Muscular Dystrophy (MD) & Spinal Muscular Atrophy (SMA) Flashcards
1
Q
What is MD?
A
- Hereditary progressive disorder
- Most common serious muscle disease
- Characterised by muscle weakness from birth to late adulthood.
- Primarily affects skeletal muscle however smooth and cardiac muscle are also affected
- Dystrophic muscle appearance in all forms
2
Q
What are the types of MD?
A
- Duchenne
- Becker
- Congenital
- Fascioscapulohumeral
- Myotonic
3
Q
What is Duchenne MD (DMD)?
A
- Most common type
- No dystrophin in muscle, heart or brain
- Mean age of diagnosis is 5 years
4
Q
What are the primary impairments of DMD?
A
- Progressive weakness secondary to loss of myofibrils
- Present from birth but evident by 3-5yrs
- Mean IQ is 85, intellectual impairment and language delay common
- Also increased rates of ADHD, autism and OCD
5
Q
What are the secondary impairments of DMD?
A
- Contractures
- Cardiomyopathy
- Respiratory infections & reduced vital capacity
- Fatigue
- Possible obesity
6
Q
What is the role of dystrophin?
A
- Large rod-like cytoskeletal protein located on the inner surface of the plasma membrane of muscle fibres
- Major role is maintenance of muscle membrane structure
7
Q
What are the consequences of a loss of dystrophin?
A
- Segmental necrosis - large calibre fibres, e.g. trunk & legs are more prone to necrosis.
- Progressive muscle fibre loss with fibrous & adipose tissue replacement in continuing cycles of degeneration & regeneration
- Muscle susceptible to damaged caused by torsional forces during muscle contraction
- Elevated CPK levels
8
Q
What does the medical management of DMD involve?
A
- Aims to slow rate of decline & lessen impact of secondary complications
- Cortico-steroids now considered to be gold standard for ambulant boys with DMD
- RCTs have demonstrated cortico-steroids alter the natural course of DMD
9
Q
What are the benefits of steroid therapy?
A
- Preservation of muscle strength & motor function with ambulation to mid-teens
- Improvement & prolonged stabilisation of pulmonary function
- Preservation of cardiac function
- Delay in or prevention of need for scoliosis surgery
- Retention of upper limb strength
10
Q
What are the possible side effects of steroid therapy?
A
- Excessive weight gain
- Osteoporosis
- Slowing of growth
- Delayed puberty
- Behaviour changes
- Immune suppression
11
Q
What are the 3 orthopaedic surgery approaches for DMD?
A
- Minimalist: Limited to symptom relief
- Rehabilitative: Tendon lengthening transfers aimed at prolonging ambulation in callipers or orthotics
- Prophylactic tendon releases
12
Q
What is the incidence of scoliosis in DMD?
A
- If not treated with steroids, 90% chance of developing scoliosis within 2 years of loss of ambulation
- Management by spinal instrumentation and arthrodesis
13
Q
What are the characteristics of DMD during the early stage?
A
- Cognitive/language delays, behaviour issues may be first presenting symptom
- 50% delayed in walking (18mths)
- Toe walking may be evident
- Reduced head control or mild hypotonia (weak neck flexors)
- May be lordotic if weak gluteals, further increased with mild winging of scapulae.
- Positive Gowers sign may be evident from >3yrs
- No limitations in ROM typically before 5yrs
- Mild tightness in gastroc/ soleus & TFL
- Pseudo hypertrophy of calves
14
Q
What education is provided during the early stage of DMD?
A
- Diagnosis given by medical team
- Appropriate activity levels discussed including avoiding fatigue (don’t push through fatigue)
- Social/functional activities encouraged e.g. swimming, bike riding, ball play
- Importance of activities to promote respiratory function- aquatic therapy
- Consider family’s coping responses and goals
15
Q
What interventions are implemented during the early stage of DMD?
A
- Early intervention for development of mobility skills
- Daily manual stretches (calves, hamstrings, hip flexors, ITB)
- Activity levels maintain muscle strength at this stage
