Jump to comment:

• In response: "Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome"
  Christian Dejaco
  Published on: 23 December 2013
• Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome
  Jiaan Zhu
  Published on: 10 December 2013

• Published on: 23 December 2013

  In response: "Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome"

  • Christian Dejaco, Dr
  • Other Contributors:
    • Martin Stradner, Dorothea Zauner, Werner Seel, Nicole Elisabeth Simmet, Alexander Klammer, Petra Heitzer, Kerstin Brickmann, Judith Gretler, Florentine F?rst-Moazedi, Rene Thonhofer, Rusmir Husic, Josef Hermann, Winfried B. Graninger, Stefan Quasthoff

  Dear Editor,

  our and several previous studies demonstrated a high diagnostic value of ultrasound for carpal tunnel syndrome (CTS) [1,2]. Among the various abnormalities within the carpal tunnel reported, the increase of the cross -sectional area (CSA) of the median nerve is the most commonly studied ultrasound abnormality [3]. In addition, ultrasound allows the identification of secondary causes of CTS such as sy...

  Show More

  Dear Editor,

  our and several previous studies demonstrated a high diagnostic value of ultrasound for carpal tunnel syndrome (CTS) [1,2]. Among the various abnormalities within the carpal tunnel reported, the increase of the cross -sectional area (CSA) of the median nerve is the most commonly studied ultrasound abnormality [3]. In addition, ultrasound allows the identification of secondary causes of CTS such as synovitis, tenosynovitis, calcified masses or tophaceous gout, as pointed out by Zhu et al. We acknowledge that the diagnostic value of ultrasound is not perfect as some patients may suffer from CTS despite a normal ultrasound result and vice versa, abnormal ultrasound findings do not necessarily indicate CTS [1]. In these cases, additional tests such as nerve conduction studies (although the sensitivity and specificity of this method are far away from 100% as shown in our and several other studies) are required to establish the final diagnosis [1,4].
  A specific aspect of our study is the determination of a relevant cut-off for the median nerve CSA. We decided to determine two cut-offs: one resulting in a ?90% sensitivity implying that patients with a CSA below this limit are unlikely to suffer from CTS and a second cut-off revealing a ?90% specificity for the diagnosis. Decreasing the cut-off certainly increases the sensitivity (theoretically up to 100%), but at the cost of specificity and conversely, increasing the cut-off would result in a better specificity. A perfect cut-off providing 100% sensitivity and specificity is unrealistic and misclassification of a proportion of patients has, unfortunately, to be accepted [2].
  Another aspect to consider is the selection of the study population. One strength of our study is the focus on patients with suspected CTS, rather than investigating patients with established CTS and healthy controls (as it was performed in previous studies) [2,5]. Our results are therefore directly applicable to daily clinical routine, whereas studies investigating patients with known CTS and healthy controls were prone to result in artificially high diagnostic values.
  We were the first to investigate the value of intranerval Power Doppler (PD) signals as a diagnostic criterion for CTS diagnosis systematically [1]. We observed a reasonable sensitivity and specificity and found this sign particularly valuable for patients with intermediate median nerve CSA. We acknowledge, however, that the sensitivity of PD depends on the power of the ultrasound device and that our results may not be generalizable given that older and/or low-power machines are commonly used [6]. Further validation studies using different devices are thus necessary to investigate the value of PD for CTS diagnosis.
  In summary, our data indicate that ultrasound is a good but not perfect diagnostic test for patients with suspected CTS. Apart from measurement of median nerve CSA and detection of intranerval PD signals, it provides the possibility to identify secondary causes of CTS such as synovitis, tenosynovitis, abnormal masses or other abnormalities within the carpal tunnel.

  References

  1 Dejaco C, Stradner M, Zauner D, et al. Ultrasound for diagnosis of carpal tunnel syndrome: comparison of different methods to determine median nerve volume and value of power Doppler sonography. Ann Rheum Dis 2013;72:1934-9. doi:10.1136/annrheumdis-2012-202328

  2 Fowler JR, Gaughan JP, Ilyas AM. The sensitivity and specificity of ultrasound for the diagnosis of carpal tunnel syndrome: a meta-analysis. Clin Orthop Relat Res 2011;469:1089-94. doi:10.1007/s11999-010-1637-5

  3 Mallouhi A, Pulzl P, Trieb T, et al. Predictors of carpal tunnel syndrome: accuracy of gray-scale and color Doppler sonography. AJRAmerican J Roentgenol 2006;186:1240-5. doi:10.2214/AJR.04.1715

  4 Seror P. Sonography and electrodiagnosis in carpal tunnel syndrome diagnosis, an analysis of the literature. Eur J Radiol 2008;67:146-52. doi:10.1016/j.ejrad.2007.06.017

  5 Klauser AS, Halpern EJ, De Zordo T, et al. Carpal tunnel syndrome assessment with US: value of additional cross-sectional area measurements of the median nerve in patients versus healthy volunteers. Radiology 2009;250:171-7. doi:10.1148/radiol.2501080397

  6 Duftner C, Sch?ller-Weidekamm C, Mandl P, et al. Clinical implementation of musculoskeletal ultrasound in rheumatology in Austria. Rheumatol Int Published Online First: 26 September 2013. doi:10.1007/s00296-013-2863-4 .

