THE IMMUNOCYTOCHEMICAL DEMONSTRATION OF A RELATIVE LACK OF NERVE-FIBERS IN THE ATRIOVENTRICULAR NODE AND BUNDLE OF HIS IN THE SUDDEN-INFANT-DEATH-SYNDROME (SIDS)

Whilst examining the variation with age of the nerve fibre content of the cardiac conduction system (CCS), using an immunocytochemical appro ach, it became evident that in two sudden infant death syndrome (SIDS) cases there was a selective lack of S100 positive nerve fibres in the atrioventricular (AV) node and His bundle. In the present study there fore, the examination of CCS with S100 was extended to a further five SIDS cases and three cases of sudden explained death. Also, in additio n to S100 - which selectively marks Schwann cells associated with both myelinated and non-myelinated nerves - PGP 9.5 (protein gene product) was used to reveal the presence of nerve axonal elements associated w ith the CCS. The results showed a uniform presence of S100 and PGP 9.5 positive nerve fibres in the sinoatrial (SA) node, the AV node and Hi s bundle tissue of all three control cases. In contrast, five out of s even SIDS cases showed a uniform lack of staining with these markers i n the AV node and His bundle tissue, whilst in the two remaining cases it was present in greatly diminished amounts. Staining in the SA node , although present in all seven cases, was reduced when compared with the control cases. This is the first time the CCS of SIDS cases has be en studied with immunocytochemical markers of nerve elements. The over all results taken in conjunction with the epidemiology of SIDS suggest that the lack of AV node and His bundle innervation most probably ref lects a delay in the development or maturation of the nerve elements o f the CCS, similar to that noted for other parts of the central and pe ripheral nervous systems in SIDS.