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Equine Laryngeal Disorders: Left Laryngeal Hemiplegia & Epiglottic Entrapment

Equine Laryngeal Disorders: Left Laryngeal Hemiplegia & Epiglottic Entrapment

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  • Elevated ary tissue and did not visualize ulcers on the ventral aspectElevated ary tissue and retracted rostral, allowing epig to temporarily free itself – no adhesions present between ary and epiglottis
  • Both pharyngeal collapse and dorsal displacement of soft palate encountered during surgery – prolonging procedure

Equine larynx Equine larynx Presentation Transcript

  • LARYNGEAL DYSFUNCTION: 1. Left Laryngeal Hemiplegia 2. Epiglottic Entrapment Dec. Dane Tatarniuk, DVM12, 2012
  • ANATOMY & FUNCTION
  • Equine Larynx Anatomy  Paired arytenoids  Epiglottis  Thyroid  Cricoid
  • Equine Larynx Intrinsic muscles  Move laryngeal cartilages in relation to each other  Cricoarytenoideus dorsalis – abduction of arytenoids & tensing of vocal folds  Thyroarytenoideus, ar ytenoideus transversus, cricoaryte noideus lateralis – adduction of arytenoids
  • Equine Larynx Arytenoid Function  Situated on either side of cricoid  Composed of hyaline cartilage  Cricoarytenoid joint – diarthrodial  Facilitates adduction & abduction movement  3 processes  Corniculate, cuneate & muscular process  Arytenoids adduct (close) during swallowing reflex  Arytenoids abduct (rima glottidis dilates) fully at high- intensity exercise to maximize airflow  Abduction of arytenoid counter-acts increasing negative inspiratory pressure (which acts to adduct arytenoids)  Decreased airflow  hypoxemia  hypercarbia  metabolic acidosis  musculoskeletal fatigue  poor performance
  • Equine Larynx Epiglottis Anatomy & Function  Triangular structure with apex pointing rostral  Attached to thyroid via thyroepiglottic ligament  Composed of elastic cartilage  Normally situated above soft palate  Soft palate against epiglottic base  Scallop appearance laterally  Vascular pattern dorsally  Flips caudally to cover rima glottis during swallowing
  • CASE #1
  • Case #1- Signalment 7 years old Gelding Canadian Warmblood Discipline: Eventing
  • Case #1 - History Tiring with exercise 6 month history Noise  Less of a concern Evaluation by rDVM  Standing endoscopy  Laryngeal paralysis  Referred to UMEC
  • Case #1 – Diagnostics  Normal vital parameters  Resting endoscopy, standing, un- sedated  Left laryngeal hemiplegia  Grade 4  Recurrent laryngeal neuropathy  No other concurrent upper airway
  • Left Laryngeal Paralysis Neurogenic atrophy of intrinsic laryngeal musculature (94% of cases) Loss of abductor and adductor arytenoid function  Cricoarytenoideus dorsalis muscle Progressive loss of function (not immediate) Other causes:  Perivascular damage from IV injection, guttural pouch mycosis, neck trauma, abscessation of head/neck, neck neoplasms, organophosphate toxicity, plant poisoning, hepatic
  • Laryngeal Paralysis Grades Grade 1  Arytenoid movements synchronous & symmetrical  Full adduction attained Grade 2  Arytenoid movements are asynchronous or asymmetrical at times  Full adduction attained Grade 3  Arytenoid movements are asynchronous or asymmetrical  Full adduction can not be attained Grade 4  Complete immobility of arytenoid cartilage
  • Case #1 - Therapy Recommendation:  Prosthetic Laryngoplasty  “Tie Back”  Prosthesis between arytenoid and cricoid  Create abduction  Provide adequate airflow but not allow aspiration +/- ventriculectomy via laryngotomy  Eliminate noise, further stabilize airway  Can be used as sole procedure in draft horses +/- ventriculocordectomy via standing laser endoscopy  2 cm crescent wedge of tissue removed from leading edge of vocal fold
