196. Muscular Dystrophies

Question 1

What is Duchenne muscular dystrophy (DMD)?

Answer 1

Pseudohypertrophic progressive muscular dystrophy inherited as a recessive X-linked disorder with an incidence of 1 in 3300 male births

DMD is caused by a mutation in the dystrophin gene on the X chromosome.

Question 2

What causes the absence of dystrophin protein in DMD?

Answer 2

A mutation in the dystrophin gene on the X chromosome (Xp21)

Lack of dystrophin creates an unstable membrane in muscle fibers.

Question 3

What is the incidence of DMD?

Answer 3

1 in 3300 male births

Question 4

What percentage of female carriers of the DMD mutation show symptoms?

Answer 4

20%

Question 5

What are the common diagnostic methods for DMD?

Answer 5

• Genetic testing
• Muscle biopsy for dystrophin studies
• Elevated blood creatine kinase levels

Question 6

At what age do boys with DMD typically exhibit motor delays?

Answer 6

By 1 year of age

Question 7

What is Gowers sign?

Answer 7

Indicates weakness of proximal leg muscles in the hip and thigh

Question 8

What complications arise from muscular weakness in DMD?

Answer 8

• Skeletal deformities
• Restrictive lung disease
• Respiratory failure by age 20

Question 9

What is the typical life expectancy of males with DMD?

Answer 9

Few survive beyond their 30s

Question 10

What treatments are available for DMD?

Answer 10

• Symptomatic treatment
• Management of respiratory parameters
• Cardiac function maintenance
• Prednisone for strength improvement
• Scoliosis surgery

Question 11

What is Becker muscular dystrophy (BMD)?

Answer 11

Pseudohypertrophic benign muscular dystrophy inherited as a recessive X-linked disorder with an incidence of 1 in 20,000 male births

Question 12

How does BMD differ from DMD in terms of symptom onset?

Answer 12

BMD muscle weakness presents much later in childhood and worsens at a much slower rate than DMD

Question 13

What is the life expectancy for males with BMD?

Answer 13

Can survive into their 40s or beyond

Question 14

What is Emery-Dreifuss muscular dystrophy (EDMD)?

Answer 14

A syndrome of progressive muscle weakness with several genetic patterns of inheritance

Question 15

What are the genetic inheritance patterns of EDMD?

Answer 15

• X linked
• Autosomal dominant
• Autosomal recessive

Question 16

What is myotonic dystrophy (DM)?

Answer 16

Characterized by persistent contraction of skeletal and bulbar muscles (myotonic episodes) with delayed relaxation

Question 17

What genetic changes cause myotonic dystrophy type 1 (DM1)?

Answer 17

Expansion of a CTG-trinucleotide repeat causing an abnormality in the DMPK gene

Question 18

What distinguishes myotonic dystrophy type 2 (DM2) from DM1?

Answer 18

Results from mutations in the CNBP gene

Question 19

What are the prominent features of DM?

Answer 19

• Prolonged muscle contractions
• Cognitive impairment
• Cardiac arrhythmias
• Insulin resistance

Question 20

What triggers rhabdomyolysis in patients with muscular dystrophies?

Answer 20

• Lack of dystrophin
• Altered dystrophin protein
• Defects in cell membrane ion channels

Question 21

Which anesthetic agents should be avoided in patients with DMD and BMD?

Answer 21

• Volatile anesthetics
• Succinylcholine

Question 22

What are the anesthetic considerations for patients with muscular dystrophies?

Answer 22

• Heightened sensitivity to anesthetic agents
• Preoperative assessment of vital capacity
• Noninvasive ventilation support

Question 23

What is the risk associated with succinylcholine in patients with DM?

Answer 23

Can cause laryngospasm and precipitate rhabdomyolysis

Question 24

What are the common postoperative complications for patients with muscular dystrophies?

Answer 24

• Respiratory insufficiency
• Cardiac collapse
• Aspiration

Question 25

What is the recommended anesthetic approach for patients with undiagnosed hypotonia?

Answer 25

Consider total intravenous anesthesia (TIVA) with propofol for a short duration