Ganglion cyst involvement of peripheral nerves

Hypoglossal Nerve Neuropathies-Analysis of Causes and Anatomical Background

The hypoglossal nerve is the last, and often neglected, cranial nerve. It is mainly responsible for motor innervation of the tongue and therefore the process of chewing and articulation. However, tumors, aneurysms, dissections, trauma, and various iatrogenic factors such as complications after surgeries, radiotherapy, or airway management can result in dysfunction. Correct differential diagnosis and suitable treatment require a thorough knowledge of the anatomical background of the region. This review presents the broad spectrum of hypoglossal neuropathies, paying particular attention to these with a compressive background. As many of these etiologies are not common and can be easily overlooked without prior preparation, it is important to have a comprehensive understanding of the special relations and characteristic traits of these medical conditions, as well as the most common concomitant disorders and morphological traits, influencing the clinical image. Due to the diverse etiology of hypoglossal neuropathies, specialists from many different medical branches might expect to encounter patients presenting such symptoms.

Ganglia-Induced Tarsal Tunnel Syndrome

BACKGROUND

Tarsal tunnel syndrome (TTS) is a common entrapment neuropathy that is sometimes elicited by ganglia in the tarsal tunnel.

METHODS

Between August 2020 and July 2022, we operated on 117 sides with TTS. This retrospective study examined data from 8 consecutive patients (8 sides: 5 men, 3 women; average age 67.8 years) with an extraneural ganglion in the tarsal tunnel. We investigated the clinical characteristics and surgical outcomes for these patients.

RESULTS

The mass was palpable through the skin in 1 patient, detected intraoperatively in 1 patient, and visualized on MRI scanning in the other 6 patients. Symptoms involved the medial plantar nerve area (n = 5), lateral plantar nerve area (n = 1), and medial and lateral plantar nerve areas (n = 2). The interval between symptom onset and surgery ranged from 4 to 168 months. Adhesion between large (≥20 mm) ganglia and surrounding tissue and nerves was observed intraoperatively in 4 patients. Of the 8 patients, 7 underwent total ganglion resection. There were no surgery-related complications. On their last postoperative visit, 3 patients with a duration of symptoms not exceeding 10 months reported favorable outcomes.

CONCLUSIONS

Because ganglia eliciting TTS are often undetectable by skin palpation, imaging studies may be necessary. Early surgical intervention appears to yield favorable outcomes.

Surgery for mononeuropathies

Advancement in microsurgical techniques and innovative approaches including greater use of nerve and tendon transfers have resulted in better peripheral nerve injury (PNI) surgical outcomes. Clinical evaluation of the patient and their injury factors along with a shift toward earlier time frame for intervention remain key. A better understanding of the pathophysiology and biology involved in PNI and specifically mononeuropathies along with advances in ultrasound and magnetic resonance imaging allow us, nowadays, to provide our patients with a logical and sophisticated approach. While functional outcomes are constantly being refined through different surgical techniques, basic scientific concepts are being advanced and translated to clinical practice on a continuous basis. Finally, a combination of nerve transfers and technological advances in nerve/brain and machine interfaces are expanding the scope of nerve surgery to help patients with amputations, spinal cord, and brain lesions.

Intraneural ganglion cysts originating from the hip joint: A single-center experience

INTRODUCTION/AIMS

Intraneural ganglion cysts (INGCs) are non-neoplastic mucinous cysts within the epineurium of peripheral nerves. Characteristics of INGCs around the hip joint have not been adequately described. We aimed to describe clinical features, imaging findings, and treatment outcomes in patients with INGCs originating from the hip joint.

METHODS

We retrospectively included cystic lesions around the hip joint satisfying the following inclusion criteria over 6 years: (1) multilocular elongated hyperintense cystic mass on T2-weighted imaging; and (2) distribution along the course of the peripheral nerve and its branches on magnetic resonance imaging (MRI).

RESULTS

Six patients with an INGC around the hip joint were identified. Parent peripheral nerves were the sciatic nerve (four patients), the superior gluteal nerve (one patient), and the nerve to quadratus femoris (one patient). Buttock, groin, or lower extremity pain/paresthesias were the initial symptoms in all patients. INGCs within the articular branches of the hip joint were identified on MRI. Four patients underwent arthroscopic debridement and capsulotomy. All patients showed generally favorable outcome regardless of treatment.

DISCUSSION

Physicians should consider the possibility of INGCs originating from the hip joint as a cause of nontraumatic hip, buttock, or lower extremity pain. This can occur in any nerve innervating the hip joint, and usually it originates in the posterior capsule of the hip joint. Arthroscopic surgery shows promising results; however, more information about the surgical technique and long-term follow-up results are needed.

Persistent Symptoms of Ganglion Cysts in the Dorsal Foot

Background

A ganglion is a common benign cystic lesion, containing gelatinous material. Ganglia are most commonly asymptomatic, except for a lump, but symptoms depend on the location. A dorsal foot ganglion is typically painful. On the dorsal foot, the dorsalis pedis artery and the medial branch of the deep peroneal nerve are located under the fascia.

Objective

Five female patients of average age 45.8 ± 20 years (range, 12 to 60 years) with a painful ganglion in the dorsal foot were analyzed.

