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Steel CM, Walmsley EA, Anderson GA, Coles CA, Ahern B, White JD. Immunohistochemical analysis of laryngeal muscle of horses clinically affected with recurrent laryngeal neuropathy. Equine Vet J 2020; 53:710-717. [PMID: 33001503 DOI: 10.1111/evj.13362] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 09/04/2020] [Accepted: 09/20/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND As myosin heavy chain (MyHC) profile of muscle fibres is heavily influenced by neural input, changes in MyHC expression are expected in horses clinically affected with recurrent laryngeal neuropathy (RLN) yet, this has not been thoroughly investigated. OBJECTIVES To describe the changes in MyHC and fibre diameter in left cricoarytenoideus dorsalis (L-CAD) muscle of horses with clinical signs of RLN. STUDY DESIGN Observational cohort study. METHODS Immunohistochemistry was used to assess the MyHC-based fibre-type proportion, size and grouping in the L-CAD of 10 Thoroughbred horses, five clinically affected with RLN and five unaffected controls based on resting endoscopic examination. The Mann-Whitney U test was used to compare the two groups. RESULTS Compared to controls (of mean age 3.0 ± 1.7 years) which only expressed type I, IIA and IIX MyHC, the L-CAD of affected horses (of mean age 2.8 ± 0.8 years) had obvious fibre-type grouping, and despite apparent compensatory hypertrophy of a small number of fibres, a decrease in overall fibre diameter (median difference -35.2 µm, 95% CI -47.4 to -7.9, P = .02) and diameter of type IIA fibres (median difference -46.8 µm, 95% CI -52.1 to -5.0, P = .03) was observed. Anti-fast MyHC (MY32) cross-immunoreacted with embryonic-MyHC. Whereas MY32-positive fibres were identified as type IIX in controls, in affected horses these fibres were less than 50 µm diameter with internal nuclei and were MYH3-positive for embryonic myosin indicating depletion of type IIX fibres, yet active regeneration and fibre renewal. MAIN LIMITATIONS Small sample size that did not include subclinical cases. Fibre size and appearance rather than staining colour were relied upon to differentiate embryonic from type IIX MyHC. CONCLUSIONS Horses clinically affected with RLN have overall atrophy of fibres, loss of IIX fibres and expression of embryonic myosin indicating regenerative capacity. Despite hypertrophy of some remaining fibres, the overall decline in the bulk of fibres, including those most fatigue-resistant, may be the critical change that results in failure to maintain arytenoid abduction during exercise although direct comparison to subclinical cases is needed to confirm this.
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Affiliation(s)
- Catherine M Steel
- School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia
| | - Elizabeth A Walmsley
- School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia
| | - Garry A Anderson
- School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia
| | - Chantal A Coles
- Murdoch Children's Research Institute, The Royal Children's Hospital, Parkville, VIC, Australia
| | - Benjamin Ahern
- School of Veterinary Science, Equine Specialist Hospital, University of Queensland, Gatton, QLD, Australia.,School of Animal and Veterinary Science, The University of Adelaide, Roseworthy, Australia
| | - Jason D White
- Office of the Pro Vice Chancellor Research and Innovation, Charles Sturt University, Wagga Wagga, NSW, Australia
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Satoh M, Higuchi T, Inoue S, Miyakoshi D, Kajihara A, Gotoh T, Shimizu Y. External transcutaneous ultrasound technique in the equine cricoarytenoideus dorsalis muscle: Assessment of muscle size and echogenicity with resting endoscopy. Equine Vet J 2020; 52:500-508. [PMID: 31736125 DOI: 10.1111/evj.13209] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 09/05/2019] [Accepted: 11/08/2019] [Indexed: 11/30/2022]
Abstract
BACKGROUND Recent studies have assessed the cricoarytenoideus dorsalis muscle (CAD) using transoesophageal ultrasonography in equine recurrent laryngeal neuropathy (RLN). We assessed the CAD using the external transcutaneous ultrasound technique, which may constitute an easier method in horses. OBJECTIVES To evaluate ultrasonographic imaging of the left cricoarytenoideus dorsalis muscle (LCAD) and right cricoarytenoideus dorsalis muscle (RCAD) as a diagnostic tool for RLN using the transcutaneous ultrasound technique. STUDY DESIGN Cross-sectional study. METHODS The axial plane thickness, cross-sectional area and echogenicity of the LCAD and RCAD were measured using transcutaneous ultrasonography in 164 horses. Assessments of LCAD were compared with those of RCAD. The LCAD:RCAD ratios in thickness and area were compared between control horses (resting grades 1 and 2) and horses with resting laryngeal grades 3 and 4 using the Havemeyer 4-point grading system with subgrades. RESULTS The LCAD:RCAD ratios for thickness and area were 0.69 and 0.66 in horses with resting grades 3 and 4 respectively; LCAD was more hyperechogenic than RCAD in resting grades 3 and 4. LCAD:RCAD ratios for thickness and area in grades 3.II, 3.III and 4 were significantly lower than those in control horses. Thickness and area of the LCAD were negatively correlated with resting laryngeal grade MAIN LIMITATIONS: Overground endoscopy was not performed in this study. There were some differences in methodology: measurement of the physical thickness of the LCAD and clipping of hair at the laryngeal region were only performed in horses that underwent laryngoplasty. CONCLUSIONS Results of ultrasonographic assessments of the CAD using transcutaneous ultrasonography were similar to those obtained by transoesophageal ultrasonography. This technique enables a simple, noninvasive, direct and easy examination. Assessment of the CAD using transcutaneous ultrasonography may be a useful technique and a potential option for determining whether to perform nerve graft or laryngoplasty.
