Please confirm topic selection

Are you sure you want to trigger topic in your Anconeus AI algorithm?

Please confirm action

You are done for today with this topic.

Would you like to start learning session with this topic items scheduled for future?

Updated: Feb 23 2024

Duchenne Muscular Dystrophy

Images
https://upload.orthobullets.com/topic/4092/images/17_moved.JPG
https://upload.orthobullets.com/topic/4092/images/calf pseudohypertrophy.jpg
https://upload.orthobullets.com/topic/4092/images/dystrophin_stains_moved.jpg
  • summary
    • Duchenne Muscular Dystrophy is a common congenital condition caused by an X-linked recessive mutation leading to the absence of dystrophin protein that affects young males who present with progressive muscle weakness, scoliosis, and cardiomyopathy. 
    • Diagnosis is made with DNA testing showing an absence of the dystrophin protein.
    • Treatment involves a multidisciplinary approach to address cardiomyopathy, pulmonary dysfunction, scoliosis, and foot deformities. 
  • Epidemiology
    • Prevalence 
      • 2-3/10,000
    • Demographics
      • affects young males only
      • age of onset is between 2-6 years of age
  • Etiology
    • Pathophysiology
      • dystrophin absence leads to
        • poor muscle fiber regeneration
        • progressive replacement of muscle tissue with fibrous and fatty tissue
      • skeletal and cardiac muscle lose elasticity and strength
    • Genetics
      • Xp21.2 dystrophin gene defect due to point deletion and nonsense mutation
      • one third of cases result from spontaneous mutations
    • Associated conditions
      • orthopaedic manifestations
        • calf pseudohypertrophy
        • scoliosis
        • equinovarus foot deformity
        • joint contractures
      • nonorthopaedic conditions
        • cardiomyopathy
        • static encephalopathy
      • Becker's Muscular Dystrophy
        • similar to Duchenne's in that
          • it is sex-linked recessive
          • calf pseudohypertrophy is present
          • CPK is elevated
        • differs from Duchenne's in that
          • dystrophin protein is decreased instead of absent
          • later onset with slower progression and longer life expectancy (average diagnosis occurs at age 8 compared to 2 years of age with Duchenne's)
          • more prone to cardiomyopathy
  • Physical Exam
    • Symptoms
      • progressive weakness affecting proximal muscles first (begins with gluteal muscle weakness)
      • gait abnormalities
        • delayed walking
        • toe walking
        • clumsy, waddling gait
        • difficulty climbing stairs, hopping, or jumping
      • decreased motor skills
    • Physical exam
      • calf pseudohypertrophy (infiltration of normal muscle with connective tissue)
      • deep tendon reflexes present (unlike spinal muscular atrophy)
      • lumbar lordosis
        • compensates for gluteal weakness
      • Gower's sign
        • rises by walking hands up legs to compensate for gluteus maximus and quadriceps weakness
      • Trendelenburg sign
  • Evaluation
    • Labs
      • markedly elevated CPK levels (10-200x normal)
        • CPK leaks across defective cell membrane
    • Muscle biopsy
      • will show connective tissue infiltration and foci of necrosis
      • will show absent dystrophin with staining
    • DNA testing
      • shows absent dystrophin protein
    • EMG
      • myopathic
        • decreased amplitude, short duration, polyphasic motor
  • Differential 
      • Similarity and Distinguishing features of differential diagnosis
      • Similar traits to Duchenne's
      • Distinguishing traits from Duchenne's
      • Becker's
      • Calf pseudohypertrophy
      • Markedly elevated CPK
      • X-linked transmission
      • Becker's has slower progression of weakness with diagnosis made later (~8 yrs)
      • Prone to cardiomyopathy
      • Spinal muscular atrophy
      • Proximal weakness
      • Onset of weakness is earlier in childhood
      • Absent deep tendon reflexes and fasciculations
      • CPK levels are normal
      • Pseudohypertrophy is absent
      • Emery-Dreifuss dystrophy
      • Similar clinical picture
      • No calf pseudohypertrophy
      • CPK levels near normal
      • Elbow and ankle contractures develop early
      • Limb girdle dystrophy
      • Progressive motor weakness
      • No calf pseudohypertrophy