  Conflict of Interest:

  None declared

  Show Less

  Conflict of Interest:
  None declared.

  • Back to top
• Published on: 10 December 2013

  Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome

  • Jiaan Zhu, Associate Director
  • Other Contributors:
    • Fang Liu

  Dear Editor,

  We read with great interest the report by Dejaco and co-authors related to diagnosis of carpal tunnel syndrome (CTS) by ultrasound [1]. Dejaco et al. compared ultrasound measurement of median nerve cross- sectional area (CSA) at different anatomical landmarks in great detail and evaluated the value of intranerval power Doppler signals for CTS diagnosis. It provided a good data support for the ultrasonic...

  Show More

  Dear Editor,

  We read with great interest the report by Dejaco and co-authors related to diagnosis of carpal tunnel syndrome (CTS) by ultrasound [1]. Dejaco et al. compared ultrasound measurement of median nerve cross- sectional area (CSA) at different anatomical landmarks in great detail and evaluated the value of intranerval power Doppler signals for CTS diagnosis. It provided a good data support for the ultrasonic evaluation of CTS. However, this study prompts questions on the three following points:

  1. CSA as an important indicator for CTS diagnosis also has limitations. We do agree that CSA is the most commonly used for evaluation of nerve swelling. However, some patients had typical clinical symptoms, but those median nerves did not necessarily present obviously swelling and compression at the carpal tunnel inlet or outlet. Instead, the ultrasonography showed the abnormal echo of contents within carpal tunnel. Several reports also have been published on CTS caused by space occupying lesions including tenosynovitis [2-4], tumors[2,4,5], calcified mass[4,6] or tophaceous gout[4,7]. We also found such cases were common in systemic diseases such as rheumatoid arthritis, diabetes mellitus, gout and so on. Take tenosynovitis for example, transverse sonography of the median nerve at the level of the pisiform bone showed an ovoid hypoechoic reticular structure without swelling. However, the deep tissue of nerve showed swelling and hypoechoic (Fig.1A). On the longitudinal sonograms, the nerve appeared as a consistent thickness of strip structure without a sudden thinning or thickening (Fig.1B). However, power Doppler showed increased blood flow signal within the nerve and carpal tunnel (Fig.1B, 1C). CSA as a diagnostic criterion will increase the false negative rate of CTS.

  2. Ultrasound also has disadvantages for diagnosis of CTS. As we know, the diagnosis of CTS is based primarily on clinical examination and nerve conduction studies (NCS). In the last 20 years, Ultrasound has been employed as an important imaging tool for CTS. The value of sonographic assessment for CTS depended mainly on three sonographic techniques: measurement of median nerve CSA at differential locations along the carpal tunnel, structural analysis of the median nerve and bowing of the flexor retinaculum [8]. We agree ultrasound can evaluate morphological changes of median nerve and provide a good data support for CTS. More specifically, ultrasound is not much an evaluation as a diagnostic tool for CTS..

  3. The term "volume" mentioned in the title was used inappropriately. Volume of median nerve should be measured on the 3-dimensional space image. However, Dejaco et al. [1] measured CSA of nerves on the 2D image. In order to avoid ambiguity, we proposed to use the term "area".

  References

  1. Dejaco C, Stradner M, Zauner D et al. Ultrasound for diagnosis of carpal tunnel syndrome: comparison of different methods to determine median nerve volume and value of power Doppler sonography. Ann Rheum Dis 2013;72:1934-9.

  2.Chen CH, Wu T, Sun JS et al. Unusual causes of carpal tunnel syndrome: space occupying lesions. J Hand Surg Eur Vol 2012;37:14-9.

  3.Klauser AS, Faschingbauer R, Bauer T et al. Entrapment neuropathies II: carpal tunnel syndrome. Semin Musculoskelet Radiol. 2010;14:487-500.

  4. Kang HJ, Jung SH, Yoon HK et al. Carpal tunnel syndrome caused by space occupying lesions. Yonsei Med J 2009;50:257-61.

  5. Ait Essi F, Younsi A, Abkari I et al. Diffuse tenosenovial giant cell tumor of the wrist revealed by carpal tunnel syndrome: report of a case. Chir Main 201;31:256-8.

  6. Takada T, Fujioka H, Mizuno K. Carpal tunnel syndrome caused by an idiopathic calcified mass. Arch Orthop Trauma Surg 2000;120:226-7.

  7. Patil VS, Chopra A. Watch out for 'pins and needles' in hands--it may be a case of gout. Clin Rheumatol 2007;26:2185-7.

  8. Nakamichi K, Tachibana S. Ultrasonographic findings in isolated neuritis of the posterior interosseous nerve: comparison with normal findings. J Ultrasound Med 2007;26:683-687.

  ELetter and Figures will be available on the Electronic Pages soon

  Figure Legends
  Figure 1
  Transverse and longitudinal sonograms of the median nerve at the carpal tunnel
  A Transverse sonogram of the median nerve at the level of the pisiform bone (CSA:7mm2)
  B Longitudinal sonogram of the median nerve
  C Transverse sonogram of the carpal tunnel with abundant blood flow signal

  Conflict of Interest:

  None declared

  Show Less

  Conflict of Interest:
  None declared.

  • Back to top