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254: SPINAL MUSCULAR ATROPHY

Kay Tasso, PhD, PT, PCS

CONDITION/DISORDER SYNONYMS

  • Bulbospinal muscular atrophy

  • Hereditary neuronopathy

  • Progressive muscular atrophy1

  • Werdnig-Hoffman disease

ICD-9-CM CODES

  • 335.0 Werdnig-Hoffman disease

  • 335.1 Spinal muscular atrophy

  • 335.10 Spinal muscular atrophy unspecified

  • 335.19 Other spinal muscular atrophy

ICD-10-CM CODES

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

  • G12.8 Other spinal muscular atrophy and related syndromes

  • G12.9 Spinal muscular atrophy, unspecified

PREFERRED PRACTICE PATTERN

  • 5E: Impaired Motor Function and Sensory Integrity Associated with Progressive Disorders of the Central Nervous System

PATIENT PRESENTATION

A 10-month-old child is referred for physical therapy in the natural environment (at home) through an early intervention program with a diagnosis of infantile spinal muscular atrophy type 1. The child is on a ventilator with an oxygen saturation machine and G-tube for all feeding. There is no active muscle function or head control. Passive dorsiflexion is limited to –10 degrees. The child is dependent for all mobility and ADLs. The family is interested in assistance with obtaining the appropriate equipment for positioning and transportation.

KEY FEATURES

Description

  • 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)

Essentials of Diagnosis

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

FIGURE 254-1

Summary of changes occurring in a neuron and the structure it innervates when its axon is crushed or cut at the point marked X. Hypersensitivity of the postsynaptic structure to the transmitter previously secreted by the axon occurs largely due to the synthesis or activation of more receptors. There is both orthograde (wallerian) degeneration from the point of damage to the terminal and retrograde degeneration of the axon stump to the nearest collateral (sustaining collateral). Changes also occur in the cell body, including chromatolysis. The nerve starts to regrow, with multiple small branches projecting along the path the axon previously followed (regenerative sprouting). (From Barrett KE, Berman SM, Boitano S, Brooks HL. Ganong’s Review of Medical Physiology. 24th ed. New York, NY: McGraw-Hill; 2012.)

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General Considerations

  • 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 and 9 years of age

  • SMA type IV: Adult onset

Demographics2

  • Type I: 27% of all SMA cases

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

  • Type ...

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