Results

Average lesion size was 2.94 ± 1.1 cm (range, 1.5 to 4.0 cm) and patients had experienced pain for a median of 2-3 years (range, 6 months to 3 years). Four patients had a single cystic lesion and 1 patient had developed multiple cystic lesions over the time that were associated with hypoesthesia. In 3 cases, symptomatic lesions were located deep beneath the fascia and were resected. In 2 cases, the depth of the non-resected lesions was shallow.

Conclusion

The cause of a painful dorsal foot ganglion can be attributed to its location in the thin subcutaneous tissue over the foot bone, in addition to its proximity to a nearby artery and nerve. Mild symptoms caused by a dorsal foot ganglion seem to be persistent, and the deeper the location, the more likely is the need for resection. To avoid nerve injury, anatomical knowledge is prerequisite to any puncturing procedure or operation performed.

Cystic lesions of peripheral nerves: Are we missing the diagnosis of the intraneural ganglion cyst?

AIM

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Intraneural Ganglion Cyst of the Ulnar Nerve at the Elbow Masquerading as a Malignant Peripheral Nerve Sheath Tumor

BACKGROUND

Ulnar neuropathy at the elbow (UNE) is the second most common mononeuropathy of the upper extremity. One rare cause of UNE is nerve mass lesions, including intraneural ganglion cysts (IGCs). IGC imaging studies provide important information that may determine the nature of a peripheral nerve mass lesion.

CASE DESCRIPTION

We present the case of a 73-year-old woman who presented with rapid deterioration of left hand function over 2 months with weakness of fine motor control, grip strength, and dysesthesia in the ulnar nerve distribution. Preoperative imaging studies, including magnetic resonance imaging (MRI) of the elbow, postcontrast studies, diffusion-weighted imaging, and apparent diffusion coefficient measurements, suggested a highly cellular tumor. Diffusion tensor tractography also revealed imaging features suggestive of a malignant peripheral nerve sheath tumor. During the operation, a sample of the lesion was sent for frozen section. There were no features of malignancy, and the pathologist could not determine a diagnosis based on the tissue sample sent. An intraoperative decision was made not to divide the ulnar nerve above and below the lesion. The IGC was successfully managed by identifying a suitable plane of dissection and cyst resection.

CONCLUSIONS

This case demonstrates that MRI studies indicating malignant peripheral nerve sheath tumor must be considered with some caution and corroborated with supportive features on operative inspection and biopsy before radical resection is undertaken. Furthermore, for any nerve mass lesion immediately adjacent to a joint, the differential diagnosis of an IGC should be considered.

Intraneural ganglion cysts: a systematic review and reinterpretation of the world's literature

OBJECTIVE The etiology of intraneural ganglion cysts has been controversial. In recent years, substantial evidence has been presented to support the articular (synovial) theory for their pathogenesis. The authors sought to 1) perform a systematic review of the world's literature on intraneural cysts, and 2) reinterpret available published MR images in articles by other authors to identify unrecognized joint connections. METHODS In Part 1, all cases were analyzed for demographic data, duration of symptoms, the presence of a history of trauma, whether electromyography or nerve conduction studies were performed, the type of imaging, surgical treatment, presence of a joint connection, intraneural cyst recurrence, and postoperative imaging. Two univariate analyses were completed: 1) to compare the proportion of intraneural ganglion cyst publications per decade and 2) to assess the number of recurrences from 1914 to 2003 compared with the years 2004-2015. Three multivariate regression models were used to identify risk factors for intraneural cyst recurrence. In Part 2, the authors analyzed all available published MR images and obtained MR images from selected cases in which joint connections were not identified by the original authors, specifically looking for unrecognized joint connections. Two univariate analyses were done: 1) to determine a possible association between the identification of a joint connection and obtaining an MRI and 2) to assess the number of joint connections reported from 1914 to 2003 compared with 2004 to 2015. RESULTS In Part 1, 417 articles (645 patients) were selected for analysis. Joint connections were identified in 313 intraneural cysts (48%). Both intraneural ganglion cyst cases and cyst recurrences were more frequently reported since 2004 (statistically significant difference for both). There was a statistically significant association between cyst recurrence and percutaneous aspiration as well as failure to disconnect the articular branch or address the joint. In Part 2, the authors identified 43 examples of joint connections that initially went unrecognized: 27 based on their retrospective MR image reinterpretation of published cases and 16 of 16 cases from their sampling of original MR images from published cases. Overall, joint connections were more commonly found in patients who received an MRI examination and were more frequently reported during the years 2004 to 2015 (statistically significant difference for both). CONCLUSIONS This comprehensive review of the world's literature and the MR images further supports the articular (synovial) theory and provides baseline data for future investigators.

Recurrent intraneural ganglion cysts: Pathoanatomic patterns and treatment implications

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.

Case Report: Intraneural Intracanalicular Ganglion Cyst of the Hypoglossal Nerve Treated by Extradural Transcondylar Approach

We report a case of an intraneural ganglion cyst of the hypoglossal canal. The patient presented with unilateral hypoglossal nerve palsy, and magnetic resonance imaging showed a small lesion in the hypoglossal canal with no contrast enhancement and high signal on T2-weighted imaging. The lesion was assumed to be a cystic schwannoma of the hypoglossal nerve. Stereotactic irradiation was considered, but in accordance with the patient's wishes, surgical exploration was performed. This revealed that, rather than a schwannoma, the patient had an intraneural ganglion cyst, retrospectively contraindicating irradiation as an option. This case illustrates a very rare location of an intraneural ganglion cyst in the hypoglossal nerve. To our knowledge there are no previous reports of an intraneural ganglion cyst confined to the hypoglossal canal.

