Intramuscular Ganglion Cyst of the Flexor Hallucis Brevis Secondary to Muscle Tear: A Case Report

In the current study, we present a case of an intramuscular ganglion cyst in the flexor hallucis brevis muscle (FHB) that arose secondary to a muscle tear. Through this study, we propose a possible aetiology for the development of intramuscular ganglionic cysts. A 50-year-old woman presented with acute pain and swelling over the right mid-plantar area after prolonged kneeling for scrubbing floors. Ultrasonography examination performed at 5 days after the onset of symptoms revealed a partial tear of the right FHB. Follow-up evaluations were conducted, with magnetic resonance imaging and ultrasonography, at 24 and 54 days after symptom onset. MRI revealed a ganglion cyst in the mid-portion of the FHB without connection to the adjacent joint capsule or tendon sheath. On the ultrasonography examination at 45 days after onset, at the same location where a tear was seen on the initial examination, an anechoic defect in the mid-portion of the FHB was observed, compatible with a ganglion cyst. Given the favourable natural evolution, no aspiration or surgery were performed. The patient was discharged with minimal symptoms. The results suggest that the intramuscular ganglion cyst can develop following a muscle tear.