Sonography of the neonatal craniocervical junction.

To determine the value of ultrasound scanning of the craniocervical junction in neonates via a posterior approach, we examined 50 infants with normal posterior fossae, 10 with congenital abnormalities, and eight with intracranial hemorrhage. Good evaluation of the cisterna magna, medulla, tonsils, vermis, cervical cord, and central canal was possible in most cases. In nine patients with spinal dysraphism, all displayed a Chiari II malformation; of these, a kink at the medullary cord junction was seen in six, and a cerebellar peg was noted in four. In one case, the Chiari malformation was confirmed by myelography, and all nine patients had some of the intracranial features of Chiari II malformation seen via the standard anterior fontanelle approach. The 10th patient in this group had a quadrigeminal plate cyst and gross hydrocephalus. In another four infants, diffuse subarachnoid blood in the cisterna magna was seen after recent intraventricular hemorrhage. A further two of four patients with posthemorrhagic hydrocephalus had localized clots. Direct scanning at the craniocervical junction was easily performed and allowed good evaluation of this area in normal infants and in patients with Chiari II malformation. This technique also allowed visualization of subarachnoid blood and clots obstructing the outlet of the fourth ventricle.