Role of somatostatin and apoptosis in breathing control in sudden perinatal and infant unexplained death.

OBJECTIVES

To obtain basic information about the expression of somatostatin in the human central nervous system and, in particular, to evaluate its possible involvement in unexplained perinatal and in sudden infant death syndrome.

MATERIAL

Sixty-seven brainstems from subjects aged from 30 gestational weeks to 12 postnatal months, dying of both known and unknown causes, were selected for this study. The unexplained deaths included 17 sudden intrauterine deaths, 5 sudden neonatal deaths and 28 sudden infant deaths.

METHOD

All brainstems were fixed in 10% phosphate-buffered formalin, processed and embedded in paraffin, according to our protocol available on the web site: http://users.unimi.it/-pathol/sids/riscontro_diagnostico_e.html. The distribution of the somatostatin in the brainstem was studied by immunohistochemistry on serial sections.

RESULTS

We observed an intense somatostatin positivity in many brainstem nuclei prevalently involved in the respiratory activity (parabrachial/Kölliker-Fuse complex, locus coeruleus, hypoglossus nucleus, dorsal vagus motor nucleus, tractus solitarii nucleus, ambiguus nucleus, reticular formation) in stillbirths. In 10 fetuses with unexplained death the neurons of the hypoglossus nucleus were somatostatin-negative. In the postnatal deaths, we observed immunopositivity in the ventrolateral and ventral subnuclei of the tractus solitarii nucleus. Besides, in 15 sudden infant death victims and in 1 control case, somatostatin-positive neurons were also present in the hypoglossus nucleus. In 10 of these 15 cases, a high apoptotic index was also reported.

CONCLUSIONS

We suggest that abnormalities in the distribution of SS in the hypoglossus nucleus before and after birth may contribute to the induction of both fatal breathing in prenatal life and abnormal ventilatory control after birth leading to irreversible apnea.