Eur J Pediatr (1989) 148: 412-413 European Journal of Pediatrics 9 Springer-Verlag 1989 Ultrasound measurement of the subarachnoid space in infants P. Govaert ~, W. Pauweis 2, P. Vanhaesebrouck 1, C. De Praeter 1, and M. Afschrift 2 1Department of Paediatrics and 2Department of Ultrasonography, State University Gent, De Pintelaan 185, B-9000 Gent, Belgium Abstract. An original non-invasive method for easy and re- producible measurement of the subarachnoid space width in infants is described. Preliminary results of normal values dur- ing the neonatal period are presented as well as of the validity of the ultrasound method for abnormal values obtained by available computed tomography scanning. Key words: Sino-cortical-width index - Ultrasound - Sub- arachnoid space - Infancy Results Measurements of the SCW index performed in nine healthy and normocephalic infants during the neonatal period showed values below 0.2 cm in all but one case (Fig. 2). Normal values throughout later infancy are not yet avail- able, but some preliminary data are included in Fig. 2. In eight infants with benign infantile macrocephaly and large subarrachnoid spaces, CT showed the SCW to be well above the 0.2 cm cutoff limit (Fig. 2). Introduction Reproducible measurements of the subarachnoid space in childhood have been documented by computed tomography (CT) [3-5] and pneumoencephalography [2]. These studies pointed out that the subarachnoid space may be quite large in normal infants less than 2-3 years old. However, the radiation hazards or the invasiveness of these methods limit their use in the follow-up of small infants. Until now ultrasonography was not successful in the quantitative study of the subarachnoid space. Material and method In an effort to find an easily accessible and reproducible quan- titative index of subarachnoid space width, we developed the concept of ultrasonographic sino-cortical-width index (SCW). Until recently, detailed visualisation of structures close to the ultrasound transducer was difficult due to the presence of ar- tefacts. The introduction of high-frequency (10 Megaherz) transducers overcame this technical problem. When applied to the anterior fontanel it is possible to identify the superior sagittal sinus and the adjacent outer surface of the cerebral cortex. Figure 1 illustrates the anatomical landmarks and method. With a high-frequency transducer (ATL-Ultramark 8) placed on the anterior fontanelle, the brain is scanned in a coronal plane. As an index of subarachnoid space the shortest distance is determined between the lateral wall of the triangular supe- rior sagittal sinus and the surface of the adjacent cerebral cor- tex. To minimize the interference of artefacts, plenty of trans- mission gel is used to avoid direct contact between the trans- ducer and the scalp. Offprint requests to: P. Govaert Abbreviations: CT = computed tomography; SCW = sino-corti- / cal-width-index fig. 1. Anatomical landmarks in a coronal plane high-frequency scan (10 MHz) through the anterior fontanelle. SSS, superior sagittal sinus; SCW, sino-cortical-width; CS, cerebral surface; DM, dura mater 0~ " i- .= 0.6- _.= .~ 0.4 o ~ - .'E o 0.2' r ak .~ ~0 ~ 9 0 0 0 tOo~ 8 0 9 0 0 0 I I I I ]J I I I I l I I 2 4 6 8 1 3 5 7 9 11 13 Days Months of life Fig.2. Measurements of the sino-cortical-width during infancy by 10MHz-ultrasound scan: values obtained in nine healthy and nor- mocephalic newborns (O), in eight infants with benign macrocephaly (*) and in ten normocephalic infants (O)