliding exercise GH which included finger adduction and abduction. Researchers found a statistically significant difference of median nerve movement within the carpal tunnel when comparing exercise GH with exercise A-G. In terms of distance, finger adduction to abduction was found to create 13.8mms of movement at the carpal tunnel. Wrist extension, elbow extension, and cervical contralateral and ipsilateral flexion were found to contribute 6.6mms of movement at the carpal tunnel. Movement proximal to the flexor retinaculum was similar (AG 12mm; GH 13.2mm respectively).
Bringing it Home
This research provides an interesting perspective on nerve gliding exercises and demonstrates improved distal nerve movement. This article helps to address the gap in the literature regarding median nerve movement within the carpal tunnel. The minimal invasiveness of this study is a strength as previous research into nerve mobility has been conducted on cadavers who have had significant alterations to normal anatomy. Cadavers are hardly a substitute for healthy live volunteers and the mean age of the sample did not reflect the typical age range of individuals struggling with carpal tunnel syndrome. The researchers noted this as an inherent weakness, however, due to the methodology it would have been impossible to conduct this study on live subjects. The article may not have an extraordinary impact on the current level of evidence and efficacy of nerve gliding treatment due to the fact that the axiom of the debate rests on the question, does lack of nerve mobility contribute to compression of the median nerve?
The research does provide promising evidence for a new nerve gliding exercise that promotes increased mobility of the median nerve at the site of concern. The exercise is also easy to teach and easy for patients to understand. In additional, it is one of the first studies to examine the longitudinal movement of the median nerve within the carpal tunnel. Continued research will be needed to assess the functional outcomes of patients who use the newly designed nerve gliding technique. If you would like to add this novel exercise into your nerve gliding repertoire see the images below for easy to follow instructions.
Step One: Begin with shoulder and elbow at roughly 90 degrees and digits adducted.
Step Two: Abduct Digits
Step Three: Adduct Digits
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