Intraneural pseudocyst (so-called ganglion) in an unusual retroperitoneal periadnexal location?

A case of an unusual unilocular cystic lesion of diameter 7 cm located retroperitoneally in the pelvis in close connection to the right adnexa of a 61 year-old woman is presented. Macroscopically, the lesion had a smooth outer and inner surface and was filled with translucent fluid. Histological examination revealed a fibrous and hyalinized wall which lacked a specific lining. Numerous nerve bundles in the cyst wall constituted the most conspicuous element of its histology possibly with some contribution of perineurial and/or mesothelial components. The morphology and immunohistochemistry speak for an intraneural pseudocyst sometimes called intraneural ganglion cyst which is rare in this location.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1357862917132314.

Spectrum of superficial nerve-related tumor and tumor-like lesions: MRI features

Superficial soft-tissue masses arising from skin appendages, metastasis, and inflammatory lesions have been widely reported. However, nerve-related superficial mass-like lesions other than peripheral nerve sheath tumors are less commonly described. High resolution magnetic resonance imaging (MRI) is an excellent non-invasive tool for the evaluation of such lesions. In this article, the authors discuss the entire spectrum of these lesions and also outline a systemic diagnostic approach.

Peroneal and tibial intraneural ganglion cysts in children

BACKGROUND/AIMS

Intraneural ganglion cyst is a rare and underrecognized clinical entity in the pediatric population, which may cause pain as well as motor and sensory neurological deficits. This study presents 4 pediatric patients harboring ganglion cysts involving the peroneal and tibial nerves.

METHODS

Data encompassing pre- and postoperative analyses of 4 pediatric patients with intraneural ganglion cyst was evaluated.

RESULTS

Out of these 4 patients, 3 had an intraneural ganglion cyst involving the peroneal nerve, and 1 patient had his tibial nerve involved. Two patients were operated for recurrent ganglion cysts with severe postoperative neurological deficits, after preceding operations in other institutions. The other 2 patients had no history of previous surgery, and they had their initial surgical treatment in our institute for primarily diagnosed ganglion cysts. With a mean follow-up of 24 months, all patients experienced pain relief. Significant improvement of motor deficits was achieved in 3 patients. No recurrences were encountered during the 24-month follow-up.

CONCLUSION

Intraneural ganglion cysts in children can be treated with excellent outcome in experienced and dedicated centers, which specialize in peripheral nerve microsurgery.

Sciatic nerve tumor and tumor-like lesions - uncommon pathologies

Sciatic nerve mass-like enlargement caused by peripheral nerve sheath tumors or neurocutaneous syndromes such as neurofibromatosis or schwannomatosis has been widely reported. Other causes of enlargement, such as from perineuroma, fibromatosis, neurolymphoma, amyloidosis, endometriosis, intraneural ganglion cyst, Charcot-Marie-Tooth disease, and chronic inflammatory demyelinating polyneuropathy are relatively rare. High-resolution magnetic resonance imaging (MRI) is an excellent non-invasive tool for the evaluation of such lesions. In this article, the authors discuss normal anatomy of the sciatic nerve and MRI findings of the above-mentioned lesions.

Case report: intraneural ganglion cyst of the ulnar nerve at the wrist

We report a case of a 69-year-old male who presented with pain, weakness, and clumsiness of his right hand. Initial evaluation suggested possible neoplastic process affecting his cervical spine, which was fortunately ruled out by bone biopsy. Subsequent electrodiagnostic studies and magnetic resonance imaging confirmed a lesion of the deep ulnar motor branch. Exploration of Guyon's canal was performed, and an intraneural ganglion involving the deep motor branch of the ulnar nerve was found and excised. Despite more than 14 months of symptomatic duration, the patient made a near-complete recovery with virtually no functional limitations. This provides supporting evidence for a functional benefit of intraneural ganglion excision and nerve decompression even in cases of chronic muscle atrophy.

Extreme intraneural ganglion cysts

Object

The mechanism responsible for exceptional examples of intraneural ganglia with extensive longitudinal involvement has not been understood. Such cases of intraneural cysts, seemingly remote from a joint, have been thought not to have articular connections. Decompression and attempted resection of the cyst has led to intraneural recurrence and poor neurological recovery. The purpose of this report is not only to clarify the pathogenesis of these cysts, but also to discuss their treatment based on modern concepts of intraneural ganglia.

Methods

Two examples of extreme longitudinal propagation of intraneural ganglia are presented.

