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Alzahrani S, Brito da Silva H, Chu TH, Tariq Z, Umansky D, Elliott DA, Midha R. Successful retrograde regeneration using a sensory branch for motor nerve transfer. J Neurosurg 2023; 138:858-867. [PMID: 35907191 DOI: 10.3171/2022.6.jns22734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/02/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The objective of this study was to test whether regenerating motor axons from a donor nerve can travel in a retrograde fashion using sensory branches to successfully reinnervate a motor nerve end organ. METHODS This study has two parts. In part I, rats (n = 30) were assigned to one of five groups for obturator nerve (ON)-to-femoral nerve transfer: group 1, ON-to-saphenous nerve (SN) distal stump; group 2, ON-to-SN proximal stump without femoral nerve proper (FNP) injury; group 3, ON-to-SN proximal stump with FNP crush injury; group 4, ON-to-SN proximal stump with FNP transection injury; and group 5, gold standard transfer, ON-to-motor femoral nerve (MFN) branch. At 8 weeks, retrograde labeling was done from the distal MFN, and the spinal cords were examined to assess the degree of obturator motor axon regeneration across the five groups. In part II, only group 4 was examined (n = 8). Through use of immunostaining and optical tissue clearing methods, the nerve transfer networks were cleared and imaged using light-sheet fluorescence microscopy to visualize the regeneration pathways in 2D and 3D models at 2- and 8-week time points. RESULTS Proximal FNP transection (group 4) enabled a significantly higher number of retrogradely regenerated motor axons compared with control groups 1-3. Moreover, group 4 had modest, but nonsignificant, superiority of motor neuron counts compared with the positive control group, group 5. Optical tissue clearing demonstrated that the axons traveled in a retrograde fashion from the recipient sensory branch to the FNP mixed stump, then through complex turns, down to distal branches. Immunostaining confirmed the tissue clearing findings and suggested perineurium disruption as a means by which axons could traverse across fascicular boundaries. CONCLUSIONS Sensory branches can transmit regenerating axons from donor nerves back to main mixed recipient nerves, then distally toward target organs. The extent of retrograde regeneration is markedly influenced by the type and severity of injury sustained by the recipient nerve. Using a sensory branch as a bridge for retrogradely regenerating axons can open new potential horizons in nerve repair surgery for severely injured mixed nerves.
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Affiliation(s)
- Saud Alzahrani
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
| | - Harley Brito da Silva
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
| | - Tak-Ho Chu
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
| | - Zain Tariq
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
| | - Daniel Umansky
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
| | - David A Elliott
- 3Hotchkiss Brain Institute Advanced Microscopy Platform, University of Calgary, Alberta, Canada
| | - Rajiv Midha
- 1Department of Clinical Neurosciences, University of Calgary.,2Hotchkiss Brain Institute, University of Calgary
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Abstract
Partial nerve recovery either after expectant observation following an injury in-continuity or after nerve repair is not an uncommon occurrence. Historically, treatment strategies in these situations-late repair, revision repair, or acceptance of a mediocre result-were unsatisfying. The reverse end-to-side, or supercharging, nerve transfer was conceived to offer a more palatable option. Partially validated primarily through small animal research, supercharging has been rapidly translated to clinical practice. Many have extended the indications beyond the original intent, though the final place of this technique in the peripheral nerve surgeon's armamentarium is still yet to be determined.
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Affiliation(s)
- Jonathan Isaacs
- Virginia Commonwealth University Medical Center, Richmond, USA
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Aguirre-Güemez AV, Mendoza-Muñoz M, Jiménez-Coello G, Rhoades-Torres GM, Pérez-Zavala R, Barrera-Ortíz A, Quinzaños-Fresnedo J. Nerve transfer rehabilitation in tetraplegia: Comprehensive assessment and treatment program to improve upper extremity function before and after nerve transfer surgery, a case report. J Spinal Cord Med 2021; 44:621-626. [PMID: 31525150 PMCID: PMC8288124 DOI: 10.1080/10790268.2019.1660841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
CONTEXT A 28-year-old male, sustained a traumatic Spinal Cord Injury (SCI) in January 2015, and was classified as AIS A, neurological level of injury (NLI) C4. As an inpatient at the SCI rehabilitation unit, he underwent multidisciplinary assessment involving SCI specialists, peripheral nerve surgeons, psychologists, occupational and physical therapists. Team consensus determined he was a candidate for nerve transfer surgery to improve upper extremity function. The patient undertook a pre-surgical neurorehabilitation program of 3 months duration. Surgery was performed bilaterally at 11 and 13 months after SCI (right and left arm respectively). FINDINGS Upon completion of surgical procedures, the patient underwent an intensive post-surgical rehabilitation program based on established goals, with follow-up every 3 months, up to 24 months after the surgery. Notable improvements were wheelchair propulsion, the ability to relieve pressure, grasp, pinch, and release an object. Standardized measures for SCI individuals (SCIM-III, CUE-Q, LiSAT-9 and UEMS) showed significant improvements. CLINICAL RELEVANCE Nerve transfers in tetraplegia are an underused technique. The benefits of surgery along with an intensive neurorehabilitation program, can improve independence and function in daily living activities for a properly selected group of individuals.
