Transcranial direct current stimulation over the primary motor cortex and dorsolateral prefrontal cortex for Achilles’ tendon pain modulation: a case report of an elite soccer player

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Abstract
INTRODUCTION: Managing partial Achilles’ tendon tears in elite soccer players during a competitive season requires a balance between structural healing and performance maintenance. Transcranial direct current stimulation (tDCS) has emerged as a potential neuromodulatory adjunct to manage pain and optimize motor efficiency through top-down regulation. OBJECTIVES: This case report evaluates the effects of a 17-session dual-site tDCS protocol on pain modulation, competitive performance, and structural tendon repair in a professional top-level soccer player. MATERIALS AND METHODS: The intervention consisted of 17 tDCS sessions (2mA) using a dual-target montage: anodal stimulation over the left primary motor cortex (M1) and left dorsolateral prefrontal cortex (DLPFC), with cathodal electrodes over the supraorbital and contralateral frontal midline areas. Assessments included the Visual Analog Scale (VAS) for pain and the Rating of Perceived Exertion (RPE) for recovery training and competitive matches. Structural evolution was monitored via serial ultrasonography (US) and confirmed by multi-sequence magnetic resonance imaging (MRI). RESULTS: The athlete exhibited a positive pain-exertion dissociation: a consistent progressive reduction in VAS pain scores occurred simultaneously with an increasing trend in match-play RPE, indicating a higher capacity for physical exertion despite the injury. Training RPE remained stable and low (1–3), reflecting controlled recovery workloads. Serial axial US initially identified a partial tear in the lateral and deep fibers with laminar fluid. A 30-day follow-up US and MRI (T1, T2-weighted with fat saturation) confirmed successful tissue repair, with intermediate-signal intensity tissue filling the defect, indicating organized scar formation without transfixing lesions. Serial axial ultrasonography initially identified a partial tear within the lateral and deep fibers of the tendon midbody, accompanied by localized laminar fluid. A 30-day follow-up, utilizing US and multi-sequence MRI (T1; T2-weighted with fat saturation), confirmed structural restoration. The previous defect was replaced by tissue of intermediate-signal intensity, consistent with organized fibroblastic repair and scar formation, in the absence of residual transfixing lesions. CONCLUSION: The dual-site tDCS intervention was associated with significant pain modulation and improved motor efficiency, allowing the athlete to increase competitive output during the structural healing phase. The correlation between reduced pain (VAS), increased match effort (RPE), and confirmed biological repair suggests that tDCS facilitated an optimal environment for recovery. This suggests that tDCS is a promising adjunct for maintaining elite performance during injury rehabilitation, though further controlled research is needed to elucidate the specific mechanisms of tDCS-mediated tissue repair.