Marie Noëlle Hébert-Blouin

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

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

Adipose lesions of nerve: the need for a modified classification.

OBJECT Adipose lesions of nerve are rare and poorly understood. Their current classification, although not universally accepted, generally includes lipomatosis of nerve with or without localized macrodactyly, and intra- as well as extraneural lipoma. The authors believe that the spectrum of these lesions and their interrelationships are not currently appreciated. They propose an adaptation to the existing framework to illustrate the expanding spectrum of adipose lesions of nerve by considering lipomatosis and lipoma singly or in combination. METHODS Fourteen representative cases are presented to demonstrate not only the intraneural and extraneural examples of lipomatosis and lipoma, but also their anatomical combinations. RESULTS Based on the cases presented and a careful literature review, a conceptual approach to the classification of adipose lesions of nerve is generated. This approach incorporates the 2 essential lesions, lipomatosis of nerve and lipoma, in both their intra- and extraneural forms. This permits expansion to encompass combinations. CONCLUSIONS To press the concept that adipose tumors of nerve are a broad but interrelated spectrum of lesions, the authors propose modification of the present classification system. This approach provides an orderly platform for progress, reflects understanding of these interrelated lesions, and facilitates optimal treatment by distinguishing resectable from nonresectable components.

Hilton's law revisited.

Hiltons Law, put forth 150 years ago, is well known and frequently taught in anatomy courses. We critically analyzed the complex description of associated muscular, cutaneous, and articular innervations in order to assess the general applicability of Hiltons Law. We applied rules for interpretation of the Law extrapolated upon but based on Hiltons original writings, and excluded obscure supplementary clauses not considered as part of the Law. We found the Law, as originally written and as we interpreted with some latitude, to be reliable and applicable to all cranial and peripheral nerves. Hiltons Law is a powerful springboard to understand articular anatomy and pathophysiology. Clin. Anat. 548–555, 2014.

Short- and long-term peripheral nerve regeneration using a poly-lactic-co-glycolic-acid scaffold containing nerve growth factor and glial cell line-derived neurotrophic factor releasing microspheres†

Addition of neural growth factors to bioengineered scaffolds may improve peripheral nerve regeneration. The aim of this study is to evaluate the short- and long term effect of microsphere delivered nerve growth factor (NGF) and glial cell derived neurotrophic factor (GDNF) in the 10 mm rat sciatic nerve gap. Eighty-four rats were assigned to seven groups (n = 6) at two endpoints (6 and 16 weeks): saline, saline NGF, saline NGF-microspheres, saline GDNF, saline GDNF-microspheres, saline blank microspheres, and autologous nerve graft. Total fascicular area and total number of myelinated fibers at mid-tube increased in all conduit groups between 6 and 16 weeks. Autologous, saline NGF-microsphere and saline GDNF-microsphere groups reached maximal histomorphometric values by 6 weeks (p < 0.05). Compound muscle action potentials returned after 6 weeks for the autologous graft and continued to increase to a level of 3.6 ± 1.9 mV at endpoint. No significant differences were found between study groups as measured by ankle angle. These experiments show an initial beneficial effect of incorporation of NGF- or GDNF-microspheres in a PLGA 85/15 nerve conduit, since histomorphometric values reached their maximum by 6 weeks compared to control groups. These results do not yet extrapolate into improved electrophysiological or functional improvement.

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 cysts 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.

Multinodular/plexiform (multifascicular) schwannomas of major peripheral nerves: an underrecognized part of the spectrum of schwannomas

OBJECT In clinical practice, schwannomas are among the most common types of nerve sheath tumors. Their clinical presentation, imaging characteristics, and operative features are well known. Over the past 20 years, clinical outcomes have improved due to resection of these tumors at a fascicular level. Despite these advances, a subgroup of patients with schwannomas is associated with a disappointing neurological outcome following resection. The purpose of this study was to correlate the imaging and histological features in this group of patients with more anatomically complex forms of schwannomas. METHODS In a retrospective review performed at their institution over a 10-year period, the authors found a subgroup of patients with complex multinodular/plexiform schwannomas affecting major peripheral nerves. Eleven patients were identified, and the clinical, imaging, and pathological features of their disease were reviewed. RESULTS The clinical presentation of multinodular/plexiform schwannomas of major peripheral nerves may be similar to that of conventional schwannomas, but their imaging features, operative appearance, and outcomes differ. CONCLUSIONS Preoperatively and intraoperatively, the distinguishing features of multinodular/plexiform schwannomas of major peripheral nerves may be subtle and can easily go unrecognized, thus explaining the often suboptimal surgical results. Familiarity with the imaging and operative features of multinodular/plexiform schwannomas will no doubt alter treatment approaches and improve neurological function in this subgroup of patients.

