Background Carpal tunnel syndrome (CTS) is the commonest entrapment neuropathy affecting 9% of women.(1, 2) Ultrasound (US) has been used to assess the median nerve in carpal tunnel since 1992 by assessing the cross-sectional area (CSA) primarily.(3) However, there is very limited published research looking at the changes in the median nerve after treatment with corticosteroid injection. (4, 5) Elastography assessment of the median nerve after injection has not been documented.

Objectives 1. To assess the median nerve and carpal tunnel before and after corticosteroid injection by means of US, NCS and clinical assessment. 2. To establish if US findings can be used to predict whether a patient will respond to local steroid injection. 3. To establish what the clinical outcome is at 6 months to corticosteroid injection in CTS.

Methods Patient with symptoms and signs of idiopathic CTS based on clinical assessment were recruited from outpatients' clinics. Patients were assessed with US (including elastography and power doppler), NCS and the Levine- Katz CTS questionnaire (LKQ) and visual analogue score (VAS) for pain at baseline, 6 weeks and 6 months. LKQ was the primary outcome measure. Healthy volunteers were also recruited to act as a control group.

Results A total of 29 patients (40 wrists) and 12 controls (23 wrists) were included in the study. The LKQ scores improved significantly between baseline and 6 weeks (p= <0.001) but this significant improvement was not maintained at 6 months. VAS improved significantly between baseline and 6 weeks but again this was not maintained at 6 months. There was a statistically significant reduction in CSA of the median nerve at 6 weeks and 6 months (p=0.002 and 0.038 respectively). Vascularity and median nerve stiffness as assessed by elastography did not change significantly during the study period. All six NCS parameters assessed improved significantly. CSA of the median nerve could not predict response to injection as there was no significant difference in CSA of the median nerve in responders versus non responders.

Conclusions Corticosteroid injection leads to significant improvement in median nerve CSA as assessed by US and function as assessed by NCS up to 6 months. However patients' subjective assessment of improvement in symptoms and function did not match the objective measures at 6 months. US cannot be used to predict response to treatment based on this study.

References

1. de krom M, Knipschild P, Kester A, Thijs C, Boekkooi P, Spaans F. Carpal tunnel syndrome: prevalence in the general population. J Clin Epidemiol. 1992;45:373-6.

2. Bongers F, Schellevis F, van den Bosch W, van der Zee J. Carpal tunnel syndrome in general practice (1987 and 2001): Incidence and the role of occupational and non occupational factors. Br J Gen Pract. 2007;57:36-9.

3. Buchberger W, Judmaier W, Birbamer G, Lener M, Schmidauer C. Carpal tunnel syndrome: diagnosis with high-resolution sonography. AJR Am J Roentgenol. 1992;159:793-8.

4. Cartwright M, White D, Demar S, Wiesler E, Sarlikiotis T, Chloros G, et al. Median nerve changes following steroid injection for carpal tunnel syndrome. Muscle Nerve. 2011;44:25-9.

5. Jeong J, Yoon J, Kim S, Park B, Won S, Cho J, et al. Usefulness of ultrasonography to predict response to injection therapy in carpal tunnel syndrome. Ann Rehabil Med. 2011;35:388- 94.

Disclosure of Interest None declared