P37.06: Subdural space in fetal period—normal variation?

Abstract

Introduction: Subarachnoid space normally exists around the cerebral hemispheres in fetuses with normal intracranial structure and demonstrated by transvaginal sonography or MRI. Recent advanced technology of high-frequent ultrasound scan can reveal the detailed structure around the hemispheres. Material and method: Transvaginal 3D image datasets of parietal region were obtained from 168 fetuses with no structural abnormalities between 18 and 36 weeks of gestation. The equipment used in the study was Voluson E8 with 12-MHz transvaginal 3D/4D transducer. The datasets were obtained with highest resolution and maximum 3D acquisition. Each 3D image dataset was carefully evaluated on the three orthogonal view. Results: Subarachnoid space was clearly demonstrated in all cases. In 12 cases between 23 and 32 weeks of gestation, translucent subdural space was recognizable between the dura mater and arachnoid mater. The echogenicity was clearly different from subarachnoid space. Discussion: Subarachnoid space, demonstrated by sonography or MRI, has been thought as a physiological phenomenon in fetal life. In postnatal life, subdural space between the dura mater and arachnoid mater is one of pathological phenomena, such as subdural hemorrhage or fluid collection due to trauma. In this study, the subdural space was demonstrated in 7% of normal fetuses. This space has not been recognizable even by high frequency vaginal scan and not reported so far. The advanced new technology of ultrasound equipment and transducer may have discovered a new phenomenon. Conclusions: Subdural space was detected by 12-MHz transvaginal ultrasound scan in normal fetuses. The existence of subdural space may be one of normal variations during fetal life. Further investigation will be required.