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Allen JA, Clarke AE, Harbo T. A Practical Guide to Identify Patients With Multifocal Motor Neuropathy, a Treatable Immune-Mediated Neuropathy. Mayo Clin Proc Innov Qual Outcomes 2024; 8:74-81. [PMID: 38283096 PMCID: PMC10819864 DOI: 10.1016/j.mayocpiqo.2023.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2024] Open
Abstract
Multifocal motor neuropathy (MMN) is a rare immune-mediated motor neuropathy characterized by asymmetric weakness that preferentially affects distal upper limb muscles. The clinical features of MMN may be difficult to differentiate from motor neuron disease. Other conditions that may be mistaken for MMN include inclusion body myositis, chronic inflammatory demyelinating polyradiculoneuropathy, hereditary neuropathy with liability to pressure palsy, focal neuropathies, and radiculopathies. A key distinguishing electrophysiologic feature of MMN is the motor nerve conduction block located at noncompressible sites. MMN is a treatable neuropathy; therefore it is important that primary care physicians are aware of the features of the disease to identify potential patients and make referrals to a neuromuscular specialist in a timely manner. This review provides an overview of the disease, highlights key differential diagnoses, and describes available treatment options for patients with MMN.
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Affiliation(s)
- Jeffrey A. Allen
- Department of Neurology, University of Minnesota, Minneapolis, MN
| | | | - Thomas Harbo
- Department of Neurology, Aarhus University Hospital, Aarhus, DK
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Kollech HG, Chao MR, Stark AC, German RZ, Paniello RC, Christensen MB, Barkmeier-Kraemer JM, Vande Geest JP. Extracellular matrix deformations of the porcine recurrent laryngeal nerve in response to hydrostatic pressure. Acta Biomater 2022; 153:364-373. [PMID: 36152909 PMCID: PMC10627241 DOI: 10.1016/j.actbio.2022.09.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 08/22/2022] [Accepted: 09/15/2022] [Indexed: 11/25/2022]
Abstract
Damage to the recurrent laryngeal nerve (RLN) caused by supraphysiological compression or tension imposed by adjacent tissue structures, such as the aorta, may contribute to onset of idiopathic unilateral vocal fold paralysis (iUVP) resulting in difficulty speaking, breathing, and swallowing. We previously demonstrated in adolescent pigs that the right RLN epineurium exhibits uniform composition of adipose tissue, with larger quantities along its length within the neck region in contrast to the left RLN that shows greater collagen composition in the thoracic region and greater quantities of adipose tissue in the neck region. In contrast, the epineurium in piglets was primarily composed of collagen tissue that remained uniform along the length of the left and right RLNs. Tensile testing of the left and right RLN in piglets and pigs showed associated differences in strain by RLN side and segment by age. The goal of this study was to investigate how external hydrostatic compression of the RLN affects the nerve's connective tissue and microstructure. RLN segments were harvested from the distal (cervical/neck) regions and proximal (subclavian for the right RLN, thoracic for the left RLN) regions from eight adolescent pigs and nine piglets. RLN segments were isolated and assessed under fluid compression to test hypotheses regarding epineurium composition and response to applied forces. Second harmonic generation (SHG) imaging of epineurial collagen was conducted at 0, 40, and 80 mmHg of compression. The cartesian strain tensor, principal strain (Eps1), and principal direction of the RLN collagen fibers were determined at each pressure step. Significantly larger values of the 1st principal strain occurred in the proximal segments of the pig left RLN when compared to the same segment in piglets (p = 0.001, pig = 0.0287 [IQR = 0.0161 - 0.0428], piglet = 0.0061 [IQR = 0.0033 - 0.0156]). Additionally, the median transverse strain Eyy) for the second pressure increment was larger in the right proximal segment of pigs compared to piglets (p < 0.001, pig = 0.0122 [IQR = 0.0033 - 0.0171], piglet = 0.0013 [IQR = 0.00001 - 0.0028]). Eyy values were significantly larger in the right proximal RLN versus the left proximal RLNs in pigs but not in piglets (p < 0.001). In contrast to piglets, histological analysis of pig RLN demonstrated increased axial alignment of epineurial and endoneurial collagen in response to compressive pressure. These findings support the hypothesis that the biomechanical response of the RLN to compressive pressure changed from being similar to being different between the right and left RLNs during development in the porcine model. Further investigation of these findings associated with age-related onset of idiopathic UVP may illuminate underlying etiologic mechanisms. STATEMENT OF SIGNIFICANCE: Damage to the recurrent laryngeal nerve (RLN) caused by compression imposed by the aorta may contribute to the onset of left-sided idiopathic unilateral vocal fold paralysis resulting in difficulty speaking, breathing, and swallowing. The goal of this study was to investigate how compression affects the connective tissue and microstructure of the RLN. We quantified the pressure induced deformation of the RLN using multiphoton imaging as a function of both location (proximal versus distal) and age (piglets, adolescent pigs). Our results demonstrate that the biomechanical response of the RLN to compression changes in the right versus left RLN throughout development, providing further evidence that the the left RLN is exposed to increasing dynamic loads with age.
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Affiliation(s)
- Hirut G Kollech
- Computational Modeling and Simulation Program, University of Pittsburgh, Pittsburgh, PA, USA
| | - Melissa R Chao
- Department of Bioengineering, University of Utah, Salt Lake City, UT, USA
| | - Amanda C Stark
- National Center for Voice and Speech, University of Utah, Salt Lake City, UT, USA
| | - Rebecca Z German
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, OH, USA
| | - Randal C Paniello
- Department of Otolaryngology - Head and Neck Surgery, Washington University School of Medicine, St. Louis, MO, USA
| | | | - Julie M Barkmeier-Kraemer
- Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Utah, UT, USA
| | - Jonathan P Vande Geest
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Mechanical Engineering and Material Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
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