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Affiliation(s)
| | - Mario Mendoza-Muñoz
- Servicio de Cirugía de la Mano y Microcirugía, Instituto Nacional de Rehabilitación, Mexico City, Mexico
| | - Gabriela Jiménez-Coello
- Médicos residentes de la especialidad de Medicina de Rehabilitación Instituto Nacional de Rehabilitación, Mexico City, Mexico
| | - Gerald Martín Rhoades-Torres
- Médicos residentes de la especialidad de Medicina de Rehabilitación Instituto Nacional de Rehabilitación, Mexico City, Mexico
| | - Ramiro Pérez-Zavala
- División de Rehabilitación Neurológica, Instituto Nacional de Rehabilitación, Mexico City, Mexico
| | - Aida Barrera-Ortíz
- División de Rehabilitación Neurológica, Instituto Nacional de Rehabilitación, Mexico City, Mexico
| | - Jimena Quinzaños-Fresnedo
- División de Rehabilitación Neurológica, Instituto Nacional de Rehabilitación, Mexico City, Mexico,Correspondence to: Jimena Quinzaños-Fresnedo, División de Rehabilitación Neurológica, Instituto Nacional de Rehabilitación, Avenida México-Xochimilco No. 289, Col. Arenal de Guadalupe, CP 14389, Delegación Tlalpan, México D.F.; Ph: 52(55)59991000, ext. 13410.
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Reconstructive Options for Inferior Alveolar and Lingual Nerve Injuries After Dental and Oral Surgery. Ann Plast Surg 2019; 82:653-660. [DOI: 10.1097/sap.0000000000001783] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Cross-Face Nerve Grafting with Infraorbital Nerve Pathway Protection: Anatomic and Histomorphometric Feasibility Study. PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN 2016; 4:e1037. [PMID: 27757349 PMCID: PMC5055015 DOI: 10.1097/gox.0000000000001037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 07/26/2016] [Indexed: 11/25/2022]
Abstract
Smiling is an important aspect of emotional expression and social interaction, leaving facial palsy patients with impaired social functioning and decreased overall quality of life. Although there are several techniques available for facial reanimation, staged facial reanimation using donor nerve branches from the contralateral, functioning facial nerve connected to a cross-face nerve graft (CFNG) is the only technique that can reliably reproduce an emotionally spontaneous smile. Although CFNGs provide spontaneity, they typically produce less smile excursion than when the subsequent free functioning muscle flap is innervated with the motor nerve to the masseter muscle. This may be explained in part by the larger number of donor motor axons when using the masseter nerve, as studies have shown that only 20% to 50% of facial nerve donor axons successfully cross the nerve graft to innervate their targets. As demonstrated in our animal studies, increasing the number of donor axons that grow into and traverse the CFNG to innervate the free muscle transfer increases muscle movement, and this phenomenon may provide patients with the benefit of improved smile excursion. We have previously shown in animal studies that sensory nerves, when coapted to a nerve graft, improve axonal growth through the nerve graft and improve muscle excursion. Here, we describe the feasibility of and our experience in translating these results clinically by coapting the distal portion of the CFNG to branches of the infraorbital nerve.
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Žygelytė E, Bernard ME, Tomlinson JE, Martin MJ, Terhorst A, Bradford HE, Lundquist SA, Sledziona M, Cheetham J. RetroDISCO: Clearing technique to improve quantification of retrograde labeled motor neurons of intact mouse spinal cords. J Neurosci Methods 2016; 271:34-42. [PMID: 27268155 PMCID: PMC5620662 DOI: 10.1016/j.jneumeth.2016.05.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 05/16/2016] [Accepted: 05/31/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND Quantification of the number of axons reinnervating a target organ is often used to assess regeneration after peripheral nerve repair, but because of axonal branching, this method can overestimate the number of motor neurons regenerating across an injury. Current methods to count the number of regenerated motor neurons include retrograde labeling followed by cryosectioning and counting labeled motor neuron cell bodies, however, the process of sectioning introduces error from potential double counting of cells in adjacent sections. NEW METHOD We describe a method, retroDISCO, that optically clears whole mouse spinal cord without loss of fluorescent signal to allow imaging of retrograde labeled motor neurons using confocal microscopy. RESULTS Complete optical clearing of spinal cords takes four hours and confocal microscopy can obtain z-stacks of labeled motor neuron pools within 3-5min. The technique is able to detect anticipated differences in motor neuron number after cross-suture and conduit repair compared to intact mice and is highly repeatable. COMPARISON WITH EXISTING METHOD RetroDISCO is inexpensive, simple, robust and uses commonly available microscopy techniques to determine the number of motor neurons extending axons across an injury site, avoiding the need for labor-intensive cryosectioning and potential double counting of motor neuron cell bodies in adjacent sections. CONCLUSIONS RetroDISCO allows rapid quantification of the degree of reinnervation without the confounding produced by axonal sprouting.
