Abstract
Background: Intraneural ganglion cysts are rare benign mucinous lesions that arise within the epineurium of peripheral nerves. They represent an uncommon but surgically treatable cause of common peroneal neuropathy. Because their clinical presentation may mimic lumbar radiculopathy, entrapment neuropathy, or peripheral nerve sheath tumour, significant diagnostic delay is frequent.
Case Presentation: We report a 35-year-old man who presented with progressive foot drop and gait impairment. Magnetic resonance imaging (MRI) demonstrated a cystic lesion along the common peroneal nerve at the fibular neck, producing focal neural compression. Microsurgical exploration through a lateral approach was performed. The common peroneal nerve was identified, decompressed, and preserved. Intraoperative neurophysiological monitoring—including motor evoked potentials (MEPs) and direct nerve stimulation—guided safe fascicular dissection. A translucent cystic lesion containing gelatinous material was evacuated and excised. Histopathological examination confirmed a fibrous cyst wall with mucinous contents and no epithelial lining or malignant features, consistent with a ganglion cyst. The postoperative course was uneventful; foot drop resolved completely, and the patient regained normal independent walking.
Conclusion: This case highlights the importance of considering intraneural ganglion cyst in young adults with non-traumatic foot drop. Early MRI diagnosis, meticulous nerve-preserving microsurgery, and neurophysiological monitoring may permit excellent functional recovery. The articular/synovial theory of pathogenesis underscores the need to identify and address the joint connection and articular branch to reduce recurrence.
