Background: Proximal tibiofibular joint (PTFJ) ganglion cyst is a rare condition with a high rate of recurrence. Optimal treatment has not yet been determined. Purpose: We aimed to answer the following questions: (1) What are the most common treatments for PTFJ cysts and their associated recurrence rates? (2) What are the risk factors for failure to completely recover from symptoms? (3) What are the risk factors for cyst recurrence? Methods: A systematic review was performed using PubMed and EMBASE databases. Studies were assessed for inclusion and exclusion criteria, and quality analysis following the PRISMA guidelines. Information on demographic, clinical, and treatment characteristics was retrieved from articles. Results: The most common surgical treatment was cyst excision (75.3%). Patients with PTFJ arthrodesis and PTFJ resection had the lowest recurrence rates at 0% and 4.4%, respectively. Complete recovery from symptoms was more common in PTFJ resection (70.8%) than in PTFJ arthrodesis (42.9%). Risk factors for failure to achieve complete recovery from symptoms included intraneural compromise (odds ratio [OR] = 3.93), cyst recurrence (OR = 6.04), and being a contact sports athlete (OR = 9.85). Ligation of the articular branch of the peroneal nerve (PN) was a protective factor (OR = 0.29). A history of knee arthritis was the most important risk factor for cyst recurrence (OR = 20.01); PTFJ arthrodesis was a protective factor (OR = 0.04). Conclusion: This systematic review of level-IV studies found PTFJ resection or arthrodesis to be the most effective treatment options. Intraneural compromise of the common peroneal nerve, cyst recurrence, and participation in contact sports are risk factors for incomplete symptom recovery, and ligation of the articular branch of the PN is a protective factor. Knee arthritis is a risk factor for cyst recurrence. More rigorous study is needed.

We report a case of a 67-year-old woman suffering from intermittent claudication secondary to severe popliteal stenosis due to compression by a popliteal ganglion cyst extending into the adventitia of the popliteal artery. After declining vein bypass grafting, this patient was successfully treated using ultrasound-guided aspiration of the cyst, which restored normal flow to the popliteal artery. Whilst aspiration of Baker's cysts causing claudication has been attempted before, this represents the first reported case of successful recanalization of the popliteal artery by ganglion cyst aspiration and further supports an important possible aetiology and treatment for cystic adventitial disease.

Intraneural ganglion cysts (IGCs) are mucinous cysts located within peripheral nerves, often associated with an articular nerve branch and the adjacent synovial joint capsule. These cysts, while rare, can occur in various nerves, with the tibial nerve being an infrequent site. Tibial nerve IGCs are rare pathologies. We present a case of a tibial nerve IGC in a 78-year-old male patient with pre-existing grade III gonarthrosis. Furthermore, we performed a brief review of the existing literature for tibial nerve IGCs. To our knowledge, we present the second case of an IGC in a patient with known pre-existing gonarthrosis. This case raises the potential association between IGCs and degenerative knee pathologies and underscores the crucial role of early and accurate diagnosis. Differential diagnosis of nerve sheath tumors and extra-articular calf neuropathy is essential not only for definitive treatment but also to rule out more serious alternative diagnoses. While ultrasound-guided aspiration of cystic fluid with steroid injection and conservative management are also treatment methods defined in the literature, we believe that exploratory surgery is the critical point of treatment. Early and accurate diagnosis is paramount, as delayed diagnosis and treatment may cause persistent functional and sensory deficits.

Intraneural ganglion cysts involving the tibial nerve are rare. Recent evidence has supported an articular (synovial) theory to explain the joint-related origin of these cysts; however, optimal operative treatment for cysts originating from the STFJ remains poorly understood. Therefore, we present a novel strategy: addressing the joint itself without addressing the articular branch and/or the cyst.

Records of patients with tibial intraneural ganglion cysts with a connection to the STFJ who were treated with a joint resection alone at a single academic institution were reviewed. The clinicoradiographic features, operative intervention, and postoperative course were recorded.

We identified a consecutive series of 7 patients. These patients (4/7 male, 57%) were 43 (range 34-61) years of age and all presented with symptoms of neuropathy. The patients underwent resection of the synovial surfaces of the STFJ without disconnection of the articular branch or decompression of the cyst. Postoperatively, three patients regained partial motor function (43%, n=7), although four patients noted continued sensory abnormality (57%, 4/7). All six patients with postoperative MRIs had some evidence of regression of the cyst.

This novel surgical technique serves as a proof of concept-highlighting the fact that treating the primary source (the joint origin) can be effective in eliminating the secondary problem (the cyst itself). While this study shows that this simplified approach can be employed in select cases, we believe that superior results (faster, fuller recovery) can be achieved with combinations of disconnecting the articular branch, decompressing the cyst, and/or resecting the joint.

