Muscle Dystrophies and Spinal Muscle Atrophy

Question 1

Muscular Dystrophy

Answer 1

• Definition: group of hereditary myopathies
• Characteristics:
  
  • Progressive muscle weakness, deterioration, destruction, and regeneration of muscle fibers
  • Muscle fibers gradually replaced by fibrous and fatty tissues
• Types
  
  • Beckers dystrophy
  • Myotonic dystrophy
  • Limb girdle dystrophy
  • Facioscapulohumeral dystrophy

Question 2

Congenital/myotonic muscular dystrophy

Answer 2

birth

dominant

Typically slow with significant intellectual impairment

Question 3

Duchenne’s Muscular Dystrophy

Answer 3

• Incidence
  
  • One of the most prevalent and disabling types of MD
  • Between 1/3500 male births
• Prognosis
  
  • Mortality usually due to respiratory or cardiorespiratory insufficiency
  • Many are surviving into their 30s
    
    • New challenges for therapy, education, and vocation

Question 4

Etiology Duchenne’s Muscular Dystrophy

Answer 4

• Sex linked recessive disorder
• Abnormality on X chromosome at band Xp21
• Results in a disorder of encoding dystrophin and dystrophin associated proteins (DAP)
• Dystrophin acts as an anchor in the intracellular lattice to enhance tensile strength
• If dystrophin is absent from the muscle 🡪 fragility in the muscle membrane during muscle contraction + relative muscle hypoxia as a result of an aberrant vascular response to exercises
• Early breakdown of muscle fiber plasma membrane

Question 5

Duchenne’s Muscular Dystrophy Characteristics

Answer 5

• Creatine kinase is elevated early in the disease
  
  • Present at birth long before symptoms are present
• Muscle biopsy shows degeneration with loss of fibers, variation in fiber size, and a proliferation of connective and adipose tissue

Question 6

Duchenne’s Muscular Dystrophy: Clinical Presentation

Answer 6

• Insidious onset
  
  • May be misdiagnosed
• Early symptoms
  
  • Reluctance to walk/run at appropriate ages
  • Falling
  • Difficulty with stairs
  • Toe walking
  • Clumsiness
  • Pseudohypertrophy
    
    • Gastroc
    • Deltoids
    • Quads
    • Forearm extensors
  • Proximal muscles weak early on
  • Weakness of hip and knee extensors early
• Gower’s sign
  
  • Initial weakness of the neck/trunk flexors, hip extensors, and interscapular muscles
• Intellectual impairment
• Emotional disturbance
• With progression
  
  • Exaggerated lordosis
  • Wide BOS
  • Waddling gait
  • ITB contracture
  • Heel cord contracture
• Loss of unassisted ambulation at ages 9-10

Question 7

Duchenne’s Muscular Dystrophy: Medical Intervention

Answer 7

• Steroids
  
  • Prolong life by 3 years
  • Improve isometric UE strength by 60%
  • Improve isometric LE strength by 85%
  • Improve pulmonary and cognitive function
  • Side effects
    
    • Weight gain
    • Growth suppression
    • Cataracts
    • Osteoporosis
• Other interventions
  
  • Myoblast transplant
  • Gene therapy
  • Cell based replacement therapy
  • Creatine
    
    • Improved muscle strength/endurance
    • Less joint stiffness
• Surgical interventions
  
  • Muscle releases (Achilles, fasciotomy of TFL/ITB)
  • Scoliosis stabilization

Question 8

Prognostic factors Duchenne’s Muscular Dystrophy

Answer 8

• Timed functional activities closely related to muscle strength and predictive of loss of ambulation
  
  • 10M walk/run time greater than 9 seconds predicts loss of ambulation within 2 years
  • Inability to rise from the floor predicts loss of ambulation within 2 years
  • 10M walk/run time greater than 12 seconds predicts loss of ambulation within a year

Question 9

Duchenne’s Muscular Dystrophy: Evidence Based Tests and Measures

Answer 9

• Northstar Ambulatory Assessment
• The Performance of Upper Limb for Duchenne
• Brook Scale
• Vignos Scale
• Egen Klassifikation Scale

Question 10

Vignos Scale

Answer 10

1-10 scale with 1 being able to walk and climb stairs without assistance and 10 being confined to bed.

Question 11

Duchenne’s Muscular Dystrophy: PT Role

Answer 11

• Early diagnosis
• Education, referral, and support for the family
• Weight control
• Sleep and respiratory concerns
• B&B concerns
• Goals
  
  • Prolong function
  • Prevent contractures/deformities
  • Adapt equipment
  • Encourage peer and community interaction
  • Pain control
    
    • Many experience spasms and pain
    • Massage and gentle stretching appear to help

Question 12

DMD: Interventions for Infancy-Preschool Age

Answer 12

• Characteristics
  
  • May see developmental delay related to weakness
  • Mild tightness of the gastroc/TFL
• PT goals
  
  • Family support and education
  • Consider daily ROM and night splinting

Question 13

DMD: Interventions for Early School Age Period Characteristics

Answer 13

• Characteristics
  
  • Limitations in activity more apparent
    
    • Clumsiness
    • Falling
    • Difficulty with stairs
    • Rising to standing/running
    • Gait deviations
      
      • Increased BOS
      • Compensated Trendelenburg
      • Toe walking
      • Lordosis with shoulder retraction
      • Lack of arm swing

Question 14

DMD: Interventions for Early School Age Period

Answer 14

• Family support and education
• Obtain baseline data on ROM/MMT
• Strength and exercise
  
  • Widely accepted that eccentric exercise and immobilization are detrimental
  • Key muscles: abdominals, hip ext/abd, knee extensors
• Maintain ROM/flexibility
  
