Successful Surgical Treatment of an Intraneural Ganglion of the Common Peroneal Nerve
Intraneural ganglion cysts of peripheral nerves occurring within the epineural sheath are rare, and their mechanism of formation and treatment options are debated. We present a case of a 41-year-old man who presented with a complaint of lateral-sided left knee pain with numbness on the lateral side of the foot who was diagnosed with an intraneural ganglion of the common peroneal nerve (CPN). He was treated initially with common peroneal epineural decompression only to have symptoms recur 6 weeks postoperatively. The patient was subsequently treated utilizing the suggestions of the “unified articular theory,” which proposes a small recurrent articular branch of the CPN as the source of cyst fluid. This branch was surgically detached, leading to complete alleviation of his symptoms. When the patient was reevaluated 2 years postoperatively, his preoperative symptoms had resolved, and a follow-up magnetic resonance image showed resolution of the enlargement of the CPN.
The applications of the unified articular theory also extend beyond intraneural ganglia of the CPN. While the CPN is the most common location for intraneural ganglion occurrence,6,17,20 cases have also been described of intraneural ganglion cysts of the tibial nerve at the proximal tibiofibular joint, as well as via the posterior tibial and medial plantar nerves at the subtalar joint within the tarsal tunnel.11,18-23 Most cases involving the posterior tibial and medial plantar nerves were found in patients presenting with signs of tarsal tunnel syndrome.22,23 Intraneural ganglia have also been found within the superficial peroneal nerve arising from the inferior tibiofibular joint.20 In certain cases, these ganglia have also been noted to connect to the joint via a small articular branch.19,22 In 1 case of an intraneural ganglion of the tibial nerve at the superior tibiofibular joint, initial conservative surgery led to early recurrence of symptoms.19 Just as in our case, the patient returned to the operating room and, after isolation and ligation of an articular branch, the patient experienced long-term resolution of both the symptoms and the cyst.19
Given the overwhelming evidence in support of the unified articular theory, we agree with the recommendation by Spinner and colleagues19 to search for an articular branch both via preoperative imaging and during the operation itself in all cases of intraneural ganglia. Assuming the mechanism of cyst formation is the same in most cases of intraneural ganglia, one could reasonably apply the same surgical techniques used in our case to the management of all intraneural ganglia, drastically reducing recurrence rates.
Conclusion
Based on research and corroborated by this case, the key to successful operative treatment of a common peroneal intraneural ganglion is division of the recurrent articular branch, which connects the proximal tibiofibular joint to the CPN.6,9,11,12,14 Evidence has shown that disconnecting the articular branch and disrupting the source of the intraneural ganglion can resolve the condition and dramatically diminish the chance of recurrence.6,8,12,14 This has become known as the unified articular theory.6,12,14 Reports also suggest that, without disconnecting this articular branch, intraneural ganglion recurrence rates may be higher than 30%.6,12,14,19 This case, therefore, supports the findings of previous authors9-11,14 and provides an example of successful utilization of the treatment protocol delineated by Spinner and colleagues.10,11
