Original articleUlnar nerve morphology on magnetic resonance imaging predicts nerve recovery after surgery for cubital tunnel syndromeLa morphologie du nerf ulnaire en imagerie par résonance magnétique prédit la récupération nerveuse après chirurgie du syndrome du tunnel cubital
Introduction
Cubital tunnel syndrome (CuTS) is the second most common nerve entrapment syndrome affecting the upper extremity [1], [2]. Diagnosis is based on clinical signs and symptoms, which include both motor and sensory abnormalities involving ulnar nerve distribution over the forearm and hand. Electrodiagnostic testing (EDX) and magnetic resonance imaging (MRI) aid in confirming the diagnosis, quantifying disease severity, and identifying the exact site of ulnar nerve compression [3], [4].
Several prognostic factors for poor surgical outcome have been identified: advanced age, intrinsic muscle atrophy, and prolonged symptom duration [5], [6], [7], [8]. Functional aspects of the ulnar nerve are evaluated by EDX, while MRI reveals morphological aspects such as size and signal intensity [9]. Previous studies using MRI showed its value in diagnosing CuTS [10], but its value in predicting surgical outcome is unclear [11].
The purpose of this study was to determine whether ulnar nerve morphology on MRI correlated with outcome after surgery for CuTS.
Section snippets
Patients
We obtained approval from the Institutional Review Board of our institution for this study (SNUBH IRB No: B-1905-543-109), which waived informed consent. We reviewed the medical records of patients who had surgery for CuTS at our referral teaching hospital located in an urban area, between January 2014 and June 2019. The inclusion criteria comprised surgery for CuTS and both EDX and elbow MRI examination. Diagnosis was confirmed on EDX, performed following the guidelines of the American
Baseline characteristics and MRI findings
There were 27 men and 13 women in the study, with a mean age of 48 (range, 17–75) years. Preoperatively, 15 patients (38%) were classified as McGowan grade IIA, 19 (48%) grade IIB, and six (15%) grade III (Table 1).
The ulnar nerve CSA was largest at the ME and smallest at 3 cm distal to the ME (Fig. 2). Increased ulnar nerve signal intensity changes were found in 34 subjects (85%) and increased forearm muscle signal intensity changes in 3 (8%). Ten patients (25%) had space-occupying lesions
Discussion
MRI can evaluate ulnar nerve morphology in patients with CuTS, while EDX evaluates functional aspects of the nerve. This study demonstrated that unfavorable outcomes at 6 months after surgery were associated with both large preoperative ulnar nerve CSA on MRI and low mNCV on EDX. However, these associations were not present at 2 years after surgery. Therefore, the study suggests that both morphologic changes and functional aspects of the ulnar nerve can predict delayed nerve recovery at 6
Conclusion
This study demonstrated that increased ulnar nerve cross-sectional area on MRI was associated with suboptimal improvement after surgery for CuTS at 6 months, but this relation was not present at 2 years’ follow-up. The study suggests that morphologic changes in the ulnar nerve can predict delayed nerve recovery after surgery for CuTS. Assessment of morphologic changes in the ulnar nerve can be helpful for patient consultation on the prognosis of surgery for CuTS.
Human and animal rights
The authors declare that the work described has not involved experimentation on humans or animals.
Informed consent and patient details
The authors declare that the work described does not involve patients or volunteers.
Disclosure of interest
The authors declare that they have no competing interests.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Author contributions
All authors attest that they meet the current International Committee of Medical Journal Editors (ICMJE) criteria for authorship.
Ethics
This study obtained approval from the Institutional Review Board of our institution (No: B-1905-543-109), which waived informed consent. The authors declare that this report does not contain any personal information that could lead to the identification of patients.
Acknowledgments
The authors thank the Division of Statistics in Medical Research Collaborating Center at Seoul National University Bundang Hospital for statistical analyses.
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- 1
Jong Seop Kim and Gajendra Mani Shah should be considered the co-first authors of this study.