Abstract
Background
Carpal tunnel syndrome (CTS) is by far the most common entrapment neuropathy (Adams et al. Am J Ind Med 25:527–536, 1994; Cheadle et al. Am J Public Health 84:190–196, 1994; Stevens et al. Neurology 38:134–138, 1988). A combination of described symptoms, clinical findings and electrophysiological testing is used to confirm the diagnosis. Several studies have suggested that in patients with a clinical diagnosis of CTS, the accuracy of nerve sonography is similar to that for electromyography (Chen et al. BMC Med Imaging 11:22, 2011; Guan et al. Neurol Res 33:970–953, 2011; Kele et al. Neurology 61:389–391, 2003; Tai et al. Ultrasound Med Biol 38:1121–1128, 2012). In special cases though, the nerve sonography can reveal the cause of the median entrapment neuropathy (Fumière et al. JBR-BTR 85:1–3, 2002; Kele et al. J Neurosurg 97:471–473, 2002; Kele et al. Neurology 61:389–391, 2003; Zamora et al. J Clin Ultrasound 39:44–47, 2011).
Methods
A 43-year-old farmer was admitted to our department with 1 year of intermittent pain in the left hand and numbness of the thumb, index and middle finger. The pain and the numbness could be reproduced by extension of the wrist and fingers. The electrophysiological testing revealed signs of an entrapment median neuropathy in carpal tunnel.
Results
The high-resolution sonography (18 MHz) revealed signs of entrapment neuropathy with increased cross-sectional area, disturbed echostructure of the nerve and pathological wrist-to-forearm ratio, confirming the results from a similar study (Kele et al. Neurology 61:389–391, 2003). In addition, an elongated muscle belly of the flexor digitorum superficialis in the carpal tunnel could be identified. During the extension of the wrist and fingers, a greater protrusion of the muscle belly could be demonstrated causing compression of the median nerve.
Conclusions
We present a video case report of the sonographic findings of a patient diagnosed with carpal tunnel syndrome due to an elongated muscle belly of the flexor digitorum superficialis in the carpal tunnel. Our case highlights the importance of nerve sonography in the differential diagnosis of the cause of a carpal tunnel syndrome. With the aid of ultrasonography, it is possible to obtain very important information concerning different aspects of this case. First, in showing the presence of the elongated muscle belly of the flexor digitorum superficialis, the cause of the symptoms could be explained. Second, it was possible through the ultrasound study to explain the atypical clinical appearance in this case, demonstrating the compression neuropathy only after extension of the wrist and fingers. There have been no previous reports in which authors described an elongated muscle belly as cause of a CTS. Third, and perhaps most important, ultrasonography had a direct influence on our selection of therapeutical strategy and approach. As a result, we recommended in this patient a surgical therapy to completely solve the problem, but the patient declined this option and preferred a conservative therapy with a hand orthosis to prevent wrist extension. In conclusion we recommend ultrasonography as a very useful method in the diagnostic evaluation of carpal tunnel syndrome. We have clearly demonstrated that ultrasonography can be used to discover the cause of median nerve compression, especially in cases with an atypical clinical presentation.
Similar content being viewed by others
References
Adams ML, Franklin GM, Barnhart S. Outcome of carpal tunnel surgery in Washington State workers' compensation. Am J Ind Med. 1994;25:527–36.
Cheadle A, Franklin G, Wolfhagen C, et al. Factors influencing the duration of work-related disability: a population-based study of Washington State workers' compensation. Am J Public Health. 1994;84:190–6.
Chen SF, Lu CH, Huang CR, Chuang YC, Tsai NW, Chang CC, et al. Ultrasonographic median nerve cross-section areas measured by 8-point “inching test” for idiopathic carpal tunnel syndrome: a correlation of nerve conduction study severity and duration of clinical symptoms. BMC Med Imaging. 2011;11:22.
Fumière E, Dugardeyn C, Roquet ME, Delcour C. US demonstration of a thrombosed persistent median artery in carpal tunnel syndrome. JBR-BTR. 2002;85(1):1–3.
Guan J, Ji F, Chen W, Chu H, Lu Z. Sonographic and electrophysiological detection in patients with carpal tunnel syndrome. Neurol Res. 2011;33(9):970–5.
Kele H, Verheggen R, Reimers CD. Carpal tunnel syndrome caused by thrombosis of the median artery: the importance of high-resolution ultrasonography for diagnosis. Case report. J Neurosurg. 2002;97(2):471–3.
Kele H, Verheggen R, Bittermann HJ, Reimers CD. The potential value of ultrasonography in the evaluation of carpal tunnel syndrome. Neurology. 2003;61(3):389–91.
Stevens JC, Sun S, Beard CM, O'Fallon WM, Kurland LT. Carpal tunnel syndrome in Rochester, Minnesota, 1961 to 1980. Neurology. 1988;38:134–8.
Tai TW, Wu CY, Su FC, Chern TC, Jou IM. Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy. Ultrasound Med Biol. 2012;38(7):1121–8.
Zamora CA, Zamora MA, Soto JD, Garcés MÁ. Myoepithelioma of the hand and carpal tunnel: an unusual cause of median nerve compression. J Clin Ultrasound. 2011;39(1):44–7.
Disclosures of all authors
A. Kerasnoudis reports no disclosures. This study was not industry sponsored.
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
(MP4 228 kb)
About this article
Cite this article
Kerasnoudis, A. Elongated muscle belly of the flexor digitorum superficial causing carpal tunnel syndrome. HAND 7, 333–334 (2012). https://doi.org/10.1007/s11552-012-9435-z
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11552-012-9435-z