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Debenham MIB, Franz CK, Berger MJ. Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations. Muscle Nerve 2024; 70:12-27. [PMID: 38477416 DOI: 10.1002/mus.28070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 02/13/2024] [Accepted: 02/17/2024] [Indexed: 03/14/2024]
Abstract
The spinal cord facilitates communication between the brain and the body, containing intrinsic systems that work with lower motor neurons (LMNs) to manage movement. Spinal cord injuries (SCIs) can lead to partial paralysis and dysfunctions in muscles below the injury. While traditionally this paralysis has been attributed to disruptions in the corticospinal tract, a growing body of work demonstrates LMN damage is a factor. Motor units, comprising the LMN and the muscle fibers with which they connect, are essential for voluntary movement. Our understanding of their changes post-SCI is still emerging, but the health of motor units is vital, especially when considering innovative SCI treatments like nerve transfer surgery. This review seeks to collate current literature on how SCI impact motor units and explore neuromuscular clinical implications and treatment avenues. SCI reduced motor unit number estimates, and surviving motor units had impaired signal transmission at the neuromuscular junction, force-generating capacity, and excitability, which have the potential to recover chronically, yet the underlaying mechanisms are unclear. Furthermore, electrodiagnostic evaluations can aid in assessing the health lower and upper motor neurons, identify suitable targets for nerve transfer surgeries, and detect patients with time sensitive injuries. Lastly, many electrodiagnostic abnormalities occur in both chronic and acute SCI, yet factors contributing to these abnormalities are unknown. Future studies are required to determine how motor units adapt following SCI and the clinical implications of these adaptations.
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Affiliation(s)
- Mathew I B Debenham
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Colin K Franz
- Biologics Laboratory, Shirley Ryan AbilityLab, Chicago, Illinois, USA
- Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
- Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Michael J Berger
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Robinson LR, Dengler J. Understanding the role of the lower motor neuron in spinal cord injury and its impact on electrodiagnostic assessment. Muscle Nerve 2024; 70:6-8. [PMID: 38712656 DOI: 10.1002/mus.28108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/08/2024]
Affiliation(s)
- Lawrence R Robinson
- Physical Medicine and Rehabilitation, University of Toronto, Toronto, Ontario, Canada
| | - Jana Dengler
- Division of Plastic, Reconstructive and Aesthetic Surgery, University of Toronto, Toronto, Ontario, Canada
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Berger MJ, Adewuyi AA, Doherty C, Hanlan AK, Morin C, O'Connor R, Sharma R, Sproule S, Swong KN, Wu H, Franz CK, Brown E. Segmental infralesional pathological spontaneous activity in subacute traumatic spinal cord injury. Muscle Nerve 2024; 69:403-408. [PMID: 38294062 DOI: 10.1002/mus.28053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 01/13/2024] [Accepted: 01/21/2024] [Indexed: 02/01/2024]
Abstract
INTRODUCTION/AIMS There is a dearth of knowledge regarding the status of infralesional lower motor neurons (LMNs) in individuals with traumatic cervical spinal cord injury (SCI), yet there is a growing need to understand how the spinal lesion impacts LMNs caudal to the lesion epicenter, especially in the context of nerve transfer surgery to restore several key upper limb functions. Our objective was to determine the frequency of pathological spontaneous activity (PSA) at, and below, the level of spinal injury, to gain an understanding of LMN health below the spinal lesion. METHODS Ninety-one limbs in 57 individuals (53 males, mean age = 44.4 ± 16.9 years, mean duration from injury = 3.4 ± 1.4 months, 32 with motor complete injuries), were analyzed. Analysis was stratified by injury level as (1) C4 and above, (2) C5, and (3) C6-7. Needle electromyography was performed on representative muscles innervated by the C5-6, C6-7, C7-8, and C8-T1 nerve roots. PSA was dichotomized as present or absent. Data were pooled for the most caudal infralesional segment (C8-T1). RESULTS A high frequency of PSA was seen in all infralesional segments. The pooled frequency of PSA for all injury levels at C8-T1 was 68.7% of the limbs tested. There was also evidence of PSA at the rostral border of the neurological level of injury, with 58.3% of C5-6 muscles in those with C5-level injuries. DISCUSSION These data support a high prevalence of infralesional LMN abnormalities following SCI, which has implications to nerve transfer candidacy, timing of the intervention, and donor nerve options.