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Affiliation(s)
- Masato Satoh
- Hokkaido South Agricultural Mutual Aid Association, Mitsuishi Animal Medical Center, Hidaka-gun, Hokkaido, Japan
| | - Tohru Higuchi
- Hokkaido South Agricultural Mutual Aid Association, Mitsuishi Animal Medical Center, Hidaka-gun, Hokkaido, Japan
| | - Satoshi Inoue
- Hokkaido South Agricultural Mutual Aid Association, Mitsuishi Animal Medical Center, Hidaka-gun, Hokkaido, Japan
| | - Daisuke Miyakoshi
- Hokkaido South Agricultural Mutual Aid Association, Mitsuishi Animal Medical Center, Hidaka-gun, Hokkaido, Japan
| | - Ayako Kajihara
- Hokkaido South Agricultural Mutual Aid Association, Mitsuishi Animal Medical Center, Hidaka-gun, Hokkaido, Japan
| | - Tadahiro Gotoh
- Federation of Hokkaido Agricultural Mutual Aid Associations, Large Animal Clinic and Research Center, Ebetsu, Hokkaido, Japan
| | - Yasuhito Shimizu
- Hokkaido South Agricultural Mutual Aid Association, Central Animal Clinic, Niikappu-gun, Hokkaido, Japan
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Parente EJ. Fifty years of recurring struggles with recurrent laryngeal neuropathy. Equine Vet J 2017; 50:155-158. [PMID: 28976020 DOI: 10.1111/evj.12763] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/25/2017] [Indexed: 11/26/2022]
Abstract
Recurrent laryngeal neuropathy appears to be a simple problem that should have a simple solution, yet the complexity and dynamic nature of laryngeal function is underappreciated. This review highlights the challenges and accomplishments that work towards that greater understanding of what is necessary to find a successful solution.
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Affiliation(s)
- E J Parente
- New Bolton Center, University of Pennsylvania, Kennett Square, Pennsylvania, USA
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Karlheim B, Barton AK, Rohn K, Ohnesorge B. Validity of laryngeal ultrasonography in reference to endoscopy at rest and during exercise in Warmblood horses. EQUINE VET EDUC 2014. [DOI: 10.1111/eve.12285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- B. Karlheim
- Clinic for Horses; University of Veterinary Medicine Hannover; Germany
| | - A. K. Barton
- Clinic for Horses; University of Veterinary Medicine Hannover; Germany
- Equine Clinic; Free University of Berlin; Germany
| | - K. Rohn
- Institute for Epidemiology; University of Veterinary Medicine Hannover; Germany
| | - B. Ohnesorge
- Clinic for Horses; University of Veterinary Medicine Hannover; Germany
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5
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Fjordbakk CT, Revold T, Goodwin D, Piercy RJ. Histopathological assessment of intrinsic laryngeal musculature in horses with dynamic laryngeal collapse. Equine Vet J 2014; 47:603-8. [PMID: 25256848 DOI: 10.1111/evj.12357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 09/03/2014] [Indexed: 12/01/2022]
Abstract
REASONS FOR PERFORMING STUDY The pathogenesis of bilateral dynamic laryngeal collapse associated with poll flexion (DLC) of horses is unknown but might be associated with intrinsic laryngeal muscle weakness. OBJECTIVES To investigate histopathological characteristics of the cricoarytenoideus dorsalis, the cricothyroid (CT) and the cricoarytenoideus lateralis muscles in DLC-affected horses and compare these with unaffected controls. Our hypotheses were that evidence of neurogenic atrophy of the CT or cricoarytenoideus dorsalis muscles would be found in DLC-affected horses and that observed changes would be symmetrically (left/right) distributed, or that muscle fibre diameter would be significantly reduced in DLC-affected horses compared to unaffected controls, reflecting an underlying paresis. STUDY DESIGN Case-control study. METHODS Five DLC horses and 8 controls were included. Muscle samples were harvested immediately following euthanasia. Fibre type proportions and size were evaluated by multiple immunofluorescence labelling of cryosections, and compared between sides (left/right) and groups (DLC-affected cases/ unaffected controls). Subjective and objective assessments of fibre type grouping were compared between sides and groups. RESULTS Fibre type proportions, fibre size and the subjective assessment of fibre type grouping did not reveal any statistically significant differences between the groups. Objective assessment of fibre type grouping revealed significantly more large clusters of T1 fibres within the left cricoarytenoideus lateralis muscle of DLC-affected cases versus controls, and within the right CT muscle of control horses compared to the DLC-cases. CONCLUSIONS The absence of bilateral symmetric fibre type grouping, fibre type loss and fibre atrophy in the DLC-affected cases do not support a neuromuscular component within the pathogenesis of DLC. The objective assessment of fibre type grouping revealed some statistical differences between the DLC-affected cases and the unaffected controls; however, these findings were inconsistent with regard to DLC. An alternative aetiology of DLC seems likely.