Palmaris profundus: One name, several subtypes, and a shared potential for nerve compression

The palmaris profundus is a rare, but known anatomic variation which may lead to compression of the median nerve and/or its branches. Two patients with carpal tunnel syndrome are presented in whom a palmaris profundus was discovered at operation. In these cases, median nerve compression at the wrist was attributed to the course of the extra tendon and its local mass effect on the nerve (i.e., the palmaris profundus and median nerve shared a common sheath); more commonly, the resultant decreased available space for the median nerve within the carpal tunnel due to the presence of an accessory (10th) flexor tendon is thought to be responsible. Postoperative 3 Tesla magnetic resonance imaging (MRI) was performed to demonstrate the full course of the variant muscle; despite variations in the size and longitudinal extent of the accessory musculotendinous unit, an important similarity was noted: the intimate relationship of the median nerve and the palmaris profundus. These two cases and our review of the literature highlight the fact that one name (i.e. palmaris profundus) reflects several anatomic subtypes. However, the close relationship of the palmaris profundus with the median nerve in the forearm and the palm is a common theme which emphasizes the potential pathoanatomic consequences of this relationship: nerve compression. Clin. Anat. 22:643–648, 2009.

Addendum: Evidence supports a 'no-touch' approach to neuromuscular choristoma

To The ediTor: Our article1 called attention not only to an association between these 2 rare disorders, neuromuscular choristoma (NMC) and fibromatosis, but also to the role of biopsy in that association (Hébert-Blouin MN, Scheithauer BW, Amrami KK, et al: Fibromatosis: a potential sequela of neuromuscular choristoma. Clinical article. J Neurosurg 116:399–408, February 2012). Since the publication of this article, the association has been further strengthened by additional evidence provided by 2 patients evaluated at our institution as well as information from a radiological review5 and a case report.6 An 11-year-old boy (Case 1) presenting at another institution with a several-year history of buttock and lowerextremity pain was found to have a unilateral sciatic neuropathy, hammer toes, and a smaller leg and foot. Imaging revealed a sciatic nerve lesion (Fig. 1A and B) extending over 30 cm in length. He underwent first an ultrasoundguided biopsy, then a CT-guided biopsy (Fig. 1C and D), and finally an open biopsy, the last biopsy confirming a histological diagnosis of NMC. This patient was recently reported on by the original group for his NMC,2 but follow-up was not provided. We then saw him in consultation and have witnessed aggressive fibromatosis in evolution. At our initial evaluation (6 months postbiopsy), MRI findings concerning for early development of fibromatosis were seen along the previous biopsy track and surrounding the sciatic nerve in that area (Fig. 1E and F).5 We recently reviewed 18-month postbiopsy MR images demonstrating aggressive fibromatosis, with the epicenter being at the biopsy site (Fig. 1G–I).

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

BackgroundA 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 FindingsOne 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.ConclusionsThis 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.

Concomitant Traumatic Spinal Cord and Brachial Plexus Injuries in Adult Patients

BACKGROUND Combined injuries to the spinal cord and brachial plexus present challenges in the detection of both injuries as well as to subsequent treatment. The purpose of this study is to describe the epidemiology and clinical factors of concomitant spinal cord injuries in patients with a known brachial plexus injury. METHODS A retrospective review was performed on all patients who were evaluated for a brachial plexus injury in a tertiary, multidisciplinary brachial plexus clinic from January 2000 to December 2008. Patients with clinical and/or imaging findings for a coexistent spinal cord injury were identified and underwent further analysis. RESULTS A total of 255 adult patients were evaluated for a traumatic traction injury to the brachial plexus. We identified thirty-one patients with a combined brachial plexus and spinal cord injury, for a prevalence of 12.2%. A preganglionic brachial plexus injury had been sustained in all cases. The combined injury group had a statistically greater likelihood of having a supraclavicular vascular injury (odds ratio [OR] = 22.5; 95% confidence interval [CI] = 1.9, 271.9) and a cervical spine fracture (OR = 3.44; 95% CI = 1.6, 7.5). These patients were also more likely to exhibit a Horner sign (OR = 3.2; 95% CI = 1.5, 7.2) and phrenic nerve dysfunction (OR = 2.5; 95% CI = 1.0, 5.8) compared with the group with only a brachial plexus injury. CONCLUSION Heightened awareness for a combined spinal cord and brachial plexus injury and the presence of various associated clinical and imaging findings may aid in the early recognition of these relatively uncommon injuries.