Results

A patient with a moderate tibial neuropathy was found to have a tibial intraneural ganglion. Prospective interpretation of the MR imaging study demonstrated the cyst's origin from the posterior portion of the superior tibiofibular joint (STFJ), with proximal extension within the sciatic nerve to the lower buttock region. Communication between the STFJ and the cyst was confirmed with direct knee MR arthrography. The tibial intraneural cyst was treated successfully by a relatively limited exposure in the distal popliteal fossa: the cyst was decompressed, the articular branch disconnected, and the STFJ resected. Postoperatively, the patient improved neurologically and there was no evidence of recurrent cyst on postoperative MR imaging. A second patient, previously reported by another group, was reexamined 22 years after surgery. This patient had an extensive peroneal intraneural ganglion that extended into the sciatic nerve from the knee to the buttock; no joint connection or recurrent cyst had initially been described. In this patient, the authors hypothesized and established with MR imaging the presence of both: a joint connection to the anterior portion of the STFJ from the peroneal articular branch as well as recurrent cyst within the peroneal and tibial nerves.

Conclusions

This paper demonstrates that extreme intraneural cysts are not clinical outliers but represent extreme examples of other more typical intraneural cysts. They logically obey the same principles, previously described in the unified articular (synovial) theory. The degree of longitudinal extension is probably due to high intraarticular pressures within the degenerative joint of origin. The generalizability of the mechanistic principles is highlighted by the fact that these 2 cases, involving the tibial and the peroneal nerve respectively, both extended well distant (that is, to the buttock) from the STFJ via their respective articular branch of origin. These extensive intraneural cysts can be treated successfully by disconnecting the affected articular branch and by resection of the joint of origin, rather than by a more aggressive operation resecting the cyst and cyst wall.

Intraneural ganglion of the superficial peroneal nerve: a case report

Ganglia affecting the peripheral nerves of the foot and ankle are rare. The most frequent location of occurrence is the common peroneal nerve at the level of the fibular neck. We report the case of an intraneural ganglion of the superficial peroneal nerve and its branches. Although there have been many previous reports of intraneural ganglion involvement with the common peroneal nerve, deep peroneal nerve, sural nerve, and the posterior tibial nerve, to our knowledge, this is the first reported occurrence of an intraneural ganglion distinctly localized to the superficial peroneal nerve and its branches. The presumptive diagnosis was made preoperatively using magnetic resonance imaging, and then confirmed postoperatively by pathologic examination. Despite the use of operative magnification, it was impossible to remove all of the cyst elements within the nerve trunk, because the nerve fascicles were intimately intertwined. Therefore, complete resection of the common trunk of the superficial peroneal nerve and its terminal branches was performed, and the proximal stump was buried in a hole in the distal fibula. Two years after the surgery, the patient was pain free and asymptomatic except for cutaneous anesthesia in the distribution of the superficial peroneal nerve.

Proximal sciatic nerve intraneural ganglion cyst

Intraneural ganglion cysts are nonneoplastic, mucinous cysts within the epineurium of peripheral nerves which usually involve the peroneal nerve at the knee. A 37-year-old female presented with progressive left buttock and posterior thigh pain. Magnetic resonance imaging revealed a sciatic nerve mass at the sacral notch which was subsequently revealed to be an intraneural ganglion cyst. An intraneural ganglion cyst confined to the proximal sciatic nerve has only been reported once prior to 2009.

Intraneural ganglia in the hip and pelvic region. Clinical article

OBJECT

The authors describe their experience in a series of cases of intraneural ganglia within the hip and pelvic regions, and explain the mechanism of formation and propagation of this pathological entity.

METHODS

Five patients with 6 intraneural ganglia are presented. Four patients presented with symptomatic intraneural ganglia in the buttock and pelvis affecting the sciatic and lumbosacral plexus elements. An asymptomatic cyst affecting the opposite sciatic nerve was found on MR imaging in 1 patient. The fifth patient, previously reported on by another group, had an obturator intraneural ganglion that the authors reinterpreted.

RESULTS

All 5 intraneural ganglia affecting the sciatic and lumbosacral plexus elements were found to have a joint connection to the posteromedial aspect of the hip joint; the obturator intraneural cyst had a joint connection to the anteromedial aspect of the hip joint. In all cases, initial review of the MR images led to their misinterpretation.

CONCLUSIONS

To the authors' knowledge, these are the first cases of intraneural ganglia demonstrated to have a connection to the hip joint. This finding at a rare site provides further evidence for the unifying articular (synovial) theory for the formation of intraneural ganglia and reveals a shared mechanism for their propagation. Furthermore, understanding the pathogenesis of these lesions provides insight into their successful treatment and their recurrence.

Adherence of intraneural ganglia of the upper extremity to the principles of the unifying articular (synovial) theory

OBJECT

Intraneural ganglia are nonneoplastic mucinous cysts contained within the epineurium of peripheral nerves. Their pathogenesis has been controversial. Historically, the majority of authors have favored de novo formation (degenerative theory). Because of their rarity, intraneural ganglia affecting the upper limb have been misunderstood. This study was designed to critically analyze the literature and to test the hypothesis that intraneural ganglia of the upper limb act analogously to those in the lower limb, being derived from an articular source (synovial theory).

METHODS

Two patients with digital intraneural cysts were included in the study. An extensive literature review of intraneural ganglia of the upper limb was undertaken to provide the historical basis for the study.