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Affiliation(s)
- Emilija Žygelytė
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Megan E Bernard
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Joy E Tomlinson
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Matthew J Martin
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Allegra Terhorst
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Harriet E Bradford
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States; The Royal Veterinary College, University of London, North Mymms, Hertfordshire, UK
| | - Sarah A Lundquist
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Michael Sledziona
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States; The Royal Veterinary College, University of London, North Mymms, Hertfordshire, UK
| | - Jonathan Cheetham
- Department of Clinical Sciences, Cornell College of Veterinary Medicine, Cornell University, Ithaca, NY, United States.
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Khoshnoodi MA, Ebenezer GJ, Polydefkis M. Epidermal innervation as a tool to study human axonal regeneration and disease progression. Exp Neurol 2016; 287:358-364. [PMID: 27317299 DOI: 10.1016/j.expneurol.2016.06.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 01/14/2023]
Affiliation(s)
- Mohammad A Khoshnoodi
- Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Meyer 5-119, Baltimore, MD 21287, USA.
| | - Gigi J Ebenezer
- Neurology, Cutaneous Nerve Laboratory, Johns Hopkins University School of Medicine, The John G Rangos Building, 855 N. Wolfe Street, room 440, Baltimore, MD 21205, USA.
| | - Michael Polydefkis
- Neurology, Johns Hopkins University School of Medicine, Cutaneous Nerve Laboratory, Johns Hopkins Bayview EMG Laboratory, The John G Rangos Building, 855 N. Wolfe Street, room 435, Baltimore, MD 21205, USA.
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Pulley BR, Luo TD, Barnwell JC, Smith BP, Smith TL, Li Z. A chronically-denervated versus a freshly-harvested autograft for nerve repair in rats. HAND AND MICROSURGERY 2016; 5:124-129. [PMID: 30828670 DOI: 10.5455/handmicrosurg.215015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Objectives Autologous nerve grafting remains the gold standard for repair of peripheral nerve injuries. Its use, however, is limited by donor nerve availability and donor site morbidity. This is especially problematic after failure of an initial autograft that requires a repeat nerve graft, resulting in a second surgical site with associated morbidity. Based on the molecular differences in nerve degeneration in the proximal and distal segments after transection, we hypothesized that a chronically-denervated proximal stump may be viable for autologous nerve repair. Methods 20 Sprague-Dawley rats underwent right sciatic nerve excision and sural nerve transection. After 8 weeks, nerve repair was performed by harvesting the proximal segment of the sural nerve (n=10) or a fresh sural nerve (n=10) from the contralateral hind limb. Electrophysiological changes were analyzed to compare the fresh and denervated grafts. Results Electrophysiological testing demonstrated higher compound motor action potential in the denervated group compared to the fresh autograft group, however this difference was not statistically significant (p=0.117). Conclusion The proximal segment of a chronically-denervated sural nerve can be as effective as a fresh sural nerve for autologous repair of peripheral nerve injuries in a rodent model.
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Affiliation(s)
| | | | | | - Beth P Smith
- Wake Forest Baptist Medical Center, Winston-Salem, NC, USA
| | - Thomas L Smith
- Wake Forest Baptist Medical Center, Winston-Salem, NC, USA
| | - Zhongyu Li
- Wake Forest Baptist Medical Center, Winston-Salem, NC, USA
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Khuong HT, Kumar R, Senjaya F, Grochmal J, Ivanovic A, Shakhbazau A, Forden J, Webb A, Biernaskie J, Midha R. Skin derived precursor Schwann cells improve behavioral recovery for acute and delayed nerve repair. Exp Neurol 2014; 254:168-79. [PMID: 24440805 DOI: 10.1016/j.expneurol.2014.01.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 12/31/2013] [Accepted: 01/02/2014] [Indexed: 12/23/2022]
Abstract
Previous work has shown that infusion of skin-derived precursors pre-differentiated into Schwann cells (SKP-SCs) can remyelinate injured and regenerating axons, and improve indices of axonal regeneration and electrophysiological parameters in rodents. We hypothesized that SKP-SC therapy would improve behavioral outcomes following nerve injury repair and tested this in a pre-clinical trial in 90 rats. A model of sciatic nerve injury and acellular graft repair was used to compare injected SKP-SCs to nerve-derived Schwann cells or media, and each was compared to the gold standard nerve isograft repair. In a second experiment, rats underwent right tibial nerve transection and received either acute or delayed direct nerve repair, with injections of either 1) SKP-SCs distal to the repair site, 2) carrier medium alone, or 3) dead SKP-SCs, and were followed for 4, 8 or 17weeks. For delayed repairs, both transected nerve ends were capped and repaired 11weeks later, along with injections of cells or media as above, and followed for 9 additional weeks (total of 20weeks). Rats were serially tested for skilled locomotion and a slip ratio was calculated for the horizontal ladder-rung and tapered beam tasks. Immediately after nerve injury and with chronic denervation, slip ratios were dramatically elevated. In the GRAFT repair study, the SKP-SC treated rats showed statistically significant improvement in ladder rung as compared to all other groups, and exhibited the greatest similarity to the sham controls on the tapered beam by study termination. In the ACUTE repair arm, the SKP-SC group showed marked improvement in ladder rung slip ratio as early as 5weeks after surgery, which was sustained for the duration of the experiment. Groups that received media and dead SKP-SCs improved with significantly slower progression. In the DELAYED repair arm, the SKP-SC group became significantly better than other groups 7weeks after the repair, while the media and the dead SKP-SCs showed no significant improvement in slip ratios. On histomorphometrical analysis, SKP-SC group showed significantly increased mean axon counts while the percent myelin debris was significantly lower at both 4 and 8weeks, suggesting that a less inhibitory micro-environment may have contributed to accelerated axonal regeneration. For delayed repair, mean axon counts were significantly higher in the SKP-SC group. Compound action potential amplitudes and muscle weights were also improved by cell therapy. In conclusion, SKP-SC therapy improves behavioral recovery after acute, chronic and nerve graft repair beyond the current standard of microsurgical nerve repair.
