Rahul Kasukurthi

Fibrin glue mitigates the learning curve of microneurosurgical repair.

Microneurosurgical technique has a steep learning curve. An alternative to microepineurial suture repair of peripheral nerves that circumvents this learning curve would be ideal. We investigated the effect of surgeon experience on suture versus fibrin glue coaptations in a mouse sciatic nerve graft model. Sixty‐four mice received sciatic nerve grafts with either suture or fibrin glue repair by either a naïve surgeon (medical student) or a surgeon with extensive microsurgical experience. Grafts underwent quantitative histomorphometry at 3 weeks postoperatively. Suture repairs performed by the naïve surgeon demonstrated significantly poorer distal regeneration than all other repairs. Histomorphometric parameters of suture and glue repairs performed by the experienced surgeon were not significantly different from the glue coaptation by the naïve surgeon. Fibrin glue may be considered as an alternative to microepineurial suture repair, particularly in the setting of relative surgeon inexperience with microsurgical technique.

A transgenic rat expressing green fluorescent protein (GFP) in peripheral nerves provides a new hindlimb model for the study of nerve injury and regeneration

BACKGROUND In order to evaluate nerve regeneration in clinically relevant hindlimb surgical paradigms not feasible in fluorescent mice models, we developed a rat that expresses green fluorescent protein (GFP) in neural tissue. METHODS Transgenic Sprague-Dawley rat lines were created using pronuclear injection of a transgene expressing GFP under the control of the thy1 gene. Nerves were imaged under fluorescence microscopy and muscles were imaged with confocal microscopy to determine GFP expression following sciatic nerve crush, transection and direct suturing, and transection followed by repair with a nerve isograft from nonexpressing littermates. RESULTS In each surgical paradigm, fluorescence microscopy demonstrated the loss and reappearance of fluorescence with regeneration of axons following injury. Nerve regeneration was confirmed with imaging of Wallerian degeneration followed by reinnervation of extensor digitorum longus (EDL) muscle motor endplates using confocal microscopy. CONCLUSION The generation of a novel transgenic rat model expressing GFP in neural tissue allows in vivo imaging of nerve regeneration and visualization of motor endplate reinnervation. This rat provides a new model for studying peripheral nerve injury and regeneration over surgically relevant distances.

Schwann cells seeded in acellular nerve grafts improve functional recovery

Introduction: This study evaluated whether Schwann cells (SCs) from different nerve sources transplanted into cold‐preserved acellular nerve grafts (CP‐ANGs) would improve functional regeneration compared with nerve isografts. Methods: SCs isolated and expanded from motor and sensory branches of rat femoral and sciatic nerves were seeded into 14mm CP‐ANGs. Growth factor expression, axonal regeneration, and functional recovery were evaluated in a 14‐mm rat sciatic injury model and compared with isografts. Results: At 14 days, motor or sensory‐derived SCs increased expression of growth factors in CP‐ANGs versus isografts. After 42 days, histomorphometric analysis found CP‐ANGs with SCs and isografts had similar numbers of regenerating nerve fibers. At 84 days, muscle force generation was similar for CP‐ANGs with SCs and isografts. SC source did not affect nerve fiber counts or muscle force generation. Conclusions: SCs transplanted into CP‐ANGs increase functional regeneration to isograft levels; however SC nerve source did not have an effect. Muscle Nerve 49: 267–276, 2014

Transcardial perfusion versus immersion fixation for assessment of peripheral nerve regeneration

Accurate assessment of peripheral nerve regeneration requires fixation techniques that preserve tissue in a natural state with minimal artifact. While transcardial perfusion fixation is accepted as the gold standard for tissue fixation, the less cumbersome approach of immersion fixation has been criticized for introducing artifacts in brain tissue. We investigated whether immersion fixation increased artifact compared to perfusion fixation in the rat sciatic nerve. Eighteen Lewis rats were randomized into three groups: glutaraldehyde immersion fixation; glutaraldehyde transcardial perfusion; and paraformaldehyde transcardial perfusion. All animals underwent sciatic nerve transection and repair followed by tissue harvest and fixation at three weeks. Qualitative assessment of neural architecture and histological features was followed by quantitative analysis of nerve regeneration parameters. Outcome measures included quantitative histomorphometry, analysis of axon/myelin ratios, assessment of fiber distributions, and ultrastructural analysis. No qualitative or quantitative differences were observed with immersion fixation when compared to the transcardial perfusion fixation methods. Immersion fixation is a valid method for assessment of peripheral nerve regeneration in a rat model.

Intramedullary capillary hemangioma of the thoracic spine: case report and review of the literature

Capillary hemangiomas are benign vascular neoplasms. When associated with the spine, these growths frequently involve the vertebral body, but rarely have they been reported to occur as intradural lesions, while even more rarely occurring in a true intramedullary location. We report a rare case of an intramedullary capillary hemangioma of the thoracic spinal cord and a review of the literature.

