Microcephaly literally means “small head” or head circumference 2 SD below the mean, and is usually associated with a generalized reduction of the brain mass (micrencephaly). It was presented by the authors at the Eighteenth Annual Meeting of the Japanese Society of Neurology in Nagoya, May 18,1977, that CSF uric acid concentrations were decreased in most of the infants and the children with microcephaly.
The purpose of this paper is to find out the difference between microcephaly of hypoplastic type and that of atrophic type.
The concentrations of uric acid, cAMP and cGMP in CSF were investigated in 10 cases of normal control from 2 months to 2 years and in 22 cases of microcephaly from 3months to 4 years. The mean values and standard deviations in normal controls were as follows:
Uric acid concentrations in CSF(n=10): 0.30±0.11mg/dl
cAMP concentrations in CSF(n=5): 9.96±3.84 pmol/ml
cGMP concentrations in CSF(n=5): 7.32±4.00 pmol/ml
CSF uric acid concentrations were decreased in the microcephalies of genetic etiology with DQ below 50. The responsible factor is thought to be decreased turnover of the nucleic acid due to hypoplasia of the brain. On the contrary, CSF uric acid concentrations were increased in the microcephalies of postnatal etiology with DQ below 50. The responsible factors are thought to be (1) increased permeability of blood-CSF barrier and (2) cerebral cell necrosis, due to progressive atrophy of the brain secondary to trauma or infection.
CSF cAMP and cGMP concentrations were decreased in the microcephalies of postnatal etiology with DQ below 50. The responsible factors for the decreased concentrations in the microcephalies of postnatal etiology are thought to be (1)damage to the cyclase enzymes, (2) inadequate delivery of cyclase-activating hormons, and (3) deficiency of the enzyme's substrates such as ATP and GTP.
Finally, it should be kept in mind that the concentrations of uric acid, cAMP and cGMP were all normal in the CSF of 2microcephalies of genetic etiology without mental retardation.
