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copyright A Hotston Moore
Laryngeal paralysis in dogs
Alasdair Hotston Moore
Bath Veterinary Referrals
copyright A Hotston Moore
About me
• Qualified Cambridge, 1990
• Post graduate training at Bristol vet school incanine medicine and general/ENT surgery until1994
• Lecturer and Senior Lecturer in Small Animal SoftTissue Surgery, University of Bristol 1997-2009
• Presently Head Of Surgical Referrals, BathVeterinary Referrals
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Introduction
• Laryngeal paralysis has been recognised indogs for many years
• Most cases have been seen in medium tolarge breeds but an increasing number ofgiant breed dogs, such as Newfies, aretreated
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What is laryngeal paralysis?
• A loss of movement of the vocal cords
• Due to loss of the nerve supply to themuscles of the larynx
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The larynx
• “the voice-box”/ “Adam’s apple”
• Joins the mouth/pharynx to the trachea(“windpipe”)
• Key functions:
– free air movement
– cough
– voice
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Normalcaninelarynx
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Symptoms of laryngeal disease
• Loss of opening of vocal folds: leads todifficulty breathing and abnormal noise
• Loss of movement of vocal cords: changein bark
• Loss of closure of vocal folds: cough
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Difficulty in breathing(dyspnoea)
• Results in tendency to pant
• Also reluctant to exercise or restrictedexercise ability
• In some cases, may lead to fainting onexercise
• Occasionally, can result in asphyxiation
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Dyspnoea
Worsened by:
• Exercise
• Excitement
• Distress
• Heat
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Respiratory noise
• Most obvious when panting
• Classically, on inspiration
• Described as stridor (“wheezing, roaring”):harsh, dry rasp
• The noise of “a man sawing wood”
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Change in bark (dysphonia)
• 60% of owners report a change in theirdog’s bark
• This is an early symptom
• Since it is gradual, it is often notappreciated by owners
• Bark becomes muted, hoarse or absent
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Cough
• Most dogs with LP cough
• In some dogs, coughing is the mainsymptom
• The cough tends to be harsh and“ineffectual”: retching, throat clearing,smoker’s cough
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Other causes of similarsymptoms
• Many diseases of the respiratory or cardiacsystems can cause these symptoms!
• Examples are the common conditions ofbronchitis and cardiomyopathy
• In addition, arthritis etc. can causereluctance to exercise
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Confirming the diagnosis
• Confirming the diagnosis is critical beforeconsidering treatment!
• Steps in diagnosis:
– History
– Clinical examination
– Blood samples
– Xray
– Examination under anaesthesia
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History
• The typical symptoms have beenmentioned already
• Other questions to check for unrelated orother diseases
• Often, this is a key part of the diagnosis
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Airway noises(inspiratory)
• Stridor: wheezing, roaring or whistling.A harsh, dry noiseAssociated with laryngeal or trachealdisease
• Stertor: snoring or snufflingA moist, grumbling noiseAssociated with nasal or pharyngeal disease
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Other airway noises
• Honking cough: musical, wheezing coughSuggestive of dynamic obstruction of thetrachea
• Reverse sneezing: sudden onset and offsetretching inspiratory noiseDog appears very distressedsuggestive of nasopharyngeal spasm
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Clinical examination
• Focuses on evaluation of the respiratory,cardiac and locomotor systems
• In some cases, observation at exercise canbe helpful
• Important to try and confirm LP, check forother causes of symptoms and to identifycomplicating factors
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Blood samples
• There is no blood test for LP!
• Blood samples are mostly useful to assessfor other diseases and as a pre-anaesthetictest
• Some clinicians also like to check thyroidfunction
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Xrays
• Radiographs of the chest are important to:
• Look for possible causes of LP
• Check for other disease
• Check for complications of LP e.g.pneumonia
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Normal chestXray
Chest Xray ofdog with atumour in thechest
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Examination under anaesthesia
• The definitive diagnostic test
• Does require some experienceto be reliable
• Occasionally, dogs with LPhave difficulty recoveringfrom GA
• Often sensible to combineradiography and EUA withanaesthesia for surgery
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Vets approach to the acute case
• Avoid stress!
