Abstract â–¡ 84

Prevailing hypothesis indicate a possible association between maturation delay or deficiency in certain regions of the brain and some cases of SIDS, but as of yet, there has been no single identified neuropathological (or other) cause of SIDS.

The right cerebral hemisphere from 17 control cases ranging in age from 3 weeks to 8 months postnatally, where the cause of death was either meningitis, septicemia or acute peritonitis were selected. 31 normal birth weight (NBW) SIDS, 11 low birth weight (LBW) SIDS and 16 SIDS ?BW (cases of unknown birth weight), ranging in age from 3 days to 8 months, cause of death verified from a postmortem report, were selected from either archived or prospectively collected material. The total number of neocortical neurons was estimated using design based stereological techniques incorporating the Cavalieri's Principle for the estimation of neocortical volume and the optical brick for numerical density estimation. By multiplying the volume of the neocortex with the numerical density, the total number of neurons and glial cells were estimated for each case.

10 aged matched cases from each group (excluding SIDS ?BW) were further examined for mean neuronal nuclear volume estimation using the nucleator estimator technique. Results were analysed using linear regression over age and the Mann-Whitney rank sum test for comparison between groups.

There was no significant difference in neocortical volume between control cases and any of the SIDS groups. Only the SIDS ?BW group failed to show any statistically significant increase in neocortical volume with age. No group displayed any change in either total number of neocortical cells, total neuronal number or total number of glial cells with age. However, there was a statistically significant difference in total neuronal number between control cases and SIDS NBW cases (p=0.006). Both control and SIDS LBW cases showed an increase in mean nuclear volume with age, SIDS NBW showed no such increase. At 8 months, SIDS NBW showed a reduced mean nuclear volume (p=0.011) when compared with control cases. SIDS LBW cases showed no statistically significant difference (p=0.146) when compared with control cases.

The total compliment of neocortical neurons present at birth shows no loss during the first 8 months of life through epigenetic neuronal cell death in either the control or SIDS cases. If nuclear volume is regarded as an indicator of functional maturity for neurons, the results show a reduced neocortical neuronal maturity in all SIDS LBW and SIDS NBW cases beyond 5 weeks of age. Results of this and other quantitative studies supply evidence of subtle cellular pathology in the CNS of SIDS cases.