Nikhil K. Prasad

The successful arthroscopic treatment of suprascapular intraneural ganglion cysts

OBJECT High-resolution magnetic resonance imaging (MRI) can distinguish between intraneural ganglion cysts and paralabral (extraneural) cysts at the glenohumeral joint. Suprascapular intraneural ganglion cysts share the same pathomechanism as their paralabral counterparts, emanating from a tear in the glenoid labrum. The authors present 2 cases to demonstrate that the identification and arthroscopic repair of labral tears form the cornerstone of treatment for intraneural ganglion cysts of the suprascapular nerve. METHODS Two patients with suprascapular intraneural ganglion cysts were identified: 1 was recognized and treated prospectively, and the other, previously reported as a paralabral cyst, was identified retrospectively through the reinter-pretation of high-resolution MR images. RESULTS Both patients achieved full functional recovery and had complete radiological involution of the intraneural ganglion cysts at the 3-month and 12-month follow-ups, respectively. CONCLUSIONS Previous reports of suprascapular intraneural ganglion cysts described treatment by an open approach to decompress the cysts and resect the articular nerve branch to the glenohumeral joint. The 2 cases in this report demonstrate that intraneural ganglion cysts, similar to paralabral cysts, can be treated with arthroscopic repair of the glenoid labrum without resection of the articular branch. This approach minimizes surgical morbidity and directly addresses the primary etiology of intraneural and extraneural ganglion cysts.

Subparaneurial ganglion cysts of the fibular and tibial nerves: A new variant of intraneural ganglion cysts

Over the last decade, the mechanism of formation of intraneural ganglion cysts has been established through a meticulous review of clinical findings and correlation with patterns produced on magnetic resonance imaging (MRI). Pathognomonic imaging patterns distinguish these rare lesions from the more common extraneural variants in almost all cases. In this report, we present a new pattern of cyst occurrence in the subparaneurial compartment of the nerve and provide potential anatomic explanations for its pathogenesis. Using an anatomic framework of connective tissue compartments of the nerve, we reviewed 63 (56 fibular and seven tibial) intraneural ganglion cysts in the knee region evaluated at our institution and all reports with MRI in the worlds literature for evidence of cyst occurrence in the subparaneurial compartment. We identified six cases (five in the common fibular nerve and one in the tibial nerve) at our institution that had MR evidence of cyst in the subparaneurial compartment with a new complex lobulated pattern. All cases had articular branch connections to the superior tibiofibular joint, which at operation were resected along with the joints. Follow‐up revealed complete recovery in all instances and no clinical or radiological signs of recurrence. Three cases out of 80 in the literature exhibited the new complex lobulated MRI pattern. We present a new pattern of intraneural ganglion cyst occurrence in a potential space that surrounds peripheral nerves‐ the subparaneurial compartment. We believe that the unifying articular theory applies to the pathogenesis and management of these rare variants. Clin. Anat. 29:530–537, 2016.

The subparaneurial compartment: A new concept in the clinicoanatomic classification of peripheral nerve lesions

Based on our experience in treating peripheral non‐neural sheath derived pathology, we have identified a novel pattern of lesion progression along the anatomic course of nerves. This report highlights the existence of a subparaneurial compartment around peripheral nerves. We first applied an anatomic framework to review MR images and intraoperative photographs of patients treated by the senior author in the last 10 years. After identifying a pattern that was consistent with subparaneurial lesion progression, we searched for other examples of cases that might exhibit this pattern. Four examples of subparaneurial pathology were identified, a hemangioma of the ulnar nerve, a ganglion cyst of the common fibular nerve, a lymphoma of the sciatic nerve and a lipoma of the ulnar nerve. All four patients were operated on and had intraoperative photographs; three had high resolution MR imaging. This report highlights the existence of pathology contained within a subparaneurial compartment, outside of the epineurium, that follows the course of the nerve and surrounds it circumferentially. The subparaneurial localization of peripheral nerve lesions has hitherto received little attention. Identification of this new pattern on preoperative MRI may have implications for surgical management. Clin. Anat. 28:925–930, 2015.

Clinical anatomy leading the way for solutions: An important paradigm for translational research.

