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Low Muscle Tone and Developmental Delays
What is muscle tone?
Muscle tone is your body's degree of muscle tension. Adequate muscle tone is necessary in order to provide a stable base of support for the head and trunk, which are first needed to develop efficient limb movement.
Muscle tone can be classified as normal, low (hypotonia), or high (hypertonia). Hypotonia, which is most associated with developmental delays, is associated with poor posturing and floppiness. Children who are hypotonic lack the muscle resistance that provides support to their joints.
Why is appropriate muscle tone so important?
A study conducted at The Children's Hospital of Philadelphia revealed that 46% of the premature infants examined displayed abnormal shoulder girdle muscle tone. Of these, 26% used scapular retraction as compensation for neck and trunk hypotonicity.
Shoulder girdle abnormalities in the first year of life inhibit crawling, sitting, and object manipulation and, therefore, may manifest as delays in motor development.
Premature infants have a high incidence of abnormal muscle tone. According to a study from Pediatrics, infants with truncal or lower extremity hypotonicity are associated with a worse developmental out come.
What can be done to help?
Identification of infants with significant neonatal risk factors for tone abnormalities is important to allow for earlier therapeutic intervention. Referral to physical therapy will allow for treatment focusing on developing postural control and strength in order to facilitate appropriate developmental growth.
References:
Georgieff, MK and Bernbaum, JC (1986). Abnormal shoulder girdle muscle tone in premature infants during their first 18 months of life. Pediatrics, 77(5):664-9.
Georgieff, MK., et al (1986). Abnormal truncal muscle tone as a useful early marker for developmental delay in low birth weight infants, Pediatrics, 77(5):659-63.