Spinner, Robert J.

Abstract 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.

Intraneural perineuriomas are benign peripheral nerve sheath tumors that cause progressive debilitating focal extremity weakness. The etiology of perineuriomas is largely unknown. We utilized whole exome sequencing, copy number algorithm evaluation, and high‐resolution whole genome microarray to investigate for a genetic causal link to intraneural perineuriomas. Ten of 16 (60%) tumor cases had mutations in the WD40 domain of TRAF7, the same location for causal mutations of meningiomas. Two additional perineurioma cases had large chromosomal abnormalities in multiple chromosomes, including chromosome 22q. This study identifies a common cause for intraneural perineuriomas and an unexpected shared pathogenesis with intracranial meningiomas. Ann Neurol 2017;81:316–321

Neuromuscular choristoma (NMC) is a very rare, developmental malformation characterized by the endoneurial intercalation of mature muscle fibers among peripheral nerve fibers. NMC typically arises in the major proximal peripheral nerves, most commonly the sciatic nerve, and may involve the lumbosacral and brachial plexus. Patients present clinically with progressive neuropathy or plexopathy. NMC is strongly associated with development of a fibromatosis, histologically identical to conventional desmoid-type fibromatosis (NMC-fibromatosis). The development of NMC-fibromatosis is often precipitated by iatrogenic trauma (ie, biopsy). Desmoid-type fibromatosis is characterized by CTNNB1 exon 3 mutations, which result in aberrant nuclear β-catenin localization and dysregulated canonical Wnt signaling. In contrast, the pathogenesis of NMC and NMC-fibromatosis is unknown. Desmoid-type fibromatosis expresses estrogen receptors (ER), specifically the ER-beta isoform (ERβ), and endocrine therapies may be used in surgically unresectable cases. In contrast, the ER expression profile of NMC-fibromatosis is unknown. We evaluated a series of NMC and NMC-fibromatosis for CTNNB1 mutations, β-catenin expression, and ER isoform expression. Five NMCs occurred in 2 female and 3 male patients (median age: 14 y, range <1 to 42 y), as masses involving the sciatic nerve (N=4) or brachial plexus (N=1). Four (of 5) NMCs had CTNNB1 mutations: 3 c.134 C>T (p.S45F) and 1 c.121 A>G (p.T41A). Four patients subsequently developed NMC-fibromatosis, and all 4 cases contained CTNNB1 mutations, including 1 p.T41A and 3 p.S45F mutations. In 3 patients, the NMC and NMC-fibromatosis had identical CTNNB1 mutations. Only 1 NMC had no detectable CTNNB1 mutation; however, the patient’s subsequent NMC-fibromatosis had a CTNNB1 p.T41A mutation. All NMC and NMC-fibromatosis showed aberrant nuclear localization of β-catenin, nuclear ERβ expression, and no ERα expression. The presence of CTNNB1 mutations both in NMC and NMC-fibromatosis may be a shared molecular genetic abnormality underlying their pathogenesis.

PurposeOur objective was to determine the prevalence and quality of restored external rotation (ER) in adult brachial plexus injury (BPI) patients who underwent spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer, and to identify patient and injury factors that may influence results.MethodsFifty‐one adult traumatic BPI patients who underwent SAN to SSN transfer between 2000 and 2013, all treated less than 1 year after injury with >1 year follow‐up. The primary outcome measured was shoulder ER. The outcomes we utilized included “clinically useful ER” (motion ≥ −35° with ≥MRC 2 strength), modified British Medical Research Council (MRC) grading, and electromyographic (EMG) reinnervation.ResultsEMG evidence of re‐innervation was found in 85% of patients. Surgery resulted in improved ER in 41% (21/51) of shoulders at an average of 28 months follow‐up. Of these, only 31% (17/51) had clinically useful ER. The average ER active range of motion was 12° from full internal rotation (Range: −60° to 90°) and MRC grade 2.2 (2–4). The only predictor of ER improvement was an isolated upper trunk (C5‐C6) injury. Improved ER was clinically evident in 76%, 37% and 26% of upper trunk (UT), C5‐C6‐C7 and panplexus injuries, respectively (P < 0.03).ConclusionsAlthough 85% had EMG signs of recovery, the SAN to SSN transfer failed to provide useful recovery of ER through reinnervation of the infraspinatus muscle in injuries involving more levels than a C5‐C6 root/upper trunk pattern. In patients with greater than C5‐6 level injuries alternatives to SAN to SSN transfer should be considered to restore shoulder ER. © 2016 Wiley Periodicals, Inc. Microsurgery 37:365–370, 2017.