Severe Parsonage-Turner Syndrome and Surgically Managed Traumatic Brachial Plexopathy: Motor-Unit Reinnervation and Functional Recovery.

Long-term motor recovery after absent motor-unit activation on EMG is incompletely characterized in Parsonage-Turner syndrome (PTS) and traumatic brachial plexopathy (TBP). Surgery has been proposed for focal nerve constrictions in PTS, whereas nerve reconstruction is standard for severe TBP. We compared muscle-level reinnervation and functional outcomes in electrodiagnostically severe PTS and surgically treated TBP, and assessed MRI-identified focal nerve constrictions in PTS. Between January 2001 and December 2024, patients with PTS or TBP demonstrating absent motor-unit activation on baseline EMG and follow-up were reviewed. TBP inclusion required surgical management. In PTS, MRIs were reviewed in a blinded fashion to assess for focal nerve constrictions. Kaplan-Meier methods evaluated time to reinnervation. Functional outcomes were assessed using Disabilities of the Arm, Shoulder, and Hand (DASH) scores, comparing earliest available baseline and last follow-up assessments. Eighty-five patients with PTS (217 muscles; median age 57, 28% female) and 150 surgically treated TBP patients (683 muscles; median age 31; 19% female) met inclusion criteria. Among PTS muscles without activation, spontaneous reinnervation occurred in 86% (88% shoulder, 71% arm, and 87% forearm/hand), with median time to reinnervation of 344 days (95% CI 304-419). Functional improvement was greater in PTS than TBP, with mean DASH improving from 54.1 to 9.4 (Δ44.7, d = 3.17) vs 60.4 to 50.6 (Δ9.8, d = 0.47). PTS patients with residual disability (DASH ≥15) had higher recurrence rates and broader muscle involvement. Among 52 PTS MRIs undergoing blinded rereview, 2 (4%) demonstrated high-grade focal nerve constrictions and varied outcomes. In TBP, nerve-reconstructed muscles had higher reinnervation rates than nonreconstructed muscles (73% vs 33%), particularly proximally. Earlier reconstruction was associated with higher reinnervation (<3 months 88% vs > 6 months 59%; p = 0.02). Late tendon transfers restored joint motion in 60% (mean 650 days; range 130-2096). In electrodiagnostically severe PTS, spontaneous reinnervation occurred in most muscles with substantial functional improvement. High-grade focal nerve constrictions were uncommon in patients with PTS. Although TBP outcomes demonstrated benefits of reconstructive strategies for traumatic nerve injury, the recovery pattern in PTS cautions against extrapolating TBP surgical strategies to an immune-mediated plexopathy. This study provides Class III evidence among those without motor unit activation on initial EMG of high spontaneous recovery rates in PTS compared with TBP where nerve reconstruction and tendon transfers are required for modest improvements.