The term “translational research” has rightfully gained popularity over the last decade. It classically refers to the application of basic science discoveries to meaningful improvement in patient outcomes, i.e., from “bench to bedside,” and implies the novel discovery of treatment principles to positively affect the health of its intended medical population (Woolf, 2008). It is also widely recognized to involve a continuous cycle of feedback between a clinical question, discovery, translation, and application, leading to point of care treatment (i.e., from “bedside to bench to bedside”). While the emphasis has largely been on basic science, such as genomics and molecular or cancer biology for medical advances, we propose that it can and should also be on anatomy and surgical advances as well: the bench where discovery begins, does not have to be in a laboratory surrounded by test tubes and pipettes, but rather, can happen in the anatomy laboratory through dissection. The “bedside to bench and back” model can be applied in clinical anatomy by answering clinical problems with anatomic explanations, and translating the discoveries to targeted treatments in patients (Fig. 1).

How to explain cystic adventitial disease coexisting in an adjacent artery and vein

Our group recently reviewed the literature to support the role of joint connections in cystic adventitial disease (CAD) (Desy and Spinner, 2014): cyst (joint) fluid would egress from a synovial joint and dissect along the adventitia of an articular (capsular) branch to a parent vessel. A recent meta-analysis of 503 reports (724 patients) revealed two patients, one involving the femoral (Ohta et al., 1984), and the other, the popliteal vessels (Alioti et al., 2005) with concurrent disease in adjacent arterial and venous adventitia at the time of operation. Neither case explained the location or the coexistence of the cysts. We believe there is an anatomical basis for both questions. Based on the evidence we have provided in previous publications (Spinner et al., 2013; Desy and Spinner, 2014), we feel that a joint connection was present but unrecognized in both cases (i.e., to the hip and knee, respectively). This is supported by the para-articular location of the cysts, similar to others in the literature including the popliteal and femoral vessels individually (Campbell and Millar, 1985; Hall et al., 1985; Chen et al., 2013; Spinner et al., 2013; Michaelides et al., 2014). Unfortunately, imaging data were not available for our retrospective review nor was postoperative follow-up provided in these two cases. Building on the articular theory that we have proposed, we supply three anatomic possibilities for the coexistence of arterial and venous cysts: (1) Simultaneous or sequential dissection along two separate articular branches from the artery and vein into the parent vessels; (2) Ascent toward the sheath surrounding parent vessels, via a common sheath encircling the capsular artery and vein; or (3) Ascent along a single capsular vessel with “cross-over” to the other vessel within a common (parental) sheath. The first option is supported by nine cases of CAD at the superior tibiofibular joint occurring together with peroneal intraneural ganglion cysts (Spinner et al., 2006). Extrapolating from this, we suggest that a cyst could also progress along capsular arterial and venous branches toward their parent artery and vein (Figs. 1A and 1B). The drawing in Ohta’s paper and the brief description by Alioti would support this mechanism as there appeared to be two separate cysts. The second option would necessitate a common sheath around the capsular vessels (Figs. 1C and 1D). Arteries and veins share a common adventitial layer in smaller mucosal vessels (Gray, 1918), retinal vessels (Jefferies et al., 1993), and the larger carotid vessels (Hayashi, 2007). It is possible that this also applies at the level of capsular vessels, providing a common conduit by which the cyst could ascend. At the bifurcation of this sheath, where the capsular artery and vein divide toward their parent vessels, cyst could progress via either route. If disease were to affect the artery first (Ohta et al., 1984), adventitial fibrosis might increase resistance within the cystic cavity, diverting cyst to the adjacent vein via the common capsular sheath (Fig. 1D); this could potentially explain the sequential development of two cysts from a single conduit. The third option demands the presence of a fibrous sheath investing both the parent artery and vein as is widely recognized in the popliteal and femoral vessels (Moore and Dalley, 2014). Cyst could either dissect circumferentially with the common sheath, or via a septum between the two vessels; explaining a cyst that surrounds the entire vascular bundle (Figs. 1E, 1F). We do not believe that the finding of coexisting artery/ vein cysts is coincidental, or that the two cases are outliers from the articular theory: these examples of CAD must have joint connections. We provide possible mechanisms to explain the concurrent disease, though we do not have proof to answer the question. We also recognize that compression of the adjacent vein by an arterial adventitial cyst (or vice versa) can happen and this must be carefully considered when reviewing images to determine whether in fact that cyst associated with the vein is within the adventitia. An understanding of these cases is essential to prevent recurrence of disease which can occur if the articular connection(s) is/are not addressed. High resolution MRI and MR or CT arthrography would best provide information to the surgeon about the cyst origin and even inter-cyst communication.

