Accessory soleus muscle causing tarsal tunnel syndrome: A case report

Abstract

The accessory soleus muscle is a rare anatomical variant which can cause significant clinical symptoms such as tarsal tunnel syndrome (TTS) due to extrinsic compression of the posterior tibial nerve. This case report describes a 40-year-old male with a persistent left ankle mass, presenting with exercise-induced pain and discomfort. Despite conservative treatments including physical therapy and anti-inflammatory medications, his symptoms persisted. Physical examination revealed a non-mobile mass at the medial aspect of the left ankle and a positive Tinel's sign over the posterior tibial nerve. MRI confirmed the presence of an accessory soleus muscle. Surgical excision of the hypertrophic muscle resulted in complete resolution of symptoms. Postoperative follow-up over three years demonstrated a well-healed surgical site, intact motor function, and no recurrence of the mass. This case underscores the clinical significance of considering this anatomical variant in the differential diagnosis of persistent ankle masses and the efficacy of surgical intervention in symptomatic cases.