  • Case #1 - Therapy Pre-operative medication  Potassium penicillin, 22,000iu/kg, IV  Gentamicin, 6.6mg/kg, IV  Phenylbutazone, 4.4mg/kg, IV  Tetanus toxoid, IM General anesthesia  Small endotracheal tube  Left lateral recumbancy  Neck extended  IV catheter low in left jugular vein or on right side  5L fluid bag under proximal neck  Help extend throatlatch upwards
  • Case #1 - Therapy Surgery  ~10cm cranial-caudal incision, cranial extent starting at left ramus of mandible  Ventral and parallel to lingual-facial vein  Blunt dissect lingual-facial vein from omohyoideus muscle  Avoid pertinent nerves and vasculature  Dissect between sternocephalicus and cricothyroideus muscles  Follow plane of dissection under lingual-facial vein until expose larynx & associated laryngeal musculature
  • Case #1 - Therapy Palpate caudal aspect of cricoid cartilage & muscular process of left arytenoid cartilage Assistant retracts upwards Suture  #5 Ethibond (Polyester)  Alternatives: Stainless steel wire, nylon, polyethylene Pass suture through cricoid cartilage (x 2)  Walk needle off caudal aspect of cricoid  Stay axial to dorsal sagittal ridge  „Notch‟ of cricoid cartilage Auer & Stick
  • Case #1 - Therapy Intra-operative endoscopic exam  Ensure suture does not penetrate laryngeal mucosa Tunnel leading edges of suture  Under cricopharyngeus muscle Pass suture in caudal-medial to cranial- lateral direction through muscular process (x2)  Engage spine, not tip, of muscular process Tie cranial suture strand to caudal strand (x2) Assess abduction of left arytenoid with endoscope  Curvature of corniculate cartilage comes into contact with pharyngeal wall Close musculature & skin routinely  Stent bandage Auer & Stick
  • Case #1 – Post Op Care Post operative medication  Potassium penicillin, 22,000iu/kg, IV, QID, 3 days  Gentamicin, 6.6mg/kg, IV, SID, 3 days  Phenylbutazone, 2.2mg/kg, PO, BID, 5 days  Trimethoprim sulfa, 15mg/kg, PO, BID, 5 days Fed on the ground Exercise 4 weeks of stall rest then 2 weeks of small paddock  Return to exercise at 6 to 8 weeks post-op
  • Case #1 – Recheck Endoscopy 24 hour recheck endoscopy  Maintained abducted position  Estimate 60 to 70% of rima glottidis area attained 4 week follow up  Horse doing well
  • Prognosis Success depends on use of horse and measurement of success Between 50% to 70% of horses have improved performance following laryngoplasty surgery Success better in horses not intended to race Decreased noise production not a measure of improved airway function
  • Complications Complications decrease prognosis  Dysphagia  Bilateral nasal discharge  Feed, water, saliva  Aspiration pneumonia  Chronic coughing  Incisional infection  Prosthesis failure  Chondritis
  • CASE #2
  • Case #2 - Signalment 11 years old Gelding Quarter Horse Discipline: Mounted shooting
  • Case #2 - History History of intermittent coughing Severe coughing fit while at show Difficulty eating No performance issues Attended by rDVM
  • Case #2 – rDVM Diagnostics Oral exam: normal Head radiographs: normal Endoscopy:  Epiglotticentrapment  Severe thickening and necrotic ulceration of aryepiglottic tissue  Intermittent dorsal displacement of soft palate  Small ulcer present on the left rim of soft palate
  • Case #2 – rDVM Endoscopy
  • Case #2 – rDVM Therapy Procaine Penicillin 22,000iu/kg IM BID Flunixin Meglumine 1.1mg/kg PO SID Recheck Endoscopy by rDVM:  At 7 days - continued entrapment with intermittent soft palate displacement; improvement of the ulcer  At 14 days - continued healing of ulcers, intermittent soft palate displacement, periodic ventral pharyngeal collapse