A new pattern of lipomatosis of nerve: case report

Lipomatosis of nerve (LN) is a rare disorder of peripheral nerves that produces proliferation of interfascicular adipose tissue. It may be associated with soft-tissue and bony overgrowth within the affected nerve territory. LN has been almost exclusively reported in appendicular peripheral nerves; the median nerve at the wrist and palm is among the most common locations. The authors present a new pattern of LN that shows circumferential proliferation of fat around the epineurium of the nerve. They believe that this case and the two other documented examples in the literature (also affecting cervical and thoracic spinal nerves) share the same new pattern of LN. Defining the full spectrum of adipose lesions of the nerve and establishing a cause-effect relationship with nerve-territory overgrowth disorders may offer options for future management through targeted nerve lesioning.

Recurrent desmoid-type fibromatosis associated with underlying neuromuscular choristoma

OBJECTIVEDesmoid-type fibromatosis (DTF) presents a therapeutic dilemma. While lacking metastatic potential, it is a locally aggressive tumor with a strong propensity for occurrence near nerve(s) and recurrence following resection. In this study, the authors introduce the association of an occult neuromuscular choristoma (NMC) identified in patients with DTF.METHODSAfter experiencing a case of DTF found to have an occult NMC, the authors performed a retrospective database review of all other cases of biopsy-proven DTF involving the extremities or limb girdles in patients with available MRI data. Two musculoskeletal radiologists with expertise in peripheral nerve imaging reviewed the MRI studies of the eligible cases for evidence of previously unrecognized NMC.RESULTSThe initial case of a patient with an occult sciatic NMC is described. The database review yielded 40 patients with DTF-18 (45%) in the upper limb and 22 (55%) in the lower limb. Two cases (5%) had MRI findings of NMC associated with the DTF, one in the proximal sciatic nerve and the other in the proximal tibial and sural nerves.CONCLUSIONSThe coexistence of NMC may be under-recognized in a subset of patients with extremity DTF. This finding poses implications for DTF treatment and the likelihood of recurrence after resection or biopsy. Further study may reveal crucial links between the pathogenesis of NMC and DTF and offer novel therapeutic strategies.

Can Intraneural Perineuriomas Occur Intradurally? An Anatomic Perspective

Background Intraneural perineuriomas are rare, benign lesions produced by the neoplastic proliferation of perineurial cells. They typically present in adolescents and affect nerves of the limbs. In our experience, we have not encountered a single case of classic intraneural perineurioma at an intradural location. Objective To determine whether intraneural perineuriomas could occur intradurally, given the prevalence of intradural nerve sheath tumors, and explain our findings with an anatomic perspective. Methods We retrospectively reviewed the high-resolution magnetic resonance images of 56 patients from an institutional registry of patients with intraneural perineurioma. All cases were analyzed for signs of proximal extension toward spinal nerves, roots, and spinal cord. A literature review was performed. The clinical, radiological, and histopathological features of potential intradural lesions were critically appraised against strict criteria for a diagnosis of classic intraneural perineurioma. Results Fifteen of 56 (27%) patients with intraneural perineurioma had a proximal localization in the lumbosacral or brachial plexus. Not a single case occurred proximal to the dorsal root ganglia (DRG). One case of trigeminal intraneural perineurioma occurred distal to the gasserian ganglion. A literature review did not reveal any convincing cases of classic intraneural perineuriomas occurring in an intraspinal intradural location and revealed only 1 possible case in an intracranial intradural location. Conclusion Based on our study, the occurrence of classic intraneural perineuriomas intradurally is exceedingly rare, if at all present. This may be related to the paucity of perineurial cells at the nerve root level and reciprocal interactions between neuroglial cells at the central-to-peripheral transition zones.

Concurrent Lateral Dorsal Cutaneous and Deep Peroneal Intraneural Ganglion Cysts in the Foot

Intraneural ganglion cysts are non-neoplastic collections of mucinous material within the epineurium of peripheral nerves. We present a rare case of 2 intraneural ganglion cysts in separate nerves of the foot, originating from different joints within the same joint complex. Our findings add to the large body of evidence supporting the unifying articular (synovial) theory. We emphasize the importance of delineating the cyst morphology and origins using high-resolution magnetic resonance imaging before surgery and searching for and resecting the articular branch or branches during surgery.

Intraneural Hematoma: A Proposed Anatomic Classification with Potential Treatment Implications

Intraneural hematoma is a rare entity with fewer than 20 cases reported in the literature. There is no consensus on surgical treatment due to its rarity. We present a novel classification for intraneural hematomas based on a review of the literature and illustrated by 4 cases that were treated in our 3 centers. This classification system localizes the hematoma to the different connective tissue layers that compose the nerve: the paraneurium, epineurium, and perineurium. We believe that this classification has consequences for surgical treatment and can form the foundation for future research into the natural history of these types of lesions.