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WorkinguptheWeaknessNeuromuscularDiseasesofDogsandCats

Simon Platt, BVM&S, MRCVS, Dip. ACVIM (Neurology), Dip. ECVN University of Georgia – College of Veterinary Medicine

Athens, GA, USA

Anatomy

•  NeuromuscularSystem–  Cellbodyintheventralhornofthespinalcord

–  Ventralnerveroot

–  Spinalnerve

–  Peripheralnerve

–  NeuromuscularjuncBon

–  Musclecell

LMN cell body

Peripheral nerve

Muscle

NM Junction

ClinicalSignsofNeuromuscularDisease

•  Similarsignswithdifferentunderlyingcauses

•  WeaknessworsenswithexercisewithmuscleandNMjuncBondisease

•  NOATAXIA!

•  Short-stridedchoppygaitvs.highsteppinggait

•  PlanBgradestance

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ClinicalSignsofNeuromuscularDisease•  Decreasedreflexes•  Decreasedmuscletone•  Severemuscleatrophy•  Animalswithseverediseasemayappearlikea“dishrag”

•  Ventroflexionincatscommon•  MustdifferenBatefromC1-T2spinaldisease

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SpinalReflexAssessment

NeuromuscularDisease

FurtherClinicalSigns•  Dysphagia•  Dysphonia•  Laryngealparesis•  Intercostalweakness•  Diaphragmparesis•  Contractures•  Urinary/faecaldysfuncBon?•  Spinalpain?

DifferenBaBonofspinalcordandneuromuscularlesions

•  C1-C5spinalcord?–  Tetraparesisorhemiwithnormalorincreasedreflexes

•  C6-T2spinalcord?–  Tetraparesisorhemiwithnormalordepressedthoraciclimbreflexes

•  Neuromuscular?–  Tetraparesiswithdepressedorabsentreflexesall4

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NeuromuscularDiseaseNeurodiagnosBcInvesBgaBon

•  Minimumdatabaseincl.CreaBnekinaselevel•  Thoracicandabdominalradiographs•  InfecBousdiseaseBters•  ‘Tensilon’Test/AnB-AchRABBter•  CSFtap

•  ElectrodiagnosBcs1.  Electromyography2.  NerveconducBonvelocity3.  CorddorsumpotenBals4.  F-waves•  Nerve&MuscleBiopsy

DiagnosBcExaminaBonElectromyography

•  Performedundergeneralanesthesia

•  Needleisinsertedintomusclebelly

•  Allmusclesassessed•  Spontaneouselectrical

acBvitypresentinmanycasesofmuscledisease

•  Notspecific

DiagnosBcExaminaBon

NerveConducBonVelocity•  Requiregeneralanesthesia

•  SBmulateproximalnervesegment

•  RecorddistalacBonpotenBals

•  ReducedvelocityusuallywithdemyelinaBon(occasionallywithaxonaldisease)

•  Normals=70-90m/sspeciesandnervedependent

DiagnosBcExaminaBonNerveConducBonVelocity

•  Requiregeneralanesthesia

•  SBmulateproximalnervesegment

•  RecorddistalacBonpotenBals

•  ReducedvelocityusuallywithdemyelinaBon(occasionallywithaxonaldisease)

•  Normals=70-90m/sspeciesandnervedependent

DiagnosBcProcedures

Muscle & Nerve Biopsy • Choose affected area • Guided by EMG • Muscle & nerve from same area • More than 1 sample • Fresh & Fixed specimens • Use recognised laboratory (UC SD - comparative NM lab – Dr Diane Shelton)

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DiagnosBcExaminaBonMuscleBiopsy

•  Surgicalprocedure•  Exposemuscle•  Cutcylinderawayfromforceps

1cm3

DiagnosBcExaminaBon

NerveBiopsy

•  Similarsurgicalapproach•  Fascicularbiopsy•  SciaBc-Bbialnerveorulnarnerve•  Minimalmorbidity•  Freshandfixed•  Ogennon-specificfindings

