Foot Drop Caused by an Intraneural Ganglion Cyst: A Case Report

Foot drop (FD) refers to a clinical picture characterized by the inability to lift the foot against gravity due to weakness of the dorsiflexor muscles. Patients with FD typically present with an abnormal gait marked by exaggerated flexion of the knee and hip joints, along with internal rotation of the foot, which may increase the risk of falls and injuries. Intraneural ganglion cysts are benign, fluid-filled lesions located within the epineurium of peripheral nerves. We report the case of a 22-year-old male who presented with right lower limb pain and numbness and later developed acute weakness of the right foot, resulting in complete FD that persisted for four months. He denied any history of trauma and was otherwise medically healthy. On examination, there was muscle wasting in the anterior and lateral compartments of the right leg, complete FD with 0/5 power in dorsiflexion and eversion, and reduced sensation along the distribution of the right common peroneal nerve (CPN). Local examination revealed a palpable and tender swelling around the neck of the right fibula. Plain X-rays revealed no abnormalities; however, MRI demonstrated a small cystic soft tissue lesion located posterolateral to the proximal fibular head, measuring 5 x 1.5 x 2.5 cm. Surgical exploration of the right CPN was performed with neurolysis and excision of the lesion. Histopathological examination confirmed the diagnosis of a ganglion cyst. Postoperatively, the patient had an uneventful recovery, and after two weeks of physical and occupational therapy, he reported improvement in pain and numbness, although motor function remained unchanged at that time. The association between FD and ganglion cysts is a rare pathology; however, it should be included in the differential diagnosis of FD, particularly in the absence of trauma.