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  • Motor neuron disease


  • 335.24 Primary lateral sclerosis


  • G12.2 Motor neuron disease


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


A 49-year-old man reports to physical therapy stating that he has had an increase in the number of falls he experiences weekly. He was diagnosed with primary lateral sclerosis (PLS) 2 years ago, works as a handyman at a small island resort, is married and has two teenage children. He walks without an assistive device. On testing, his lower extremities test grossly 3/5 to 3+/5 with an increase in tone on fast, passive motion testing. His dynamic gait index (DGI) score is 19/24 with the greatest difficulty when changing gait speed, stepping over obstacles, and going up/down steps. He was out of breath following administration of the DGI and his oxygen saturation dropped from 98% to 92%. During static balance testing, he was able to maintain standing with his feet together for 8 seconds with his eyes open and 7 seconds with his eyes closed. He maintained single-leg stance on each leg for 4 seconds with his eyes open.



  • Motor neuron disease

  • Degenerative neurologic disorder of the upper motor neurons in the brain and spinal cord

  • First described by Dr Jean-Martin Charcot

  • Progressive weakness in the voluntary muscles

  • Nerve cells degenerate causing weakness

Essentials of Diagnosis1

  • Progression of symptoms over 3 years without evidence of lower motor neuron dysfunction

  • Disease is progressive, but may persist for decades

  • Evidence of loss of function in the lower extremities (LEs) first, then progressing to the muscles of speech and swallowing, and then loss in the upper extremities (UEs)

FIGURE 100-1

Adult-onset motor neuron disease syndromes. Upper motor neurons are shown with filled circles and lower motor neurons with open circles for cell bodies. Cerebral cortex is indicated with dark, brainstem white, and spinal cord light shading. (From Greenberg DA, Aminoff MJ, Simon RP. Clinical Neurology. 8th ed. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

General Considerations

  • Spontaneous onset for adults.

  • Breathing may be affected in the later stages of the disease.

  • Juvenile primary lateral sclerosis (JPLS) is linked to a mutation in the ALS2 gene.


  • Onset 40 to 60 years old; mean of 50 years old

  • JPLS



  • Antalgic gait

  • Dysarthria

  • Drooling, weakness of bulbar ...

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