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Condition/Disorder Synonyms

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  • Bulbospinal muscular atrophy

  • Hereditary neuronopathy

  • Progressive muscular atrophy1

  • Werdnig-Hoffman disease

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ICD-9-CM Codes

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  • 335.0 Werdnig-Hoffman disease

  • 335.1 Spinal muscular atrophy

  • 335.10 Spinal muscular atrophy, unspecified

  • 335.19 Other spinal muscular atrophy

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ICD-10-CM Codes

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  • G12.0 Infantile spinal muscular atrophy, type I [Werdnig-Hoffman]

  • G12.8 Other spinal muscular atrophies and related syndromes

  • G12.9 Spinal muscular atrophy, unspecified

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Preferred Practice Pattern

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Key Features

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Description

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  • Group of four subtypes of degeneration of anterior horn cells that results in progressive muscle atrophy

    • Spinal muscular atrophy (SMA I), Werdnig-Hoffman (acute)

    • Spinal muscular atrophy (SMA II), Werdnig-Hoffman (chronic)

    • Spinal muscular atrophy (SMA III), Kugelberg-Welander

    • Spinal muscular atrophy (SMA IV)

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Essentials of Diagnosis

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  • Autosomal recessive genetic disorder that results in a lack of survival motor neuron gene1 on chromosome 5q11.2-132

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General Considerations

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  • SMA type I: weakness between birth and 3 months of age

  • SMA type II: signs and symptoms by 3 years of age

  • SMA type III: signs and symptoms between 2 to 9 years of age

  • SMA type IV: adult onset

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Demographics2

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  • Type I: 27% of all SMA cases

  • Types II and III: 46% of all SMA cases

  • Type IV: 8% of all SMA cases

  • Werdnig-Hoffman 1:10,000 births

  • Kugelberg-Welander 6:100,000 births

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Clinical Findings

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Signs and Symptoms

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  • Fasciculations (especially of tongue)

  • Muscle weakness

  • Hypotonia

  • Muscle atrophy

  • Decreased or absent deep tendon reflexes

  • Difficulty feeding (infant)

  • Lack of extension during Landau reflex

  • Contractures (type 1)

  • Scoliosis

  • Trendelenburg sign during gait

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Functional Implications

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  • Inability to sit independently

  • Inability to ambulate

  • Require assistance with ADLs

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Possible Contributing Causes

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  • Autosomal recessive genetic disorder on chromosome 5q11.2-132

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Differential Diagnosis

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  • Muscular dystrophy

  • Guillain-Barré

  • Brachial plexus birth injury

  • Other genetic syndromes

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Means of Confirmation or Diagnosis

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Laboratory Tests

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  • Genetic testing

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Imaging

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  • Plain radiograph for scoliosis

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Diagnostic Procedures

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  • Electromyography (EMG)

  • Muscle biopsy

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Treatment

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Medication

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Referrals/Admittance

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  • Geneticist

  • Occupational therapist

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Impairments

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  • Head lag when infant pulled into a sitting position from supine

  • Poor head control

  • Inability to sit

  • Inability to pull to stand

  • Inability to walk

  • Contractures of biceps and wrist flexors

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Tests and Measures

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