Motor Disorders

Question 1

What are muscular dystrophies?

Answer 1

Inherited group of progressive myopathic disorders - defective genes- for normal muscle function
Duchenne + Becker - X linked recessive- on dystrophin gene on chr 21.
Duchennes- present in early childhood w/ weakness in proximal muscles in legs. Severe disability and death at late teens. No cure.

Becker: muscle dystrophy present late, milder clinical weakness.

Question 2

Whatbare some causes of proximal myopathy?

Answer 2

Proximal muscle weakness: diff rising from chairs, getting out of bath.

Prolonged high steroid therapy 
Cushings syndrome
Thyrotoxicosis
Hypothyroidism (occasionally) 
Osteomalacia
Hypokalaemia
Prolonged alcohol abuse
Drugs: diamorphine, lithium, quinine, chloroquinine

Question 3

Whats myasthenia gravis?

Answer 3

Aquired condition- characterised by weakness + fatiguability of proximal limbs, ocular and bulbar muscles. Heart not affected.
3rd decade , 2x F>M

Aeriology
Unknown! Serum IgG apAbs to ACh receptors in postsynaptic membrane of the neurooMuscular J -> caussing neural loss.
Assc w/ thymic hyperplasia in 70%

Question 4

How would you investigate for Muasthania gravis?

Answer 4

Serum -ACh receptor Abs-90% sensitive
+ve Tensilon test- 10mg injection- edrophinium- anticholinesterase - - rapid temp improvement

Nerve stimulation- decrement evoked potential followinh motor stimulation.

Mediastinal imaging- CT/MRI to look for thyoma.

Question 5

Management of myasthania Gravis

Answer 5

Anticholinesterase - pyridostigmnie, neostigmine.

W/o thyoma- anticholinestares meds alone for mild.

Question 6

Myopathies- what are they?

Answer 6

Weakness predominant f
Inherited (muscular dystrophies)
Inflamatory lesions: commonest- polymyositis + assc w/ drugs, toxins, endocrine disease.

Other group:
Produces weakness of the limb girdles (proximal myopathy) typicly the pt unable to rise from seated position, without the use of their arms.
Severe Hypokalaemia- generalised flaccid weakness.