Background: Muscle MRI is increasingly used as a diagnostic and research tool in muscle disorders. However, the correlation between MRI abnormalities and histopathological severity is largely unknown. Objective: To investigate correlations between muscle MRI abnormalities and histopathological severity in healthy controls and patients with muscle disease. Methods: We performed quantitative MRI and histopathological analysis in 35 patients with inclusion body myositis, facioscapulohumeral muscular dystrophy or oculopharyngeal muscular dystrophy and 12 healthy controls. Participants contributed needle biopsies of the vastus lateralis and/or tibialis anterior, yielding 77 muscle biopsies with matched T1, T2 and TIRM MRI imaging. Muscle biopsies were evaluated with a semi-quantitative histopathology severity grading scale (range 0–12) and an inflammation severity grading scale (range 0–3). Results: In muscle disease, histopathology sum scores ranged from 0 to 11 and correlated significantly with fat percentage as measured on MRI (Spearman’s rho = 0.594, p < 0.001). Muscle edema on muscle MRI was associated with increased amounts of inflammation (p < 0.001). Mild abnormalities occured in 95% of control biopsies and were more pronounced in tibialis anterior (median sum score of 1±1 in vastus lateralis and 2±1 in tibialis anterior (p = 0.048)). Conclusion: In muscle disease, fatty infiltration on MRI correlates moderately with muscle histopathology. Histopathological abnormalities can occur prior to the onset of fatty infiltration. In middle-aged controls, almost all biopsies showed some histopathological abnormalities. The findings from this study may facilitate the choice for appropriate imaging sequences as outcome measures in therapeutic trials.

Carpal tunnel syndrome (CTS) is the most frequently operated neurological disorder of the hand. Incidence of patients remaining symptomatic has been reported up to 30% after primary release. Revision surgery remains challenging although multiple surgical options have been described. In this case series a simple novel technique, the palmaris longus interposition, is described for the treatment of recurrent and persistent CTS. Patients who underwent PLI between October 2013 and 2018 and without underlying neurological or hand disorders severely affecting the operated hand were eligible for inclusion. All were preoperatively diagnosed with recurrent or persistent CTS based on clinical assessment. Eighteen patients with 20 operated hands consented to the study. Patient characteristics were retrospectively reviewed, including nerve conduction studies and ultrasound scans. Patients were postoperatively asked to classify their symptoms as resolved, improved, not improved or worsened. In addition, postoperative symptom severity and functional status were assessed using the Boston Carpal Tunnel Questionnaire. Ten hands showed recurrent symptoms while the other 10 showed persistent symptoms. The average follow-up was 15 months. No improvement was reported in 5 hands, whereas improvement or complete relief of symptoms was reported in 15 hands. The mean total score of the Boston Carpal Tunnel Questionnaire postoperatively was 2.29 and ranged between 1.26 and 4.32. These results suggest that using the palmaris longus tendon as interposition graft between the leaves of the flexor retinaculum may be a suitable technique for the management of patients with mild to moderate symptoms of recurrent and persistent CTS. Further research should investigate whether this technique has better outcome compared to other procedures.

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