RESULTS

In both cases, the digital intraneural ganglia were demonstrated to have joint connections; the one patient in whom an articular branch was not appreciated initially had evidence on postoperative MR images of persistence of intraneural cyst after simple decompression was performed. Eighty-six cases of intraneural lesions were identified in varied locations of the upper limb: the most common sites were the ulnar nerve at the elbow and wrist, occurring 38 and 22 times, respectively. Joint connections were present in only 20% of the cases published by other groups.

CONCLUSIONS

The authors believe that the fundamental principles of the unifying articular (synovial) theory (that is, articular branch connections, cyst fluid following a path of least resistance, and the role of pressure fluxes) previously described to explain intraneural ganglia in the lower limb apply to those cases in the upper limb. In their opinion, the joint connection is often not identified because of the cysts' rarity, radiologists' and surgeons' inexperience, and the difficulty visualizing and demonstrating it because of the small size of the cysts. Furthermore, they believe that recurrence (subclinical or clinical) is not only underreported but also predictable after simple decompression that fails to address the articular branch. In contrast, intraneural recurrence can be eliminated with disconnection of the articular branch.

Sciatic cross-over in patients with peroneal and tibial intraneural ganglia confirmed by knee MR arthrography

BACKGROUND

A predictable mechanism and stereotypic patterns of peroneal intraneural ganglia are being defined based on careful analysis of MRIs. Peroneal and tibial intraneural ganglia extending from the superior tibiofibular joint which extend to the level of the sciatic nerve have been observed leading to the hypothesis that sciatic cross-over could exist. Such a cross-over phenomenon would allow intraneural cyst from the peroneal nerve by means of its shared epineurial sheath within the sciatic nerve to cross over to involve the tibial nerve, or vice versa from a tibial intraneural cyst to the peroneal nerve.

METHOD AND FINDINGS

One patient with a peroneal intraneural ganglion and another with a tibial intraneural ganglion each underwent a knee MR arthrogram. These studies were not only definitive in demonstrating the communication of the cyst to the superior tibiofibular joint connection but also in confirming sciatic cross-over. Contrast injected into the knee could be demonstrated tracking to the superior tibiofibular joint and then proximally into the common peroneal or tibial nerve respectively, crossing over at the sciatic nerve, and then descending down the tibial and peroneal nerves. The arthrographic findings mirrored MR images upon their retrospective review.

CONCLUSIONS

This study provides direct in vivo proof of the nature of sciatic cross-over theorized by critical review of MRIs and/or experimental dye injections done in cadavers. This study is important in clarifying the potential paths of propagation of intraneural cysts at points of major bifurcation.

The clock face guide to peroneal intraneural ganglia: critical "times" and sites for accurate diagnosis

OBJECTIVE

The aim of this study is to exploit the normal nature of peroneal nerve anatomy to identify constant magnetic resonance imaging (MRI) patterns in peroneal intraneural ganglia.

DESIGN

This study is designed as a retrospective clinical study.

MATERIALS AND METHODS

MR images of 25 patients with peroneal intraneural ganglia were analyzed and were compared to those of 25 patients with extraneural ganglia and 25 individuals with normal knees. All specimens were interpreted as left-sided. Using conventional axial images, the position of the common peroneal nerve and either intraneural or extraneural cyst was determined relative to the proximal fibula and the superior tibiofibular joint using a symbolic clock face. In all patients, the common peroneal nerve could be seen between the 4 and 5 o'clock position at the mid-portion of the fibular head. In patients with intraneural ganglia, a single axial image could reproducibly and reliably demonstrate both cyst within the common peroneal nerve at the mid-portion of the fibular head (signet ring sign) between 4 and 5 o'clock and within the articular branch at the superior tibiofibular joint connection (tail sign) between 11 and 12 o'clock; in addition, cyst within the transverse limb of the articular branch (transverse limb sign) was seen at the mid-portion of the fibular neck between the 12 and 2 o'clock positions on serial images. Extraneural ganglia typically arose from more superior joint connections with the epicenter of the cyst varying around the entire clock face without a consistent pattern. There was no significant difference between the visual and template assessment of clock face position for all three groups (intraneural, extraneural, and controls). We believe that the normal anatomic and pathologic relationships of the common peroneal nerve in the vicinity of the fibular neck/head region can be established readily and reliably on single axial images. This technique can provide radiologists and surgeons with rapid and reproducible information for diagnosis and treatment planning.

CONCLUSIONS

By using conventional bony anatomy as reference points (namely fibular neck and mid-portion of fibular head), standard axial images can be used to interpret key features of peroneal intraneural ganglia and to establish their accurate diagnosis (rather than extraneural ganglia) and pathogenesis from an articular origin (rather than from de novo formation), a fact that has important therapeutic implications. Because of the relative rarity of peroneal intraneural cysts and physicians' (radiologists and surgeons) inexperience with them and the complexity of their findings, they are frequently misdiagnosed and joint communications are not appreciated preoperatively or intraoperatively. As a result, outcomes are suboptimal and recurrences are common.

