Muscle and Neuromuscular Junction

Question 1

Presynaptic Disorders

Answer 1

Botulism
Botuilin Toxin
Lambert Eaton Myasthenia Syndrome (LEMS)

Question 2

Lambert Eaton Myasthenia Syndrome (LEMS)

Answer 2

Antibodies to presynaptic calcium channel blockers.
Less vesicle release of calcium.
Strong assoc with small cell carcinoma

Question 3

Postsynaptic Disorders

Answer 3

Myasthenia Gravis

Question 4

Myasthenia Gravis

Answer 4

Most common disorder of neuromuscular junction.
Autoimmune
Antibodies to acetylcholine receptors (AChR).
Reduced number of ACh receptors and flattening of endplate folds.

Question 5

Myasthenia Gravis (treatment)

Answer 5

Acetylcholinesterase inhibitor - Pyridostigmine

Thymectomy (75% have hyperplasia or thymoma - CT to check).
Steroids/azathioprine

Question 6

Myotonia

Answer 6

Failure of muscle to relax after use

Chloride channels

Question 7

Inflammatory muscle disease

Answer 7

Polymyositis - symmetrical progressive proximal weakness developing over weeks to months, raised CK, responds to steroids.
Dermatomyositis - Heliotrope rash, clinically similar to above, 50% have underlying malignancy

Question 8

Degenerative muscle disease

Answer 8

Inclusion body myositis
Myotonic Dystrophy
Muscular Dystrophies

Question 9

Myotonic Dystrophy

Answer 9

Autosomal Dominant

Myotonia
Weakness
Cataracts
Ptosis
Frontal balding
Cardiac defects

Trinucleotide repeat disorder with anticipation