Spinal Muscular Atrophy

Question 1

Pathology of SMA

Answer 1

Abnormality of the large anterior horn cells in the spinal cord (# cells reduced and progressive degeneration of the remaining cells is correlated with loss of function) large groups of atrophic fibers are dispersed among groups of normal or hypertrophic fibers

Question 2

What kind of disease is it?

Answer 2

Fatal recessive disease (2nd most common after CF)

Question 3

SMA type I

Answer 3

Childhood onset (acute); 0-3 mo
Rapidly progressive, death within first year common d/t resp complications. Resp distress present early (paradoxical breathing and bell shaped trunk)

Question 4

SMA type II

Answer 4

Childhood onset (chronic); 3-4 mo
Rapid progression that stabilizes, shortened lifespan

Question 5

SMA type III

Answer 5

Juvenile-onset; 5-10 years

Slowly progressive, mild impairment

Question 6

SMA primary impairments

Answer 6

muscle weakness, possibly contractures (secondary to limited fetal movement)

Question 7

SMA secondary impairments

Answer 7

Contractures
Scoliosis
Fractures
Hip subluxation/dislocation (secondary to weakness, dec WB/mechanical loading)
Dec resp capacity
Easy fatigability

Question 8

What is SMA type I characterized by?

Answer 8

Severe hypotonia
Inability to perform antigravity movement
Posturing in gravity dependent positions
Greatest weakness in proximal musculature
Impaired head control
Usually never attain ability to sit.

Question 9

What is SMA type II characterized by?

Answer 9

Moderate to severe hypotonia
Primarily proximal weakness but less severe (weakness usually greatest in hip and knee extensors and trunk musculature)
Delayed motor milestones
Most attain ability to sit
Range from never obtaining ability to sit to attained independent walking but later lost ability

Question 10

What is SMA type III characterized by?

Answer 10

Walking usually maintained lifelong
Proximal LE weakness and postural compensations
Trendelenburg gait
Lumbar lordosis
Difficulty arising from floor/climbing stairs
Upper extremity disability usually not noted
*Similar to DMD but typically ankle plantarflexion contractures not as frequent and UEs not as affected

Question 11

SMA type IV

Answer 11

Adult onset

Question 12

PT assessment

Answer 12

ROM, posture, MMT, Outcome measures.

Question 13

How will you differentiate the types?

Answer 13

only passage of time will tell. Tx should begin early.

Question 14

Education on feeding

Answer 14

breast feeding may be difficult, small frequent feedings, care to avoid aspiration, may end up with g-tube
* frequently require respiratory care

Question 15

What would you do to maintain flexibility and comfort?

Answer 15

ROM/Stretching, positioning, developmental activities/strengthening

Question 16

Positioning

Answer 16

Avoid supine if resp distress syndrome. Midline positioning if using supine, SL allow for midline play w/o gravity, monitor resp res in sitting (consider binder), external head and trunk control in sitting.

Question 17

At what age would you initiate use of a stander?

Answer 17

If not standing by age of 16-18 months equipment for standing as rate of fx ranges from 12%-15%, weightbearing decreases frequency of LE fx