Muscle & Nerve Disease Flashcards
Think about what sort of way muscle diseases could present?
- Babies may have poor feeding, failure to thrive & floppy
- Weakness
- SOB from resp muscles
- Poor swallowing or aspiration
- Cardiomyopathy
- Cramp, pain, myoglobinuria
- Wasting or hypertrophy
- Reduced tone & reflexes
- Motor Weakness
What is myoglobinuria?
Myoglobin leaked from muscles that are breaking down due to certain muscle diseases.
Itll appear after exercise as black urine
List the classifications of muscle disorders?
- Dystrophies
- Chanellopathies
(ion channel problems -> unrelaxable or weak muscles) - Metabolic muscle diseases
- Inflammatory muscle diseases
- Congenital Myopathies
- Iatrogenic
Name a drug that can cause iatrogenic muscle disease?
Statins
They can cause muscle degeneration leading to pain & weakness
What special blood test could you do for muscle disease?
Creatine Kinase (CK) Elevated in muscle damage
What investigations are common for muscular diseases?
- History & exam
- Creatine Kinase
- Electromyography
- Biopsy
- Genetic Tests (Most muscular dystrophies are genetic)
How does electromyography (EMG) work?
APs within a muscle measured (either surface or intramuscular) to assess its function.
It can be routine (tests a whole motor unit) or Single Fibre (Assesses just one motor fibre at a time)
List some muscular dystrophies?
- Duchenne’s MD & Becker’s MD
- Facioscapulohumeral
- Limb Girdle MD (Proximal limb weakness)
Describe a channelopathy?
Familial Hypokalemic Periodic Paralysis causes episodes of sudden muscle weakness lasting seconds -> days
Can also be Familial Hyperkalemic Periodic Paralysis
List some types of metabolic muscle disease?
Endocrinopathies such as thyroid or cushing’s disease can affect the muscles.
Carb or Lipid metabolism problems can affect the ability to produce ATP for muscle contraction.
Carb will be most pronounced on heavy exercise and Lipid on prolonged excercise)
What are the subtypes of Inflammatory Muscle Disorders?
Polymyositis
Dermatomyositis (A paraneoplastic syndrome of muscle weakness and rash)
How would you investigate/treat Inflammatory Muscle Disorders?
Biopsy to inspect inflammatory cells, both diagnoses and differentiates between polymyositis and dermatomyositis.
Steroids and immunosuppresants
What is myasthenia gravis?
Fatigable weakness in skeletal muscles
Most often noticed in the eye muscle (cos they move so much) so your fine in the morning but by the afternoon you start getting ptosis and diplopia
Notably does not affect the reflexes, any sensory nerves or cause the muscles to waste
What causes myasthenia gravis?
An antibody blocks ACh receptors in the NMJ.
Its fatigable because early in the day you produce lots of ACh so it can compete with the antibody but by the end of the day its depleted and the antibody wins out so you get weaker until you rest again
What investigations can you do for Myasthenia Gravis?
- Antibody Tests
70% +ve & takes a while - CT chest to exclude a thymoma
- Electromyography