Hypotonia in Infants and Young Children: an Etiological Analysis

Objective: To determine the relative frequency of specific disorders that present with hypotonia in Iran. Methodology: It is a retrospective, cross–sectional study in which 107 children with hypotonia, aged one month to three years, were evaluated in Baqyiatallah Hospital between June 2003 and June 2006. Children were categorized into groups of central and peripheral hypotonia, and specific diagnosis of each of the two groups was made by clinical findings, neuro imaging, metabolic and genetic tests, muscular enzymes, EMG-NCV (Electromyography-Nerve conduction velocity) and thyroid function tests. Results: Of the 107 infants, one hundred four (94.4%) children had central hypotonia, four (3.7%) had peripheral hypotonia and in two (1.9%) the hypotonia had other causes. The most common cause of central hypotonia was idiopathic central hypotonia thirty four (31.8%), followed by cerebral palsy in twenty two (20.6%), brain structural abnormality in nineteen (17.8%), inborn errors of metabolism fourteen (13.1%), genetic disorders seven (6.5%) and the TORCH(Toxoplasma, Rubella, Cytomegalovirus, Herpes simplex) syndrome three (2.9%). Conclusion: In our study “central hypotonia” was most prevalent etiology of hypotonia. 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 the TORCH syndrome.