Outcomes Following Surgery for Common Peroneal Nerve Intraneural Ganglion Cysts: A Case Series and Systematic Review

Intraneural ganglia are benign, mucinous, cystic structures that pathologically exist in the epineural tissue of peripheral nerves and differ in location from extraneural ganglia, which are external to the neural sheath.¹ They are most frequently found in the common peroneal nerve, although their occurrence in tibial and ulnar nerves has also been well described.^2,3 It is currently hypothesized that these cysts originate at the point of entry of articular branches of nerves crossing a neighboring joint and may propagate along this branch to reach the main nerve trunk.^3,4 Signs and symptoms are consistent with a local compressive effect, resulting in distal neuropathy of the affected nerve. In the case of the common peroneal nerve, a motor and sensory deficit may be observed in the lateral and anterior compartments of the leg, often associated with a swelling adjacent to the fibular neck.^3,5

Several treatment modalities exist, from nonoperative measures, such as image-guided aspiration, to operative intervention. The former is relatively unsuccessful and associated with cyst recurrence. The latter often consists of decompressing the nerve, cyst excision, and segmental excision of the articular branch in the case of the common peroneal nerve.^3,6 Various outcomes have been reported in the literature; however, the success of these procedures should be defined by the rate of neurological recovery and absence of recurrence of the lesions.

This study presents a case series of clinical outcomes following surgical intervention for common peroneal nerve intraneural ganglion cysts at our center over the past decade. These findings are reported in parallel with a review of the existing literature.

Case Series

This project was registered with the clinical audit department at University Hospitals Birmingham National Health Service Foundation Trust. A list of all patients undergoing excision of common peroneal nerve intraneural ganglia from January 2012 to January 2022 was retrieved, and a retrospective chart review was undertaken. Demographic data, pre- and postoperative history, and examination findings were collected and analyzed. 

Patient Assessment and Surgical Technique

Following referral to our peripheral nerve service, patients are assessed per a standard protocol in which a comprehensive patient history is obtained and examination, including peripheral neurological examination of the lower limbs, is performed. Magnetic resonance imaging (MRI) scanning is undertaken if an intraneural ganglion is suspected. On T2-weighted imaging, a ganglion appears as a hyperintense lesion often associated with the superior tibiofibular joint (STFJ; Figure 1). Such changes as reduced anterior compartment muscle mass and secondary denervation edema may also be observed. General anesthesia without neuromuscular paralysis and intraoperative nerve stimulation is recommended for the surgical excision. Preoperatively, the patient is placed in the lateral position with the ipsilateral leg uppermost. A pneumatic thigh tourniquet may be used; however, protracted tourniquet ischemia beyond 30 minutes renders nerve stimulation thresholds unreliable due to conduction block. A curvilinear incision is made along the course of the common peroneal nerve from posterior to the biceps femoris insertion, over the peroneal nerve at the fibula neck to the junction of the septum between anterior and lateral compartments of the lower leg, with deep dissection to expose the common peroneal nerve. The common peroneal nerve is mobilized circumferentially at the level of the fibula head, and a silicone loop is passed around the nerve and used for gentle retraction. The nerve is dissected in a proximal to distal direction, releasing the fascia of the peroneus longus to expose the bifurcation of superficial and deep branches, which are each tagged with silicone loops (Figure 2). The fascia incision continues obliquely along the course of the nerve, over the anterior compartment to expose the tibialis anterior muscle. The fascial septum between the peroneus longus and the tibialis anterior is excised superficially and deep to the tibialis anterior motor branch, which is tagged with a silicone loop. The articular branch to the proximal tibiofibular joint is identified and tagged in the same way. 

The peroneus longus branches should also be identified and tagged to confirm the anatomy, which may be distorted due to displacement from the ganglion or scar from previous ganglion ruptures. The branches are stimulated to measure stimulation thresholds and the quality of retained function. A normal nerve motor branch should contract at 0.1 mA stimulation with evidence of recruitment as the stimulation is increased to 0.5 to 1.0 mA to produce a maximum contraction. 

Often the intraneural ganglion will have tracked along the articular branch to the STFJ, adjacent to the deep peroneal nerve branch to the tibialis anterior, which is often denervated. The superficial peroneal nerve branches are usually involved later as a ganglion propagates into the main common peroneal nerve trunk. The ganglion is traced from the STFJ to the main nerve. A cuff of capsule should be excised around the articular branch to reduce the rate of ganglion recurrence. This may then be held and used to provide gentle traction as the fascicles to the articular branch are carefully dissected from the peroneal nerve. The epineurium must be incised, and interfascicular dissection is recommended using the operating microscope. The ganglion may propagate along the intrafascicular epineurium, distorting the nerve and enlarging it, making it susceptible to extrinsic compression from the overlying peroneal tunnel roof. The neuropathy associated with intraneural ganglia is a combination of compression and scar following rupture. The excised tissue is then sent to the histopathology laboratory for formal diagnosis.⁷

