|Sarah Bagher (2009)
Is a condition of decreased muscle ton. Hypotonia can result from a many central or peripheral causes. Therefore, hypotonia is a phenotype of many clinical conditions with variable prognosis (1).
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.
Muscle tone; It is the resistance to passive movement .It is important to recognize that hypotonia is not equivalent to weakness. Infants with central causes, such as Down syndrome, may have severe hypotonia and normal muscle strength (1).
Causes; Hypotonia are usually of unknown origin. Scientists believe that they may be caused by trauma, environmental factors, or by other genetic, muscle, or central nervous system disorders. A retrospective, cross–sectional study was done in Iran to find out the main cause of hypotonia, they found that central hypotonia was the cause in (94.4%) and peripheral in (3.7%), The most common cause of central hypotonia was idiopathic central hypotonia , followed by cerebral palsy, brain structural abnormality , inborn errors of metabolism , genetic disorders and syndrome (2).
Causes of Central Hypotonia;
Idiopathic central hypotonia ( persistent hypotonia without other cause)
Hypotonic cerebral palsy
Hypoxic ischemic encephalopathy(damage to cells in the central nervous system due to inadequate oxygen)
Structural brain anomalies:
Holoprosencephaly (caused by the failure of the embryonic forebrain to divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects that may affect the eyes, nose, and upper lip.
Mitochondrial encephalomyopathies (chronic progressive disorders affecting neuromuscular system. Symptoms are induced by insufficient energy supply resulting from a deficiency of oxidative phosphorylation.
Peroxisomal disorders (group of congenital diseases characterized by the absence of normal peroxisomes in the cells of the body. Peroxisomes are special organelles within a cell that contain enzymes responsible for critical cellular processes, including oxidation of fatty acids, biosynthesis of membrane phospholipids and cholesterol.
The patient usually has developmental delay and mental retardation . Hypotonia, which in the most severe cases is generalized. Facial abnormalities, including high forehead, frontal bossing (swelling), small face, and slanted eyes.