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Affiliation(s)
- Michael J Berger
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
| | - Adenike A Adewuyi
- Regenerative Neurorehabilitation Laboratory, Shirley Ryan AbilityLab, Chicago, Illinois, USA
- Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
- Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Christopher Doherty
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
- Division of Plastic Surgery, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - Amy K Hanlan
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
| | - Cynthia Morin
- Division of Plastic Surgery, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - Russ O'Connor
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
| | - Radhika Sharma
- Regenerative Neurorehabilitation Laboratory, Shirley Ryan AbilityLab, Chicago, Illinois, USA
- Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Shannon Sproule
- Division of Plastic Surgery, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kevin N Swong
- Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Harvey Wu
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Colin K Franz
- Regenerative Neurorehabilitation Laboratory, Shirley Ryan AbilityLab, Chicago, Illinois, USA
- Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
- Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Erin Brown
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
- Division of Plastic Surgery, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
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Berger MJ, Dengler J, Westman A, Curt A, Schubert M, Abel R, Weidner N, Röhrich F, Fox IK. Nerve Transfer After Cervical Spinal Cord Injury: Who Has a "Time Sensitive" Injury Based on Electrodiagnostic Findings? Arch Phys Med Rehabil 2024; 105:682-689. [PMID: 37979641 DOI: 10.1016/j.apmr.2023.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 11/20/2023]
Abstract
OBJECTIVE To use the ulnar compound muscle action potential (CMAP) to abductor digiti minimi (ADM) to identify the proportion of individuals with cervical spinal cord injury (SCI) who have lower motor neuron (LMN) abnormalities involving the C8-T1 spinal nerve roots, within 3-6 months, and thus may influence the response to nerve transfer surgery. DESIGN Retrospective analysis of prospectively collected data. Data were analyzed from European Multicenter Study About SCI database. SETTING Multi-center, academic hospitals. PARTICIPANTS We included 79 subjects (age=41.4±17.7, range:16-75; 59 men; N=79), who were classified as cervical level injuries 2 weeks after injury and who had manual muscle strength examinations that would warrant consideration for nerve transfer (C5≥4, C8<3). INTERVENTIONS None. MAIN OUTCOME MEASURES The ulnar nerve CMAP amplitude to ADM was used as a proxy measure for C8-T1 spinal segment health. CMAP amplitude was stratified into very abnormal (<1.0 mV), sub-normal (1.0-5.9 mV), and normal (>6.0 mV). Analysis took place at 3 (n=148 limbs) and 6 months (n=145 limbs). RESULTS At 3- and 6-month post-injury, 33.1% and 28.3% of limbs had very abnormal CMAP amplitudes, respectively, while in 54.1% and 51.7%, CMAPs were sub-normal. Median change in amplitude from 3 to 6 months was 0.0 mV for very abnormal and 1.0 mV for subnormal groups. A 3-month ulnar CMAP <1 mV had a positive predictive value of 0.73 (95% CI 0.69-0.76) and 0.78 (95% CI 0.75-0.80) for C8 and T1 muscle strength of 0 vs 1 or 2. CONCLUSION A high proportion of individuals have ulnar CMAPs below the lower limit of normal 3- and 6-month post cervical SCI and may also have intercurrent LMN injury. Failure to identify individuals with LMN denervation could result in a lost opportunity to improve hand function through timely nerve transfer surgeries.