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Affiliation(s)
- C T Fjordbakk
- Department of Companion Animal Clinical Sciences, Equine Teaching Hospital, Norwegian School of Veterinary Science, Oslo, Norway
| | - T Revold
- Department of Companion Animal Clinical Sciences, Equine Teaching Hospital, Norwegian School of Veterinary Science, Oslo, Norway
| | - D Goodwin
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, London, UK
| | - R J Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, London, UK
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McClellan NR, Santschi EM, Hurcombe SDA, Litsky AS. An ex vivo model to evaluate the effect of cyclical adductory forces on maintenance of arytenoid abduction after prosthetic laryngoplasty performed with and without mechanical arytenoid abduction. Vet Surg 2014; 43:598-605. [PMID: 24702612 DOI: 10.1111/j.1532-950x.2014.12178.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 05/20/2012] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To (1) develop a model of cyclical adduction force on an abducted left arytenoid cartilage that mimics swallowing or coughing; (2) determine if arytenoid abduction by a clamp before knot tying will improve the maintenance of abduction under cyclical adduction testing. STUDY DESIGN Experimental. SAMPLE POPULATION Cadaveric equine larynges (n = 14). METHODS Left laryngoplasty performed using a single suture of #5 Ethibond with (n = 7) and without (n = 7) abducting the arytenoid with a clamp before knot tying. Each laryngoplasty was loaded cyclically from 2 to 26 N at 0.5 Hz for 5000 cycles in a servohydraulic test frame. Arytenoid displacement data were collected at 1 Hz intervals and median percent loss of abduction compared between groups. Significance was set at P < .05. RESULTS Median left arytenoid abduction distance was 16.9 mm (range, 9.8-19.8 mm). One larynx in each group failed at <1000 cycles. Loss of abduction was determined by progressive displacement of the testing actuator and confirmed by measurement. There was no difference in loss of abduction between clamped and non-clamped larynges after 5000 cycles. This model of cyclical adduction resulted in arytenoid displacements similar to those seen in the 1st week postoperatively. CONCLUSIONS Ex vivo cyclical adductory forces produced a significant loss of laryngoplasty abduction. The use of a clamp to abduct the arytenoid cartilage before knot tying did not reduce the loss of abduction.
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Affiliation(s)
- Nathaniel R McClellan
- Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio
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O'Neill HD, Ballegeer EA, De Feijter-Rupp HL, Stick JA, Derksen FJ, Robinson NE. Ultrasound-guided biopsy of the cricoarytenoideus lateralis muscle: technique and safety in horses. Equine Vet J 2013; 46:244-8. [PMID: 23679063 DOI: 10.1111/evj.12105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
REASONS FOR PERFORMING STUDY Current diagnosis of recurrent laryngeal neuropathy (RLN) depends upon disease recognition in the clinically affected horse. Biopsy of the intrinsic laryngeal muscles may provide a method to identify the changes in fibre-type composition that occur in RLN before clinical signs become apparent. OBJECTIVE To develop an ultrasound-guided biopsy technique of the left cricoarytenoideus lateralis muscle (CALM) and evaluate its efficacy and safety in vivo. STUDY DESIGN A longitudinal descriptive study. METHODS Six standing horses underwent ultrasound-guided biopsy of the left CALM. Frozen muscle cores were obtained with a breast biopsy tool. Serial endoscopic, ultrasonographic and physical examinations before and for 8 weeks after the biopsy were assessed for iatrogenic trauma. Histologies of representative muscle core cross-sections were analysed for the total number of muscle fibres obtained with each biopsy. RESULTS There were no immediate complications of the procedure and the left CALM was harvested in all instances. Biopsy samples had an average weight of 0.043 g (range = 0.023-0.077 g) and contained 3418 fibres in cross-section (range = 711-7143). Laryngeal endoscopic grade did not change significantly between prebiopsy and the end of the 8 week follow-up. The left CALM had significantly greater echogenicity than the right throughout the study (P<0.001), but there was no difference between the prebiopsy CALM echogenicity and that at completion of the study. CONCLUSIONS Ultrasound-guided biopsy of the left CALM is safe and well tolerated, providing a minimally invasive method to obtain muscle from healthy horses. This new technique may be applicable in research and clinical settings.
