Objective: This study examined the activation difference of muscles innervated by cervical cord 5-6 (C5-C6) and cervical cord 8- thoracic cord 1 (C8-T1) in upper limb flexion synergy after stroke.Methods: Surface electromyography (sEMG) signals were collected during elbow flexion in stroke patients and healthy controls. The study compared normalized activation of two pairs of muscles that could cause similar joint movement but which dominated different spinal cord segments (clavicular part of the pectoralis major, PC vs. Sternocostal part of the pectoralis major, PS; Flexor carpi radialis, FCR vs. Flexor carpi ulnaris, FCU). In each muscle pair, one muscle was innervated by the same spinal cord segment (C5-C6), dominating the elbow flexion and the other was not. The comparison of the activation of the same muscle between patients and healthy controls was undertaken after standardization based on the activation of the biceps brachii in elbow flexion.Results: There was no difference between the PC and PS's normalized activation in healthy controls while the PC's normalized activation was higher than PS in stroke patients during elbow flexion. Similarly, there was no significant difference in normalized activation between FCR and FCU in healthy controls, and the same is true for stroke patients. However, the standardized activation of both FCR and FCU in stroke patients was significantly lower than that in healthy controls.Conclusion: After stroke, the activation of the distal muscles of the upper limb decreased significantly regardless of the difference of spinal cord segments; while the activation of the proximal muscles innervated by the same spinal cord segment (C5-C6) dominating the elbow flexion showed higher activation during flexion synergy. The difference in muscle activation based on spinal cord segments may be the reason for the stereotyped joint movement of upper limb flexion synergy.

Objective: To study differential post-stroke changes of excitability of spinal motor neurons innervating a group of antagonist muscles of ankle and their effects on foot inversion.Methods: F waves in tibialis anterior (TA) and peroneus muscles (PN) were recorded. The condition of spasticity and foot inversion in stroke patients were also evaluated. The differences of F wave parameters between patients and healthy controls (HC), as well as TA and PN, were investigated.Results: There were natural differences in the persistence of the F waves (Fp) and F/M amplitude ratio (F/M) between TA and PN in HC. Stroke patients showed significantly higher F/M in TA and PN, while there was no difference in Fp comparing to HC. The natural differences in F wave parameters between TA and PN were differentially retained after stroke. The natural difference of the two muscles in Fp remained unchanged and the F/M difference disappeared in those without spasticity or foot inversion, while the Fp difference disappeared and the F/M difference remained in those with spasticity or foot inversion.Conclusion: Based on the natural difference of the number and size of spinal motor neurons innervating TA and PN, their excitability may change differently according to the severity of the stroke, which may be the reason of foot inversion.

Objectives: To characterize urodynamic findings after lower-level spinal cord injury (LSCI) and to evaluate a new pressure-based classification framework—the bladder–sphincter dyscoordination syndrome (BSDS)—for describing voiding patterns. We also introduce a descriptive “neurogenic bladder outlet obstruction” (NBOO) phenotype for straining-dependent voiding difficulty. Methods: We retrospectively analyzed the first urodynamic studies (December 2020–August 2024) in 81 men with LSCI (injury at T10 or below). Key urodynamic measures included detrusor and intravesical pressures during filling and voiding, bladder volumes (first desire to void and capacity), compliance, maximum flow rate (Q_max), post-void residual (PVR), voiding efficiency, and the ratio of detrusor to abdominal pressure rise (ΔPdet/ΔPabd). We compared cases with detrusor overactivity (DO) versus those without DO. Among those with voiding discoordination, we distinguished classical detrusor–sphincter dyssynergia (DSD) from a proposed NBOO phenotype (characterized by abdominal straining pressure ≥ 40 cmH₂O, detrusor pressure < 20 cmH₂O, incomplete emptying, and no anatomic obstruction). We further classified discoordination cases using the BSDS framework into four subtypes—dual high-pressure (DHP), detrusor-muscle predominant (DMP), dual low-pressure (DLP), and abdominal-pressure predominant (APP)—based on reference pressure thresholds (detrusor 20 cmH₂O; abdominal 40 cmH₂O). Results: Patients with DO (43.2%) showed significantly higher detrusor pressures during filling (at first desire to void and at capacity) and a lower first desire volume than non-DO patients, while maximum capacity was similar (p = 0.105). During voiding, DO cases had lower PVR and higher emptying rates, although the detrusor-vs-abdominal pressure contribution (ΔPdet/ΔPabd) was comparable between groups. Among 63 patients with voiding discoordination, 32 (50.8%) met NBOO criteria; these NBOO cases exhibited lower detrusor and intravesical voiding pressures but worse emptying (higher PVR) compared to classical DSD cases. Overall, 76 of 81 patients (93.8%) fit within the BSDS classification—distributed as 22 DHP, 13 DMP, 15 DLP, and 26 APP patterns. Conclusions: The BSDS framework (and the NBOO descriptor when conventional indices cannot be applied) offers a novel way to describe voiding patterns after LSCI. It links urodynamic observations to potential management strategies (by identifying whether the bladder or outlet is the primary issue). Prospective studies are needed to validate this framework against outcomes such as upper tract integrity, continence, and dependence on catheterization.