Extra- and intraneural ganglion cysts have been described in the literature. The tibial nerve ganglion is uncommon and its occurrence without intra-articular extension is atypical. The pathogenesis of cystic degeneration localized to connective and perineural tissue secondary to chronic mechanical irritation or idiopathic mucoid degeneration is hypothesized. Since the above pathology is extremely rare and the magnetic resonance imaging examination detects the defining characteristics of the intrinsic alterations of the tibial nerve, the authors illustrate such a case of tibial intaneural ganglion cyst with its magnetic resonance neurography and sonography appearances.

Intraneural cysts are benign lesions located within the epineurium of some peripheral nerves and their aetiopathogenesis is controversial. Most are located at the level of the lower limbs. In the upper limbs, the most frequently affected nerve is the ulnar nerve. Suprascapular nerve entrapment syndrome due to the formation of an intraneural cyst is rare. In this article, we show a new case and perform a literature review of intraneural cysts located in the suprascapular nerve.

We present a 49-year-old woman with pain in the lateral shoulder region of several months' evolution. A brachial plexus MR showed a tumour of approximately 2×1.5cm, with a cystic appearance, in relation to the upper trunk of the right brachial plexus.

We used a supra-infraclavicular approach. The cystic tumour affected the suprascapular nerve. After locating a zone on the surface without nervous fascicles, we performed a partial resection of the capsule and emptying of the cyst, with a xanthochromic gelatinous content. The anatomopathological examination confirmed the diagnosis of intraneural cyst.

The suprascapular nerve is a mixed nerve, coming from the upper trunk. It provides the motor branches to the supraspinatus and infraspinatus muscle. Compression of the suprascapular nerve leads to atrophy of these muscles. This entity is one of the differential diagnoses in a patient with pain irradiating to the shoulder, and its correct treatment often results in complete remission of symptoms.

To highlight the salient magnetic resonance imaging (MRI) features of the intraneural ganglion cyst (INGC) of various peripheral nerves for their precise diagnosis and to differentiate them from other intra and extra-neural cystic lesions.

A retrospective analysis of the magnetic resonance (MR) images of a cohort of 245 patients presenting with nerve palsy involving different peripheral nerves was done. MR images were analyzed for the presence of a nerve lesion, and if found, it was further characterized as solid or cystic. The serial axial, coronal and sagittal MR images of the lesions diagnosed as INGC were studied for their pattern and the anatomical extent along the course of the affected nerve and its branches. Its relation to identifiable anatomical landmarks, intra-articular communication and presence of denervation changes in the muscles supplied by involved nerve was also studied.

A total of 45 cystic lesions in the intra or extraneural locations of the nerves were identified from the 245 MR scans done for patients presenting with nerve palsy. Out of these 45 cystic lesions, 13 were diagnosed to have INGC of a peripheral nerve on MRI. The other cystic lesions included extraneural ganglion cyst, paralabral cyst impinging upon the suprascapular nerve, cystic schwannoma and nerve abscesses related to Hansen's disease involving various peripheral nerves. Thirteen lesions of INGC were identified in 12 patients. Seven of these affected the common peroneal nerve with one patient having a bilateral involvement. Two lesions each were noted in the tibial and suprascapular nerves, and one each in the obturator and proximal sciatic nerve. An intra-articular connection along the articular branch was demonstrated in 12 out of 13 lesions. Varying stages of denervation atrophy of the supplied muscles of the affected nerves were seen in 7 cases. Out of these 13 lesions in 12 patients, 6 underwent surgery.

INGC is an important cause of reversible mono-neuropathy if diagnosed early and surgically treated. Its classic MRI pattern differentiates it from other lesions of the peripheral nerve and aid in its therapeutic planning. In each case, the joint connection has to be identified preoperatively, and the same should be excised during surgery to prevent further cyst recurrence.

A 52-year-old male complained of numbness and radiating pain affecting the plantar region of his left foot. He was found to have recurrent tarsal tunnel syndrome due to posterior tibial nerve compression by 3 different types of ganglion during a 12-year period. To the best of our knowledge, a similar case has not been documented. At the first operation, flexor retinaculum release and simple excision of an epineural ganglion were performed without injuring the nerve fascicles; however, an intrafascicular ganglion developed approximately 2 years later. At the second operation, the ganglion cyst was resected completely to prevent recurrence, despite the risk of nerve fiber injury. The cyst originated from the subtalar joint; thus, the joint was closed, and a free fat graft was placed to prevent adhesion formation. However, an extraneural ganglion occurred about 3 years later. At the third operation, the cyst was resected completely, and a free periosteal graft was used to close the joint more effectively. No recurrence had developed at 6 years after the third operation. The findings of the present case show the need for long-term monitoring of patients with tarsal tunnel syndrome caused by a ganglion owing to the possibility of recurrence related to different ganglion types.