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Affiliation(s)
- H D O'Neill
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, USA
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8
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Dixon PM, McGorum BC, Else RW. Cricopharyngeal-laryngeal dysplasia in a horse with sudden clinical onset idiopathic laryngeal hemiparesis. N Z Vet J 2011; 41:134-8. [PMID: 16031712 DOI: 10.1080/00480169.1993.35752] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A 7-year-old Thoroughbred racehorse developed loud exercise-related respiratory noises and exercise intolerance over a short period. Examination showed congenital cricopharyngeal-laryngeal dysplasia (rostral displacement of the palatopharyngeal arch) and also left sided idiopathic laryngeal hemiparesis, the latter appearing to be of recent clinical onset. The animal developed colic some months after laryngeal surgery and a nephrosplenic entrapment was surgically corrected. Aerophagia and regurgitation worsened after surgery and, after developing inhalation pneumonia, the animal was destroyed. Post-mortem examination confirmed the presence of idiopathic laryngeal hemiparesis and of cricopharyngeal-laryngeal dysplasia which had some previously undescribed laryngeal muscle abnormalities.
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Affiliation(s)
- P M Dixon
- Department of Veterinary Clinical Studies, Department of Veterinary Pathology, Royal (Dick) School of Veterinary Studies, Veterinary Field Station, Easter Bush, Roslin, Midlothian, Scotland, EH25 9RG
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9
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GARRETT KS, WOODIE JB, EMBERTSON RM. Association of treadmill upper airway endoscopic evaluation with results of ultrasonography and resting upper airway endoscopic evaluation. Equine Vet J 2010; 43:365-71. [DOI: 10.1111/j.2042-3306.2010.00216.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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10
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Histological and ultrastructural evidence that recurrent laryngeal neuropathy is a bilateral mononeuropathy limited to recurrent laryngeal nerves. Equine Vet J 2010; 40:666-72. [DOI: 10.2746/042516408x335711] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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11
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Rhee HS, Steel CM, Derksen FJ, Robinson NE, Hoh JFY. Immunohistochemical analysis of laryngeal muscles in normal horses and horses with subclinical recurrent laryngeal neuropathy. J Histochem Cytochem 2009; 57:787-800. [PMID: 19398607 PMCID: PMC2713078 DOI: 10.1369/jhc.2009.953844] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 04/16/2009] [Indexed: 11/22/2022] Open
Abstract
We used immunohistochemistry to examine myosin heavy-chain (MyHC)-based fiber-type profiles of the right and left cricoarytenoideus dorsalis (CAD) and arytenoideus transversus (TrA) muscles of six horses without laryngoscopic evidence of recurrent laryngeal neuropathy (RLN). Results showed that CAD and TrA muscles have the same slow, 2a, and 2x fibers as equine limb muscles, but not the faster contracting fibers expressing extraocular and 2B MyHCs found in laryngeal muscles of small mammals. Muscles from three horses showed fiber-type grouping bilaterally in the TrA muscles, but only in the left CAD. Fiber-type grouping suggests that denervation and reinnervation of fibers had occurred, and that these horses had subclinical RLN. There was a virtual elimination of 2x fibers in these muscles, accompanied by a significant increase in the percentage of 2a and slow fibers, and hypertrophy of these fiber types. The results suggest that multiple pathophysiological mechanisms are at work in early RLN, including selective denervation and reinnervation of 2x muscle fibers, corruption of neural impulse traffic that regulates 2x and slow muscle fiber types, and compensatory hypertrophy of remaining fibers. We conclude that horses afflicted with mild RLN are able to remain subclinical by compensatory hypertrophy of surviving muscle fibers.
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Affiliation(s)
- Hannah S Rhee
- Discipline of Physiology, Bosch Institute, School of Medical Sciences, Faculty of Medicine, The University of Sydney, Australia
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Dixon PM, Hahn CN, Barakzai SZ. Recurrent laryngeal neuropathy (RLN) research: where are we and to where are we heading? Equine Vet J 2009; 41:324-7. [PMID: 19562891 DOI: 10.2746/042516409x423082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- P M Dixon
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Midlothian, Scotland, UK
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Collins N, Milne E, Hahn C, Dixon P. Correlation of the Havemeyer endoscopic laryngeal grading system with histopathological changes in equine Cricoarytenoideus dorsalis muscles. Ir Vet J 2009; 62:334-8. [PMID: 21851734 PMCID: PMC3113812 DOI: 10.1186/2046-0481-62-5-334] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The establishment of a single validated endoscopic laryngeal grading system for assessing recurrent laryngeal neuropathy (RLN) is desirable to facilitate direct comparisons between the findings of different clinical and research groups worldwide. The objective of this study was to assess the relationship between the Havemeyer endoscopic laryngeal grading system and histopathological changes consistent with RLN in the left cricoarytenoideus dorsalis (CAD) muscle of horses of different breeds with a full range of clinical severities of RLN, i.e., from normal endoscopic laryngeal function to complete laryngeal hemiplegia. Endoscopic grading of laryngeal function of 22 horses was performed using the Havemeyer endoscopic laryngeal grading system. A biopsy sample of the left CAD muscle was obtained from each horse, either at post mortem examination (n = 16), or during routine laryngoplasty surgery (n = 6). A semi-quantitative histopathological scoring system was used to grade the severity of histopathological lesions consistent with RLN in the left CAD muscle of each horse. A significant positive correlation (rs = 0.705, p < 0.001) was found between the Havemeyer grades and sub-grades of laryngeal function and the semi-quantitative assessment of histopathological lesions consistent with RLN in the left CAD muscle. However, a wide spread of muscle histopathological scores was obtained, particularly from horses with Havemeyer sub-grades II.1, III.1 and III.2. In conclusion, the Havemeyer endoscopic laryngeal grading system was found to broadly correlate with histopathological changes consistent with RLN in equine cricoarytenoideus dorsalis muscle.
