Neuromuscular disease Flashcards
What is the typical history seen with neuromuscular disease?
- Weakness
- Difficulty rising
- Exercise intolerance
- Altered voice
- Change in musculature
- Regurgitation
- Lameness, pain
What might be seen on physical exam in an animal presenting with neuromuscular disease?
- Gait abnormalities (paresis, ataxia)
- Muscle loss
- Altered respiratory effort or inspiratory stridor
What might be seen on neurological exam an animal presenting with neuromuscular disease?
- Tetraparesis +/- proprioceptive ataxia
- Muscle atrophy/pain
- Reduced spinal reflexes and muscle tone
- May see sensory deficits or self-mutilation
- BUT if you see paresis without ataxia, it’s likely to be muscular in origin
What clinical signs are seen in autonomic neuropathy?
- Dilated pupils
- Decreased tear production
- Hyposalivation
- Bradycardia
- Constipation
- Urinary retention
- Reduced perianal reflex
What gait abnormalities can be seen in neuromuscular disease?
- Paresis +/- ataxia
- Frequent sitting down
- Exercise intolerance
- Low head carriage
- Choppy and stilted gait (hypometria)
What does electrophysiology tell you about a lesion?
Localization and may support suspected diagnosis eg. see abnormal repetitive nerve stimulation in MG
What diagnostics can you use for neuromuscular disease?
- Biochem + Haem + Urinalysis = checking Creatinine kinase activity and Glucose, electrolytes, cholesterol
- Imaging - Neoplasia
- Serological tests- Neospora, Toxoplasma
- Endocrine testing - HypoT4, Hyperadrenocorticism
- AChR ab, Edrophonium response test - myasthenia gravis
What is a normal EMG (electromyogram)?
It is silent and a fat signal
What are fibrillation potentials in an EMG?
They are spontaneous action potentials of single myofibers, biphasic
Can be due to denervation or inflammation
Sounds like frying eggs/wrinkling of tissue paper/rain on a tin roof
What are positive sharp waves in an EMG?
Positive deflection followed by shallow, negative deflection; spontaneous action potentials of single myofibers.
Can be due to denervation
Sounds like a race car driving by
What are complex repetitive discharges?
Due to many myofibers firing in near synchrony
Polyphasic and serrated, usually uniform shape
Sounds like a machine gun
What is a myotonic potential?
Due to independent repetitive discharges of singled, injured myofibers
unusual
Frequency and amplitude waxing and waning
Sounds like a revving motorcycle or chainsaw
Are electrodiagnostics useful?
Yes They provide definitive evidence of neuromuscular dysfunction Localization (nerve vs muscle) Extent and severity Treatment monitoring Prognosis Which muscles/nerves are affected
What are the components of the neuromuscular system?
- Neuromuscular junction
- Peripheral nerve
- Muscle
What is the signalment of immune-mediated myasthenia gravis?
- Older than 3 months, any age
- Breed: GSD, Lab, Golden Retrievers
What are the three forms of immune-mediated myasthenia gravis?
- Focal MG with megaesophagus/regurgitation (30%)
- Generalized MG exercise intolerance with megaesophagus (60%)
- Fulminating form (come into the clinic flat and depressed)
What is the pathophysiology of immune-mediated myasthenia gravis?
Ach receptor reduction due to autoantibodies
How is immune-mediated myasthenia gravis diagnosed?
- Edrophonium chloride (tensilon test)
- Serology
- Check for paraneoplastic disease (thymoma)
What is the treatment and prognosis of immune-mediated myasthenia gravis?
- Pyridostygmine (start low and increase dose)
- Immunomodulatory drugs (?)
- Relatively fair prognosis
What is the signalment of congenital myasthenia gravis?
- 6 to 8 weeks old
- Breed: Jack Russel Terrier, Springer spaniels, mini dachshund
What is the pathophysiology of congenital myasthenia gravis?
Decrease of AChR
How is congenital myasthenia gravis diagnosed?
- Tensilon test (edrophonium chloride)
- Muscule biopsy of intercostal muscles
What is the treatment of congenital myasthenia gravis?
Pyridostygmine
What are equine botulism outbreaks associated with?
Contaminated feed