We report a 19-year-old woman with a 6-month history of nontraumatic left foot numbness associated with intermittent weakness. Nerve conduction studies and electromyography localized the lesion to the posterior tibial nerve, below the innervation to the soleus and medial gastrocnemius muscles. MRI of the left leg revealed a multiloculated cystic collection near the proximal tibiofibular joint. Surgical excision and pathology confirmed the diagnosis of a ganglion cyst, in an atypical location distal to the popliteal fossa. We believe this is the first reported case of fascicular posterior tibial nerve involvement by a ganglion cyst in the calf.

The etiology of intraneural ganglion cysts has been poorly understood. This has resulted in the development of multiple surgical treatment strategies and a high recurrence rate. We sought to analyze these recurrences in order to provide a pathoanatomic explanation and staging classification for intraneural cyst recurrence. An expanded literature search was performed to identify frequencies and patterns in cases of intraneural ganglion cyst recurrences following primary surgery. Two univariate analyses were completed to identify associations between the type of revision surgery and repeat cyst recurrences. The expanded literature search found an 11% recurrence rate following primary surgery, including 64 recurrences following isolated cyst decompression (Group 1); six after articular branch resection (Group 2); and none following surgical procedures that addressed the joint (Group 3). Eight cases did not specify the type of primary surgery. In group 1, forty-eight of the recurrences (75%) were in the parent nerve, three involved only the articular branch, and one travelled along the articular branch in a different distal direction without involving the main parent nerve. In group 2, only one case (17%) recurred/persisted within the parent nerve, one recurred within a persistent articular branch, and one formed within a persistent articular branch and travelled in a different distal direction. Intraneural recurrences most commonly occur following surgical procedures that only target the main parent nerve. We provide proven or theoretical explanations for all identified cases of intraneural recurrences for an occult or persistent articular branch pathway.

To review 15 patients who were treated for intraneural ganglions of the hand and wrist.

Between 1990 and 2012, 15 patients were treated for intraneural ganglions of the hand and wrist. There were 9 women and 6 men, averaged age 42 years. Ten patients presented with a mass and 5 with symptoms of entrapment neuropathy. The ganglions involved the ulnar nerve at the wrist in 5 patients, the dorsal branch of the ulnar nerve in 2, the superficial radial nerve in 2, a digital nerve in 4, and the dorsal branch of a digital nerve in 2. Eight patients had magnetic resonance imaging evaluations that showed cystic masses that did not confirm intraneural ganglions. In all patients diagnosis was made intraoperatively. Ganglions were treated by intraneural dissection and excision of the cyst in 10 patients, excision of the articular branch and decompression of the cyst in 4, and excision of the ganglion and the nerve in 1.

Postoperative follow-up averaged 57 months. There were no complications or recurrences. Five patients had transient paresthesias that improved after an average of 2 months. Preoperative symptoms improved in all patients. Patients returned to normal daily and work activities at an average of 10 days.

Intraneural ganglions should be considered in the differential diagnosis of a mass in the vicinity of a nerve. Surgical excision is usually curative but simple excision of the articular branch and decompression of the cyst seems simpler and equally effective.

Therapeutic IV.

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

Clinical compression neuropathy caused by para-articular cysts is rare. Only recently, the unifying articular theory was proposed to clarify its true etiologic nature. The authors attribute 17 cases to this theory in order to illustrate the shift in the diagnostic and treatment protocol, and the possible impact on patient outcome.

Eight intraneural and nine extraneural cysts were included. The proposed diagnostic protocol includes electromyography and ultrasound, followed by magnetic resonance imaging to characterize the cyst. The proposed treatment protocol consists of (1) ligation of the pedicle connecting the cyst with the afflicted joint, (2) decompression of the nerve and, when needed and (3) disarticulation of the superior tibiofibular joint (in case of peroneal nerve involvement).

Outcome was good to excellent in all patients, with recovery of sensory and motor function. Cyst recurrence was observed in three intraneural cases (18 %). Analysis of our own diagnostic protocol showed that atypical compression neuropathies should follow a strict diagnostic protocol to exclude missing the presence of a cyst. Ultrasound needs to play a crucial role, with MRI for cyst characterization and pedicle identification.

Retrospective proof in favor of the articular theory was found in all cases. An explanation for the cyst recurrences was formed based on the articular theory. In addition, a diagnostic and therapeutic protocol is proposed for all atypical peripheral compression neuropathies with the ultimate goal to achieve optimal patient outcome.

