Weakness and principle of neuromuscular disease Flashcards
What are the 3 areas that can be affected in the neuromuscular system?
LMN nerves: neuropathy
neuromuscular junctions NMJ: junctionopathy
Skeletal muscle: myopathy
When should we suspect neuromuscular disease?
weakness (generalised or focal)
exercise intolerance (walks normal then progressively weak/stiff)
What is an important clinical sign suggestive of neuromuscular disease in cats?
cervical ventroflexion
myopathy
not seen in dogs due to passive support from the nuchal ligament (not present in cats)
What others systems could cause weakness?
cardiovascular
respiratory
systemic/metabolic
neuro
What could make us suspicious that weakness is from CVRS? What dx tests can help confirm this?
Hx: cough, CHF
PEx: murmur, arrhythmia, pulse quality
Dx tests: bp, ecg, thoracic radiographs, echocardiography, cardiac troponin 1
What could make us suspicious that weakness is from systemic/metabolic? What dx tests help confirm this?
Hx/PEx: pale mm, pyrexia, distended abdomen
Dx tests: haematology, serum biochem, electrolyte analysis, blood gas analysis, abdomen/thorax ultrasound
What electrolytes can affect weakness?
hypokalaemia: hypokalaemic myopathy
hypocalcaemia: puerperal tetany/eclampsia
What would make us suspicious that weakness is from neuro?
is the patient neuro normal or abnormal?
what is the neuroanatomical location?
- mentation not affected by neuromuscular dz
- nociception is a sensory process, also not in neuromuscular disease
What clinical signs in weak animals (esp. dogs) raises suspicion for neuromuscular disease?
regurgitation! (make sure not vomiting aka passive after eating)
can be important CS for megaoesophagus
dysphonia: loosing bark especially with progressive weakness
paresis with minimal ataxia
palmigrade/plantigrade
inatct/mildly reduced postural reaction when weight supported
reduced spinal reflexes
focal or generalised muscleatrophy
What are the clinical signs for neuropathy specifically?
reduced to absent spinal reflexes
plantigrade/palmigrade stance
reduced to absent muscle tone
+/- neurogenic muscle atrophy
What are the clinical signs of a junctionopathy specifically?
normal to reduced spinal reflexes
exercise intolerance (may be normal on examination prior to exercise)
What are the clinical signs of a myopathy specifically?
often normal spinal reflexes
exercise intolerance
cervical ventroflexion in cats
+/- myalgia, muscle atrophy/hypertrophy
What diagnostic tests allow us to know its likely a myopathy vs neuropathy or junctionopathy?
muscle enzymes: elevated CK, AST, ALT
urinalysis: myoglobinuria
What does electromyography EMG tell us?
functional test
if electrically silent at rest: normal muscle or disuse atrophy
spontaneous electrical activity: neuropathy or myopathy
What does decreased amplitude on nerve conduction studies indicate?
axonal disease: neuropathy