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Affiliation(s)
- Helene T Khuong
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada; Service de Neurochirurgie, Département des Sciences Neurologiques, CHU-de Québec (Hôpital de l'Enfant-Jésus), Centre de Recherché du CHU-de Québec, Canada; Division de Neurochirurgie, Département de Chirurgie, Université Laval, 1401, 18e rue, Québec, Québec G1J 1Z4, Canada
| | - Ranjan Kumar
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Ferry Senjaya
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Joey Grochmal
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Aleksandra Ivanovic
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Antos Shakhbazau
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Joanne Forden
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Aubrey Webb
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Jeffrey Biernaskie
- Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada; Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada
| | - Rajiv Midha
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada.
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Kuffler DP, Reyes O, Sosa IJ, Santiago-Figueroa J. Neurological recovery across a 12-cm-long ulnar nerve gap repaired 3.25 years post trauma: case report. Neurosurgery 2012; 69:E1321-6. [PMID: 21712738 DOI: 10.1227/neu.0b013e31822a9fd2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND IMPORTANCE The standard clinical technique for repairing peripheral nerve gaps is the use of autologous sensory nerve grafts. The present study tested whether a collagen tube filled with autologous platelet-rich fibrin could induce sensory and motor recovery across a 12-cm nerve gap repaired 3.25 years post trauma, and reduce or eliminate neuropathic pain. CLINICAL PRESENTATION Two years postrepair, good ring and small finger motor function had developed that could generate 1 kg of force, and topographically correct 2-point discrimination and sensitivity to vibration in the small and ring finger and proximal but not distal wrist had developed. The patient's excruciating neuropathic pain was reduced to tolerable, and he avoided the indicated extremity amputation. The 12-cm-long nerve gap was bridged with a collagen tube filled with autologous platelet-rich fibrin. CONCLUSION We demonstrate that a conduit filled with platelet-rich fibrin can induce limited, but appropriate, sensory and motor recovery across a 12-cm nerve gap repaired 3.25 years post trauma, without sacrificing a sensory nerve, can reduce existing excruciating neuropathic pain to tolerable, and allow avoidance of an indicated upper-extremity amputation. We believe the technique can be improved to induce more extensive and reliable neurological recovery.
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Affiliation(s)
- Damien P Kuffler
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico 00901, USA.
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Isaacs J, Loveland K, Mallu S, Adams S, Wodicka R. The use of anabolic steroids as a strategy in reversing denervation atrophy after delayed nerve repair. Hand (N Y) 2011; 6:142-8. [PMID: 22654697 PMCID: PMC3092896 DOI: 10.1007/s11552-011-9331-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND Denervation atrophy is one factor contributing to suboptimal motor recovery following major nerve repair. The hypertrophic effects of anabolic steroids may have a potential role in improving reinnervated muscle strength after delayed repair. METHODS Forty-five immature female Sprague-Dawley rats underwent three surgeries and final testing. The tibial nerve was transected in the hind limb of the experimental (n = 13) and control (n = 14) animals and exposed, but not transected in the sham (n = 15) group animals. Three months later, once denervation atrophy was established, all transected nerves underwent repair using an autograft from the contralateral limb. After waiting an additional month to allow axonal regeneration to the gastrocnemius muscles, the rodents were implanted with a subcutaneous infusion pump. For the experimental group, nandrolone was administered over the next 30 days via this pump, while the control and sham group pumps were filled with carrier only. RESULTS Final testing, 6 weeks later, showed improved muscle contraction strength in the steroid-treated animals (72% of sham group strength) compared to control animals (57% of sham group strength, p < 0.5). A trend towards increased weight and muscle belly diameter in the steroid-treated group was not statistically significant. CONCLUSIONS These findings support the potential role of anabolic steroids in improving recovery of atrophic muscle after delayed reinnervation.
