Muscular Dystrophies Flashcards
Spinal Muscular atrophy Muscular dystrophy- Duchenne/ becker's Facioscapulohumeral muscular dystrophy
What is spinal muscle atrophy?
- A disease of progressive motor weakness
- with loss of alpha motor neurone in the anterior horn cells of spinal cord
- significant variability in severity of disease
What is the epidemiology of spinal muscle atrophy?
- Most common genetic disease resulting in death during childhood
- 1 in 10,000 live births
- Progressive weakness starts Proximally and moves distally
- Autosomal RECESSIVE
-
Survivial Motor Neurone (SMN) gene mutation on chromosome 5
- Present in 90% cases of spinal muscle atrophy
- A telomeric gene deletion
- SMN critical to RNA metabolism, mediator of apoptosis
- In SMA reduction in SMN protein-> motor neurone death
- there are 2 SMN genes
- _all pts w SMA lack SMN-1 protein _
- severity of disease based on number of functional copies of SMN -2
- so more SMN-2 copied the more production of SMN protein and later the presentation of the disease
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What are the associated conditions of spinal muscle atrophy?
- Hip dislocation and subluxation
- scoliosis
- lower extremity contractures
What is the classification of spinal muscle atrophy?
-
Type 1
- Acute Werndnig- Hoffman disease
- present @< 6 months
- Absent Deep Tenodon Reflexes
- Tongue fasciculations
- prognosis poor usually die by 2 years
- Type 2
- Chronic Werndig- Hoffman disease
- present @ 6mo- 12 mo
- muscle weakness worse in LE
- Can sit but can’t walk
- May live to 5th decade
-
Type 3
- Kugelberg-welander disease
- present @ 2-15 yrs
- proximal weakness
- walk as a child, wheelchair as adult
- normal life expectancy- may need respiratory support
What are the symptoms and signs of spinal muscle atrophy?
Symptoms
-
Symmetrical progressive weakness
- more profound in lower extremity than Upper
- More profound proximally cf distally
Signs
-
Absent deep tendon reflexes
- distinguish from Duchenne Muscular dystrophy where DTR are present
- Fasciculations present
What is diagnosis based on?
- DNA analysis
- Muscle biopsy
- Prenatal diagnosis is possible
What is the tx for spinal muscle atrophy?
- No medical tx for underlying disease
-
Operative
- tx hip dislocation
- scoliosis
- lower extremity contractures
- tx hip dislocation
What is the tx for hip dislocations in spinal muscle atrophy pts?
- hip subluxation/dislocation occurs in 62% type 2 SMA and less frequently in type 3
- tx is observation alone
- standard of care in dislocated hip typically remains painless and high reocurrance rate if open reduction attempted
What is the tx of scoliosis in spinal muscle atrophy?
- Scoliosis is almost universal
- long c right sided thoracolumbar curve
- Usually occurs by age 2-3 yrs
- often progressive
non operative
-
Bracing
- devices may delay but not prevent surgery in children younger than 10 yrs
Surgery
-
PSF with fusion to pelvis
- for progressive curve, >50-60o
- adress hip contracture and any other lower extremity contractures before PSF to ensure seating balance
- outomes= improved wheelchair sitting
- may lead to tempoarary loss of upper extremity function
Define Duchenne muscular dystrophy?
- Disorder of worsening neurological dysfunction characterised by Progressive muscle weakness
- casued by absent Dystrophin protein
What is the epidemiolgy of Duchenne muscular dystrophy?
- Prevalence is 2-3/10,000
- affects YOUNG MALES ONLY
- age of onset 2-6 years
- X linked Recessive
- Xp21.2 dystrophin gene defect due to point deletion and nonsense mutation
- 1/3 rd of cases are spontaneous mutation
What is the pathophysiolgy of Duchenne muscular dystrophy?
-
Dystrophin absence ->
- Poor muscle fibre regeneration
- progressive replacement of muscle tissue with fibrous & Fatty tissue
- skeletal & cardiac muscle lose elasticity and strength
Name associated conditions of Duchenne muscular dystrophy?
- Calf pseudohypertrophy
- scoliosis
- equinovarus foot deformity
- joint contractures
- cardiomyopathy
- static encephalopathy
What is the prognosis of Duchenne muscular dystrophy?
- Most unable to ambulate independently by age **10 **
- most are wheelchair dependent by 15 yrs
- most die of cardiorespiratory problems age 20 yrs
What is Becker’s muscular dystrophy?
- A congential neurological disorder characterised by progressive muscular weakness
- X linked Recessive
- CPK elevated
- calf hypertrophy present
How is Becker’s muscular dystrophy different from Duchenne muscular dystrophy?
- Dystrophin Protein is decreased cf absent in Duchenne
- Later onset with slower progression
- Longer life expectancy ( av diagnosis occur age 8 cf 2 yrs Duchenne)
- more prone to cardiomyopathy
Describe the symptoms and signs of pt with Duchenne Muscular dystrophy?