Tarsal tunnel syndrome associated with a neurilemoma in posterior tibial nerve: a case report

Compression neuropathy of the posterior tibial nerve (PTN) and its branches in the tarsal tunnel is called tarsal tunnel syndrome (TTS) and has various aetiologies. Space-occupying lesions in the tunnel, such as neurilemomas, can cause such a disease. When a neurilemoma occupies the tarsal tunnel, it can compress the PTN directly or indirectly and results in restriction of the tunnel volume. Symptoms due to this restricted volume may vary in TTS. A case of neurilemoma of PTN in tarsal tunnel with a complaint of posteromedial ankle intermittent pain in a 20-year-old patient is presented here. A mass was observed at the ankle posteromedially during clinical examinations and the patient underwent magnetic resonance imaging (MRI) and radiological investigation. Radiographic evaluation of the ankle was normal. However, MRI was revealed a mass adjacent to the PTN in the tarsal tunnel. An ovoid, smooth-surfaced, encapsulated and eccentrically localized mass in the PTN was detected at surgery. The mass was excised from the nerve and pathological evaluation revealed a neurilemoma (schwannoma). Neurilemomas arising from the PTN in the tarsal tunnel should always be kept in mind as a differential diagnosis when a patient complains of a posteromedial ankle pain. Since it is a space-occupying lesion and encapsulated tumor in the tarsal tunnel, simple surgical resection is curative without a distinct morbidity.

Cross-over: a generalizable phenomenon necessary for secondary intraneural ganglion cyst formation

The appearances of intraneural ganglion cysts are being elucidated. We previously introduced the cross-over phenomenon to explain how a fibular (peroneal) or tibial intraneural ganglion cyst arising from the superior tibiofibular joint could give rise to multiple cysts: cyst fluid ascending up the primarily affected nerve could reach the level of the sciatic nerve, fill its common epineurial sheath and spread circumferentially (cross over), at which time pressure fluxes could result in further ascent up the sciatic or descent down the same parent nerve or the opposite, previously unaffected fibular or tibial nerves. In this study, we hypothesized that cross-over could occur in other nerves, potentially leading to the formation of more than one intraneural ganglion cyst in such situations. We analyzed the literature and identified a single case that we could review where proximal extension of an intraneural ganglion cyst involving a nerve at a different site could theoretically undergo cross-over in another major nerve large enough for available magnetic resonance images to resolve this finding. A case of a suprascapular intraneural ganglion cyst previously reported by our group that arose from the glenohumeral joint and extended to the neck was reanalyzed for the presence or absence of cross-over. An injection of dye into the outer epineurium of the suprascapular nerve in a fresh cadaveric specimen was performed to test for cross-over experimentally. Retrospective review of this case of suprascapular intraneural ganglion cyst demonstrated evidence to support previously unrecognized cross-over at the level of the upper trunk, with predominant ascent up the C5 and the C6 nerve roots and subtle descent down the anterior and posterior divisions of the upper trunk as well as the proximal portion of the suprascapular nerve. This appearance gave rise to multiple interconnected intraneural ganglion cysts arising from a single distant connection to the glenohumeral joint. The injection study also demonstrated the cross-over phenomenon and produced a similar pattern as the cyst dissection. This article illustrates that cross-over can occur in another nerve (apart from the prototype fibular nerve). Furthermore, understanding the more complex anatomic nature of the upper trunk cross-over model provides insight into important mechanistic information regarding the bidirectional propagation patterns and formation of primary and secondary intraneural ganglion cysts not afforded by the previously described sciatic nerve cross-over model.

Epineurial compartments and their role in intraneural ganglion cyst propagation: An experimental study

New patterns of intraneural ganglion cyst formation are emerging that have not previously been explained in current pathoanatomic terms. We believe there are three important elements underlying the appearance of these cysts: (a) an articular branch of the nerve that connects to a nearby synovial joint; (b) ejected synovial fluid following the path of least resistance along tissue planes; and (c) the additional effects of pressure and pressure fluxes. The dynamic nature of cyst formation has become clearly apparent to us in our clinical, operative and pathologic practice, but the precise mechanism underlying the process has not been critically studied. To test our hypothesis that a fibular (peroneal) or tibial intraneural cyst derived from the superior tibiofibular joint could ascend proximally into the sciatic nerve, expand within it and descend into terminal branches of this major nerve, we designed a series of simple, qualitative laboratory experiments in two cadavers (four specimens, six experiments). Injecting dye into the outer or "epifascicular" epineurium of the fibular and the tibial nerves we observed its ascent, cross over and descent patterns in three of three specimens as well as its cross over after an outer epineurial sciatic injection. In contrast, injecting dye into the inner or "interfascicular" epineurium led to its ascent within the tibial nerve and its division within the sciatic nerve in one specimen and lack of cross over in a sciatic nerve injection. Histologic cross-sections of the nerves at varying levels demonstrated a tract of disruption within the outer epineurium of the nerve injected and the nerve(s) into which the dye, after cross over, descended. Those specimens injected in the inner epineurium demonstrated dye within this tract but without disruption of or dye intrusion into the outer epineurium. In no case did the dye pass through the perineurial layers. Coupled with our observations in previous detailed studies, these anatomic findings provide proof of concept that sciatic cross over occurs due to the filling of its common epineurial sheath; furthermore, these findings, support the unifying articular theory, even in cases wherein patterns of intraneural ganglion cyst formation are unusual. Additional work is needed to be done to correlate these anatomic findings with magnetic resonance imaging and surgical pathology.

Dynamic phases of peroneal and tibial intraneural ganglia formation: a new dimension added to the unifying articular theory

OBJECT

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.