• Key issues are excitement/distress,hyperthermia and oxygen delivery
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Manage stress
• Reassurance
• Sedation: with airway obstruction, benefitsof sedation outweigh concerns aboutrespiratory depression
• Avoid manual restraint e.g. for Xrays
• Give time to settle
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Hyperthermia
• A key feature in animals with severe airwayobstruction
• Manage with sedation
• Also controlled cooling:environmentwet towelsfansavoid dramatic measures (hoses, ice, enemas)
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Oxygen delivery
• Cooling and calming will reducerequirements
• Supplementary oxygen should be suppliedwith care. Avoid:
– Stress (e.g. mask)
– Overheating (e.g. oxygen tent)
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Management of the chronic case
• Remember, if the condition is chronic, theanimal may have decompensated but maybe stabilised and returned to the chronicstate
• With medical treatment, cooling andsedation, emergency surgery or tracheotomyis rarely required
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Common laryngeal diseases(dog)
• Laryngeal paralysis (90%)
• Laryngeal collapse (10%)
• Laryngeal neoplasia (rare)
• Laryngeal chondritis/granuloma (rare)
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Laryngeal paralysis
• Much the commonest upper airway obstructionin dogs
• Bilateral (cf. horses)
• Elderly (over 9yo), medium-large breed dogsparticularly Labrador and Golden Retrievers,Irish Setters and Afghan Hounds
• Very common but often missed by owners andvets: gradual onset, often assumed that old dogis slowing up, stridor may not be apparent atrest
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Treatment of LP
• Conservative management (steroids,Corvental) suppresses cough
• LP severely inhibits lifestyle of dog
• LP occasionally results on asphyxiation
• Surgery can be highly successful
• Various techniques in texts but only “tie-back” recommended as primary treatment
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Surgery for LP
• Surgery highly successful inthe right hands
• In the hands of theinexperienced, the surgery isdangerous and stressful
• Given the outcome (over 90%owner satisfaction), surgery isrecommended even in theseelderly patients
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Alternatives to tie back surgery
• Various other surgeries have been described
• None are as well evaluated or assafe/effective
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Tracheotomy tube
• Compared to people orhorses, managing dogswith tubes is extremelydemanding
• Tracheotomy is onlyuseful as a emergencymeasure, and even in thatcontext is best avoided
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Permanent tracheotomy
• Creation of a “window”between the skin and thetrachea
• Aim is to create a permanentbypass of the larynx
• Uncommonly performed butuseful when other surgeryfails
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Should my dog have surgery?
• Surgery is best suited for dogs where thereis an obvious reduction in ability to exercise
• Also where the possibility of asphyxiationis a real concern
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Dogs where surgery is notadvised
• If coughing is the major symptom, ratherthan dyspnoea
• In dogs with concurrentswallowing/vomiting diseases (e.g.megaoesophagus)
• Dogs with moderate-severe concurrentdisease (heart, other)
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Alternatives to surgery
• Lifestyle changes
• Medication: corticosteroids reducecoughing by have little effect on exerciseability
• Medication: other drugs for bronchitis alsoreduce cough, but do not “open the airway”
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Results of surgery
• Following surgery by an experienced surgeon,owner satisfaction is reported as 90-95%
• Most dogs are greatly improved within a few days(maximum improvement takes several weeks)
• Significant problems are surgical failure,pneumonia and chronic cough
• All dogs will cough more after surgery!
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Care after surgery
• Usually hospitalisedovernight (if nursingcare is available anddog is calm)
• Close attention toexercise and feedingfor the first fewweeks is important
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Post op feeding
• Risk of inhalation of food/fluids aftersurgery, especially in first 6 weeks
• Water only, no milk
• Feed a soft but firm food: pate consistency
• In long term, can re-introduce usual diet,but stop if coughing worsens
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Post op exercise
• Minimal initially and lead exerciseonly for 4-6 weeks in most cases
• May require halter or harness
• Well behaved dogs can be walkedto heel
• Swimming is not recommendedexcept under controlled conditions
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Why do dogs get LP?
• In most dogs it is considered “idiopathic”:no identified cause
• Often it is part of a generalised degenerationof the nerves
• In some breeds it is part of a definedneurological disease e.g. “Inheritedpolyneuropathy of Leonbergers”
• Has been linked to hypothyroidism
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Other symptoms
• Since it is often part of a generalised nervedegeneration, other symptoms may be seen
• In most dogs, these are not severe enough tobe important to the patient
• Common findings are poor hind footcarriage/stumbling
• If not severe, these do not preclude surgery
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Disease in Newfies
• Is it becoming more common, or morecommonly recognised?
• Is it part of a specific disease syndrome, ordoes it fit the “idiopathic” group?
• Is the outcome of surgery similar to otherbreeds?: probably, if performed by anexperienced surgeon
• Is the surgery harder than in other breeds?:probably, therefore best done by a surgeonwith substantial experience of the technique
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Summary of LPmanagement
• Surgery can bechallenging and hazardous
• Done well, surgery usually is very successful,although a small number will have problems withaspiration and pneumonia
• Not all dogs will benefit from surgery, althoughselecting the right cases can be difficult
copyright A Hotston Moore
copyright A Hotston Moore