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Affiliation(s)
- N Collins
- The Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Easter Bush Veterinary Centre, Roslin, Midlothian, EH25 9RG, Scotland.
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Valentine BA. Pathologic findings in equine muscle (excluding polysaccharide storage): a necropsy study. J Vet Diagn Invest 2008; 20:572-9. [PMID: 18776088 DOI: 10.1177/104063870802000506] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Gross and histopathologic evaluation of skeletal muscle was performed in 229 equids (217 horses, 8 ponies, 3 donkeys, and 1 mule) 1 year of age or older undergoing postmortem examination at Oregon State University in a 2.5-year period. Animals were evaluated for grossly evident muscle lesions, and muscle samples were fixed in formalin, processed routinely, and stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) for glycogen. Muscle lesions were detected in 149 animals (65%). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses without polysaccharide storage myopathy and was the most common finding (36 animals; 15.7%). Chronic myopathic change was more common in older animals. Generalized muscle atrophy was present in 30 animals (13.1%). Myonecrosis was attributed to endotoxic injury (11 animals; 4.8%), bone fracture (8 animals; 3.5%), bacterial infection (5 animals; 2.2%), muscle rupture (3 animals; 1.3%), selenium deficiency (2 animals; 0.9%), and exertional rhabdomyolysis (1 horse; 0.4%); cause was not determined in 9 animals (3.9%). Intramyofiber protozoa were detected in 19 horses and ponies (8.3%). Denervation atrophy was detected in 14 animals (6.1%). Neoplasia involving muscle occurred in 3 animals (1.3%), injection site reactions were detected in 4 animals (1.7%), and focal lymphocytic infiltrates were found in 6 animals (2.6%). Other findings were ring fibers (2 horses; 0.9%), fiber splitting (2 horses; 0.9%), and fat infiltration (1 horse; 0.4%). Skeletal muscle lesions are common in equids examined at postmortem. Transverse sections stained with HE and PAS are invaluable when evaluating equine muscle.
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Affiliation(s)
- Beth A Valentine
- College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, USA.
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15
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Adreani CM, Li ZB, Lehar M, Southwood LL, Habecker PL, Flint PW, Parente EJ. Myosin heavy chain composition in normal and atrophic equine laryngeal muscle. Vet Pathol 2007; 43:881-9. [PMID: 17099144 DOI: 10.1354/vp.43-6-881] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The myosin heavy chain (MHC) composition of a given muscle determines the contractile properties and, therefore, the fiber type distribution of the muscle. MHC isoform expression in the laryngeal muscle is modulated by neural input and function, and it represents the cellular level changes that occur with denervation and reinnervation of skeletal muscle. The objective of this study was to evaluate the pattern of MHC isoform expression in laryngeal muscle harvested from normal cadavers and cadavers with naturally occurring left laryngeal hemiplegia secondary to recurrent laryngeal neuropathy. Left and right thyroarytenoideus (TA) and cricoarytenoideus dorsalis (CAD) were obtained from 7 horses affected with left-sided intrinsic laryngeal muscle atrophy and from 2 normal horses. Frozen sections were evaluated histologically for degree of atrophy and fiber type composition. MHC isoform expression was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of muscle protein. Histologic atrophy was seen in all atrophic muscles and some right-sided muscles of 3 affected horses, as well as the left TA of 1 normal horse. Fiber type grouping or loss of type I muscle fibers was observed in the left-sided laryngeal muscles in all but 1 affected horse, as well as in the right muscles of 2 affected horses, and the left TA of 1 normal horse. SDS-PAGE showed 2 bands corresponding to the type I and type IIB myosin isoforms in the CAD and TA of the 2 normal horses. Affected horses demonstrated a trend toward increased expression of the type IIB isoform and decreased expression of the type I isoform in atrophic muscles. This study confirmed the presence of histologic abnormalities in grossly normal equine laryngeal muscle, and it demonstrated an increased expression of type IIB MHC with a concurrent decreased expression of type I MHC in affected muscles. Evaluation of muscle fiber changes at the cellular level under denervated and reinnervated conditions may aid in assessing future strategies for reinnervation or regeneration of atrophic laryngeal muscle.
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Affiliation(s)
- C M Adreani
- Department of Clinical Studies, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348, USA.