Systematic Review

The terms intraneural and ganglion were combined to perform a thorough literature search using the EMBASE and MEDLINE databases (via Ovid). Title, abstract, and subsequent full-text article screening were performed in parallel by 2 independent investigators (HKNK and LD). Only articles reporting outcomes following excision of intraneural ganglia in common peroneal nerves were included. Studies with fewer than 5 patients and those solely assessing pediatric patients (<18 years of age) were excluded. Editorials, case reports, and conference abstracts were not included. All coauthors discussed any disagreement between the 2 investigators before reaching a final verdict regarding study inclusion. 

Where available, the following data were extracted from each included study: country of study, number of patients, location of ganglia, length of follow-up, outcome measures, pre- and postoperative power of foot dorsiflexion, foot eversion and hallux extension according to Medical Research Council (MRC) grade, recurrence of ganglion cysts, and other outcomes. Due to the heterogeneity of outcome measures, only qualitative analyses were performed. Risk of bias was assessed for each study using the National Institutes of Health (NIH) Quality Assessment Tool for Case Series.⁸

Case Series

Over the study period, 5 patients underwent procedures to decompress the common peroneal nerve with resection of an intraneural ganglion and neurectomies of articular branches to the proximal tibiofibular joint (Table 1). The majority of patients were male, with a median age of 49 years (range, 37-57 years). Foot drop or loss of foot control, pain, and swelling in the region of the peroneal tunnel were common presenting complaints. Preoperative examinations frequently revealed deficits in sensation in the deep and superficial peroneal nerve territories (with the former more pronounced) and reduced power in extensor hallucis longus (EHL), extensor digitorum longus (EDL), tibialis anterior, peroneus longus, and brevis functions. 

Following an initial postoperative clinic visit 1 week after his procedure, one patient did not attend any further appointments. Although no complications were reported, there was no documentation of procedure outcomes regarding foot function. In the remaining cases, follow-up duration ranged from 4 to 14 months. 

Motor function of the muscles of the anterior and lateral compartments of the leg improved in most patients following surgery. In 3 cases, sensory deficit was documented, with an improvement in the deep peroneal nerve distribution following surgery. However, sensation in the superficial peroneal nerve territory was inconsistent with variable results seen. There were no cases of ganglion cyst recurrence. In 1 case (Patient E), a 9-cm intraneural ganglion extending into the common peroneal and posterior tibial nerves was identified. Power of the muscles in the posterior compartments also improved following excision of the ganglion in this case.

Systematic Review

The initial search returned 377 articles in MEDLINE and EMBASE (via Ovid). Following de-duplication and title, abstract, and full-text screening, 6 studies were identified for inclusion (Figure 3).^2,6,9-13 These reports included a total of 128 patients, 93 with intraneural ganglia only and 35 with both intraneural and extraneural ganglia. A summary of the findings is shown in Table 2. Postoperative examinations demonstrated increased power of ankle dorsiflexion, eversion, and hallux extension when reported as outcomes of interest. Although pain and sensation were often not reported, excision of intraneural ganglia improved these parameters. Recurrence of ganglia ranged from 0% to 25%. Except for 1 study,¹⁰ all cases of recurrence were extraneural. All studies were relatively well-designed case series; however, most did not document whether cases were consecutive or provide details on individual patients. A summary of the quality assessment is presented in Table 3.

The pathogenesis of intraneural ganglia has long been debated, with several mechanisms proposed. However, the most widely accepted theory, often termed the “articular” or “synovial” theory, suggests that these benign structures originate from the synovium of neighboring joints. First proposed by Spinner and colleagues in 2003, the theory suggests that the lesion arises from the compromised capsule of an adjacent joint, often secondary to a traumatic event or degenerative disease. In the case of a common peroneal nerve intraneural ganglia, the STFJ is responsible. Synovial fluid migrates within the epineurium of its articular branch before emerging along the common peroneal nerve, resulting in compression neuropathy of the deep and superficial branches of this nerve.^3,4,14 Therefore, the lesion is associated with clinical signs and symptoms of common peroneal palsy, such as foot drop, altered foot sensation,  pain, and a positive Tinel’s sign. 

