Principles of neuromuscular disease Flashcards
What are some common physical examination findings of neuromuscular disease?
Gait abnormalities as either paresis or ataxia
Muscle loss
Altered respiratory effort or inspiratory stridor
What is the typical history of an animal with neuromuscular disease?
Weakness, difficulty rising, exercise intolerance, altered voice, change in musculature, regurgitation and lameness or pain
What are some common neurological examination findings of neuromuscular disease?
Tetraparesis +/- proprioceptive ataxia
Muscle atrophy or pain
Reduced spinal reflexes and muscle tone
Sensory deficits or self mutilation (chew feet)
What is also seen if there is an autonomic neuropathy?
Dilated pupils, decreased tear production, hyposalivation, bradycardia, constipation, urinary retention and reduced perianal reflex
What diagnostic tests should be performed if neuromuscular disease is suspected?
Biochemistry, haematology, urinalysis for CK, glucose, electrolytes and cholesterol, AChR antibodies or endrophonium response test (myasthenia gravis), Endocrine testing for hyperthyroidism or hyperadrenocorticism, Serology for neospora or toxoplasma, Imaging for neoplastic disease, CSF analysis to test nerve roots and CNS, Nerve and muscle biopsy to look for infection, endocrinopathy, denervation or infection, Metabolic tests for lysosomal storage disease, Genetic tests for Labrador myopathy or other inherited diseases
What gait abnormalities are seen with neuromuscular disease?
Paresis +/- ataxia Frequent sitting down Exercise intolerance Low head carriage Hypometria
What does electrophysiology tell you?
Localisation of nerve/muscle/junction
Myelin/axon
Specific nerves or muscles affected
What is an EMG?
Electromyogram
Normally silent and performed with needle electrodes under anaesthesia
What do fibrillation potentials indicate?
Denervation and inflammation
What are the characteristics of fibrillation potentials?
Biphasic
Sound like frying eggs/rain on a tin roof
Spontaneous action potentials of single myofibres
What do positive sharp waves indicate?
Denervation
What are the characteristics of positive sharp waves?
Positive deflection followed by shallow negative deflection
Sound like a dull thud/racing car driving by
Due to spontaneous action potentials of single myofibres
What are the characteristics of complex repetitive discharges?
Polyphasic
Serrated each one with a uniform shape
Sounds like a machine gun
What causes complex repetitive discharges?
Many myofibres firing in near synchrony
What is a pseudomyotonia on an EMG?
Myotonic potential with waxing and waning amplitude and frequency due to independent, repetitive discharges of singled, injured myofibres,
Unusual and sounds like a revving moped/chainsaw