Triamcinolone-induced alteration of the notochordal-basichondrocranial relationship in the rhesus monkey.

Triamcinolone-induced alteration of the notochordal-basichondrocranial relationship in the rhesus monkey. Timed-mated pregnant rhesus monkeys received triamcinolone acetonide (10 mg/kg, IM) during early organogenesis. Treated and control embryos and fetuses were removed by hysterotomy on days 35, 42, 50, 60, and 70. All treated cases 42 days or older exhibited craniofacial and brain defects. Microscopic examination showed abnormal notochordal folding and a shortened cranial base in the 35-day embryos prior to any observed CNS involvement. Bends, deviations, focal proliferation, and persistence of the notochord and altered cranial base were observed in older cases. This study supports the hypothesis that encephalocele and related CNS disorders could be secondary to a primary paraxial mesodermal insufficiency.