Ultrasound-Guided Pulsed Radiofrequency Neuromodulation Versus Ultrasound -Guided Phenol Neurolysis in Post-Stroke Hemiplegic Shoulder Pain: A Randomized Controlled Trial

Hemiplegic shoulder pain (HSP) is a common complication following stroke. It may lead to withdrawal from rehabilitation programs, reduced upper-limb movement and poorer functional recovery; therefore, timely pain control is relevant to rehabilitation participation and long-term outcome. [1] A systematic review reported wide variation in incidence and prevalence; pooled/meta-analytic estimates included incidence ranges around 10-22% and prevalence ranges around 22-47%, while individual studies varied more widely because of differences in timing, definitions and clinical settings. Risk factors include increased tone, impaired motor function, sensory impairment, shoulder subluxation, abnormal shoulder examination, hemispastical neglect and prior shoulder pain. [1,2] The cause of post-stroke HSP is often multifactorial. The mechanisms can be grouped into: (a) impaired motor control and tone changes; (b) soft-tissue lesions and (c) altered peripheral and central nervous activity, Because these mechanisms may overlap in the same patient, baseline clinical and ultrasound phenotyping will be used to document the dominant pain/spasticity pattern and to exclude structural shoulder pathology requiring surgical management. [1,3,4] Central sensitization, defined as increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold afferent input, may contribute to persistent HSP. [4] Pulsed radiofrequency delivers radiofrequency current in intermittent pulses consisting of short periods of electrical stimulation, typically 20 ms, followed by longer silent phases, approximately 480 ms. This intermittent delivery allows heat dissipation and keeps target tissue temperature below approximately 42 degrees Celsius, thereby reducing the risk of thermal nerve injury. For this reason, the intervention is described in this enhanced protocol as PRF rather than conventional thermal radiofrequency ablation. This correction improves technical accuracy because the submitted synopsis described a PRF technique rather than destructive thermal ablation. [5] PRF stimulation may reduce pain through long-term depression of C-fiber-mediated spinal sensitization and several neuromodulatory effects on inflammatory and descending inhibitory pathways. The exact mechanism remains elucidated; therefore, the study will measure both pain and function rather than assuming a single mechanism of benefit. [5,6] Phenol is a neurolytic agent used to manage focal spasticity. Immediately after injection, phenol may produce a transient local anesthetic effect by reversibly blocking nerve conduction. At neurolytic concentrations, commonly around 5-6%, phenol causes protein denaturation with segmental demyelination, axonal degeneration, and Wallerian degeneration of exposed nerve fibers, interrupting nerve conduction and reducing overactivity. Because phenol can cause dysesthesia, pain, inflammation, hypotension or unintended motor/sensory effects, the protocol specifies ultrasound guidance, aspiration before injection, limited per-nerve volumes according to institutional SOP, post-procedure monitoring, and structured AE recording.