MRI of the olfactory bulbs and sulci in human fetuses.
BACKGROUND
There is limited knowledge of the MRI pattern of the development of fetal olfactory bulbs and sulci.


OBJECTIVE
To describe the MRI appearance of olfactory bulbs and sulci in normal in vivo fetuses according to gestational age.


METHODS
Olfactory bulbs and sulci were retrospectively assessed on brain MRI examinations of 88 normal fetuses between 24 and 39 weeks gestational age. Two reference centres were involved in the study and both used routine protocols that included axial and coronal T2- and T1-weighted sequences at 1.5 T. The results were compared both with the commonly used neuropathological data in the literature and with personal neuropathological data. Pearson's chi-squared test or Fisher's exact test were performed. One case of olfactory agenesis associated with CHARGE syndrome was identified.


RESULTS
T2-weighted coronal sequences were the most sensitive for detecting olfactory bulbs and sulci. Olfactory sulci were significantly better detected from 30 weeks onwards (90.9-100%; P<0.001). MRI showed a posteroanterior development of these sulci. Olfactory bulbs were better detected from 30 to 34 weeks (80-90.9%; P<0.002). Comparison with neuropathological data confirmed the posteroanterior development of the sulci and showed an important delay in detection of the olfactory structures (bulbs and sulci). No difference was observed between the two centres involved.


CONCLUSIONS
To date, fetal MRI can depict olfactory sulci from 30 weeks gestational age onwards and olfactory bulbs from 30 to 34 weeks gestational age. This preliminary reference standard is useful to assess the normality of the olfactory system and to diagnose olfactory agenesis.
Azoulay
Robin
R
Department of Radiology, Hôpital Saint Vincent de Paul, Paris V, Faculté de Médecine, 82 Avenue Denfert Rochereau, 75674 Paris Cedex 14, France. svp.radio@svp.ap-hop-paris.fr
Fallet-Bianco
Catherine
C
Garel
Catherine
C
Grabar
Sophie
S
Kalifa
Gabriel
G
Adamsbaum
Catherine
C
D005333:Fetus; D005865:Gestational Age; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000592:standards; D009421:Nervous System Malformations / Q000175:diagnosis* / Q000473:pathology; D009830:Olfactory Bulb / Q000002:abnormalities / Q000033:anatomy & histology* / Q000196:embryology*; D011296:Prenatal Diagnosis / Q000295:instrumentation / Q000379:methods; D012015:Reference Standards; D012189:Retrospective Studies; D013577:Syndrome