Basing the diagnosis on the history alone, however, may be challenging. The differential diagnoses are vast, including both endocrine disorders and compression neuropathy from inappropriately fitted splints.¹⁵ Thus, radiological investigations, including MRI, are useful for accurate diagnosis. Extraneural cysts do not invade the articular branch but may maintain a connection to the joint capsule.¹⁶ Histology shows evidence mucoid lumen with a surrounding collagenous membrane.¹³

Our case series consisted of 4 male patients and 1 female patient, each of whom demonstrated classic signs of common peroneal nerve intraneural ganglia upon referral to our tertiary peripheral nerve service. This is consistent with previously published literature and most of the included studies in our review, where a male preponderance was observed.^2,3,6,11-13 

Our surgical technique involved identifying the common peroneal nerve and complete excision of the intraneural ganglion, followed by excision of the articular branch. This method is based on the proposed theory of the cyst arising from the STFJ; thus, removal of the articular branch is hypothesized to reduce the recurrence rate. A similar strategy was employed by authors of all included studies in this systematic review, with the exception of one.² Papanastassiou et al performed an excision of the ganglia in isolation without identifying the articular branch to the STFJ.² Recurrence (in the form of extraneural ganglia) was noted in 25% of patients,² a rate much higher than that observed in the remaining studies.^6,9-13 Furthermore, another study reported intraneural recurrence in all patients who had undergone resection of the ganglia in isolation, with no intraneural recurrence in patients in whom an articular branch neurectomy was performed.¹³ 

More radical procedures exist, as shown by Wilson and colleagues.^6,12 As these lesions are thought to arise from the synovial fluid of the STFJ, this group also excised the articular surface of the joint in addition to ligating the articular branch. No compromise in joint stability was observed; however, a more extensive resection (as measured by the volume removed) was associated with a lower rate of extraneural recurrence.⁶ The authors proposed that extraneural recurrence is secondary to either an incomplete excision of the STFJ articular surface or synovium from the tibiofemoral (knee joint) extending distally.^6,17 Some surgeons have also described STFJ arthrodesis for the prevention of recurrence.²

The anterior and lateral compartments of the leg consist of muscles, supplied by branches of the common peroneal nerve responsible for ankle and toe dorsiflexion and eversion of the foot at the subtalar joint. Therefore, motor function was routinely assessed pre- and postoperatively by testing these movements. Where data were available in our local cohort, improvements in power per the MRC grade were observed. These findings are consistent with all of the studies included in this review with similar endpoints.^9-13 Patient-reported outcome measures were infrequently reported, although neuropathic pain resolved in many cases. One study used the Musculoskeletal Tumor Society score (MSTS) to assess outcomes, showing an improvement in the mean MSTS scores following surgery.² This tool was developed for use by a clinician who assigned a score to several domains related to the patient’s functional status.^18,19 Although this is not a true patient-reported outcome measure, certain domains (such as pain) rely on the patient’s history. Therefore, one can extrapolate that both patients and clinicians perceived intraneural ganglia excision to be beneficial.

Intraneural ganglia are relatively rare, as is the number of procedures we have performed at our center over the past decade. Furthermore, the incidence of this benign lesion without neurological sequalae is not known. Thus, the small number of patients in our case series is a key limitation of this study. Furthermore, as the case series and several studies in the systemic review were retrospective, data were often missing or incomplete. There was also inconsistent documentation of findings in clinic, with some patients only having MRC grades and sensation numerically recorded for certain nerve branch territories. One of the 4 patients in the case series was lost to follow-up after 1 week, hence no reliable conclusions can be made on the success of his procedure. Additionally, our patients did not routinely have a repeat MRI scan following the procedure to investigate for recurrence, and imaging was only undertaken based on clinical suspicion. However, this article is strengthened by the comprehensive systematic review performed in line with the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) statement.²⁰ Due to the heterogeneity in reported outcome measures, quantitative analyses were not possible. There were not enough data to determine whether there was an association between chronicity of intraneural ganglia and patient outcomes.

Surgical excision of common peroneal nerve intraneural ganglia and articular branch neurectomy is associated with improved motor and sensory foot function. Recurrence is relatively rare and predominantly arises as an extraneural entity. Further studies should be prospective in nature and conducted in multiple centers due to the scarcity of this pathology. Patient-reported outcome measures should also be addressed in future research. 

Affiliations: ¹Department of Burns and Plastic Surgery, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom; ²Institute of Inflammation and Ageing, University of Birmingham, Birmingham, United Kingdom; ³Department of Peripheral Nerve Surgery, Queen Elizabeth Hospital, Birmingham, United Kingdom; ⁴Department of Plastic, Reconstructive and Hand Surgery, Amsterdam UMC, Amsterdam, the Netherlands; ⁵Department of Plastic, Reconstructive and Hand Surgery, Erasmus MC, Rotterdam, the Netherlands; ⁶HaPPeN Research, Institute of Translational Medicine, Birmingham, United Kingdom

Correspondence: Dominic M Power, FRCS; Dominic.Power@uhb.nhs.uk

Disclosures: Hadyn K N Kankam is a National Institute for Health Research (NIHR) Academic Clinical Fellow. No direct funding was received for this review. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. The authors disclose no other relevant conflict of interest or financial disclosures for this manuscript.

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