Flashcards in Muscular Dystrophy (MD) & Spinal Muscular Atrophy (SMA) Deck (25):
What is MD?
- 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
What are the types of MD?
What is Duchenne MD (DMD)?
- Most common type
- No dystrophin in muscle, heart or brain
- Mean age of diagnosis is 5 years
What are the primary impairments of DMD?
- 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
What are the secondary impairments of DMD?
- Respiratory infections & reduced vital capacity
- Possible obesity
What is the role of dystrophin?
- 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
What are the consequences of a loss of dystrophin?
- 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
What does the medical management of DMD involve?
- 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
What are the benefits of steroid therapy?
- 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
What are the possible side effects of steroid therapy?
- Excessive weight gain
- Slowing of growth
- Delayed puberty
- Behaviour changes
- Immune suppression
What are the 3 orthopaedic surgery approaches for DMD?
- Minimalist: Limited to symptom relief
- Rehabilitative: Tendon lengthening transfers aimed at prolonging ambulation in callipers or orthotics
- Prophylactic tendon releases
What is the incidence of scoliosis in DMD?
- If not treated with steroids, 90% chance of developing scoliosis within 2 years of loss of ambulation
- Management by spinal instrumentation and arthrodesis
What are the characteristics of DMD during the early stage?
- 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
What education is provided during the early stage of DMD?
- 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
What interventions are implemented during the early stage of DMD?
- Early intervention for development of mobility skills
- Daily manual stretches (calves, hamstrings, hip flexors, ITB)
- Activity levels maintain muscle strength at this stage
What are the characteristics of DMD during the early school age stage?
- Clumsiness, falling, atypical gait pattern, waddling, can’t keep up with peers, usually can’t run or jump
- Gowers sign usually present after 1 trial of floor to stand
- Pseudohypertrophy of calves, deltoids, quads, forearm extensors.
- Muscle weakness in neck flexors, abdominals, interscapular muscles & hip extensors
- Gait: Increased BOS, lateral trunk sway (compensated Trendelenburg), toe walking, lack of reciprocal arm swing, lordosis with forward shift of centre of gravity.
- Pulmonary impairment begins (reduced vital capacity)
- Community mobility limited by inability to negotiate stairs
What does physiotherapy for DMD involve during the early school age stage?
- Assessment of functional impairment, disease progression, muscle weakness, contracture, respiratory function (chest wall excursion, cough strength, spirometry)
- Goal setting with family
- Visit school to educate & encourage participation in program with fatigue avoidance
- Equipment provision for independence - scooters
What does the evidence show regarding exercises in DMD?
- Controversial as both over- exertion and immobilisation are detrimental.
- Graded resistance exercise studies show varied results
- Resisted exercises should not be given for young children as they don’t typically have significant weakness in the early stages of the disease
- Can use submax for abdominals, hip extensors/abductors & knee extensors.
- Encourage cycling & swimming
- Breathing exercises for vital capacity & forced expiratory flow rate
What are the characteristics of DMD during the school age stage?
- Increasing falls
- More general muscle weakness
- Increased fatigue while walking
- Posterior calf contracture
- Increased intoeing (use TFL as a compensation for psoas weakness)
- Pulmonary impairment (decreased max VC)
What does physiotherapy for DMD involve during the school age stage?
- Aim to slow contractures with positioning & ROM program
- Modify PE at school
- Night splints for ankles
- Prone positioning with feet over end of mattress
- Check spine for scoliosis particularly after loss of walking ability
- Wheelchair introduced for community mobility, motorised for independence.
- Information on recreational activities, continue to encourage swimming
- Monitor respiratory function, teach use of Ambu bags and cough assist machine
What are the characteristics of DMD during adolescence?
- Progression of disability through weakness & contractures
- Loss of walking ability
- Difficulty with transfers & ADLs
- Can consider surgery and orthoses
What does physiotherapy for DMD involve during adolescence?
- Continued management of muscle & joint ROM with passive stretches
- Orthotics to minimise pull in to equinovarus
- Provision of equipment
- Stretches & mobility for ULs as contractures are now more likely
- Respiratory function monitoring & training
- Ongoing monitoring of spine
- Pre & post op (scoliosis, TA lengthening)
What is spinal muscular atrophy (SMA)?
- 2nd most common group of fatal recessive diseases after CF
- Reduced number of large anterior horn cells
- Progressive degeneration of remaining cells correlates with loss in function
- Diagnosis through EMG, muscle biopsy, genetic testing
What are the 4 types of SMA?
I. Childhood onset Werdnig-Hoffman (acute)
II. Childhood onset Werdnig-Hoffman (chronic)
III. Juvenile onset Kugelberg-Welander
IV. Adult onset SMA