Isolated medial plantar neuropathy caused by a large ganglion cyst diagnosed with MRI: A case report

INTRODUCTION Although ganglion cysts are common soft tissue tumors, nerve compression syndrome caused by a ganglion cyst in the lower extremities is very rare. Herein, we report a 57-year-old man who presented with hypoesthesia in the sole of his right foot for 6 months. We believe that reporting this rare case will help clinicians update their knowledge on possible causes of the plantar neuropathy, and avoid diagnostic delay. PRESENTATION OF CASE The patient had pain and numbness in the inner right sole, as well as a tingling and dull sensation. Tenderness around the area of abnormal sensation was not evident. Percussion at the abductor tunnel gave a positive Tinel's sign in the medial plantar nerve. No mass was palpable in the right foot. Based on the electrophysiological findings, we diagnosed medial plantar nerve entrapment in the right foot. Magnetic resonance imaging (MRI) was conducted to identify a 5.5-cm long elongated cystic lesion as the cause of entrapment. The patient underwent surgical removal of the cystic mass, with histologic examination confirming the diagnosis of a large ganglion cyst. DISCUSSION The feasibility of nerve conduction studies and electromyography for detection of nerve entrapment is still controversial. MRI is considered the best diagnostic modality, if biopsy is not feasible. CONCLUSION We suggest that foot imaging and electrophysiological studies should be considered for patients with isolated median plantar neuropathy to exclude the presence of space-occupying lesions, especially when conservative treatment is not effective.