Symptoms
- Progressive weakness
- proximal muscle first
- begins with Gluteal muscle weakness
- Gait abnormalities
- Dalyed walking
- toe walking
- clumsy, waddling gait
- difficulty climbing stairs, hopping, jumping
Signs
- Calf hypertrophy
- deep tendon refelexes present- unlike spinal muscle atrophy
-
lumbar lordosis
- compensates for gluteal weakness
-
Gower’s sign
- rises by walking hand up legs to compensate for glux max and quads weakness
How could you confirm Duchenne Muscular dystrophy dx?
-
Lab
-
marked elevation Creatinine Kinase levels (10-200 x normal)
- CPK leaks across defective cell membrane
-
marked elevation Creatinine Kinase levels (10-200 x normal)
-
Muscle biopsy
- Show connective tissue infiltration and foci of necrosis
- will show absent Dystrophin w staining
-
DNA testing
- Shows Absent Dystrophin Protein
-
EMG
- Myopathic
- Decrease amplitude, short duration, polyphasic motor
What is the tx of Duchenne Muscular dystrophy?
Non operative
-
Corticosteriod therapy ( prednisolone 0.75mg/day)
- for progressive disease child 5-7 yrs
- aim to remain ambulatory
- outcome
- significant positive effect on disease
- acutely improves strength/slow progression weakening, prevents scoliosis formation, prolongs ambulation
- delayes detoriation of pulmonary function
- SE= weight gain, osteonecrosis/cushingoid, Gi symptoms, Mood lability, headaches, short stature, cateracts
- Pulmonary care with nightly ventilation
-
Rehab
- PT/adaptive equipment/power wheelchair
Surgery
-
Soft tissue release to prolong ambulation
- Hip Abductor and Hamstring release
- Achilles tendon & post tibialis lengthening
- in ambulatory child
- post op early mobilisation/ to prevent deconditioning
- Scoliosis surgery
What is the epidemiology of scoliosis surgery in Duchenne Muscular dystrophy?
- Neurogenic curve occurs in 95% of patients after becoming wheelchair bound
- Curve Progresses rapidly from 13-14 yrs
- begins mild lordosis
- progress to general kyphosis and scoliosis w varying degrees of pelvic obliquity
- progresses 1-2o per month starting at age 8 to 10 yrs
- pts may be bed ridden by 16 yrs
- tx is complicated by Restrictive pulmonary disease
What are the indications for scoliosis surgery in Duchenne Muscular dystrophy?
for posterior spinal fusion with instrumentation
- Curve >20o in Non ambulatory pts
- Treat early <30o before pulmonary function declines
- FVC can drop below 35%
- Rapidly progressing curve
techniques
- Extension to pelvis contraversial
What are the complications of scoliosis surgery in Duchenne Muscular dystrophy?
-
Malignant hyperthermia
- pretreat with dantrolene
- intraoperative cardiac events
What foot abnormality is seen in Duchenne Muscular dystrophy?
-
Equinovarus
- seen in Duchenne Muscular dystrophy and Cerebral Palsy
What is the pathoanatomy of equinovarus?
- Tibialis posterior persistent function or overactivity, weak peroneus brevis
- Gastronemius- soleus complex contracture= equinus
- absence ligamentous laxity
What is the tx of equinovarus foot in Duchenne Muscular dystrophy?
- Non operative
- Stretching/PT/AFO use/ Botulinium toxin
- Surgery
-
TAL w tibialis posterior split transfer
- reroute 1/2 of tendon dorsally and insert into Peroneus brevis
- Indicated when affected muscle is spastic in both stance and swing phase
-
Rancho proceedure ( 3 components)
- TAL
- Tibialis posterior lengthening
- reroute 1/2 of Tibialis anterior and inert into cuboid
-
TAL w tibialis posterior split transfer
What is facioscapular muscular dystrophy?
- Disorder of progressive neurological dysfunction which causes progressive muscle weakness
- Commonly seen as slow progression of muscle weakness involving muscles of
- facial expression
- proximal upper extremity
What is the epidemiology of facioscapulohumeral muscular dystrophy?
- Autosomal Dominant
- Men affected > women
What are the signs and symptoms of facioscapulohumeral muscular dystrophy?
Symptoms
- slow muscle decline
Signs
-
Scapular winging with limited arm Abduction
- causing prominence Shoulder blades
- Unable to whistle
- eyelid droopiness
What is seen with labs results with facioscapulohumeral muscular dystrophy?
- Normal Creatinine Kinase ( unlike duchenne muscular dystrophy and Becker’s muscular dystrophy)
What is the tx of facioscapulohumeral muscular dystrophy?
- Non operative
-
PT/OT Speech therapy
- to maintain strength and ROM of affected muscles
- although arms become gradually weaker from adolescence on , pts can usually work into later life.
-
PT/OT Speech therapy
- Surgery
-
Scapulothoracic Fusion
- to tx scapular winging
-
Scapulothoracic Fusion
