Amrami, Kimberly K.

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.

A retrospective case review was carried out to report the outcomes in a contemporary case series of Ewing’s sarcoma originating in the hand. We identified five patients treated since 1995. All five had wide surgical excision, one by ray amputation. All were treated with chemotherapy. Four patients also received radiation therapy, two to treat metastases and two as an adjunct to local excision. There were no local recurrences. Two patients developed metastases. Both died of their disease. Neither of these two patients had received local postoperative radiation therapy; one did not receive chemotherapy before definitive surgery. The other three patients were alive and free of disease at last follow-up, 4 to 12 years after initial presentation.

✓ As a rule, normal human nerve does not contain glomus bodies. Nonetheless, rare examples of glomus tumors do arise in peripheral nerves of various sizes. Their pathobiological characteristics are poorly understood, but reported examples have been small and clinically benign. The authors identified in 1 patient each a glomus tumor and a glomangioma involving nerve. Clinical histories as well as imaging and surgical findings were reviewed. All available H & E–stained slides were examined in both cases. Immunohistochemical stains and electron microscopy, as appropriate, were also performed. The lesions were subtotally and completely resected, respectively. An uneventful postoperative recovery was noted in both patients. Glomus tumors and glomangiomas can involve major nerves on rare occasions. They seem to follow a favorable clinical course, and conservative resection can be of benefit.

✓ The authors report on a patient without neurofibromatosis Type 1 or 2 (NF1 or NF2) and without evidence of schwannomatosis, who was found to have an unusual combination of nerve sheath tumors—a large cellular schwannoma and multifascicular involvement of a plexiform neurofibroma arising from the same site within the radial nerve and posterior cord of the infraclavicular brachial plexus. This case broadens the spectrum of combined pathological features of nerve sheath tumors. Genetic studies revealed a combined loss of neurofibromin and merlin in both regions and chromosome arm 22q deletion within the neurofibroma component only. The latter finding supports the suggestion that these were two different clonal neoplasms, and is consistent with a collision tumor pattern.

✓ The authors describe the case of a patient with a novel cause of medial plantar symptoms due to extrinsic compression by a schwannoma arising within the adventitia of the tibial artery in the ankle region. Additionally they provide the operative, histological, and imaging findings.

Object The operative management of combined intrapelvic and extrapelvic sciatic notch dumbbell-shaped tumors is challenging. The relatively rare occurrence of these tumors and the varied extent of disease have made it difficult for surgeons to establish definitive surgical indications or predict favorable neurological outcomes based on preoperative imaging data. Methods In the past 3 years, the authors treated five patients presenting with radiating leg pain as a result of benign sciatic notch dumbbell-shaped tumors. These tumors in three patients with unilateral leg symptoms were considered unresectable by other neurosurgeons because of presumed direct intrinsic neural involvement. After high-resolution magnetic resonance (MR) imaging demonstrated that the extensive tumors were separate from the sciatic nerve and the lumbosacral plexus, however, these patients underwent a combined one-stage transabdominal and posterior transgluteal complete resection. Normal neurological status was maintained postoperatively in these three patients, and after more than 1 year of postoperative follow up, there were no tumor recurrences. In two patients with bilateral symptoms and extensive tumor burden, serial MR images showed that innumerable tumors directly involved the entire cross-sectional area of the sciatic nerves and extended longitudinally to the lumbosacral plexuses. Tumor debulking or resection in these patients would have resulted in neurological deficits and would not have addressed their neuropathic pain, and therefore no surgery was performed. These two patients were treated pharmacologically and advised to monitor their tumor status over the course of their lifetimes in case of malignant transformation of the tumor. Conclusions A combined one-stage transabdominal and transgluteal approach allows safe resection of selected benign but extensive sciatic notch tumors. High-resolution MR imaging is a useful tool in the management of these tumors because it allows the surgeon to visualize the anatomical relationships of the tumor to the sciatic nerve. The authors believe that as this imaging technology advances, it will provide surgeons with a method to predict definitively which sciatic notch tumors displace rather than directly involve the sciatic nerve, and therefore indicate which tumors can be resected safely and completely.

Object 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. Methods 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. Conclusions 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.

✓The authors present clinical, imaging, and histological features of two adult patients found to harbor a conventional schwannoma contiguous with a deep plexiform schwannoma. One patient had neurofibromatosis (NF) Type 2 (NF2), and both intracranial (bilateral oculomotor, trigeminal, acoustic, and hypoglossal schwannomas as well as meningiomas) and intraspinal (schwannomas and meningiomas) lesions. The proximal forearm lesions consisted of a conventional schwannoma and an underlying plexiform component. The second patient, who did not have NF2, presented with a similar enlarging mass in the distal arm; two contiguous lesions were resected. Both patients exhibited distinct, readily identifiable, magnetic resonance imaging features. Plexiform schwannomas are rare lesions that occur sporadically or, on occasion, in association with NF2 or meningiomas with or without multiple schwannomas. The authors believe that a more careful examination of patients with NF2 may show that these people have a higher incidence of plexiform schwannoma than previously thought. Pathological confirmation is crucial in distinguishing plexiform schwannomas from plexiform neurofibromas, because the latter are directly associated with NF1 and have a significant tendency to undergo malignant transformation. To the best of the authors’ knowledge, this is the first report of a conventional schwannoma contiguous with a deep plexiform schwannoma.

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 authors describe common modes of failure in the diagnosis and treatment of patients with peroneal intraneural ganglia. Illustrated examples correlate the modes of failure and the diagnostic or surgical errors. Understanding these pitfalls reinforces the rationale behind current treatment recommendations as outlined in the companion article. Avoiding these pitfalls will ultimately improve outcomes.