The purpose of this study was to perform a comprehensive search of the literature for all studies, case reports, and series describing Baker cyst compression of the neurovascular bundle in the popliteal fossa and index their findings according to the structures compressed.

Case reports and series obtained after a thorough MEDLINE search were indexed according to compressed structures. Patient demographics, main findings, method of diagnosis, cyst size, outcomes, and follow-up were recorded for each publication.

Signs and symptoms related to popliteal vein and tibial nerve compression were the most frequent presentation of symptomatic Baker cysts, due to the anatomic vulnerability of these structures within the popliteal fossa and their relative sensitivity to compression. Patients with tibial nerve entrapment demonstrated gastrocnemius muscle atrophy, paresthesias, and pain. Those with popliteal vein compression experienced swelling, pain, and rarely, venous thromboembolism. Isolated arterial compression, presenting with intermittent claudication, is a rare occurrence because it is a relatively stiff-walled vessel, has a higher pressure, and is located deep in the popliteal fossa. Combinations of these compression syndromes are most frequently encountered in the context of cyst rupture and resulting compartment syndrome.

Baker cyst is an important pathology for the differential diagnosis of popliteal neurovascular compression phenomena. It has a wide spectrum of presentation, therefore requiring accurate diagnosis for proper patient management. Because Baker cyst is by definition a chronic disorder, long-term follow-up is necessary to monitor patient recovery and prevent recurrence.

Intraneural ganglion cysts have been considered a curiosity for 2 centuries. Based on a unifying articular (synovial) theory, recent evidence has provided a logical explanation for their formation and propagation. The fundamental principle is that of a joint origin and a capsular defect through which synovial fluid escapes following the articular branch, typically into the parent nerve. A stereotypical, reproducible appearance has been characterized that suggests a shared pathogenesis. In the present report the authors will provide a mechanistic explanation that can then be mathematically tested using a preliminary model created by finite element analysis.

Tibial intraneural ganglia occurring in the popliteal fossa are often misdiagnosed because of their relative rarity. Their joint connection is typically not recognized and therefore not treated, leading to recurrence.

This is a retrospective clinical study.

Magnetic resonance images (MRIs) of six patients with confirmed tibial intraneural ganglia arising from the superior tibiofibular joint were analyzed and were compared to ten individuals with normal tibial nerves who were imaged with MRI. All studies were interpreted as left-sided. A previously designed clock face model introduced for peroneal intraneural ganglia was used to describe the superior tibiofibular joint connection (tail sign). A single axial image was sought to determine the normal anatomic and pathologic relationships of the tibial nerve and tibial articular branch to the superior tibiofibular joint.

In all patients with intraneural ganglia, a single conventional axial image at the mid-fibular head level could reliably demonstrate: (1) intraneural cyst within the articular branch at the superior tibiofibular joint connection (tail sign) between 8 and 9 o'clock and intraneural cyst within the tibial nerve, (2) the central location of the tibial nerve posterior to the tibia, and (3) popliteus muscle denervation changes and atrophy (popliteus sign).

This technique can provide radiologists and surgeons with rapid and reproducible information for diagnosis and treatment planning of tibial intraneural ganglia. Similar to its use with the clock face model in peroneal intraneural ganglia, a standard axial image at the mid-fibular head level can be used to interpret key features of tibial intraneural ganglia and identify the joint connection. Improved identification of the presence of a joint connection will change the therapeutic approach of this pathology and reduce cyst recurrences.

We present a patient who developed a peroneal intraneural ganglion and an adventitial cyst following the incomplete treatment of a tibial intraneural ganglion. These separate cysts all originated from the superior tibiofibular joint and dissected along their respective articular branches. A logical mechanistic explanation for these coexisting cysts is provided, which highlights the shared pathogenesis--its joint-related nature--rather than a multifocal de novo process. These observations would not only be consistent with, but would extend previous evidence in support of, the unifying articular (synovial) theory.

The pathogenesis of intraneural ganglia has been a controversial issue for longer than a century. Recently the authors identified a stereotypical pattern of occurrence of peroneal and tibial intraneural ganglia, and based on an understanding of their pathogenesis provided a unifying articular explanation. Atypical features, which occasionally are observed, have offered an opportunity to verify further and expand on the authors' proposed theory.

Three unusual cases are presented to exemplify the dynamic features of peroneal and tibial intraneural ganglia formation.

