Primary Microcephaly (MCPH) is a congenital condition characterized by congenital microcephaly at least 4 SD below the age and sex average, accompanied with a normal structure of the brain, except for a 50-60% reduction in surface area of the cerebral cortex. Interestingly, most affected patients have a normal height, weight, karyotype, as well as brain scans. In addition, although affected patients show some degree of mental retardation, no neurological findings like spasticity or cognitive decline are associated with this disorder. Seizures may form part of the clinical spectrum of MCPH. The mental retardation, itself, is of a mild to moderate form. In fact, the early developmental milestones may appear to be normal. It is only the later milestones, such as speech development, that are delayed. Most affected children have fine motor functions, are well-behaved, remain pleasant, and are compliant with instructions. Speech is, however, severely affected; many patients cannot speak more than a few words, and most can only speak simple sentences. Affected children have a characteristic appearance with a thin, backward slanting forehead, and a small chin. Cataract commonly develops in these children and some may develop epilepsy. Among Asian and Arab populations, MCPH is more common than Caucasian populations. Japanese populations show an incidence of 1 affected patient in every 30,000 infants.
Microcephaly can be diagnosed in the prenatal period by analyzing the scans of the fetus. A head circumference 3 SD below the mean raises suspicion. After birth, if this condition is found to be in association with cognitive impairment and the characteristic facies, it is a strong indicator for MCPH1. Microcephaly may also occur in association with several other congenital disorders. However, this is not the primary form of microcephaly. Treatment for MCPH is supportive. Regular eye examinations can take care of the cataract problem. Anticonvulsants are used for controlling seizures, if present.
