Low muscle tone

Hypotonia
Classification and external resources
Specialty	Pediatrics
ICD-10	P94.2
ICD-9-CM	358,781.3
DiseasesDB	21417
MedlinePlus	003298
MeSH	D009123
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Hypotonia, commonly known as floppy baby syndrome, is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Hypotonia is resistance to passive movement, whereas muscle weakness results in impaired active movement. Central hypotonia originates from the central nervous system, while peripheral hypotonia is related to problems within the spinal cord, peripheral nerves and/or skeletal muscles. Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child's development and later life depend primarily on the severity of the muscle weakness and the nature of the cause. Some disorders have a specific treatment but the principal treatment for most hypotonia of idiopathic or neurologic cause is physical therapy, occupational therapy for remediation, and/or music therapy.

Hypotonia is thought to be associated with the disruption of afferent input from stretch receptors and/or lack of the cerebellum’s facilitatory efferent influence on the fusimotor system, the system that innervates intrafusal muscle fibers thereby controlling muscle spindle sensitivity. On examination a diminished resistance to passive movement will be noted and muscles may feel abnormally soft and limp on palpation. Diminished deep tendon reflexes also may be noted. Hypotonia is a condition that can be helped with early intervention.

Hypotonic patients may display a variety of objective manifestations that indicate decreased muscle tone. Motor skills delay is often observed, along with hypermobile or hyperflexible joints, drooling and speech difficulties, poor reflexes, decreased strength, decreased activity tolerance, rounded shoulder posture, with leaning onto supports, and poor attention. The extent and occurrence of specific objective manifestations depends upon the age of the patient, the severity of the hypotonia, the specific muscles affected, and sometimes the underlying cause. For instance, some people with hypotonia may experience constipation, while others have no bowel problems.

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