Two patients with a predominant deep peroneal nerve deficit shared essential anatomical findings common to peroneal intraneural ganglia: namely, 1) joint connections to the anterior portion of the superior tibiofibular joint, and 2) dissection of the cyst along the articular branch of the peroneal nerve and proximally. Magnetic resonance (MR) images obtained in these patients demonstrated some unusual findings, including the presence of a cyst within the tibial and sural nerves in the popliteal fossa region, and spontaneous regression of the cysts, which was observed on serial images obtained weeks apart. The authors identified a clinical outlier, a case that could not be understood within the context of their previously reported theory of intraneural ganglion cyst formation. Described 32 years ago, this patient had a tibial neuropathy and was found at surgery to have tibial, peroneal, and sciatic intraneural cysts without a joint connection. The authors' hypothesis about this case, based on their unified theory, was twofold: 1) the lesion was a primary tibial intraneural ganglion with proximal extension followed by sciatic cross-over and distal descent; and 2) a joint connection to the posterior aspect of the superior tibiofibular joint with a remnant cyst within the articular branch would be present, a finding that would help explain the formation of different cysts by a single mechanism. The authors proved their hypothesis by careful inspection of a recently obtained postoperative MR image.

These three cases together with data obtained from a retrospective review of the authors' clinical material and findings reported in the literature provide firm evidence for mechanisms underlying intraneural ganglia formation. Thus, expansion of the authors' unified articular theory permits understanding and elucidation of unusual presentations of intraneural cysts. Whereas an articular connection and fluid following the path of least resistance was pivotal, the authors now incorporate dynamic aspects of cyst formation due to pressure fluxes. These basic principles explain patterns of ascent, cross-over, and descent down terminal nerve branches based on articular connections, paths of diminished resistance to fluid flow within recognized anatomical compartments, and the effects of fluctuating pressure gradients.

To demonstrate that tibial intraneural ganglia in the popliteal fossa are derived from the posterior portion of the superior tibiofibular joint, in a mechanism similar to that of peroneal intraneural ganglia, which have recently been shown to arise from the anterior portion of the same joint.

Retrospective clinical study and prospective anatomic study.

The clinical records and MRI findings of three patients with tibial intraneural ganglion cysts were analyzed and compared with those of one patient with a tibial extraneural ganglion cyst and one volunteer. Seven cadaveric limbs were dissected to define the articular anatomy of the posterior aspect of the superior tibiofibular joint.

The condition of the three patients with intraneural ganglia recurred because their joint connections were not identified initially. In two patients there was no cyst recurrence when the joint connection was treated at revision surgery; the third patient did not wish to undergo additional surgery. The one patient with an extraneural ganglion had the joint connection identified at initial assessment and had successful surgery addressing the cyst and the joint connection. Retrospective evaluation of the tibial intraneural ganglion cysts revealed stereotypic features, which allowed their accurate diagnosis and distinction from extraneural cases. The intraneural cysts had tubular (rather than globular) appearances. They derived from the postero-inferior portion of the superior tibiofibular joint and followed the expected course of the articular branch on the posterior surface of the popliteus muscle. The cysts then extended intra-epineurially into the parent tibial nerves, where they contained displaced nerve fascicles. The extraneural cyst extrinsically compressed the tibial nerve but did not directly involve it. All cadaveric specimens demonstrated a small single articular branch, which derived from the tibial nerve to the popliteus. The branch coursed obliquely across the posterior surface of the popliteus muscle before innervating the postero-inferior aspect of the superior tibiofibular joint.

The clinical, MRI and anatomic features of tibial intraneural ganglion cysts are the posterior counterpart of the peroneal intraneural ganglion cysts arising from the anterior portion of the superior tibiofibular joint. These predictable features can be exploited and have implications for the pathogenesis of these intraneural cysts and treatment outcomes. These ganglion cysts are joint-related and provide further evidence to support the unifying articular theory. In each case the joint connection needs to be identified preoperatively, and the articular branches and the superior tibiofibular joint should be addressed operatively to prevent cyst recurrence.

Intraneural ganglia are rare entities, and, as such, their pathogenesis has been extremely controversial. Recent evidence from intraneural ganglia occurring at more proximal sites-the peroneal nerve at the fibular neck (the most common site) and the tibial nerve at the knee-has suggested an articular origin rather than de novo formation. To our knowledge, of the 10 previous reports of tibial intraneural ganglia within the tarsal tunnel by others, a joint connection to the ankle joint was only identified in 2 cases. To support a hypothesis that tibial intraneural ganglia occurring within the tarsal tunnel region arise from neighboring joints, we analyzed 3 patients retrospectively, all of whom had magnetic resonance (MR) imaging and operative intervention. One of these patients was treated by a peripheral nerve surgeon specializing in foot and ankle surgery. The other 2 patients were the only ones previously published in the literature who had MR images available for reinterpretation. In none of these cases was a joint communication appreciated by radiologists interpreting the MR images preoperatively or by surgeons intraoperatively. Our review of these same cases demonstrated radiographic evidence of joint communications with the subtalar joints. Based on our findings in this article and our knowledge of intraneural ganglia occurring at more proximal sites, we believe that tibial intraneural ganglia within the tarsal tunnel originate from neighboring joints and that their connections to the joints (pedicles) are through articular branches. The importance of these connections is 2-fold: first, for their role in the pathogenesis of this entity, and second, for their potential therapeutic implications. As is highlighted by the clinical and radiographic follow-up in the 1 patient in this article and in many previously reported at other sites, intraneural cyst recurrence can occur if surgeons do not specifically address the articular connection.

