Principles of Neuromuscular Disease Flashcards
What makes up the neuromuscular system?
- Nerves (LMNs)
- Neuromuscular junction
- Skeletal muscle
What are the types/locations of neuromuscular disease?
- Neuropathy
- Junctionopathy
- Myopathy
When defining the problem, what two cardinal signs help you suspect neuromuscular disease?
- Weakness WITHOUT ataxia
i. Short strides
ii. Stilted gait
iii. Not ataxic - Exercise intolerance
What history and physical exam findings may make you suspicious of neuromuscular disease?
Hx: Dysphagia Dysphonia Regurg Dyspnoea Gait abnormality
PE:
Muscle atrophy
Muscle hypertrophy
Myalgia
When you have weakness, what system could be involved?
- CVRS
- Systemic/metabolic
- Neurological
When working up a weakness case how can you rule out CVRS dz?
History of cough/CHF PE: Murmur, arrhythmia, hypotension, pulses Diagnostic test: NIBP Thoracic xray Echocardiography Cardiac toponin I
When working up a weakness case how can you rule out systemic/metabolic dz?
Pale MM, pyrexia, distended abdomen
Diagnostics:
Haem and biochem
If you have a cat with severe cervical ventroflexion, what electrolyte could be involved?
Myopathy related to hypokalaemia
If you have a dog that is very weak with marked fine tremors, what electrolyte could be involved?
Hypocalcaemia
How can you define the system in neurological cases?
- Is the patient neurologically normal or abnormal
2. Where is the lesion
What does a palmigrade/plantigrade posture suggest?
Seen in cats with neuropathies
Are the postural reactions usually normal or abnormal in a neuromuscular diseased animal?
May be normal - support their weight
Some so weak they cannot show proprioception
When are spinal reflexes reduced?
Neuropathy
What is marked muscle atrophy suggestive of?
Neuropathy (denervation atrophy).
Much more marked than disuse atrophy
What are the possible locations for neuromuscular disease?
Generalised
Focal (Cranial nerves)
Focal (Spinal nerves)
What would help you define the location to a neuropathy?
Reduced to absent spinal reflexes
Plantigrade/palmigrade stance
Reduced to absent muscle tone
+/- Neurogenic muscle atrophy
What would help you define the location to a junctionopathy?
Normal to reduced spinal reflexes
Exercise intolerance
What would help you define the location to a myopathy?
Often normal spinal reflexes
Exercise intolerance
+/- myalgia, muscle atrophy/hypertrophy
Is it always possible to localised to neuropathy/junctionopathy/myopathy?
Often not possible to go further than localising to neuromuscular
Most marked and severe signs tend to be neuropathies
What diagnostic tests can you perform to localise neuropathy/junctionopathy/myopathy?
Muscle enzymes (myopathy) Increased CK Increased AST Increased ALT Urinalysis (myopathy) Myoglobinuria (dark brown urine) Electrodiagnostics
What is electromyography?
Cannot determine aetiology
Needle into muscle and detect spontaneous electrical activity
Spontaneous activity = muscle pathology/denervated
Silent = normal muscle/disuse atrophy
Neuropathy or myopathy (rules out junctionopathy and metabolic cause)
What are nerve conduction studies?
Look further at nerve itself - stimulation
Differentiate neuropathy and myopathy
Neuropathy = decreased amplitude/slowed conduction velocity
Myopathy = normal
How can neuromuscular ddx be grouped?
- Generalised acute
- Generalised chronic
- Focal acute
- Focal chronic
Give some examples of generalised acute neuromuscular differentials…
Acute canine polyradiculoneuritis Acquired myasthenia gravis Botulism Hypocalcaemic Hypokalaemia
