Sudden infant death syndrome (SIDS) : associated alterations of the cardiac conduction system and brainstem

The crib death or Sudden Infant Death Syndrome (SIDS) is one of the major social and health problems of today’s medicine not yet resolved. Among a total of over 100 SIDS and 30 control cases, a combined morphologic post mortem study of the cardiac conduction system and brainstem was performed in 42 cases of SIDS and in 12 controls. In every case a complete autopsy was performed, according to the autopsy protocol usually followed at our Institute in cases of sudden death, including particularly the observation of the cardiac conduction system, and of central and peripheral autonomic nervous structures involved in the cardio-respiratory reflexogenesis. The cardiac conduction system was removed in two blocks cut serially at intervals of 40-mm and stained alternately with HE and azan. Transversal serial 5-mm sections were made through the entire brainstem were stained using alternately hematoxylin-eosin, Bielschowsky, and Klüver-Barrera stains. The volume of the arcuate nucleus was measured by 3D-reconstruction. The Mahaim fibers were observed in 16% of control and in 17% of SIDS cases with arcuate nucleus (ARCn) histologically well developed, and from 50% (severe bilateral hypoplasia) to 71% (monolateral hypoplasia) in SIDS cases with ARCn hypoplasia. The Mahaim fibers are statistically more frequent in SIDS with ARCn hypoplasia than in the cases with well developed ARCn (control and other SIDS cases) (p<0.005). The resorptive degeneration, cartilaginous meta-hyperplasia, and the His bundle dispersion were statistically unrelated with the presence of ARCn hypoplasia. In order to better understand the morphologic lesions associated with crib death, we suggest that an accurate morphological and immunohistochemical approach and examination of the on serial sections of both cardiac conduction system and brainstem should be routinely employed in every case of sudden death in infancy. A disadvantage of the herein-described extensive serial section study would be the need of adequately specialized and equipped laboratory centers, with the study of more than one thousand of slides for each case.