Intraneural ganglia: a clinical problem deserving a mechanistic explanation and model

Juxtaneural ganglia arising from the hip joint: focus on magnetic resonance imaging findings and clinical manifestations

OBJECTIVE

To present cases of juxtaneural ganglia arising from the hip with a discussion of the magnetic resonance imaging (MRI) findings, presenting symptoms, and possible treatment option.

MATERIALS AND METHODS

Two radiologists performed a consensus review of MRI scans obtained between January 2013 and March 2021 to identify patients with juxtaneural ganglia around the hip. A total of 11 patients with 11 juxtaneural ganglia were identified. Medical records and MRI findings were retrospectively reviewed.

RESULTS

Eight patients had lesions involving the sciatic nerve, and three patients had lesions involving the obturator nerve. Sciatic ganglia arose from a paralabral cyst in the posteroinferior quadrant and continued through a narrow channel running along the posterior acetabulum, showing increased diameter in the sciatic foramen and intrapelvic portion. Obturator ganglia showed a J- or reverse J-shape on the coronal imaging plane and extended from a paralabral cyst in the anteroinferior quadrant via the obturator canal. Nine patients (9/11, 81.8%) had symptoms resembling those of lumbosacral radiculopathy. Four patients underwent arthroscopic surgery, and one patient underwent ultrasound-guided aspiration, all of whom showed partial improvement. Spontaneous decrease in the extent of the ganglion was observed in three patients (3/11, 27.3%).

CONCLUSION

This article describes rare cases of juxtaneural ganglia arising from the hip joint and involving the sciatic and obturator nerves. The lesions share similar MRI findings, and each type of cyst (sciatic or obturator ganglia) involves a specific labral quadrant.

A novel mechanism for the formation and propagation of neural tumors and lesions through neural highways

By recognizing anatomic and radiologic patterns of rare and often misdiagnosed peripheral nerve tumors/lesions, we have defined mechanisms for the propagation of neural diseases. The novel concept of the nervous system serving as a complex system of "highways" driving the neural and perineural spread of these lesions is described in three examples: Intraneural dissection of joint fluid in intraneural ganglion cysts, perineural spread of cancer cells, and dissemination of unknown concentrations of neurotrophic/inhibitory factors for growth in hamartomas/choristomas of nerve. Further mapping of these pathways to identify the natural history of diseases, the spectrum of disease evolution, the role of genetic mutations, and how these neural pathways interface with the lymphatic, vascular, and cerebrospinal systems may lead to advances in targeted treatments.

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.

Intradural intraneural hemorrhagic cyst resulting in progressive cauda equina syndrome after anticoagulation therapy

STUDY DESIGN

Case report.

OBJECTIVE

To report a case of lumbar intraneural hemorrhagic cyst after anticoagulation therapy that caused progressive radiculopathy and cauda equina syndrome. The possible pathogenic mechanism, associated diseases, and treatment options are discussed.

SUMMARY OF BACKGROUND DATA

Various pathological processes can cause progressive cauda equina syndrome. However, there have been no reports of progressive cauda equina syndrome due to compression from an intraneural hemorrhagic cyst after anticoagulation therapy.

METHODS

A case of lumbar intradural intraneural hemorrhagic cyst with progressive cauda equina syndrome after anticoagulation therapy is presented.

RESULTS

A 42-year-old-female patient complained at presentation of progressive bilateral lower extremity radiating pain, numbness, and urinary difficulty during the previous 2 months. Lumbar magnetic resonance imaging revealed an L1 cystic lesion with marked mass effect on the surrounding nerve roots. Complete drainage and excision of the lesion was performed, which resulted in excellent postoperative symptoms relief. Pathological examination revealed no definite neoplastic process except some nerve fibers with hemosiderin stain along the cyst wall. On the basis of a combination of intraoperative findings and pathology, an intradural intraneural hemorrhagic cyst that developed after systemic anticoagulation therapy was diagnosed.

CONCLUSION

This is the first report of an intradural intraneural hemorrhagic cyst causing progressive cauda equina syndrome due to anticoagulation therapy. Surgical excision of the cyst is the definite treatment of choice.

LEVEL OF EVIDENCE

N/A.

Unusual peroneal nerve palsy caused by intraneural ganglion cyst: pathological mechanism and appropriate treatment

The origin of the peroneal intraneural ganglion and the outcome of treatment are still controversial. We report here three cases with peroneal intraneural ganglion and discuss the appropriate treatment. In our cases, 58-, 62-, and 65-year-old patients were operated on with extraneural decompression and epineurotomy within 4 months after onset of drop foot. Two cases demonstrated intraneural ganglion connecting to the articular branch and traversing to the deep and common peroneal nerve. At the 1-year follow-up, paralyzed peroneal nerve could be recovered in all patients even with residual ganglion. We propose correct early diagnosis, simple exoneural dissection, and atraumatic epineurotomy for the successful treatment of peroneal intraneural ganglion. Disruption of the stalk in the articular branch is a key point to prevent recurrence. For early diagnosis, clinicians should be aware of the existence of this rare lesion.