To introduce the clinical entity of an intraneural ganglion cyst coexisting with a vascular adventitial cyst arising from the same joint.

Retrospective review.

Two patients presented with predominantly deep peroneal neuropathy due to complex superior tibiofibular joint-related cysts. In addition to having peroneal intraneural ganglion cysts, these patients had vascular adventitial cysts: one involving a capsular arterial branch, the other a capsular vein [as well as a large, recurrent, intramuscular (extraneural) ganglion]. We then reviewed MRIs of 12 other consecutive cases of intraneural ganglia (10 peroneal and 2 tibial) arising from the superior tibiofibular joint that we treated, as well as other reported cases in the literature to determine if there were other (unrecognized) examples supporting the combination of clinical findings and radiographic patterns.

Retrospective analysis of MRIs in the two surgically proven cases of peroneal intraneural ganglia with vascular adventitial cyst extension showed a common imaging pattern that we have termed "the wishbone sign," consisting of the connection of the ascending limb of the peroneal intraneural ganglion and the longitudinal limb of the vascular adventitial cyst in the axial plane. Our review suggests that vascular adventitial cyst extension occurs in a large proportion of cases of peroneal intraneural ganglia. A similar growth pattern was noted in a case of a tibial intraneural ganglion.

The combination of intraneural and vascular adventitial cysts is understandable given our knowledge of normal and pathologic anatomy of para-articular cysts. The combination of intraneural ganglia and vascular adventitial cysts broadens the spectrum of clinical presentations of these cysts and suggests that cysts and their content can dissect from a joint along neurovascular bundles. These cases provide important evidence to support the articular theory for the pathogenesis of not only neural but vascular adventitial cysts as well.

Nerve sheath ganglion is a relatively rare clinical entity commonly found in the peroneal nerve in the lower limb or the ulnar nerve in the upper extremity. It is rarely found in the tibial nerve. The occurrence of a nerve sheath ganglion in a patient's tibial nerve has been identified. The initial presentation of the tumor mass has been very similar to that of a Baker's cyst, namely a soft undulating popliteal mass. Yet, the case also presented symptoms and signs of tibial nerve compressive neuropathy. We present here a rare case of nerve sheath ganglion of the tibial nerve. Clinical courses of the patient were reviewed, and relevant issues were discussed with a thorough literature review.

Intraneural ganglion cyst of the tibial nerve is very rare. To date, only 5 cases of this entity in the popliteal fossa have been reported. We report a new case and review the previously reported cases. A 40-year-old man experienced a mild vague pain in the medial half of his right foot for 3 years. Magnetic resonance imaging scan demonstrated a soft-tissue mass along the right tibial nerve. At surgery, an intraneural ganglion cyst was evacuated. After 12 months, the patient was pain-free with no signs of recurrence. Trauma might be a contributing factor to the development of intraneural ganglion cysts. Application of microsurgical techniques is encouraged.

The preoperative diagnosis of peroneal intraneural ganglia has been difficult to establish, and superior tibiofibular joint connections may not be identified. Misdiagnosis leads to incomplete treatment in that the articular branch connection may not be addressed, which can result in cyst recurrences.

We analyzed 20 surgically confirmed cases of paraarticular cysts arising from the superior tibiofibular joint to assess for joint connections and to determine common magnetic resonance imaging characteristics in intraneural ganglia that would allow distinction from extraneural ganglia. We identified and tested three radiographic signs describing the cysts and analyzed cyst morphology (i.e., size, shape, pattern), muscle compartments affected (i.e., for denervation), and neighboring joints (for associated pathology).

