Duchenne Muscular Dystrophy

Question 1

Duchenne Muscular Dystrophy (DMD)

Defintion & Epi & Etiology

Answer 1

A genetic disorder characterized by progressive weakening & degeneration of mm leading to activity limitations and participation restrictions

Epi:
- ONLY males - X-linked recessive pattern
- Life expectancy typically 20-30 years

Eti:
- Mutation of the dystrophin gene = leads to tissue being prone to damage

Question 2

Diagnosis

(3)

Answer 2

1. Genetic Testing
2. Elevated creatine kinase (breakdown enzyme of mm)
   Marker for mm breakdown is 50-200x more elevated
3. Muscle biopsy finding

Question 3

Typical Progression

(4+3)

Answer 3

Clinical signs typically become apparent between 2-5 years of age

Early motor milestones are achieved at expected ages
- eg. rolling, sitting, crawling, walking

Impairments become more apparent with high level gross motor activities
- eg. running, jumping - start seeing these S/S first

Progressive mm wasting & weakness
- Lower limbs > upper limbs
- Proximal > distal - trunks/glutes
Few conditions that do that
- Muscles of the face, eyes, speech, swallowing, & sphincter are typically not involved

Question 4

Typical Progression: Age Ranges

(4)

Answer 4

3-6 years old
- Difficulty w/ running

6-8 years old
- Difficulty w/ walking

8-12 years old
- Start becoming W/C dependent

12+
- Completely dependent

Question 5

S/S

(6) + 9

Answer 5

Waddling Gait
- INC risk of falls
- Wide stance, shift over to bring CoG over stance leg (d/t weak glutes), & circumduct leg when they lean off stance leg

Gower’s Manuever
- Difficulty w/ standing up normal d/t proximal weakness
- Climb up their legs w/ use of arms

Psuedohypertrophy of the calves
- Enlargement d/t fat deposits

Lumbar Lordosis
- To maintain CoG in BOS

Wide stance w/ ER of LE
- INC BOS - do NOT want to correct this - it is the ONLY reason why they can stand
- ** Want them to maintain strength & function for as long as they can - unproductive to address it b/c it is PROGRESSIVE

Toe Walking
- mm imbalance - PF are stronger & tighter while DF are weak

Picture (pg. 355)
1. Shoulders and arms are held back ackwardly when walking
2. Sway back
3. Weak butt mms
4. ** Knees may bend back to take wt
5. Pseudohypertrophy of calves
6. Tight heel cord, child may walk on toes
7. Weak mm in front of leg cause “drop foot” & tiptoe contracture
8. Thin, weak quads
9. Belly sticks out d/t weak belly mms

Question 6

Associated Problems

(5) +

Answer 6

Cardio-respiratory Function
- Weakness in mm of respiration > DEC respiratory function
- Approx. 70% die d/t pulmonary complications
- Cardiomyelopathy
Impaired strength & structure of cardiac mm cells
Under stress from constant contractions = death

Cognitive Function
- Approx 30% have non-progressive intellectual impairments

Obesity - 2 reasons:
1. Dietary intake > energy expenditure (sedentary - W/C bound)
2. Steriod therapy used to slow the progression of mm weakness also contributes to obesity

Gastrointestinal System
- Constipation and impaction due to DEC motility (DEC mobility overall

Spine
- INC lordosis during ambulatory stage
- INC scoliosis during non-ambulatory stage (W/C bound)
Majority will develop scoliosis requiring Sx b/c if left untreated it can act as a restrictive lung disease & INC pulmonary function risk
Can also DEC discomfort in sitting

Question 7

Medical Management

(3)

Answer 7

Steriod Therapy
- Used to preserve mm function, respiratory function, cardiac function & delay scoliosis
- Use of prednisone & deflazacort has shown to prolong ambulation up to 3 years
- Increase risk of osteoporosis, weight gain, cataracts, & slowing of physical growth

Mechanical Ventilation
- BiPAP = Bi-level Positive Airway Pressure
2 different levels of air pressure. Inhalation = higher pressure & exhalation = lower pressure

Surgery
- Scoliosis correction & spinal stabilization - if curvature gets around 20-30 degrees
Bracing is ineffective
- Tendon (contracture) release used to improve alignment & function
Also easier for the caregiver when pt is not in contracture positions

Question 8

PT Intervention

(9)

Answer 8

1. Avoid agressive strengthening (especially eccentric contractions)
   Already have high levels of creatine kinase - do NOT have the ability to reover from strengthening exercises (microdamage)
2. Stretching & ROM exercises - Contraction prevention > maintain function for as long as possible & easier for caregivers later on
3. Gait Training - Keep ambulating for as long as possible - NOT trying to “fix” their gait
4. Education on overexertion (stop when tired) & energy conservation
5. Respiratory exercises
   Breath stacking, assistive cough & incentive spirometer
6. Transfer Training - at some point LE will weaken > can use UE to help w/ t/f - ie sliding board (elbow ext, scap depress to lift up & shift)
7. Equipment selection (W/C, transfer lift, power mobility - when they lose strength in arms)