"True muscle tone is the inherent ability of the muscle to respond to a stretch. For example, quickly straightening the flexed elbow of an unsuspecting child with normal tone, will cause their biceps to contract in response (automatic protection against possible injury). When the perceived danger has passed, (which the brain figures out once the stimulus is removed), the muscle relaxes and returns to its normal resting state. ""...The child with low tone has muscles that are slow to initiate a muscle contraction, contract very slowly in response to a stimulus, and cannot maintain a contraction for as long as his normal peers. Because these low-toned muscles do not fully contract before they again relax (muscle accommodates to the stimulus and so shuts down again), they remain loose and very stretchy, never realizing their full potential of maintaining a muscle contraction over time. " Cause
The most common cause of central hypotonia in newborns is hypoxic ischemic encephalopathy. Brain malformations and inborn errors of metabolism account for 13% and 3% respectively. Causes that affects the central nervous systems are: chromosomal disorders,  inborn errors of metabolism, cerebral dysgenesis, and trauma to the brain and spinal cord. Metabolic causes includes: glycogen storage disease type II, pyruvate dehydrogenase deficiency, mitochondrial disease, Zellweger syndrome, Smith–Lemli–Opitz syndrome, and congenital disorder of glycosylation. Metabolic disorders in infants are usually presented with various other features such as dysmorphic feature, seizures, encephalopathy, biochemistry profile apart from hypotonia.Some conditions known to cause hypotonia include:
Congenital – i.e.
Treatment
The outcome in any particular case of hypotonia depends largely on the nature of the underlying disease. In some cases, the underlying cause is treatable. But in general, treatment comprises providing supportive care with rehabilitation services, nutritional and respiratory support.Along with normal pediatric care, specialists who may be involved in the care of a child with hypotonia include developmental pediatricians (specialize in child development), neurologists, neonatologists (specialize in the care of newborns), geneticists, occupational therapists, physical therapists, speech therapists, orthopedists, pathologists (conduct and interpret biochemical tests and tissue analysis), and specialized nursing care. If the underlying cause is known, treatment is tailored to the specific disease, followed by symptomatic and supportive therapy for the hypotonia. In very severe cases, treatment may be primarily supportive, such as mechanical assistance with basic life functions like breathing and feeding, physical therapy to prevent muscle atrophy and maintain joint mobility, and measures to try to prevent opportunistic infections such as pneumonia. Treatments to improve neurological status might involve such things as medication for a seizure disorder, medicines or supplements to stabilize a metabolic disorder, or surgery to help relieve the pressure from hydrocephalus (increased fluid in the brain). The National Institute of Neurological Disorders and Stroke states that physical therapy can improve motor control and overall body strength in individuals with hypotonia. This is crucial to maintaining both static and dynamic postural stability, which is important since postural instability is a common problem in people with hypotonia.