Functional Recovery Following an End to Side Neurorrhaphy of the Accessory Nerve to the Suprascapular Nerve: Case Report

The use of end-to-side neurrorhaphy remains a controversial topic in peripheral nerve surgery. The authors report the long-term functional outcome following a modified end-to-side motor reinnervation using the spinal accessory to innervate the suprascapular nerve following a C5 to C6 avulsion injury. Additionally, functional outcomes of an end-to-end neurotization of the triceps branch to the axillary nerve and double fascicular transfer of the ulnar and medial nerve to the biceps and brachialis are presented. Excellent functional recoveries are found in respect to shoulder abduction and flexion and elbow flexion.

Effect of cold nerve allograft preservation on antigen presentation and rejection

OBJECT Nerve allotransplantation provides a temporary scaffold for host nerve regeneration and allows for the reconstruction of significant segmental nerve injuries. The need for systemic immunosuppression, however, limits the current clinical utilization of nerve allografts, although this need is reduced by the practice of cold nerve allograft preservation. Activation of T cells in response to alloantigen presentation occurs in the context of donor antigen presenting cells (direct pathway) or host antigen-presenting cells (indirect pathway). The relative role of each pathway in eliciting an alloimmune response and its potential for rejection of the nerve allograft model has not previously been investigated. The objective of this investigation was to study the effect of progressive periods of cold nerve allograft preservation on antigen presentation and the alloimmune response. METHODS The authors used wild type C57Bl/6 (B6), BALB/c, and major histocompatibility Class II-deficient (MHC-/-) C57Bl/6 mice as both nerve allograft recipients and donors. A nonvascularized nerve allograft was used to reconstruct a 1-cm sciatic nerve gap. Progressive cold preservation of donor nerve allografts was used. Quantitative assessment was made after 3 weeks using nerve histomorphometry. RESULTS The donor-recipient combination lacking a functional direct pathway (BALB/c host with MHC-/- graft) rejected nerve allografts as vigorously as wild-type animals. Without an intact indirect pathway (MHC-/- host with BALB/c graft), axonal regeneration was improved (p < 0.052). One week of cold allograft preservation did not improve regeneration to any significant degree in any of the donor-recipient combinations. Four weeks of cold preservation did improve regeneration significantly (p < 0.05) for all combinations compared with wild-type animals without pretreatment. However, only in the presence of an intact indirect pathway (no direct pathway) did 4 weeks of cold preservation improve regeneration significantly compared with 1 week and no preservation in the same donor-recipient combination. CONCLUSIONS The indirect pathway may be the predominant route of antigen presentation in the unmodified host response to the nerve allograft. Prolonged duration of cold nerve allograft preservation is required to significantly attenuate the rejection response. Cold preservation for 4 weeks improves nerve regeneration with a significant effect on indirect allorecognition.

Intraneural synovial sarcoma of the median nerve

Synovial sarcomas are soft-tissue malignancies with a poor prognosis and propensity for distant metastases. Although originally believed to arise from the synovium, these tumors have been found to occur anywhere in the body. We report a rare case of synovial sarcoma arising from the median nerve. To our knowledge, this is the twelfth reported case of intraneural synovial sarcoma, and only the fourth arising from the median nerve. Because the diagnosis may not be apparent until after pathological examination of the surgical specimen, synovial sarcoma should be kept in mind when dealing with what may seem like a benign nerve tumor.

Costimulation blockade inhibits the indirect pathway of allorecognition in nerve allograft rejection.

Nerve allografts provide a temporary scaffold for host nerve regeneration. The need for systemic immunosuppression limits clinical application. Characterization of the immunological mechanisms that induce immune hyporesponsiveness may provide a basis for optimizing immunomodulating regimens. We utilized wild‐type and MHC class II–deficient mice, as both recipients and donors. Host treatment consisted of triple costimulatory blockade. Quantitative assessment was made at 3 weeks using nerve histomorphometry, and muscle testing was performed on a subset of animals at 7 weeks. Nerve allograft rejection occurred as long as either the direct or indirect pathways were functional. Indirect antigen presentation appeared to be more important. Nerve allograft rejection occurs in the absence of a normal direct or indirect immune response but may be more dependent on indirect allorecognition. The indirect pathway is required to induce costimulatory blockade immune hyporesponsiveness. Muscle Nerve, 2011

Simplified Negative Pressure Wound Therapy in Pediatric Hand Wounds

Negative pressure wound therapy (NPWT) is commonly used as a bolster for skin grafts. The technique offers the benefit of negative pressure as well as reduced dressing changes. Skin grafting of the hand provides a unique challenge, and currently, the only commercially available NPWT hand dressings are adult-sized, precluding their use in small children. We present our custom NPWT “mitten” technique for use with skin grafts on the pediatric hand.