<Tr> <Td_colspan="2"> A baby with microcephaly (left) compared to a baby with a typical head size </Td> </Tr> <Tr> <Th> Specialty </Th> <Td> Medical genetics, Psychiatry, Neurology </Td> </Tr> <P> Microcephaly is a medical condition in which the brain does not develop properly resulting in a smaller than normal head . Microcephaly may be present at birth or it may develop in the first few years of life . Often people with the disorder have an intellectual disability, poor motor function, poor speech, abnormal facial features, seizures, and dwarfism . </P> <P> The disorder may stem from a wide variety of conditions that cause abnormal growth of the brain, or from syndromes associated with chromosomal abnormalities . A homozygous mutation in one of the microcephalin genes causes primary microcephaly . It serves as an important neurological indication or warning sign, but no uniformity exists in its definition . It is usually defined as a head circumference (HC) more than two standard deviations below the mean for age and sex . Some academics advocate defining it as head circumference more than three standard deviations below the mean for the age and sex . </P>

The meaning of the medical term microcephalus is
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