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Affiliation(s)
- Jonathan Isaacs
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University Health Systems, 1200 East Broad Street, P.O. Box 980153, Richmond, VA 23298 USA
| | - Kerry Loveland
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University Health Systems, 1200 East Broad Street, P.O. Box 980153, Richmond, VA 23298 USA
| | - Satya Mallu
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University Health Systems, 1200 East Broad Street, P.O. Box 980153, Richmond, VA 23298 USA
| | - Scott Adams
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University Health Systems, 1200 East Broad Street, P.O. Box 980153, Richmond, VA 23298 USA
| | - Ross Wodicka
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University Health Systems, 1200 East Broad Street, P.O. Box 980153, Richmond, VA 23298 USA
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Bertelli JA, Ghizoni MF, Tacca CP. Transfer of the teres minor motor branch for triceps reinnervation in tetraplegia. J Neurosurg 2011; 114:1457-60. [DOI: 10.3171/2010.12.jns101519] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In a case involving tetraplegia and paralysis of elbow extension, the authors transferred teres minor branches to the nerve of the triceps long head. Surgery was performed bilaterally 9 months after the patient sustained a spinal cord injury. Fourteen months postoperatively, elbow extension was complete (British Medical Research Council Score M4). Harvesting of the teres minor motor branch produced no deficits in shoulder function. In patients with tetraplegia, nerve transfer seems to be a promising new alternative for elbow extension reconstruction.
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Bertelli JA, Tacca CP, Winkelmann Duarte EC, Ghizoni MF, Duarte H. Transfer of axillary nerve branches to reconstruct elbow extension in tetraplegics: A laboratory investigation of surgical feasibility. Microsurgery 2011; 31:376-81. [DOI: 10.1002/micr.20883] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 12/17/2010] [Indexed: 11/11/2022]
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The potential of electrical stimulation to promote functional recovery after peripheral nerve injury — comparisons between rats and humans. HOW TO IMPROVE THE RESULTS OF PERIPHERAL NERVE SURGERY 2011; 100:3-11. [DOI: 10.1007/978-3-211-72958-8_1] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Isaacs J, Adams S, Mallu S, Loveland K, Sandbulte Z. Comparison of the performance of chronically versus freshly denervated autograft in nerve repair. J Hand Surg Am 2010; 35:2001-7. [PMID: 20971581 DOI: 10.1016/j.jhsa.2010.07.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 07/25/2010] [Accepted: 07/29/2010] [Indexed: 02/02/2023]
Abstract
PURPOSE Graft choice is one of the few variables over which the surgeon has control when reconstructing nerve gaps. Because repair of chronically denervated nerves generally yields inferior recovery, we hypothesized that the use of chronically denervated nerve tissue as a graft source may compromise axonal regeneration and clinical results. METHODS A total of 45 immature female Sprague-Dawley rats underwent transection of one peroneal nerve before being divided into 3 experimental groups: group A (n = 15) had acutely denervated nerve graft, group B (n = 15) had 2-month denervated nerve graft, and group C (n = 15) had 4-month denervated nerve graft. We included 10 additional rats as a sham group. After 2 months, groups A and B underwent removal of 1 cm of the contralateral peroneal nerve. For group A, this section of nerve was immediately sutured back in place to serve as a model for acute denervation. For group B, the defect was repaired with a 1-cm graft from the distal stump of the previously transected (denervated) peroneal nerve. Group C underwent the same procedure as group B, but after an additional 2 months. After 8 weeks of regeneration time, the 3 experimental groups and the sham group underwent testing. We assessed twitch contraction forces of the reinnervated extensor digitorum longus before we harvested the muscle belly for morphologic measurements. Histological nerve tissue evaluation assessed axonal regeneration. RESULTS We detected no statistical differences for mean muscle contraction strengths between the experimental groups; nevertheless, the reinnervated extensor digitorum longus muscle bellies from the 4-month denervated nerve graft group were statistically smaller than muscles from the other 2 experimental groups (p < .05). Axon counts decreased, whereas axon diameters increased in direct correlation with the length of time of graft denervation (p < .05). No difference in axon myelination was found between experimental groups. CONCLUSIONS Prolonged denervation of nerve graft material compromised both axon and reinnervated muscle recovery in this rodent model.
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Affiliation(s)
- Jonathan Isaacs
- Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth UniversityHealth Systems, Richmond, VA 23298, USA.
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Xu QG, Forden J, Walsh SK, Gordon T, Midha R. Motoneuron survival after chronic and sequential peripheral nerve injuries in the rat. J Neurosurg 2010; 112:890-9. [PMID: 19764828 DOI: 10.3171/2009.8.jns09812] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECT Surgical repair of peripheral nerves following chronic nerve injury is associated with poor axonal regeneration and outcome. An underlying possibility is that chronic injuries may increase motoneuron cell death. The hypothesis that substantial motoneuron death follows chronic and sequential nerve injuries was tested in adult rats in this study. METHODS Thirty adult male Lewis rats underwent bilateral multistage surgeries. At initial surgery, Fast Blue (FB) tracer was injected at a nerve-crush injury site in the right control femoral motor nerve. The left femoral motor nerve was transected at the same level and either capped to prevent regeneration (Group 1), or repaired to allow axonal regeneration and reinnervation of the target quadriceps muscle (Group 2) (15 rats in each group). After 8 weeks in 6 rats/group, the left femoral nerve was cut and exposed to FB just proximal to prior nerve capping or repair and the rats were evaluated for FB-labeled motoneuron counts bilaterally in the spinal cord (this was considered survival after initial injury). In the remaining 9 animals/group, the left nerve was recut (sequential injury), exposed to FB, and repaired to a fresh distal saphenous nerve stump to permit axonal regeneration. Following another 6 weeks, Fluoro-Gold, a second retrograde tracer, was applied to the cut distal saphenous nerve. This allowed us to evaluate the number of motoneurons that survived (maintained FB labeling) and the number of motoneurons that survived but that also regenerated axons (double labeled with FB and Fluoro-Gold). RESULTS A mean number of 350 and 392 FB-labeled motoneurons were found after 8 weeks of nerve injury on the right and the left sides, respectively. This indicated no significant cell death due to initial nerve injury alone. A similar number (mean 390) of motoneurons were counted at final end point at 14 weeks, indicating no significant cell death after sequential and chronic nerve injury. However, only 50% (mean 180) of the surviving motoneurons were double labeled, indicating that only half of the population regenerated their axons. CONCLUSIONS The hypothesis that significant motoneuron cell death occurs after chronic and or sequential nerve injury was rejected. Despite cell survival, only 50% of motoneurons are capable of exhibiting a regenerative response, consistent with our previous findings of reduced regeneration after chronic axotomy.