  • Case #2 – ReferralPresentation After 14 days medical therapy,  Improvement in ulcer  Epiglottic entrapment persists Case referred for further management Initial endoscopy:  Confirm epiglottic entrapment with mild ulceration  Ulceration less compared to previous exam images  Ventral aryepiglottic tissue normal with no ulceration  No adhesions present between epiglottis and aryepiglottic tissue
  • Case #2 - Initial Endoscopy
  • Epiglottic Entrapment  Loose aryepiglottic folds & subepiglottic mucosa displace dorsally above the epiglottis  Exercise intolerance main complaint usually  Less commonly coughing, nasal exudate  Prevalence 0.9% in Thoroughbreds  Can be induced by  Epiglottic hypoplasia  Aryepiglottic fold inflammation / swelling  Chronic cases  Thickened, fibrous tissue
  • Case #2 - Assessment Recommendation: Surgery  Entrapment unlikely to resolve without intervention Techniques:  Standing vs. general anesthesia  Laser axial transection  Sharp axial transection Determined to post-pone surgical management  Additional 7 days Allow ulcer to heal further prior to surgery
  • Case #2 – Interim Medical therapy  Procaine Penicillin, 22,000iu/kg, IM, BID, 7 days  Flunixin Meglumine, 0.55mg/kg, PO, BID, 3 days  Throat Spray, 10cc, PO, SID, 7 days  Glycerin9cc  Dimethyl sulfoxide 1cc
  • Surgical Techniques Sharp axial division of aryepiglottic tissue  Curved bistoury knife passed nasally and applied under endoscopic guidance  Scalpel transection through laryngotomy or pharyngotomy Axial division allows membrane to retract and heal in normal sub-epiglottic position  Tissue sparing, minimize scar tissue If thickened or ulcerated  Can consider taking out triangular wedge segments of aryepiglottic tissue instead of axial division
  • Surgical Techniques Laser axial division of aryepiglottic tissue  Contact vs. non-contact  Tip of laser applied to caudal aspect of tissue (on midline) and moved rostrally  10 to 12 watts  Continue dissection until elastic property of aryepiglottic tissue causes entrapping membrane to retract below epiglottis  Care to not cause collateral damage to epiglottis, soft palate or pharynx
  • Case #2 – Surgery Surgical management 7 days following initial UMEC exam  21 days following initial rDVM exam Pre-operative medication  Detomidine, 0.02mg/kg, IV, given to effect  Intranasal lidocaine, 100cc  Procaine Penicillin, 22,000iu/kg, IM  Gentamicin, 6mg/kg, IV  Phenylbutazone, 4.4mg/kg, IV
  • Case #2 - Surgery Standing axial excision of aryepiglottic tissue using diode contact laser
  • Case #2 - Surgery Standing axial excision of aryepiglottic tissue using diode contact laser
  • Case #2 - Surgery  Rostral edge of epiglottis appears hypoplastic  Blunted prominence  Residual thickening of aryepiglottic tissue present on left edge of epiglottis  Contract with time  Require transection at future date
  • Case #2 – Post Op Care Phenylbutazone, 2.2mg/kg, PO, BID, 5 days Procaine Penicillin, 22,000iu/kg, IM, BID, 3 days Throat Spray, 10cc, PO, SID, 7 days  Glycerin7.7cc  Dimethyl sulfoxide 0.8cc  Dexamethasone 1.5cc Recheck endoscopy 24 hours later  Confirmed epiglottis free Discharged 24 hours after surgery
  • Case #2 – Recheck  Recheck endoscopy 6 days post-surgery  Swellingdecreased considerably  Some residual inflammation present
  • Prognosis Reported re-entrapment rate is 5 to 15% with curved bistoury Reported re-entrapment rate is 4% with laser axial division Between 10 to 15% of cases develop DDSP following un-entrapment Complications reduce prognosis:  Thermal trauma to epiglottis, soft palate  Lacerations to epiglottis, soft palate  Cicatrix
  • REVIEW
