PAEDIATRIC NEURORADIOLOGY The ear in fetal MRI: what can we really see? Nuno Canto Moreira & João Teixeira & Raili Raininko & Johan Wikstrom Received: 5 May 2011 /Accepted: 18 July 2011 /Published online: 18 August 2011 # Springer-Verlag 2011 Abstract Introduction The aim of this study was to investigate the ability to depict the components of the ear on brain-oriented fetal MRI studies. Methods Retrospective evaluation of the ear in MRI studies was performed post-mortem in 16 fetuses ranging from 15 to 22 gestation weeks (GW), and in 122 examinations in vivo of fetuses ranging from 20 to 38 GW. The cochlea, vestibular apparatus, middle ear, and external auditory canal were separately graded according to the components that were delineated. Results The components of the inner and middle ear were fully delineated in 100% of the post-mortem examinations, but the external auditory canals were only seen in only 25%. In the in vivo group, the imaging detail was much lower. Cochlear turns could be identified in 75% of the fetuses, the vestibule and the lateral semicircular canals in 72% andossicles in 70%. Before 25 GW, the ability to identify these individual parts was 50%, 30%, and 33%, respectively, and above it was 89%, 93%, and 90% . In most cases, the external auditory canals could only be seen after 29 GW. Conclusion In fetal MRI studies in vivo, it is possible to depict the components of the ear in the majority of the fetuses, in such a manner as to exclude major malformations. However, MRI might not provide enough detail to rule out pathology of the ear before 25 GW, this being a critical age for pregnancy management in many countries Keywords Fetal . MRI . Ear . Temporal bone . Development Introduction Fetal MRI has progressively become a major tool in prenatal imaging, and its complementary role towards ultrasound (US) is now widely accepted. Ultrasound is still the gold-standard for prenatal imaging, but its capacity to rule out temporal bone pathology is limited. 3D-ultrasound is useful to delineate the pinna, it helps to rule out local malformations, and can give evidence of aneuploidy [1–3], but the visualization of the middle and inner ear is very difficult by this method. There is only one isolated report concerning the prenatal use of US for the inner ear [4], in which it was able to depict the cochlea and vestibule, but even so, with very poor detail. In contrast, MRI is capable of high spatial resolution, and several detailed MRI studies have been published on formalin-fixed specimens, regarding the development of the temporal bone structures during gestation [5, 6]. Indeed, it has been shown [5] that it is possible to fully delineate the cochlea, vestibular apparatus (vestibule and semicircular canals), and the middle ear using MRI with T2-weighted sequences, as early as at gestation week (GW) 13. N. C. Moreira (*) Neuroradiology Section C. Campos Costa, Rua Armando Rocha, S/N 3505-406 Fragosela, Viseu, Portugal e-mail: nuno.cm@radiol.uu.se N. C. Moreira e-mail: nuno.moreira@drcamposcosta.pt N. C. Moreira : R. Raininko : J. Wikstrom Department of Radiology, Uppsala University, Uppsala, Sweden J. Teixeira Department of Neuroradiology, H.G.S.Antonio, Porto, Portugal Neuroradiology (2011) 53:1001–1008 DOI 10.1007/s00234-011-0938-z