MR IMAGING OF SUPRASCAPULAR NEUROPATHIES

Suprascapular neuropathy has become increasingly recognized entity which is often overlooked and mistaken for other causes of shoulder pain and dysfunction like rotator cuff injury, shoulder impingement syndrome, cervical spondylosis and brachial plexopathy. It can be caused by a variety of anatomic and pathologic entities as the nerve courses from the brachial plexus through the suprascapular and spinoglenoid notches to innervate the supraspinatus and infraspinatus muscles. Because of the widespread availability of high-field MRI scanners now it is possible to detect the subtle perineural pathology, thereby excluding the other common causes of shoulder pain. There are scattered case reports and reviews describing suprascapular nerve (SSN) abnormalities using MRI. This article comprehensively reviews different pathologic abnormalities involving the SSN and illustrates their MR features, clinical presentation, correlation with electrophysiologic studies and surgical findings based on a review of 24 cases. We found the different clinical entities which includes trauma and a spectrum of nontraumatic etiology such as idiopathic, mass lesions compressing the nerve, intrinsic lesion like intraneural ganglion cysts of SSN, repetitive overuse, viral neuritis and chemotherapy induced neuropathy.

Peripheral neuropathy caused by joint-related cysts: a review of 17 cases

BACKGROUND

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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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.

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.

Tibial intraneural ganglia at the ankle and knee: incorporating the unified (articular) theory in adults and children

OBJECT

The etiology of intraneural ganglia has been debated for centuries, and only recently a unifying theory has been proposed. The incidence of tibial nerve intraneural ganglia is restricted to the occasional case report, and there are no reported cases of these lesions in children. While evidence of the unifying theory for intraneural ganglia of the common peroneal nerve is strong, there are only a few reports describing the application of the theory in the tibial nerve. In this report the authors examine tibial nerve intraneural ganglia at the ankle and knee in an adult and a child, respectively, and describe the clinical utility of incorporating the unifying (articular) theory in the management of tibial intraneural ganglia in adults and children.

METHODS

Cases of tibial intraneural ganglion cysts were examined clinically, radiologically, operatively, and histologically to demonstrate the application of the unified (articular) theory for the development of these cysts in adults and children.

RESULTS

Two patients with intraneural ganglion cysts of the tibial nerve were identified: an adult with an intraneural ganglion cyst of the tibial nerve at the tarsal tunnel and a child with an intraneural ganglion cyst of the tibial nerve at the knee. In each case, preoperative MR imaging demonstrated the intraneural cyst and its connection to the adjacent joint via the articular branch to the subtalar joint and superior tibiofibular joint. At surgery the articular branch was identified and resected, thus disconnecting the tibial nerve intraneural cyst from the joint of origin.

CONCLUSIONS

These cases detail the important features of intraneural ganglion cysts of the tibial nerve and document the clinical utility of incorporating the unifying (articular) theory for the surgical management of tibial intraneural ganglia in adults and children.

THE UNIFYING ARTICULAR (SYNOVIAL) ORIGIN OF INTRANEURAL GANGLIA

THE PATHOGENESIS OF intraneural ganglia has been an issue of curiosity, controversy, and contention for 200 years. Three major theories have been proposed to explain their existence, namely, 1) degenerative, 2) synovial (articular), and 3) tumoral theories, each of which only partially explains the observations made by a number of investigators. As a result, differing operative strategies have been described; these generally meet with incomplete neurological recoveries and high rates of recurrence. Recent advances in magnetic resonance imaging and critical analysis of the literature have clarified the mechanisms underlying the formation and propagation of these cysts, thereby confirming the unifying articular (synovial) theory. By identifying the shared features of the typical cases and explaining atypical examples or clinical outliers, several fundamental principles have been described. These include: 1) a joint origin; 2) dissection of fluid from that joint along an articular nerve branch, extension occurring via a path of least resistance; and 3) cyst size, extent, and directionality being influenced by pressures and pressure fluxes. We believe that understanding the pathogenesis of these cysts will be reflected in optimal surgical approaches, improved outcomes, and decreased frequency, if not elimination, of recurrences. This article describes the ongoing process of critically analyzing and challenging previous observations and evidence in an effort to prove a concept and a theory.

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.