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Affiliation(s)
- Qing-Gui Xu
- Division of Neurosurgery, Department of Clinical Neurosciences and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
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18
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Abstract
OBJECTIVE The purpose of this review is to summarize the basic science literature related to chronic nerve injuries, and to then use this as the background to provide emerging insights into the promising role of cellular therapy for nerve injury repair. METHODS The literature pertinent to the experimental and clinical aspects of chronic nerve injury was reviewed, as was emerging literature and our own recent experience in using cellular therapy to repair injured nerves. RESULTS Peripheral nerves have the potential to regenerate axons and reinnervate end organs. Yet, outcome after peripheral nerve injury, even after nerve repair, remains relatively poor. The single most important quantitative contributor to poor motor recovery is chronic denervation of the distal nerve. Chronic denervation is common because of the often extensive injury zone that prevents any axonal outgrowth or (even if outgrowth occurs) the relatively slow rate of regeneration. As a consequence, the distal nerve remains chronically devoid of regrowing axons. In turn, prolonged denervation of Schwann cells (SCs) seems to be the critical factor that makes them unreceptive for axonal regeneration. Regenerative success was demonstrated when denervated SCs were replaced with healthy SCs cultured from a secondary nerve. This cell-replacement strategy is, however, limited in the clinical setting by the inability to obtain sufficient numbers of cells and the requirement for sacrifice of additional nerve tissue. We, along with several other groups, have therefore begun investigating stem cell therapies to improve the regenerative environment. CONCLUSION There are several avenues of stem cell-based approaches to peripheral nerve repair. One of these, skin-derived precursor cells, are easily accessible, autologous adult stem cells that can survive and myelinate in the peripheral nerve environment and become SC-like in their apparent differentiation.
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Affiliation(s)
- Sarah Walsh
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
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19
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Kemp SWP, Alant J, Walsh SK, Webb AA, Midha R. Behavioural and anatomical analysis of selective tibial nerve branch transfer to the deep peroneal nerve in the rat. Eur J Neurosci 2010; 31:1074-90. [PMID: 20377620 DOI: 10.1111/j.1460-9568.2010.07130.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Stephen W P Kemp
- Department of Clinical Neuroscience, Faculty of Medicine, Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada.
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20
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Walsh SK, Gordon T, Addas BMJ, Kemp SWP, Midha R. Skin-derived precursor cells enhance peripheral nerve regeneration following chronic denervation. Exp Neurol 2009; 223:221-8. [PMID: 19477174 DOI: 10.1016/j.expneurol.2009.05.025] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 05/13/2009] [Accepted: 05/18/2009] [Indexed: 12/23/2022]
Abstract
While peripheral nerves demonstrate the capacity for axonal regeneration, outcome following injury remains relatively poor, especially following prolonged denervation. Since axon-deprived Schwann cells (SCs) in the distal nerve progressively lose their ability to support axonal growth, we took the approach of using skin-derived precursor cells (SKPs) as an accessible source of replacement SCs that could be transplanted into chronically denervated peripheral nerve. In this study, we employed a delayed cross-reinnervation paradigm to assess regeneration of common peroneal nerve axons into the chronically denervated rodent tibial nerve following delivery of SKP-derived SC (SKP-SCs). SKP-SC treated animals exhibited superior axonal regeneration to media controls, with significantly higher counts of regenerated motorneurons and histological recovery similar to that of immediately repaired nerve. Improved axonal regeneration correlated with superior muscle reinnervation, as measured by compound muscle action potentials and wet muscle weights. We therefore conclude that SKPs represent an easily accessible, autologous source of stem cell-derived Schwann cells that show promise in improving regeneration through chronically injured nerves.
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Affiliation(s)
- Sarah K Walsh
- Department of Clinical Neuroscience and Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, HMRB 109-3330 Hospital Drive NW, Calgary, Alberta, Canada T2N4N1.