  • Review: Laser Types:  Neo-dymium : yttrium aluminum garnet (Nd:YAG)  Gallium aluminum arsinate diode Quartz or silica fiber-optics to conduct laser energy Human safety - wear protective eyewear  Specific to wavelength of laser – avoid ocular injury Smoke plume  Xylene, toluene – can be toxic  If considerable amount produced consider smoke evacuator Laser energy converted to thermal energy when contacting tissue  Incise, coagulate, vaporize  Wavelength used influences amount absorbed, scattered, reflected, transmitted
  • Review: Laser Precision incision  Smaller fiber (400–600μm)  Small contact area, high power density  Direct contact with tissue  10 to 15 watts power Non-specific tissue ablation  Larger fiber (800–1000μm)  Less specific, do not require direct contact  Up to 50 watts power  Can coagulate tissue 5mm deep  Capable with Nd:YAG, not capable with diode
  • Review: Recent Literature Dart, 2009. “Effect of Prosthesis Number and Position on Rima Glottidis Area in Equine Laryngeal Specimens.”  Placed dorsal suture and lateral suture  dorsally in the cricoid & through the rostral and proximal muscular process  1.5 cm lateral to the 1st suture & more caudal and distal in the muscular process  When tied independently, no difference in rima glottis area  8.51cm2 & 8.46cm2  When both sutures were tied together, mean area was greater than when either suture was tied alone  9.31cm2
  • Review: Recent Literature Rakesh, 2008. “Implications of different degrees of arytenoid cartilage abduction on equine upper airway characteristics”.  Used computational fluid dynamics modeling to measure the effects of different degrees of abduction  Tested abduction at 100%, 88% & 75% cross sectional area of rima glottis  88% cross sectional area optimal  less reduction in airflow  less collapsing pressure  less stress on the repair
  • Review: Recent Literature Aitken, 2011. “Epiglottic abnormalities in mature non-racehorses: 23 cases.”  8+ years, non race-horses  Primary complaint  70% chronic cough  13% nasal discharge  Racehorses – exercise intolerance  57% epiglottic entrapment  All chronic: thick, ulcerated, and blunted epiglottis  74% resolution of symptoms with appropriate management  24% prolonged medical management (therapy >2 weeks) due to post-surgical epiglottic inflammation  9% developed DDSP post-epiglottic surgery
  • Review: Recent Literature Lacourt, 2011. “Treatment of Epiglottic Entrapment by Trans-nasal Axial Division in Standing Sedated Horses Using a Shielded Hook Bistoury.”  Reviewed 33 cases using conventional bistoury technique  2 – laceration of soft palate  2 – laceration of epiglottis  Shield hook in 8 standardbreds  Minimize damage to soft palate, epiglottis  Mean surgical time = 83 seconds  6 resolution with one incision  2 resolution with two incisions  Inexpensive  Faster  Authors opinion: technically easier
  • References Aitken, 2011. “Epiglottic abnormalities in mature non-racehorses: 23 cases.” JAVMA 238: 12, 1634 – 1638. Dart, 2009. “Effect of Prosthesis Number and Position on Rima Glottidis Area in Equine Laryngeal Specimens.” Vet Surg 38: 452 – 456. Lacourt, 2011. “Treatment of Epiglottic Entrapment by Trans-nasal Axial Division in Standing Sedated Horses Using a Shielded Hook Bistoury.” Vet Surg 40: 299 – 304. Fulton I: Larynx, in Auer JA, Stick JA (eds): Equine Surgery (ed 4). Philadelphia, PA, WB Saunders, 2006, pp 592 – 623. Palmer SE. “The use of lasers for treatment of upper respiratory tract disorders” Vet Clin Equine (2003) 19: p245 – 263. Rakesh, 2008. “Implications of different degrees of arytenoid cartilage abduction on equine upper airway characteristics”. EVJ 40 (7), 629 – 635.