Pilot Study: Efficacy of Ultrasound in Median Nerve Fascicular Lesions Around the Elbow in Spontaneous Anterior Interosseous Neuropathy.

BACKGROUND: This study evaluates the diagnostic efficacy of high-resolution ultrasound (US) in identifying focal swelling and focal narrowing of the anterior interosseous nerve (AIN) fascicles within the median nerve around the elbow in spontaneous anterior interosseous neuropathy. METHODS: This retrospective STROBE (Strengthing the Reporting of Observational Studies in Epidemiology)-compliant study evaluated 33 patients with spontaneous anterior interosseous neuropathy who underwent preoperative high-resolution US and surgery. Two radiologists jointly assessed the lesions, with intraoperative findings as the reference standard for calculating US diagnostic metrics. Intraclass correlation coefficients (ICCs) were analyzed for interrater reliability. RESULTS: Surgery confirmed 4 focal swellings and 56 focal narrowings of the AIN fascicles within the median nerve around the elbow. Preoperative US correctly identified all swellings and 45 narrowings, yielding a sensitivity and overall accuracy of 81.7%, and a positive predictive value of 100%. Specificity and negative predictive value were not calculable due to zero false positives. The interrater reliability was good to excellent (intraclass correlation coefficient = 0.856). US also detected denervated muscle changes (n = 5), concomitant median nerve trunk compression (n = 2), and concomitant posterior interosseous nerve narrowing (n = 2). CONCLUSIONS: High-resolution US is a sensitive, reliable, and noninvasive modality for identifying focal swelling and focal narrowing of the AIN fascicles within the median nerve around the elbow in spontaneous anterior interosseous neuropathy. Its precision in lesion localization supports its utility as a first-line imaging technique for clinical evaluation and surgical planning.