Hypotonia refers to the reduced muscle tone that occurs in virtually all infants with Down syndrome. It is commonly seen in the flexor group, muscles which act to flex a joint. The muscle weakness ranges from mild to moderate to severe. Common hypotonic symptoms are a lagging head when the child is pulled into a sitting position and arching of the back when carried upright or lying on the stomach. In addition, hypotonic children will tire more easily and adopt movement patterns requiring the least expenditure of energy.
Hypotonic conditions tend to improve with age.
Gross motor programs offered by occupational and physical therapists have been shown to diminish hypotonic symptoms. These programs improve large body movements, such as walking, turning, sitting, standing and climbing stairs. Enrollment of children in an early intervention program which includes gross motor programs is recommended at the earliest feasible age, generally between four and six weeks of age. Atlantoaxial dislocation refers to a problem caused by hypotonia. The ligaments at the first two cervical vertebra are more relaxed than they should be, putting the individual at risk of spinal cord compression and injury .