  • May not be able to prevent contractures, but can slow development
  • Key muscles: gastrocs, HS, and TFL
  • 1-2x daily, 10 reps, 30-60 seconds
  • Night splints in combination with daily stretching most effective; can prolong ambulation
• Cycling, swimming, and standing for 2-3 hours daily
• Respiratory function
  
  • Measure RR
  • Chest wall excursion
  • Coughing
  • Secretion clearing
  • Spirometry
  • Breathing exercises
  • Inspiratory muscle training
• Monitor progression
• Consider need for other mobility options (MWC, scooters, PWC)
  
  • Risk for falls if ambulation continues past when it is feasible
  • Risk for scoliosis increases once the child is nonambulatory

Question 15

DMD: Interventions for Adolescent Period

Answer 15

• Impairments
  
  • Considerable deterioration in function
    
    • Loss of walking
    • Reliance of powered mobility

Question 16

DMD: Interventions for Adolescent Period

Answer 16

• UE considerations
  
  • Encourage participation in ADLs as much as possible
    
    • May need adaptive equipment for self feeding
  • UE ergometry program
  • Focus on maintenance of muscles needed for transfers
• LE considerations
  
  • Gentle stretching (may add hip flexors, long finger flexors, shoulder, elbow, forearm, and wrist musculature)
• Respiratory function
  
  • Position of the spine is crucial: N to slightly extended is best to prevent scoliosis (loads facet joints and prevents rotation and lateral flexion)

Question 17

DMD: Interventions for Adolescent Period

Answer 17

• Continuation of standing/walking
  
  • Standers strongly encouraged
  • Walking programs
    
    • KAFOs with standby assistance
  • Bracing/therapeutic walking based on
    
    • Obesity
    • Residual muscle strength
    • Absence of severe contractures
    • Timely application of braces
    • Motivation of the family/child
• Surgical correction
  
  • May be necessary to prolong ambulation
  • Personal decision

Question 18

DMD: Interventions for Adolescent Period 2

Answer 18

• Equipment
  
  • Functional mobility
    
    • Stand pivot transfers will be replaced by one or two person lifts / lift equipment
  • Sliding board is not appropriate
    
    • UE weakness
  • Toilet and shower equipment
  • Powered mobility
    
    • Transition from powered scooter to standard power chair
      
      • Needed for use on buses, cars, etc.
  • Consider a urinal to decrease the need for transfers
  • Airflow mattress, egg crate, or memory foam/hospital bed

Question 19

DMD: Interventions for Adults

Answer 19

• Respiratory considerations
  
  • After age 18, FVC and PEF decline
  • Respiratory failure/infection are common contributing factors to death
  • Assisted ventilation can prolong life
    
    • Daytime intermittent positive pressure ventilation via mask / nasal cannula
    • Nocturnal bilevel positive airway pressure (BiPAP)
    • Negative pressure ventilators
    • Suctioning
  • Breathing exercises
  • Postural drainage

Question 20

3 types of spinal muscle atrophy

Answer 20

infantile werdnig hoffman

intermediate type 2

juvenile Kugelberg-Welander

Question 21

Spinal Muscular Atrophy etiology and characteristics

Answer 21

• Etiology
  
  • All are autosomal recessive disorders
  • Located on chromosome 5
  • Affect the anterior horn
• Characteristics
  
  • Wasting and weakness of the muscles
  • No sensory disturbances

Question 22

diagnosis for spinal muscle atrophy

Answer 22

• Clinical presentation
• EMG
  
  • Denervation with fibrillations and a paucity of motor units
• Muscle biopsy
• Muscle ultrasound
• Genetic testing
• Normal cardiac tissue

Question 23

SMA Special Examinations to Consider

Answer 23

• Clinical presentation
• EMG
  
  • Denervation with fibrillations and a paucity of motor units
• Muscle biopsy
• Muscle ultrasound
• Genetic testing
• Normal cardiac tissue

Question 24

SMA type 1 onset, characteristics, mortality

Answer 24

• Onset: almost always noted in the first 3 months of life
• Characteristics
  
  • Decreased fetal movement
  • Hypotonia but appear alert and responsive
  • Difficulty feeding
  • Respiratory distress
  • Muscle wasting
  • Few spontaneous movements
  • DTRs decreased or absent
• Mortality
  
  • Limited lifespan
  • Respiratory failure
    
    • Dependent on aggressiveness of treatment

Question 25

Type I: Infantile Werdnig-Hoffman secondary impairments, PT goals

Answer 25

• Secondary impairments
  
  • Scoliosis
  • Contractures
  • Decreased respiratory capacity
  • Fatiguability
• PT goals
  
  • ROM
  • Feeding
  • Positioning
  • Respiratory care
  • Select developmental activities
  • Assistive technology
  • Limited use of prone due to difficulty lifting head, inhibition of abdominal expansion and diaphragmatic depression
  • Breathing may become difficult in upright as well

Question 26

SMA type 2 onset, characteristics, goals

Answer 26

• Onset
  
  • Usually diagnosed at 3-6 months of age
  • Also affects infants, but not as severely
• Characteristics
  
  • Floppy, slow to develop motor milestones
  • Weak trunk/extremities with muscle atrophy
  • Few have feeding problems
  • Fine extremity tremors
  • May or may not learn to walk
  • Most require orthotic intervention
• PT Goals
  
  • Encourage stance
  • Prevent deformity
  • Respiratory interventions
  • Adapt play/writing tools

Question 27

SMA Type III: Juvenile Kugelberg-Welander

Answer 27

• Onset
  
  • Diagnosed between 1 and 10 y/o
• Characteristics
  
  • Slowly progressive weakness
    
    • Mild impairment
  • Proximal muscles are usually involved first