METHODS

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

RESULTS

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.

CONCLUSIONS

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.

Peroneal and tibial intraneural ganglia: correlation between intraepineurial compartments observed on magnetic resonance images and the potential importance of these compartments

Object

Previously the authors demonstrated that peroneal and tibial intraneural ganglia arising from the superior tibiofibular joint may occasionally extend proximally within the epineurium to reach the sciatic nerve. The dynamic nature of these cysts, dependent on intraarticular pressures, may give rise to differing clinical and imaging presentations that have remained unexplained until now. To identify the pathogenesis of these unusual cysts and to correlate their atypical magnetic resonance (MR) imaging appearance, the authors retrospectively reviewed their own experience as well as the published literature on these types of intraneural ganglia.

Methods

A careful review of MR images obtained in 22 patients with intraneural ganglia located about the knee region (18 peroneal and four tibial intraneural ganglia) allowed the authors to substantiate three different patterns: outer (epifascicular) epineurial (20 cases); inner (interfascicular) epineurial (one case); and combined outer and inner epineurial (one case). In these cases serial MR images allowed the investigators to track the movement of the cyst within the same layer of the epineurium. All lesions had connections to the superior tibiofibular joint. Nine patients were identified as having lesions with sciatic nerve extension. Seven patients harboring an outer epineurial cyst (six in whom the cyst involved the peroneal nerve and one in whom it involved the tibial nerve) had signs of sciatic nerve cross-over, with the cyst seen in the sciatic nerve and/or other terminal branches. In only two of these cases had the cyst previously been recognized to have sciatic nerve involvement. In contrast, in one case an inner epineurial cyst involving the tibial nerve ascended within the tibial division of the sciatic nerve and did not cross over. A single patient had a combination of both outer and inner epineurial cysts; these were easily distinguished by their distinctive imaging patterns.

Conclusions

This anatomical compartmentalization of intraneural cysts can be used to explain varied clinical and imaging patterns of cleavage planes for cyst formation and propagation. Compartmentalization elucidates the mechanism for cases of outer epineurial cysts in which there are primary ascent, sciatic cross-over, and descent of the lesion down terminal branches; correlates these cysts' atypical MR imaging features; and contrasts a different pattern of inner epineurial cysts in which ascent and descent occur without cross-over. The authors present data demonstrating that the dynamic phases of these intraneural ganglia frequently involve the sciatic nerve. Their imaging features are subtle and serve to explain the underrecognition and underreporting of the longitudinal extension of these cysts. Importantly, cysts extending to the sciatic nerve are still derived from the superior tibiofibular joint. Combined with the authors' previous experimental data, the current observations help the reader understand intraneural ganglia with a different, deeper degree of anatomical detail.

Dynamic phases of peroneal and tibial intraneural ganglia formation: a new dimension added to the unifying articular theory

Object

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.

Methods

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

Results

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.

Conclusions

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.

The clinico-anatomic explanation for tibial intraneural ganglion cysts arising from the superior tibiofibular joint

OBJECTIVE

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.

DESIGN

Retrospective clinical study and prospective anatomic study.

MATERIALS

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.

RESULTS

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.

CONCLUSIONS

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.

Ulnar nerve compression in the cubital tunnel by an epineural ganglion: a case report

Epineural ganglia are considered to be a usual cause of peripheral nerve compression. In this report, we present a rare case of ulnar nerve compression by an epineural ganglion in the cubital tunnel. A 28-year-old right-handed female secretary developed progressive pain, numbness, and weakness in her right elbow, forearm, and hand for 6 months. Atrophy of the adductor pollicis and the first dorsal interosseous muscles was apparent. Clinical examination revealed a cystic mass at the posterior side of the elbow. Magnetic resonance imaging identified a ganglion while electrophysiologic studies revealed a severe conduction block of the ulnar nerve at the elbow. During surgery a 2-cm diameter epineural ganglion was identified compressing the ulnar nerve and was excised using microsurgery techniques. Two months postoperatively, the clinical recovery of the patient was very satisfactory, although the postoperative electrophysiologic studies demonstrated a less dramatic improvement.

Nerve sheath ganglion of the tibial nerve presenting as a Baker's cyst: a case report

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

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 Cystic Transverse Limb of the Articular Branch: a Pathognomonic Sign Forperoneal Intraneural Ganglia Atthe Superior Tibiofibular Joint

OBJECTIVE

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.

METHODS

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).

RESULTS

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.

CONCLUSION

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.

Missile-Caused Complete Lesions of the Peroneal Nerve and Peroneal Division of the Sciatic Nerve: Results of 157 Repairs

OBJECTIVE:

There are few large-volume studies of the repair of complete missile-caused peroneal nerve and peroneal division lesions. In this prospective study, the outcomes of such repairs are studied and the factors influencing the outcomes are analyzed.

METHODS:

During a 3-year period, 157 patients with complete missile-caused lesions of the peroneal nerve or peroneal division were treated surgically in the Belgrade Military Medical Academy: 37 patients with high-level (above the middle of the thigh), 90 patients with intermediate-level (above the popliteal crease), and 30 patients with low-level repairs. After at least 4 years of follow-up, outcome was defined on the basis of motor recovery, neurophysiological recovery, and patient judgment of the quality of outcome (poor, insufficient, good, or excellent). Good and excellent outcomes were considered successful. The factors of repair level, defect length, manner of repair, preoperative interval, severity of tissue damage in the repair region, and patient age were studied for their effect on outcome.