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21
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Ebenezer GJ, Laast VA, Dearman B, Hauer P, Tarwater PM, Adams RJ, Zink MC, McArthur JC, Mankowski JL. Altered cutaneous nerve regeneration in a simian immunodeficiency virus / macaque intracutaneous axotomy model. J Comp Neurol 2009; 514:272-83. [PMID: 19296476 DOI: 10.1002/cne.22019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
To characterize the regenerative pattern of cutaneous nerves in simian immunodeficiency virus (SIV)-infected and uninfected macaques, excisional axotomies were performed in nonglabrous skin at 14-day intervals. Samples were examined after immunostaining for the pan-axonal marker PGP 9.5 and the Schwann cell marker p75 nerve growth factor receptor. Collateral sprouting of axons from adjacent uninjured superficial dermal nerve bundles was the initial response to axotomy. Both horizontal collateral sprouts and dense vertical regeneration of axons from the deeper dermis led to complete, rapid reinnervation of the epidermis at the axotomy site. In contrast to the slower, incomplete reinnervation previously noted in humans after this technique, in both SIV-infected and uninfected macaques epidermal reinnervation was rapid and completed by 56 days postaxotomy. p75 was densely expressed on the Schwann cells of uninjured nerve bundles along the excision line and on epidermal Schwann cell processes. In both SIV-infected and uninfected macaques, Schwann cell process density was highest at the earliest timepoints postaxotomy and then declined at a similar rate. However, SIV-infection delayed epidermal nerve fiber regeneration and remodeling of new sprouts at every timepoint postaxotomy, and SIV-infected animals consistently had lower mean epidermal Schwann cell densities, suggesting that Schwann cell guidance and support of epidermal nerve fiber regeneration may account for altered nerve regeneration. The relatively rapid regeneration time and the completeness of epidermal reinnervation in this macaque model provides a useful platform for assessing the efficacy of neurotrophic or regenerative drugs for sensory neuropathies including those caused by HIV, diabetes mellitus, medications, and toxins.
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Affiliation(s)
- Gigi J Ebenezer
- Department of Neurology, Johns Hopkins University, Baltimore, MD 21287-7609, USA
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22
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Kemp SWP, Walsh SK, Midha R. Growth factor and stem cell enhanced conduits in peripheral nerve regeneration and repair. Neurol Res 2009; 30:1030-8. [PMID: 19079977 DOI: 10.1179/174313208x362505] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Despite the capacity for spontaneous axonal regeneration, recovery after severe peripheral nerve injury remains variable and often very poor. In addition, autologous nerve grafts, considered to be the 'gold standard' in nerve repair technique, are plagued by restricted donor tissue availability and donor site morbidity. Our primary objective is to highlight new and emerging methods of nerve repair, which have the potential to significantly improve both the functional and behavioral outcome after clinical nerve injury. METHODS A critical analysis of nerve injury and regeneration literature concentrating on outcome measures from both immediate and chronically denervated experimental works was conducted. RESULTS Results of numerous works employing both growth factor and stem cell enhanced nerve guidance conduits have shown encouraging results. However, further research is needed to optimize guidance conduit dynamics, bioavailability and delivery of both growth factors and stem cells to enhance peripheral nerve regeneration and functional recovery. DISCUSSION This review discusses current animal and clinical growth factor and stem cell studies, specifically focusing on future bio-engineering approaches in developing a nerve guidance conduit in the future.
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Affiliation(s)
- Stephen W P Kemp
- Department of Clinical Neuroscience, Faculty of Medicine, Hotchkiss Brain Institute, University of Calgary, Calgary, Alta, Canada.
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23
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Saito H, Dahlin LB. Expression of ATF3 and axonal outgrowth are impaired after delayed nerve repair. BMC Neurosci 2008; 9:88. [PMID: 18801180 PMCID: PMC2556676 DOI: 10.1186/1471-2202-9-88] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Accepted: 09/18/2008] [Indexed: 12/13/2022] Open
Abstract
Background A delay in surgical nerve repair results in impaired nerve function in humans, but mechanisms behind the weakened nerve regeneration are not known. Activating transcription factor 3 (ATF3) increases the intrinsic growth state of injured neurons early after injury, but the role of long-term changes and their relation to axonal outgrowth after a delayed nerve repair are not well understood. ATF3 expression was examined by immunohistochemistry in motor and sensory neurons and in Schwann cells in rat sciatic nerve and related to axonal outgrowth after transection and delayed nerve repair (repair 0, 30, 90 or 180 days post-injury). Expression of the neuronal cell adhesion molecule (NCAM), which is expressed in non-myelinating Schwann cells, was also examined. Results The number of neurons and Schwann cells expressing ATF3 declined and the length of axonal outgrowth was impaired if the repair was delayed. The decline was more rapid in motor neurons than in sensory neurons and Schwann cells. Regeneration distances over time correlated to number of ATF3 stained neurons and Schwann cells. Many neurofilament stained axons grew along ATF3 stained Schwann cells. If nerve repair was delayed the majority of Schwann cells in the distal nerve segment stained for NCAM. Conclusion Delayed nerve repair impairs nerve regeneration and length of axonal outgrowth correlates to ATF3 expression in both neurons and Schwann cells. Mainly non-myelinating Schwann cells (NCAM stained) are present in distal nerve segments after delayed nerve repair. These data provide a neurobiological basis for the poor outcomes associated with delayed nerve repair. Nerve trunks should, if possible, be promptly repaired.