Twelve cases of peroneal intraneural ganglia and eight cases of extraneural ganglia were connected to the superior tibiofibular joint. Retrospective review confirmed that these cysts were frequently misdiagnosed, and joint connections often were not recognized. The magnetic resonance imaging appearance of peroneal intraneural ganglia was stereotypical. These intraneural ganglia were tubular, whereas the extraneural were more mass-like. The tail sign was 100% sensitive for identifying joint connections but could not distinguish between intra- and extraneural cysts. The "transverse limb" sign (cystic material within the portion of the articular branch traversing the anterior surface of the fibula) was present in all cases of peroneal intraneural ganglia and none of the extraneural ganglia. The signet ring sign (the eccentric displacement of fascicles by cyst within the epineurium) was 100% sensitive for peroneal intraneural ganglia and 86% specific (it did not identify two cysts that did not extend more proximally into the common peroneal nerve). There was 100% interobserver concordance between the prospective interpretations by a single, blinded, radiologist and a trained first-year medical student with intraoperative findings. In this series, muscle denervation was more common and more pronounced in the intraneural than extraneural ganglia. Abnormalities in neighboring joints were noted nearly universally.

This article demonstrates reproducible magnetic resonance imaging features that will easily allow one to identify the joint connection (the tail sign) in paraarticular cysts and also to distinguish between peroneal intraneural and extraneural ganglia (the transverse limb sign and the signet ring sign) at the superior tibiofibular joint with accuracy and confidence and with subsequent improvement in treatment and patient outcomes.

Unlike the more commonly noted paralabral cysts (extraneural ganglia), which are well known to result in suprascapular nerve compression, only four cases of suprascapular intraneural ganglia have been reported. Because of their rarity, the pathogenesis of suprascapular intraneural ganglia has been poorly understood and a pathoanatomical explanation has not been provided. In view of the growing literature demonstrating strong associations between paralabral cysts and labral (capsular) pathology, joint connections, and joint communications, the authors retrospectively reviewed the magnetic resonance (MR) imaging studies and postoperative results in the two featured patients to test a hypothesis that suprascapular intraneural ganglia would have analogous findings.

Two patients who presented with suprascapular neuropathy were found to have intraneural ganglia. Connections to the glenohumeral joint could be established in both patients through posterior labrocapsular complex tears. In neither patient was the joint connection identified preoperatively or intraoperatively, and cyst decompression was performed by itself without attention to the labral tear. The suprascapular intraneural ganglia extended from the glenohumeral joint as far proximally as the level of the nerves' origin from the upper trunk in the supraclavicular fossa. Although both patients experienced symptomatic improvement after surgery, neurological recovery was incomplete. In both cases, postoperative MR images revealed cyst persistence. In addition, previously unrecognized superior labral anteroposterior (SLAP) Type II lesions (tears of the superior labrum extending anteroposterior and involving the biceps anchor at the labrum without actual extension into the tendon) were visualized. In one patient with a persistent cyst, an MR arthrogram was obtained and demonstrated a communication between the joint and the cyst.

The findings in these two patients support the synovial theory for intraneural ganglia. Based on their experience with intraneural ganglia at other sites, the authors believe that suprascapular intraneural ganglia arise from the glenohumeral joint, egress through a superior (posterior) labral tear, and dissect within the epineurium along an articular branch into the main nerve, following the path of least resistance. Furthermore, these two cases of intraneural ganglia with SLAP lesions are directly analogous to the many cases of paralabral cysts associated with these types of labral tears. By better understanding the origin of this unusual type of ganglia and drawing analogies to the more common extraneural cysts, surgical strategies can be formulated to address the underlying pathoanatomy, improve operative outcomes, and prevent recurrences.

We present a case of multicystic ganglion of the suprascapular nerve in an 18-year-old man. Pain and shoulder weakness were present and examination showed weakness and atrophy of the supraspinatus and infraspinatus muscles. Electromyography showed severe denervation of the infraspinatus and supraspinatus muscles. At surgery a multicystic lesion of the suprascapular nerve extending approximately 5.7 cm from its origin was resected and reconstructed by sural nerve grafting.

Therapeutic, Level V.

Most of the nonneoplastic tumor-like lesions affecting the peripheral nervous system are rarely encountered. In many situations, a good history of the presenting symptoms can suggest a reactive or infectious neuroma. The physical examination can also suggest an inflammatory or hyperplastic lesion. In some cases, however, the correct diagnosis can only be made at surgery. Nonetheless, awareness of these lesions is important in limiting unnecessarily aggressive surgical procedures. Patients suspected of having nonneoplastic lesions are followed and treated surgically for symptomatic relief or when the diagnosis is unclear. In some situations, the surgical treatment of choice may be debated. Nevertheless, we adopt a conservative approach to these lesions and reserve more aggressive techniques for cases that do not respond to more conservative means.

Complications are relatively common in the evaluation and treatment of patients with peripheral nerve tumors. The complications are frequently avoidable. Physicians and surgeons managing patients with these lesions must possess sufficient knowledge about peripheral nerve tumors and their natural history as well as good diagnostic, decision-making, and technical skills. By avoiding often unnecessary complications, patients and surgeons can be rewarded with better outcomes.

