Exertional myopathies and related disorders

Question 1

EquineRhabdomyolysisSyndrome - define

Answer 1

muscle cramping / pain that occurs usually during or
following exercise
aka - Monday morning disease, set-fast, azoturia,
myoglobinuria, tying-up

Question 2

Rhabdomyolysis - define

Answer 2

lysis of muscle fibres

Question 3

DDx for Rhabdomyolysis

Answer 3

lameness
aortoiliac thrombosis
colic
laminitis - stiff stilted gait
pleuritis
tetanus

Question 4

Diagnosisofexertionalrhabdomyolysissyndromes– duringepisode

Answer 4

clinical signs
stiff movements, pain, sweating, tachycardia, myoglobinuria
plasma CK and AST activities
rule out other diseases
v.dark urine

Question 5

Treatmentofacuteexertionalrhabdomyolysis

Answer 5

analgesics (NSAIDS, opiates)
IV or oral fluids - isotonic solution
diuretics
fluids + diuretics - maintain urine output to prevent/minimise nephrotoxic effects of myoglobin

Question 6

Diagnosisofexertionalrhabdomyolysissyndromes– betweenepisode

Answer 6

Exercise test - CK measurement - >100% rise is regarded as significant

Question 7

AetiologyofExertionalRhabdomyolysis - Acquired

Answer 7

Overexertion
Eccentric contraction
Metabolic exhaustion - hyperthermia + decr ATP
Oxidative injury
Electrolyte imbalance
Hormonal influence?
Infectious causes

Question 8

AetiologyofExertionalRhabdomyolysis - inherited

Answer 8

defective calcium regulation

Polysaccharide storage myopathy

Question 9

Recurrentexertional rhabdomyolysis (RER)

Answer 9

defect in calcium regulation
Probable autosomal dominant inheritance
Most common in young nervous fillies
Approximately 5% of TBs may be affected

Question 10

preventing RER

Answer 10

oral dantrolene – a calcium release channel blocker
high fat / low carbohydrate diet
rice bran, vegetable oil, commercial
regular exercise / turn out

Question 11

RER pathophysiology

Answer 11

Muscleis hypersensitivetocaffeine+otheragentsthatprecipitateCareleasefromthesarcoplasmicreticulum
Similarinsomerespectstomalignanthyperthermia

Question 12

polysaccharide storage myopathy 1 (PSSM1)

Answer 12

Heritable (autosomal dominant)
exertional rhabdomyolysis
occasionally muscle atrophy / weakness in draft breeds
high prevalence in some draft breeds (>50%)
Abnormality of glucose metabolism
mutation in glycogen synthase gene in skeletal muscle

Question 13

internalised nuclei in muscle is a sign of…

Answer 13

muscle regeneration

Question 14

treatment + management of PSSM1

Answer 14

high fat, low carbohydrate diet is beneficial
daily exercise
start with hand walking + incr gradually every day

Question 15

Prognosisforhorseswithgeneticformsofexertionalrhabdomyolysis

Answer 15

Many horses may still continue an athletic career with appropriate management
Racehorses perform well once fit.
Horses with probable underlying genetic predisposition always susceptible

Question 16

treating the exhausted horse

Answer 16

IV or oral fluids, supplemented with additional electrolytes
if required
rapid cooling
NSAIDs
check for evidence of rhabdomyolysis (CK and AST)

Question 17

“thumps” - define

Answer 17

synchronous diaphragmatic flutter

diaphragm beats in time with the heart

Question 18

coccygeal muscle injury

Answer 18

“limber tail; cold tail; rudder tail”
working breeds – labradors, pointers etc
pain at tail base; mild elevation in CK
recovery over several days
cold, exercise, swimming and prolonged caged, transportation  predispose

Question 19

coccygeal muscle injury - treatment

Answer 19

rest, NSAIDs

Question 20

TreatmentofMuscleStrainInjury - Low grade injuries - conservative

Answer 20

ice packs 1st 24 hours then warm compresses,
compressive wraps, NSAIDs, muscle relaxants, rest,
controlled physical therapy

Question 21

TreatmentofMuscleStrainInjury - High grade injuries - surgical (dogs)

Answer 21

surgical debridement, repair or tenomyectomy
friable - mattress pattern or tension relieving sutures
75% return to racing in acute gracilis ruptures

Question 22

fibrotic myopathy in horses

Answer 22

common in QH
usually semitendinosus
sometimes semimembranosus or gracilis

Question 23

fibrotic myopathy in horses - causes

Answer 23

muscle tear
IM injection
neuropathy

Question 24

fibrotic myopathy in horses - treatment

Answer 24

rest, NSAIDs, surgical resection of fibrous tissue/tenectomy

Question 25

fibrotic myopathy in horses - characteristic gait

Answer 25

slapping the foot down d/t extra fibrous tissue

Question 26

Fibrotic myopathy ‐ dogs

Answer 26

secondary fibrotic myopathy (e.g. gracilis seen especially in German Shepherds, Dobermans and Rottweilers

Question 27

Fibrotic myopathy ‐ dogs - characteristic gait

Answer 27

shortened stride with internal rotation of the foot, external rotation of the hock and internal rotation of the stifle during the swing phase.

Question 28

Fibrotic myopathy ‐ dogs - treament

Answer 28

surgery usually offers only temporary resolution | rest, ice, NSAIDs

Question 29

Infraspinatus / Supraspinatus contracture

Answer 29

occasionally follows obvious trauma pain in shoulder + reluctance to bear weight in acute stages chronic stages, supra and infrapinatus atrophy and fibrosis forelimb abduction, external rotation and extension usually unilateral

Question 30

Quadriceps contracture

Answer 30

follow Fx of distal femur in immature dogs with voluntary or enforced immobilisation - prolonged hyperextension of stifle - adhesions prophylaxis + early recognition essential as prognosis once advanced is poor Leg amputation may be only option rigid fixation, encouragement of stifle joint motion, or splinting in fixed position

Question 31

Myositis ossificans

Answer 31

secondary to trauma hip , shoulder, quadriceps and cervical regions Large middle aged active dogs Lameness from mechanical interference Surgical debulking is preferred treatment ossification of Supraspinatus tendon

Question 32

atypical myopathy

Answer 32

severe myoglobinurea acute severe onset in horses at pasture CK + AST severely incr muscle biopsy pre/post mortem fat accumulation in skeletal + cardiac muscle 75% mortality d/t systemic muscle failure