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Dart AJ, Dowling BA, Smith CL. Upper airway dysfunction associated with collapse of the apex of the corniculate process of the left arytenoid cartilage during exercise in 15 horses. Vet Surg 2006; 34:543-7. [PMID: 16343139 DOI: 10.1111/j.1532-950x.2005.00085.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To report dynamic collapse of the apex of the left corniculate process under the right corniculate process into the airway at the dorsal apposition of the paired arytenoid cartilages during exercise as a cause of upper airway dysfunction in horses. DESIGN Retrospective study. ANIMALS Fifteen horses with a history of poor performance and/or upper respiratory tract noise during exercise. METHODS Video recordings of all horses referred for upper airway evaluation using high-speed treadmill videoendoscopy (HSTV) between January 1998 and December 2003 were reviewed. Records of horses that developed dynamic collapse of the apex of the left corniculate process into the airway were included. Clinical history, age, gender, breed, and use of the horse were retrieved. RESULTS Of 309 horses referred for examination for poor performance and/or upper respiratory tract noise during exercise, 15 (4.9%) had collapse of the apex of the left corniculate process under the right and into the airway at the dorsal apposition between the paired arytenoid cartilages during HSTV. There were 3 females and 13 males, aged from 2 to 5 years. Five horses had previous surgery for left recurrent laryngeal neuropathy (RLN): 2 had nerve muscle pedicle graft and 3 had laryngeal prosthesis. During HSTV, all 15 horses had progressive collapse of the apex of the left corniculate process under the right at the dorsal apposition of the 2 arytenoid cartilages, and into the dorsal aspect of the rima glottidis. Review of video recordings revealed that collapse of the apex of the corniculate process was followed by progressive collapse of the left aryepiglottic fold and left vocal fold. The ventral aspect of the left corniculate cartilage maintained abduction in all horses. Two horses also had progressive collapse of the right vocal fold, 1 had rostral displacement of the palatopharyngeal arch, and another had dorsal displacement of the soft palate. CONCLUSIONS Dynamic collapse of the apex of the left corniculate process of the arytenoid cartilage under the right is an uncommon cause of upper airway dysfunction in horses and the pathogenesis is unclear. We speculate that the left arytenoideus transversus muscle is unable to support the dorsal apposition between the arytenoid cartilages. This loss of support allows the elastic cartilage of the left corniculate process to collapse under the right and into the airway, as inspiratory pressure increases during exercise. This condition may be associated with an unusually advanced neuropathy of the adductor components of the left recurrent laryngeal nerve and may be an unusual manifestation of RLN; however, this is speculative and further investigation is required to determine its cause. CLINICAL RELEVANCE Dynamic collapse of the apex of the left corniculate process and into the airway at the dorsal apposition between the paired arytenoid cartilages can only be diagnosed during HSTV. It is an uncommon cause of upper airway dysfunction but may affect the athletic potential of racing Thoroughbreds and Standardbreds.
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Affiliation(s)
- Andrew J Dart
- Faculty of Veterinary Science, The University of Sydney, New South Wales, Australia.
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Dixon PM, McGorum BC, Railton DI, Hawe C, Tremaine WH, Pickles K, McCann J. Laryngeal paralysis: a study of 375 cases in a mixed-breed population of horses. Equine Vet J 2001; 33:452-8. [PMID: 11558739 DOI: 10.2746/042516401776254790] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Referred cases (n = 375) of laryngeal paralysis (1985-1998) from a mixed-breed equine population included 351 (94%) cases of recurrent laryngeal neuropathy (RLN) (idiopathic laryngeal hemiplegia) and 24 cases (6%) of laryngeal paralysis from causes other than RLN. Laryngeal movements were classified endoscopically into one of 6 grades, in contrast to the usual 4 grades. The RLN cases had a median grade 4 laryngeal paralysis, of which 96% were left-sided, 2% right-sided and 2% bilaterally affected. RLN cases included 204 (58%) Thoroughbred, 96 (27%) Thoroughbred-cross, 23 (7%) draught, 16 (5%) Warmbloods and 10 (3%) other breeds, including only 4 (1%) ponies. The median age of RLN cases at referral was 6 years (range 2-12) and their median height was 170.2 cm. The work of RLN horses included National Hunt racing (42%), flat racing (1%), hunting (19%), eventing (16%) and miscellaneous work (22%). Reported presenting signs in RLN-affected horses included abnormal exercise-related respiratory sounds in 90% and reduced exercise tolerance in only 64%. However, many horses were referred before their exercise tolerance could be fully assessed. Forty percent of the RLN cases had intercurrent disorders, including 10% with additional upper respiratory and 7% with lower respiratory tract diseases. The 24 nonidiopathic RLN cases included 12 with bilateral laryngeal paralysis, 11 (92%) of which were ponies. Bilateral laryngeal paralysis occurred with hepatic encephalopathy in 7 cases and following general anaesthesia in 2 cases. The 12 cases of acquired unilateral laryngeal paralysis included 7 caused by guttural pouch mycosis.
