Myopathies

Question 1

What are the three main type of muscular diseases?

Answer 1

Muscular dystrophies
Myopathies
Neurogenic disease

Question 2

What are muscular dystrophies?

Answer 2

Genetically determined diseases resulting in progressive deterioration

Question 3

What are myopathies?

Answer 3

Diverse group of conditions, grouped due to predominant effect on muscle

Question 4

What are neurogenic diseases?

Answer 4

Disease of peripheral nn/motor neurones, causing 2o skm atrophy

Question 5

What is the cause of Duchenne Muscular Dystrophy (DMD)?

Answer 5

Most common muscular dystrophy
X-linked recessive (30% spontaneous)
Caused by mutation in dystrophin gene, muscle fibres liable to break w/ repeated contraction

Question 6

What is the presentation of DMD?

Answer 6

Onset in early childhood

• global muscle weakness
• calf pseudohypertrophy (replace calf muscle w/ fat)
• gowers sign (turning prone to rise)

Question 7

What investigations are appropriate in suspected DMD?

Answer 7

CK (raised)

Genetic testing/muscle biopsy

Question 8

What is the prognosis of DMD?

Answer 8

Poor

Pts die as teens due to resp failure/cardiomyopathy

Question 9

What is Becker Muscular Dystrophy?

Answer 9

Less common, produces partially functioning dystrophin

Sx milder, better prognosis (pts survive til mid 40s)

Question 10

What is myotonic dystrophy?

Answer 10

AD condition, Cl- channelopathy
Shows anticipation
Characterised by muscle weakness/myotonia
Becomes apparent in adolescence (facial/lower limb weakness)

Question 11

What are the non-muscular features of myotonic dystrophy?

Answer 11

Cataracts
Frontal baldness
Mental impairment
Cardiac abnormalities

Question 12

What are the appropriate investigations in suspected myopathies?

Answer 12

Serum muscle enzymes/CK (raised in muscular dystrophies/inflammatory muscle disorders, normal in MG)
Electromyography (classical traces)
Muscle biopsy (differentiate b/w denervation/muscular disease)

Question 13

How should spasticity be managed?

Answer 13

Physio, gait retraining, remove exacerbating stimuli
Surgical management - tendon lengthening, releases for fixed deformities, electrostimulation therapy
Medical management - baclofen, dantrolene, benzo, botulinim

Question 14

How should contractures be managed?

Answer 14

Aim to prevent development
If contractures present refer to ortho
Physio/aids