RESULTS:

A successful outcome was obtained in 10.8% of high-level repairs, 31.1% of intermediate-level repairs, and 56.7% of low-level repairs (P < 0.001). Nerve defect and preoperative interval were significantly shorter for patients with a successful outcome compared with those with an unsuccessful outcome (P< 0.001). Worsening of the outcome began with the nerve defect larger than 4 cm and preoperative interval greater than 3 months (P< 0.001). Severity of local tissue damage significantly influenced the outcome (P= 0.008). Repair level (P< 0.001), preoperative interval (P= 0.001), severity of local tissue damage (P= 0.011), and length of nerve defect (P= 0.011) were independent predictors for a successful outcome.

CONCLUSION:

After peroneal nerve or peroneal division repairs, a successful outcome is most probable with low-level lesions repaired in the first 3 months after injury using grafts smaller than 4 cm. Conversely, high-level repairs delayed for more than 7 months after injury and using grafts larger than 8 cm are probably not worthwhile.

Endoscope-assisted microsurgical resection of an intraneural ganglion cyst of the hypoglossal nerve

✓ An unusual case of an intraneural ganglion cyst of the hypoglossal nerve is presented. Only one case of this rare clinical entity has been reported previously. A 51-year-old woman presented with a 6-month history of left-sided hypoglossal nerve palsy. Magnetic resonance imaging revealed a cystic lesion related to the hypoglossal canal. There was no enhancement of the lesion after administration of Gd. A high-resolution computerized tomography scan of the skull base demonstrated an enlargement of the hypoglossal canal.

To access the lesion, a far-lateral endoscope-assisted microsurgical approach was used. An intraneural ganglion lesion invading the hypoglossal nerve was found and resected. A histopathological examination confirmed that the lesion was an intraneural ganglion cyst. The occurrence of an intraneural ganglion cyst at the hypoglossal nerve is very rare. This case exemplifies an atypical location of a synovial cyst with cranial nerve involvement.

Management and outcomes in 318 operative common peroneal nerve lesions at the Louisiana State University Health Sciences Center

OBJECTIVE

This study analyzes 318 operative knee-level common peroneal nerve lesions managed at the Louisiana State University Health Sciences Center between 1967 and 1999.

METHODS

Each patient was retrospectively evaluated for injury mechanism, preoperative neurological status, electrophysiological studies, lesion type, and operative technique, i.e., neurolysis, suture, or graft repair. All lesions in continuity had intraoperative nerve action potential recordings.

RESULTS

There were 141 stretch/contusions without fracture/dislocations (44%), 39 lacerations (12%), 40 tumors (13%), 30 entrapments (9%), 22 stretch/contusions with fracture/dislocations (7%), 21 compressions (7%), 13 iatrogenic injuries (4%), and 12 gunshot wounds (4%). After neurolysis, 107 (88%) of 121 knee-level common peroneal nerve lesions with recordable intraoperative nerve action potentials recovered useful function. Nineteen patients underwent end-to-end suture repair, and 16 (84%) of these achieved good recovery by 24 months. Graft repair was performed in 138 peroneal injuries. Thirty-six patients (26%) had grafts less than 6 cm long, of which 27 (75%) achieved Grade 3 or greater peroneal function. Twenty-four (38%) of 64 patients with 6- to 12-cm grafts, and only 6 (16%) of 38 patients with 13- to 24-cm grafts, attained good peroneal function. Longer grafts correlated with more severe injuries and thus poorer outcomes. Thirty-two (80%) of 40 tumors were resected with preservation of preoperative clinical function.

CONCLUSION

Surgical exploration and repair of peroneal nerve lesions achieved good results with timely operations and thorough intraoperative evaluations. Useful function was achieved in 27 (75%) of 36 patients with grafts less than 6 cm in length and in only 88 (44%) of 202 patients with grafts greater than 6 cm in length.

Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve: report of 2 cases and review of the literature

Ganglia within the posterior tibial nerve is a rare condition. The authors report 2 cases of epineural ganglion of the posterior tibial nerve, causing tarsal tunnel syndrome. Both cases presented with numbness on the plantar surface of the foot. Magnetic resonance imaging showed the presence of the cyst within the tarsal tunnel. During surgery, these cysts were found within the epineurium of the posterior tibial nerve and were successfully removed without damage to nerve fibers. Both patients were free of symptoms after surgery. Ganglion cysts in the peripheral nerve are either intrafascicular or epineural. Intrafascicular ganglia present beneath the epineurium and involve the nerve fibers, whereas epineural ganglia are located in the epineurium and do not involve the nerve fibers. A review of the literature discusses these concepts. The authors suggest that epineural ganglion should be clinically distinctive from an intrafascicular ganglion because of the differences in surgical treatment, postoperative nerve function, and the recurrence rate.

Peroneal intraneural ganglia: the importance of the articular branch. A unifying theory

OBJECT

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.

METHODS

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.

CONCLUSIONS

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.