NerveBiopsyTechnique NerveBiopsyTechnique

NerveBiopsyTechnique DiagnosBcExaminaBonCisternalCSFTap

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AcuteNeuromuscularDisease

•  (Idiopathic)PolyradiculoneuriBs/Coonhound•  Botulism•  FulminantMyasthenia•  Tickparalysis•  SnakeBite•  OrganophosphateToxicity•  Hypokalemicmyopathy•  PolymyosiBs•  AorBcthromboembolism

AcutePolyradiculoneuriBs

•  LocalizaBonisthekey!•  MostcommoncauseforacuteLMNdiseaseindogs•  Veryrareincats•  CSFmaybemildlyabnormal•  ElectrodiagnosBcsorexclusiondiagnosis•  Self-limiBngdisease–4-6weeksintensesupporBvecare•  Steroidsdon’tseemtomakeadifference!•  RarelyrespiratorycomplicaBons

AcuteNeuromuscularDiseaseIdiopathicPolyradiculoneuriBs

(CoonhoundParalysis)

ChronicNeuromuscularDiseases•  V x•  I Immunemediated/infecBous(toxoplasma/neospora)

•  T Organophosphates,VincrisBne•  A x•  M Hypothyroid,Diabetes,Cushings,Electrolytes,

Hypoglycaemia(Insulinoma),Steroiduse•  I Idiopathic•  N ParaneoplasBc•  D DegeneraBve

InflammatoryMuscleDisease

•  Immunemediated(idiopathic)–checkforunderlyingneoplasia/ruleoutinfecBon/checkforotherimmunedisorders/respondstoimmunosuppressivetherapy

•  Infec3ous–Toxoplasma/NeosporaBtersandresponsetotrimethoprim-sulphonamideandclindamycintherapy

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IdiopathicPolymyosiBs•  MustruleoutinfecBousdiseases

•  Prednisone1-2mgbid14d-tapertoeffect

•  ConBnueforatleast4-6weeks

•  Up-to12monthsormoremaybeneeded

•  OtherimmunosuppressivessomeBmesneeded

•  Alwaysconsiderlymphoma

InflammatoryNerve/NerveRootDisease

•  Chronic•  Progressive•  Maybemorethanonelimbinvolved

•  Maynotappearpainful•  Alllimbsvs.brachialplexusneuriBsvs.radiculomyosiBs

InflammatoryNerve/NerveRootDisease

Causes•  Toxoplasma•  Neospora•  Immune-mediatedneuriBs?

Diagnosis•  Ruleouttrauma•  CSFtap/Bters/dietaryhistory•  Bonemarrow/lymphnodeaspirate•  EMG/Nervebiopsy

Treatment•  AnBbioBcs(clindamycin/trimothoprim)•  Immunosuppressives

ChronicPolyneuropathiesDegeneraBve

•  Purebred/Ogen3monthsold/otherlilermatesaffected?/inabook/ingeneralpoorprognosis

Metabolic(Diabetes/Hypothyroidism/Insulinoma)

•  Otherclinicalsigns?/rouBnelabtests/responsetotherapy

ChronicPolyneuropathies(Para)neoplasBc

•  Completetumorsearchiswarranted/canrespondtotumorresecBonortreatment

Toxic•  QuesBonowners/check

concurrentmedicaBons(vincrisBne)/performserumcholinesteraseandleadassays

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SupporBveCare

Treatment

•  Physiotherapy•  Hydrotherapy•  ElectricalsBmulaBon•  Splintstoaidextensionofjoints–

temporary•  ProtecBvefootwear•  Skincare•  GabapenBn10mg/kgPOBd

Summary•  Oncenerveormusclediseaseis

likely,thedifferenBalstobeconsideredassimilartootherneurologicaldiseases

•  SomediseaseshavegoodoutcomewithminortreatmentintervenBonsandsomecanbefatal

•  Theprognosiswillbedeterminedbytheclinicalsignsaswellastheunderlyingdisease

QUESTIONS?