Neuromuscular: Cheat sheet

Question 1

Duchenne Muscular Dystrophy

Answer 1

Most common inheritance pattern: XL only
Relative age of onset: Early childhood
Distinguishing features: 
  1. Gower sign
  2. Delayed milestones
  3. Symmetrical proximal muscle weakness
  4. Waddling gait

Question 2

Becker Muscular Dystrophy

Answer 2

Most common inheritance pattern: XL only
Relative age of onset: Adolescence- early adulthood
Distinguishing features:
1. Ambulation into adulthood

Question 3

Myotonic Dystrophy: Mild

Answer 3

Most common inheritance pattern: AD, maternal anticipation
Relative age of onset: 20s-70s
#Repeats: 50-150
Distinguishing features: 
  1.  Cataracts
  2. DM
  3. Hypotonia

Question 4

Myotonic dystrophy: Classic

Answer 4

Most common inheritance pattern: AD, maternal anticipation
Relative age of onset: 10-30
#Repeats: 100-1000
Distinguishing features: 
  1. Weakness
  2. Myotonia
  3. Cataracts
  4. Balding
  5. Cardiac arrhythmias

Question 5

Myotonic Dystrophy: Congenital

Answer 5

Most common inheritance pattern: AD, maternal anticipation
Relative age of onset: Birth-10
#Repeats: >2000
Classic signs 
1. + infantile hypotonia
2. Respiratory deficits
3. Intellectual Disability 
4. Infant mortality

Question 6

Spinal Muscular Atrophy

Answer 6

Most common inheritance pattern: AR (2% de novo)
Relative age of onset: Infancy – 12 months is average. Also prenatal and adult forms.
Multiple distinguishing features for each subtype

Question 7

Emery-Dreifuss Muscular Dystrophy

Answer 7

Most common inheritance pattern: XL (can be AD – LMNA or rarely AR).
Variable onset, severity and progression (0-20y = joint contractures; >20y = cardiac involvement)

Triad of features:

1. Joint contractures
2. Muscle weakness/wasting beginning in arms/legs
3. Cardiomyopathy

Question 8

Limb Girdle Muscular Dystrophy

Answer 8

Most common inheritance pattern: AR (LGMD2), AD is rare (LGMD1)
Relative age of onset: Late childhood/adolescence
Distinguishing features
1. Weakness in shoulder girdle (trouble raising arms)
2. Pelvic girdle (waddling gait)

Question 9

Facio-Scapulo-Humeral Dystrophy

Answer 9

Most common inheritance pattern: Only AD – somatic mosaicism common Caused by repeat contraction (DUX4 homeobox)
Relative age of onset: 5-25 years

Distinguishing features
Muscle weakness beginning in facial muscles, progresses to shoulders and upper arms/legs

Question 10

Charcot-Marie Tooth

Answer 10

Most common inheritance pattern: Mostly AD – duplication of PMP22 (can also be XL), AR is rare but can happen
Relative age of onset: 10s-20s

Distinguishing features

1. Distal muscle weakness/atrophy
2. Sensory loss
3. Foot drop
4. High-arched feet
5. Hammer toes

Question 11

Spinocerebellar Ataxias

Answer 11

Mostly AD
Usually later onset: 30s-40s
Many subtypes! General features: peripheral neuropathy,