The surgical management of benign PNSTs and some other benign tumors can result in successful outcomes. Schwannomas and nonplexiform neurofibromas can be resected with minimal deficit by sparing all but the fascicles entering and exiting the tumor. These fascicles, if not functional by NAP testing, can be resected, and the tumor can be removed. Surgery to remove other benign lesions, such as intraneural ganglion cysts, hemangiomas,and ganglioneuromas, has become more timely. The desmoid tumor, although microscopically benign, is locally and regionally invasive, and chemotherapy and radiation therapy may need to be used as adjunctive therapy. Neurogenic sarcomas and other malignancies have high morbidity and mortality despite aggressive limb ablation or limb-sparing surgery with adjunctive therapy. Thus, surgery involving decompression as well as the most complete resection possible remains the essential initial step in the management of most malignancies.

Mucoid pseudocysts are infrequent benign tumors which can develop on all peripheral nerves near joints. The origin of these cysts remains to be determined. We searched for arguments favoring an articular origin which would have an impact on management and risk of recurrence.

Twenty-three patients (21 men and 2 women, mean age 38 years, age range 13-56 years) presented mucoid pseudocysts and were followed for a mean six years. The mucoid pseudocyst was located on the common fibular nerve at the neck of the fibula in 16 patients, on the tibial nerve at the knee in one, on the median nerve in one, on the ulnar nerve in one, and on the suprascapular nerve in two. Pain was local in 18 patients and irradiated to the concerned nerve territory in 20. Motor deficit was the inaugural feature in 17 patients. EMG was performed in all patients, ultrasound exploration in 15, computed tomography in 7 and magnetic resonance imaging in 10. All patients included in this series underwent surgery: pathological diagnosis of mucoid intra-neural pseudocyst was established in all. Systematic search for communication with the neighboring joint was performed in all cases.

An articular communication was found in 17 patients. Mean time to recovery of muscle force (scored 5) and/or normal sensitivity was seven months in 17 patients. One patient did not achieve full recovery. Three patients experienced recurrence and required tibiofibular arthrodesis.

Three theories have been proposed (cystic degeneration of schwannoma, degeneration of nerve sheath connective tIssue, and an articular origin). The articular theory appears to be the most probable. The presence of an articular pedicle in 60% of the patients, the anatomic juxtaposition between the nerves involved and neighboring joints, and occasional migration along the articular nerve as well as the cyst's mucoid content argue in favor of the articular theory. The notion of recurrence after complete minute excision is also in favor of an articular pathogenic mechanism. The diagnosis of mucoid cyst should be retained as a possibility in patients with rapidly progressive signs of nerve compression near a joint. It is important to search for articular communication before and during the surgical excision in order to limit the risk of recurrence.

Based on a large multicenter experience and a review of the literature, the authors propose a unifying theory to explain an articular origin of peroneal intraneural ganglia. They believe that this unifying theory explains certain intriguing, but poorly understood findings in the literature, including the proximity of the cyst to the joint, the unusual preferential deep peroneal nerve (DPN) deficit, the absence of a pure superficial peroneal nerve (SPN) involvement, the finding of a pedicle in 40% of cases, and the high (10-20%) recurrence rate.

The authors believe that peroneal intraneural lesions are derived from the superior tibiofibular joint and communicate from it via a one-way valve. Given access to the articular branch, the cyst typically dissects proximally by the path of least resistance within the epineurium and up the DPN and the DPN component of the common peroneal nerve (CPN) before compressing nearby SPN fascicles. The authors present objective evidence based on anatomical, clinical, imaging, operative, and histological data that support this unifying theory.

The predictable clinical presentation, electrical studies, imaging characteristics, operative observations, and histological findings regarding peroneal intraneural ganglia can be understood in terms of their origin from the superior tibiofibular joint, the anatomy of the articular branch, and the internal topography of the peroneal nerve that the cyst invades. Understanding the controversial pathogenesis of these cysts will enable surgeons to perform operations based on the pathoanatomy of the articular branch of the CPN and the superior tibiofibular joint, which will ultimately improve clinical results.

The pathogenesis of intraneural ganglion cysts is unknown. Some authors have established a connection between the cysts and the joint, while others have failed to find this communication. Most intraneural ganglion cysts occur in the proximity of a joint. We present the case of a 53-year-old Caucasian male with an intraneural cyst of the sciatic nerve located high above its bifurcation and without a connection to the joint. The lesion was microsurgically removed in toto. There was no recurrence of the cyst at follow-up 9 months postoperatively; complete resolution of the clinical symptoms occurred within 8 months of surgery. This case shows that ganglion cysts can occur in locations far from a joint, supporting the extra-articular embryonic synovial remnant theory of their genesis.