gms | German Medical Science

Objective: To evaluate histopathological alterations in perineural tissue potentially involved in pathogenesis and postoperative outcome of cubital tunnel syndrome (CUTS).

Methods: 46 consecutive patients with CUTS were included. Demographic and clinical data (preop, post-op) were collected and surgery was performed as a simple open decompression of the ulnar nerve. Perinerval tissue samples proximal and distal to the ulnar sulcus were collected and semiquantitavely analyzed for histopathological changes.

Results: 27 patients (58.7%) had surgery on the left, 19 on the right hand side with a mean duration of preoperative symptoms of 8.6±11.1 months with no difference between the right and the left side (p=1.0). 34 patients presented with a mild CUTS (LSU score 4-5/5), 12 patients with a moderate CUTS (LSU score 2-3/5). Preoperative nerve conduction studies (NCS) showed a mean motor nerve conduction velocity of 27.5±10.89 m/s. There was an equal distribution of degenerative alterations in the proximal and distal samples (p=0.42) and only minor signs of inflammation and scattered Renault bodies in all samples.

Patients with slower preoperative NCS (<32m/s) showed a trend towards increased fibrosis (p=0.09), significantly more disintegration of connective tissue (p=0.015) and accumulation of mucoid material (AMM) (p=0.015). We observed a trend regarding patients with muscular atrophy showing more fibrosis (p=0.06). Patients treated on the left side showed significantly more disintegration of connective tissue/collagen fibers and AMM (p=0.0362) with a comparable duration of preoperative symptoms (p=1.0). Long-term clinical follow up was completed in 24 patients (20±18 months). LSU grade (p=0.0063) and NCS improved significantly after surgery (p<0.0001, 50±19.2 m/s) with 91.7% of the patients reporting a favorable subjective outcome.

Conclusion: Up to date, pathogenesis of CUTS and correlation of clinical and nerve conduction findings is still unclear. In this study, considerable connective tissue remodeling and degenerative changes, but only minor signs of inflammation were observed in the majority of patients, suggesting a primarily degenerative process. Of note, patients with slower preoperative NCS showed a higher degree of fibrotic changes. This possibly reflects a correlation between the alteration of perineural tissue and nerve function, which could be taken into consideration for future grading scores of CUTS.