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Affiliation(s)
- P M Dixon
- The Wellcome Trust Centre for Studies in Comparative Respiratory Medicine, The University of Edinburgh, Easter Bush Veterinary Centre, Easter Bush, Midlothian, Scotland
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Barkmeier JM, Luschei ES. Quantitative analysis of the anatomy of the epineurium of the canine recurrent laryngeal nerve. J Anat 2000; 196 ( Pt 1):85-101. [PMID: 10697291 PMCID: PMC1468043 DOI: 10.1046/j.1469-7580.2000.19610085.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The purpose of this investigation was to determine the amount of epineurium surrounding the recurrent laryngeal nerve (RLN) compared with a limb nerve, that to flexor hallicus longus (NFHL). Nerve samples were obtained from 10 adult dogs and studied using scanning electron microscopy and light microscopy to measure the relative proportion of epineurium and the relative proportions of adipose and collagenous tissue comprising the epineurium in both nerves. Significantly greater relative epineurial cross-sectional areas and adipose content were found in the RLN than in the NFHL. Based on observations on noncranial peripheral nerves, the findings indicate that the RLN is better protected against deformational forces associated with compression than stretching forces. The RLN may not be structured well for successful reinnervation after injury. The patterns observed for adipose tissue in RLN epineurial tissue appeared unique compared with those previously reported in peripheral nerves. The primary role associated with adipose tissue is to 'package' the nerve for protection. The RLN is considered to be a vital nerve in the body, as are other cranial nerves. The large proportions of adipose tissue in the epineurium may relate to the importance of protecting this nerve from injury.
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Affiliation(s)
- J M Barkmeier
- University of Arizona, Department of Speech and Hearing Sciences, Tucson 85721, USA
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Anderson BH, Kannegieter NJ, Goulden BE. Endoscopic observations on laryngeal symmetry and movements in young racing horses. N Z Vet J 1997; 45:188-92. [PMID: 16031984 DOI: 10.1080/00480169.1997.36024] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
An endoscopic survey of young race horses was performed to examine the prevalence and character of laryngeal movements during quiet respiration. The main aim was to determine whether those arytenoid movements which could possibly reflect the efficiency of left dorsal cricoarytenoid muscle function changed over a period of time. Of the 452 horses examined, 439 were Thoroughbreds and 23 were Standardbreds, 250 were less than 2 years of age (6-21 months), and 202 were 2 years old. One hundred and nine of these horses were examined again 16 months later. Arytenoid movements were given one of four grades. Grades 1 and 2 were considered normal and unlikely to be the result of abnormal left dorsal cricoarytenoid muscle function, whilst grades 3 and 4 were considered likely, or almost certainly, the result of abnormal left dorsal cricoarytenoid muscle function. The percutaneous prominence of the muscular process of left and right arytenoid cartilages, endoscopic arytenoid movement on left and right sides, age, sex and breed was recorded. Chi squared analysis was used to determine the association between age, breed, sex and the other recorded variables, and the presence or absence of abnormal laryngeal movements. At the first examination, 48% of the horses had grade 1, 37% grade 2, 15% grade 3 and 0.2% grade 4 left laryngeal movements. Of the horses examined I6 months later, 52% had grade 1, 33% grade 2, 14% grade 3 and 1% grade 4 left laryngeal movements. Fifteen percent of horses with grade 1 and 9% with grade 2 initially were found to be grade 3 at the subsequent examination. Conversely, 53% of horses with grade 3 initially were found to be grade 1 and 21% grade 2 at the subsequent examination. One horse that was grade 3 at the initial examination was grade 4 at the subsequent examination. Overall, 43% of horses were graded the same, 29% were given a better grade and 28% were given a worse grade. Age and sex were not associated with abnormal left laryngeal movements. The presence of abnormal arytenoid movements was significantly less in Standardbreds, but significantly higher in those horses that had a more prominent muscular process of the left arytenoid cartilage. The number of grade 2 and 3 laryngeal movements recorded on the left side was significantly higher than the right. It was concluded that asymmetrical laryngeal movements are common in young race horses; at this age laryngeal movements may interchange between what is considered normal and abnormal; the proportion of young horses with normal or minor variations in their left arytenoid movements that develop more obvious degrees of asynchrony is low (12%); and the proportion of horses considered to have endoscopic evidence of deficient left abductor muscle function that eventually develop laryngeal hemiplegia is also low (5%).
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Affiliation(s)
- B H Anderson
- Department of Veterinary Clinical Sciences, Massey University, Palmerston North, New Zealand
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Newton-Clarke MJ, Divers TJ, Valentine BA. Evaluation of the thoraco-laryngeal reflex ('slap test') as an indicator of laryngeal adductor myopathy in the horse. Equine Vet J 1994; 26:355-7. [PMID: 7988536 DOI: 10.1111/j.2042-3306.1994.tb04402.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A study was conducted over a 12 month period to assess the accuracy of the 'slap test' in the diagnosis of laryngeal adductor myopathy. The thoraco-laryngeal reflexes of 15 horses with no clinical signs of idiopathic laryngeal hemiplegia (ILH) were recorded using a video-endoscope. These 'slap test' responses were examined independently by 3 assessors. The horses were subsequently subjected to euthanasia and samples taken from the cricoarytenoideus lateralis (CAL) muscles for histopathological examination and assessment of denervation atrophy. Despite normal adductory responses, moderate to severe atrophy of the left CAL muscles was seen in 5 horses. The remaining horses had varying degrees of adductor myopathy, invariably worse in the left side of the larynx. The 'slap test' as performed in this study was therefore unable to differentiate between horses with moderate to severe muscle changes and those without, making it useless as a diagnostic test for adductor myopathy. The reason for the preservation in adductor function despite advanced histological atrophy of the muscle may lie in the degree of reinnervation found in the muscles.
