Castriota Scanderbeg A, Mulas M, Bisceglia M, Napolitano M L, Masala S, Fraracci L
Dipartimento di Diagnostica per Immagini, IRCCS S. Lucia, Roma.
Radiol Med. 1997 Nov;94(5):428-32.
We support the normal standards for two sonographic (US) signs of the posterior cranial fossa, namely the magnitude of the cisterna magna and the height of the fourth ventricle fastigium, in preterm and fullterm infants.
The cisterna magna was measured as the distance between the inferior aspect of the cerebella vermis and the inner aspect of the occiput. The height of the fourth ventricle fastigium was calculated as the line drawn from the fastigium to the inner aspect of the occiput, close to the opisthion.
The cisterna magna was .46 +/- .13 cm in preterm infants and .45 +/- .1 cm in fullterm infants (the difference was not significant), whereas the height of the fourth ventricle fastigium was 1.7 +/- .26 cm in preterm and 1.9 +/- .16 cm in fullterm infants (the difference was significant, p < .005).
The finding of a cisterna magna of equal size in preterm and fullterm infants is in agreement with the concept that subarachnoid and cisternal spaces of the posterior fossa are still large at birth and start to decrease in size later in life. Our results suggest that a cisterna magna smaller than .2 cm in height and/or a fastigium closer than 1.2 cm to the basiocciput in preterm and closer than 1.6 cm in fullterm infants indicate, in a proper clinical context, an abnormally low cerebellum position (Arnold-Chiari malformation). On the other hand, cisterna magna values exceeding .72 in preterm and .65 cm in fullterm infants, as well as fastigium values exceeding 2.22 cm in both groups may suggest the presence of the Dandy-Walker complex or of an arachnoid cyst.
我们支持将颅后窝两个超声（US）征象的正常标准应用于早产儿和足月儿，这两个征象分别是枕大池大小和第四脑室顶的高度。
枕大池测量为小脑蚓部下缘与枕骨内面之间的距离。第四脑室顶的高度计算为从第四脑室顶至枕骨内面靠近枕骨大孔后缘处的连线。
早产儿枕大池为0.46±0.13cm，足月儿为0.45±0.1cm（差异无统计学意义），而早产儿第四脑室顶高度为1.7±0.26cm，足月儿为1.9±0.16cm（差异有统计学意义，p<0.005）。
早产儿和足月儿枕大池大小相等这一发现与以下概念相符，即颅后窝的蛛网膜下腔和脑池在出生时仍然较大，随后在生命后期开始变小。我们的结果表明，在适当的临床背景下，早产儿枕大池高度小于0.2cm和/或第四脑室顶距枕骨基底部小于1.2cm、足月儿小于1.6cm提示小脑位置异常低（阿诺德 - 基亚里畸形）。另一方面，早产儿枕大池值超过0.72cm、足月儿超过0.65cm，以及两组中第四脑室顶值超过2.22cm可能提示存在丹迪 - 沃克综合征或蛛网膜囊肿。