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Affiliation(s)
- Michael J Berger
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
| | - Jana Dengler
- Division of Plastic Surgery, Tory Trauma Program, Sunnybrook Health Sciences Centre, Toronto, Ontario; Division of Plastic, Reconstructive and Aesthetic Surgery, Department of Surgery, University of Toronto, Toronto, Ontario
| | - Amanda Westman
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| | - Armin Curt
- Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland
| | - Martin Schubert
- Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland
| | | | - Norbert Weidner
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Frank Röhrich
- BG Klinikum Bergmannstrost, Zentrum für Rückenmarkverletzte und Klinik für Orthopädie, Halle, Germany
| | - Ida K Fox
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
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Bateman EA, Larocerie-Salgado J, Ross DC, Miller TA, Pripotnev S. Assessment, patient selection, and rehabilitation of nerve transfers. FRONTIERS IN REHABILITATION SCIENCES 2023; 4:1267433. [PMID: 38058570 PMCID: PMC10696649 DOI: 10.3389/fresc.2023.1267433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 11/07/2023] [Indexed: 12/08/2023]
Abstract
Peripheral nerve injuries are common and can have a devastating effect on physical, psychological, and socioeconomic wellbeing. Peripheral nerve transfers have become the standard of care for many types of peripheral nerve injury due to their superior outcomes relative to conventional techniques. As the indications for, and use of, nerve transfers expand, the importance of pre-operative assessment and post-operative optimization increases. There are two principal advantages of nerve transfers: (1) their ability to shorten the time to reinnervation of muscles undergoing denervation because of peripheral nerve injury; and (2) their specificity in ensuring proximal motor and sensory axons are directed towards appropriate motor and sensory targets. Compared to conventional nerve grafting, nerve transfers offer opportunities to reinnervate muscles affected by cervical spinal cord injury and to augment natural reinnervation potential for very proximal injuries. This article provides a narrative review of the current scientific knowledge and clinical understanding of nerve transfers including peripheral nerve injury assessment and pre- and post-operative electrodiagnostic testing, adjuvant therapies, and post-operative rehabilitation for optimizing nerve transfer outcomes.
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Affiliation(s)
- Emma A. Bateman
- Department of Physical Medicine & Rehabilitation, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Parkwood Institute, St Joseph’s Health Care London, London, ON, Canada
| | | | - Douglas C. Ross
- Roth McFarlane Hand & Upper Limb Centre, St Joseph’s Health Care London, London, ON, Canada
- Division of Plastic & Reconstructive Surgery, Department of Surgery, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Thomas A. Miller
- Department of Physical Medicine & Rehabilitation, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Parkwood Institute, St Joseph’s Health Care London, London, ON, Canada
| | - Stahs Pripotnev
- Roth McFarlane Hand & Upper Limb Centre, St Joseph’s Health Care London, London, ON, Canada
- Division of Plastic & Reconstructive Surgery, Department of Surgery, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
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Schibli S, Fridén J. [Surgical reconstruction of arm and hand functions in tetraplegia : Current concepts]. UNFALLCHIRURGIE (HEIDELBERG, GERMANY) 2023; 126:774-777. [PMID: 37676291 DOI: 10.1007/s00113-023-01361-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/25/2023] [Indexed: 09/08/2023]
Abstract
The reconstruction of arm and hand functions is of enormous importance for tetraplegic patients as it enables at least some degree of independence. Depending on the level of the spinal cord injury, certain residual functions are present in the arms which can be used for surgical reconstruction of upper extremity functions. By utilizing tendon and nerve transfers missing functions can at least be partially reconstructed. Tendon transfers are a proven technique with reliable results that can be performed at any time regardless of the type of accident. Due to the frequent presence of lower motor neuron damage, it is essential to consider the optimal time window for nerve transfer interventions. From the multitude of surgical options, an individual reconstruction plan must be created for each patient, which considers multiple factors. The combination of nerve transfers and later completing the functional reconstruction by tendon transfers is the preferred concept of the authors of this article.
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Affiliation(s)
- Silvia Schibli
- Schweizer Paraplegiker-Zentrum, Guido A. Zäch-Str. 1, 6207, Nottwil, Schweiz.
| | - Jan Fridén
- Schweizer Paraplegiker-Zentrum, Guido A. Zäch-Str. 1, 6207, Nottwil, Schweiz
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