      • CPK levels are only mildly elevated
      • Guillain-Barre syndrome
      • Acute onset of weakness
      • Absent deep tendon reflexes
      • CPK levels are normal
      • CSF fluid analysis is diagnostic
  • Treatment
    • Nonoperative
      • corticosteroid therapy (prednisone 0.75 mg/kg/day)
        • indications
          • 5 to 7-year-old child with progressive disease
        • goals
          • to maintain ambulatory capacity as long as possible
        • outcomes
          • significant positive effect on disease progression
            • acutely improves strength, slows progressive weakening, prevents scoliosis formation, and prolongs ambulation
            • delays deterioration of pulmonary function
        • side effects
          • osteonecrosis
          • weight gain
          • cushingoid appearance
          • GI symptoms
          • mood lability
          • headaches
          • short stature
          • cataracts
      • pulmonary care with nightly ventilation
      • rehabilitation
        • techniques
          • physical therapy for range of motion exercises
          • adaptive equipment
          • power wheelchairs
          • KAFO bracing (controversial)
    • Operative
      • soft tissue releases to prolong ambulation
        • indications
          • ambulatory child with Duchenne's
        • techniques
          • hip abduction contractures treated by release of iliotibial band
          • Hip flexion contractures treated by release of sartorius, rectus femoris, and tensor fascia lata
          • hamstring releases
          • Achilles tendon and posterior tibialis lengthenings
        • postoperative care
          • early mobilization and ambulation to prevent deconditioning
      • scoliosis surgery (see below)
  • Scoliosis
    • Introduction
      • considered a neurogenic curve
      • occurs in 95% of patients after becoming wheelchair dependent
      • curve progresses rapidly from age 13 to 14 years
        • begins with mild hyperlordosis
        • progresses with general kyphosis and scoliosis with varying degrees of pelvic obliquity
        • progresses 1° to 2° per month starting at age 8 to 10 years
      • patients may become bedridden by age 16
      • treatment is complicated by restrictive pulmonary disease (significant decrease in forced vital capacity)
      • cardiac and pulmonary function studies should be obtained pre-operatively as significant declines in function of both organ systems may make spinal fusion too high-risk
    • Treatment
      • nonoperative
        • bracing is contraindicated
          • may interfere with respiration
      • operative
        • early PSF with instrumentation
          • indications
            • curve 20-30° in nonambulatory patient
              • treat early before pulmonary function declines
              • can wait longer ~ 40° if responding well to corticosteroids
            • FVC drops ≤ 35%
            • rapidly progressive curve
        • PSF with instrumentation to pelvis
          • indications
            • curves ≥ 40°
            • pelvic obliquity ≥ 10°
            • lumbar curve where apex is lower than L1
          • complications
            • malignant hyperthermia is common intraoperatively
              • pretreat with dantrolene
            • intraoperative cardiac events
        • anterior and posterior spinal fusion
          • indications
            • rarely for stiff curves
  • Equinovarus Foot
    • Introduction
      • common foot deformity seen with Duchenne muscular dystrophy
    • Pathoanatomy
      • muscle imbalance secondary to muscle replacement with fibrofatty tissue
    • Diagnosis
      • made upon clinical exam
    • Treatment
      • nonoperative
        • stretching, physical therapy, and night time AFO use
      • operative
        • Tendinoachilles lengthening with posterior tibialis tendon transfer, toe flexor tenotomies
  • Prognosis
    • Most are unable to ambulate independently by age 10
    • Most are wheelchair dependent by age 15
    • Most die of cardiorespiratory problems by age 20
Card
1 of 11
Question
1 of 24
Private Note

Attach Treatment Poll
Treatment poll is required to gain more useful feedback from members.
Please enter Question Text
Please enter at least 2 unique options
Please enter at least 2 unique options
Please enter at least 2 unique options