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Affiliation(s)
- Harukazu Saito
- Department of Hand Surgery, Malmö University Hospital, Malmö, Sweden.
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Tannemaat MR, Boer GJ, Verhaagen J, Malessy MJ. GENETIC MODIFICATION OF HUMAN SURAL NERVE SEGMENTS BY A LENTIVIRAL VECTOR ENCODING NERVE GROWTH FACTOR. Neurosurgery 2007; 61:1286-94; discussion 1294-6. [DOI: 10.1227/01.neu.0000306108.78044.a2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Martijn R. Tannemaat
- Laboratory for Neuroregeneration, Netherlands Institute for Neuroscience, An Institute of The Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
- Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands
| | - Gerard J. Boer
- Laboratory for Neuroregeneration, Netherlands Institute for Neuroscience, An Institute of The Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Joost Verhaagen
- Laboratory for Neuroregeneration, Netherlands Institute for Neuroscience, An Institute of The Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Martijn J.A. Malessy
- Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands
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Elwakil TF, Elkharbotly A. Role of Nd:YAG laser for prevention of neuroma formation: an in vivo experimental study. Lasers Med Sci 2007; 23:163-8. [PMID: 17497192 DOI: 10.1007/s10103-007-0461-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2006] [Accepted: 03/20/2007] [Indexed: 10/23/2022]
Abstract
Nerve transection is commonly followed by the development of neuroma at the proximal stump. It can be very painful especially at exposed sites. It may arise spontaneously or after mechanical irritation. Neuroma and its high recurrence rate might be resisting problems to treat. Various treatment modalities for neuroma and its recurrence have been proposed, but none has provided satisfactory results. The present study was conducted to evaluate the neodymium:yttrium aluminum garnet (Nd:YAG) laser (1,064 nm) nerve transection technique for prevention of neuroma formation. There were 48 facial nerves out of 24 Rex rabbits divided into two equal groups. The 24 left-sided facial nerves at group A were subjected to Nd:YAG laser for nerve transection, while the 24 right-sided facial nerves at group B were subjected to scalpel nerve transection. The results were grossly and histopathologically evaluated. Grossly, laser-transected nerves showed an infrequent incidence of neuroma formation. Histopathologically, laser-transected nerves showed photothermal degenerative changes of the axons and myelin sheaths with intact perineurium and endoneurium. No Schwann cell hyperactivity could also be elicited among laser-transected nerves. Nd:YAG laser was found to be an effective tool that could be applied, whenever it is possible, for division of major nerves to prevent the formation of the subsequent stump neuroma. Moreover, this technique should be considered during treatment of well-established neuroma to prevent the challenging reported high incidence of recurrence.
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Affiliation(s)
- Tarek F Elwakil
- Unit of General Surgery, National Institute of Laser Enhanced Sciences (NILES), Cairo University, Cairo, Egypt.
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26
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Furey MJ, Midha R, Xu QG, Belkas J, Gordon T. PROLONGED TARGET DEPRIVATION REDUCES THE CAPACITY OF INJURED MOTONEURONS TO REGENERATE. Neurosurgery 2007; 60:723-32; discussion 732-3. [PMID: 17415210 DOI: 10.1227/01.neu.0000255412.63184.cc] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To investigate whether or not it is the frustrated growth state (no axon growth) that reduces regenerative capacity or the inability of axotomized motoneurons to remake muscle connections (axon growth-no muscle contact) that accounts for poor regenerative capacity of chronically axotomized motoneurons. METHODS We chronically axotomized rat femoral motoneurons for 2 months by cutting the nerve and either capping the proximal nerve to prevent axon regeneration (Group 1, no axon growth for 2 mo) or encouraging axon regeneration but not target reinnervation by suture to the distal stump of cut saphenous nerve (Group 2, axon growth with no muscle contact). In the control fresh axotomy group (axon growth with muscle contact), femoral nerve stumps were resutured immediately. Two months later, the femoral nerve was recut and sutured immediately to encourage regeneration in a freshly cut saphenous nerve stump for 6 weeks. Regenerating axons in the saphenous nerve were back-labeled with fluorogold for enumeration of the femoral motoneurons that regenerated their axons into the distal nerve stump. RESULTS We found that significantly fewer chronically axotomized motoneurons regenerated their axons than freshly axotomized motoneurons that regenerated their axons to reform nerve-muscle connections in the same length of time. The number of motoneurons that regenerated their axons was reduced in both the conditions of no axon growth and axon growth with no muscle contact; thus chronic axotomy for a 2-month period reduced regenerative success irrespective of whether the motoneurons were prevented from regenerating or encouraged to regenerate their axons in that same period of time. CONCLUSION Axonal regeneration does not protect motoneurons from the negative effects of prolonged axotomy on regenerative capacity. It is the period of chronic axotomy, in which motoneurons remain without target nerve-muscle connection, and not simply a state of frustrated growth that accounts for the reduced regenerative capacity of those neurons.
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Affiliation(s)
- Matthew J Furey
- Center for Neuroscience, University of Alberta, Edmonton, Canada
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