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Affiliation(s)
- M J Newton-Clarke
- New York State College of Veterinary Medicine, Cornell University, Ithaca 14853
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21
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Abstract
Three adductor muscles of the larynx, the cricoarytenoideus lateralis (CAL), the arytenoideus transversus (AT) and the ventricularis (Ve), from 36 horses were examined histologically. The neurogenic changes seen in each muscle were evaluated qualitatively. In addition, in 6 horses with clinical and subclinical signs of neurogenic atrophy, measurements of muscle fibre area were performed. Neurogenic changes observed in the Ve were less than in CAL and AT. Measurements of muscle fibre area also demonstrated that CAL and AT showed a wider range of pathological changes than did Ve. The results show that denervation does not uniformly affect all adductor muscles of the larynx. On the other hand, the appearance in some animals of fibre type grouping in the right AT to the same or to a greater extent than in the left AT supports the classification of equine laryngeal neuropathy as a distal axonopathy.
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Affiliation(s)
- C Lopez-Plana
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
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22
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López-Plana C, Sautet JY, Pons J, Navarro G. Morphometric study of the recurrent laryngeal nerve in young 'normal' horses. Res Vet Sci 1993; 55:333-7. [PMID: 8284497 DOI: 10.1016/0034-5288(93)90103-m] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Quantitative measurements were made on cross-sectional preparations of the distal part of the recurrent laryngeal nerve (RLN) from nine young mixed-breed horses to establish reference values for the total number of myelinated fibres, mean fibre diameter and percentage of thickest fibres (over 9.5 microns) and to delineate diameter distribution curves. The total number of myelinated fibres, mean fibre diameter and percentage of thickest fibres for the left RLN were significantly lower than those of the right RLN (P < 0.005). The distribution of fibres was unimodal. The fibre diameter ranged from 1 micron to 17 microns. Approximately, 95 per cent of fibres had a diameter larger than 5 microns.
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Affiliation(s)
- C López-Plana
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Spain
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OHNESORGE B, DEEGEN E, MIESNER K, GELDERMANN H. Hemiplegia laryngis bei Warmblutpferden - eine Untersuchung an Hengsten, Stuten und deren Nachkommen*. ACTA ACUST UNITED AC 1993. [DOI: 10.1111/j.1439-0442.1993.tb00610.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Harrison GD, Duncan ID, Clayton MK. Determination of the early age of onset of equine recurrent laryngeal neuropathy. 1. Muscle pathology. Acta Neuropathol 1992; 84:307-15. [PMID: 1384268 DOI: 10.1007/bf00227824] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The age of onset of equine recurrent laryngeal neuropathy has not been ascertained, although the clinical condition of left laryngeal hemiplegia ("roaring") has been recognized for centuries. The purpose of this study was to evaluate the laryngeal muscles of draft horse foals for the presence of fiber-type grouping, indicating denervation and reinnervation, and to determine if histological evidence of recurrent laryngeal neuropathy was present. Abductor and adductor laryngeal muscles from the left and right sides were collected immediately after euthanasia from male draft horse foals, six less than 2 weeks and four 6 months of age, and stained for myosin ATPase. A morphometric test was used to objectively evaluate several areas from each muscle for fiber-type grouping. Extensive fiber-type grouping which was characteristic of recurrent laryngeal neuropathy was found in one of the young foals and all of the older foals. Four of the young foals had some areas of fiber-type grouping suggestive of mild, early changes associated with recurrent laryngeal neuropathy. One of the young foals had no fiber-type grouping present in any of the laryngeal muscles evaluated. These findings suggest an early age of onset of recurrent laryngeal neuropathy.
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Affiliation(s)
- G D Harrison
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706
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Duncan ID, Reifenrath P, Jackson KF, Clayton M. Preferential denervation of the adductor muscles of the equine larynx. II: Nerve pathology. Equine Vet J 1991; 23:99-103. [PMID: 2044517 DOI: 10.1111/j.2042-3306.1991.tb02729.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The terminal branches of the recurrent laryngeal nerve (RLN) of three normal ponies and six horses with sub-clinical laryngeal disease were examined qualitatively and quantitatively in an attempt to explain the preferential denervation of the laryngeal adductor muscles in the neuropathy of idiopathic laryngeal hemiplegia (ILH). The myelinated fibre spectra of all the motor nerve fibres in the left and right abductor and adductor branches of the RLN in three normal ponies were measured. The density of myelinated fibres was also calculated. There was no significant difference between the larger group of myelinated fibres in the adductor or abductor branches. In the six horses with laryngeal hemiparesis, however, there was a marked preferential loss of the medium/large size myelinated fibres in the left adductor branch, although nerve fibre densities were not significantly different. While no simple morphometrical feature was found to explain the selective muscle denervation, the greater loss of large diameter myelinated fibres in the adductor branches confirms the earlier observation of adductor muscle susceptibility in the neuropathy of ILH.
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Affiliation(s)
- I D Duncan
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706
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