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Chapter 63: Weakness and Hypotonia in a Child

Elizabeth L. Ege

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
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CHAPTER PREVIEW: Conditions That May Lead to Weakness and Hypotonia in a Child
T  Trauma
COMMON
Not applicable
UNCOMMON

Brain and spinal cord injuries:

  • Concussion 1197

  • Contusion 1197

  • Peripheral nerve trauma 1197

  • Spinal cord trauma 1197
RARE
Not applicable
I  Inflammation
COMMON
Not applicable
UNCOMMON

Aseptic

Acute cerebellar ataxia 1196

Acute demyelinating polyradiculopathy (Guillain-Barré syndrome) 1196

Chronic inflammatory demyelinating polyneuropathy 1197

Septic

Encephalitis 1198

Meningitis 1200

Myelitis 1200
RARE

Aseptic

Polymyositis 1201

Septic

Poliomyelitis 1200
M  Metabolic
COMMON
Not applicable
UNCOMMON

Hyperbilirubinemia 1199

Hypoglycemia 1199

Hypothyroidism 1199

Infantile botulism 1199

Mitochondrial myopathies 1200

Pompe's disease (acid maltase deficiency, glycogen storage disease type 2) 1201

Prader-Willi syndrome 1201
RARE
Not applicable
Va  Vascular
COMMON
Hypoxic/ischemic encephalopathy 1199
UNCOMMON
Hemorrhage 1198
RARE
Not applicable
De  Degenerative
COMMON
Not applicable
UNCOMMON

Spinal muscular atrophies:

  • Type I (Werdnig-Hoffmann disease) 1201

  • Type II (Kugelberg-Welander disease) 1202

  • Type III (benign) 1202
RARE
Not applicable
Tu  Tumor
COMMON
Not applicable
UNCOMMON

Malignant Primary, such as:

• Posterior fossa tumors/medulloblastomas 1201

Malignant Metastatic:

Not applicable

Benign:

Not applicable
RARE
Not applicable
Co  Congenital
COMMON
Not applicable
UNCOMMON

Benign congenital hypotonia 1196

Congenital muscular dystrophy 1198

Congenital myotonic dystrophy (Steinert disease) 1198

Down syndrome (Trisomy 21) 1198

Myasthenia gravis:

  • Congenital 1200

  • Transient neonatal 1200
RARE
Not applicable
Ne  Neurogenic/Psychogenic
COMMON
Not applicable
UNCOMMON

Hereditary spinal motor neuropathies:

  • Charcot-Marie-Tooth disease (hereditary sensory motor neuropathy types I and II) 1198

  • Dejerine-Sottas disease (hereditary sensory motor neuropathy type III) 1199
RARE
Not applicable

Note: These are estimates of relative incidence because few data are available for the less common conditions.

Common Ages at Which Weakness and Hypotonia Present in a Child
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Common ...

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