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Description of the Symptom

The terms weakness and hypotonia are often used interchangeably even though they have very different meanings. Weakness is the absence of strength, the inability to exert a force to resist movement, and the absence of power or the inability to exert a force to change position.1,2 Hypotonia is a state of decreased muscle tone, which is defined clinically as the resistance felt to externally imposed movements in a state of voluntary relaxation.3 At rest, the muscle is in a state of partial relaxation that requires energy for its full contraction or further muscle relaxation and concurrent contraction of its antagonistic muscle to elongate.4 It is common for weakness and hypotonia to occur together; however, it is possible to have hypotonia in the absence of weakness and it is dependent on its cause. This chapter describes possible causes of weakness and hypotonia in a child.

Special Concerns

  • Any weakness/hypotonia of sudden onset (few days)

  • Any post-traumatic weakness/hypotonia

  • Any neurological signs suggesting an intracranial tumor or space-occupying tumor of the spinal cord

CHAPTER PREVIEW: Conditions That May Lead to Weakness and Hypotonia in a Child
Common Ages at Which Weakness and Hypotonia Present in a Child

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