Feasibility of intracranial surgery in the primate fetus. Model and surgical principles.

Abstract

A research model for intracranial surgery in the primate fetus was developed and tested in 10 timed-pregnant rhesus monkeys. With general anesthesia and sterile surgical technique, a laparotomy followed by a lower uterine segment hysterotomy was performed at a site avoiding the placenta. The amnion was opened carefully by use of the operative microscope and the fetal head was exposed. A scalp incision was made over the frontal region and a small craniectomy and cortical incision were carried out. In three of the fetuses, ventricular shunts were also placed. A layered closure was performed and the uterus was returned to the peritoneal cavity. Placental integrity and fetal viability were assessed before surgery and 1 week postoperatively by ultrasonography. The survival rates were 100% for the mothers and 80% for the fetuses. One fetus died in utero after an overdose of a sedative to the mother, and another was stillborn. Postmortem examination revealed no intracranial or systemic abnormalities in either case, and the cause of death was attributed to drug overdose and a naturally occurring stillbirth, respectively. Newborns were maintained either with their mothers or in a nursery, where they were observed and evaluated for 3 weeks. Weight, crown-rump length, and occipitofrontal head circumference were measured. General patterns of behavior and neurological assessments were recorded weekly. The eight surviving neonates were normal with respect to all parameters evaluated. Several principles of fetal intracranial surgery are emphasized as important: uterine relaxation by prostaglandin inhibition; low-dose halothane anesthesia supplemented by nitrous oxide in oxygen; perioperative ultrasonography and intraoperative transillumination of the uterus for placental localization; lower uterine segment opening; controlled exposure of the fetal cranium; minimization of amniotic fluid loss; enhancement of fetal anesthesia by injection of a local anesthetic agent at the fetal operative site; and multilayered watertight closure.