MAGNETIC-RESONANCE-IMAGING OF THE OLFACTO RY SULCI IN KALLMANN-SYNDROME

Introduction : Kallmann syndrome is a disease clinically characterized by the association of hypogonadotrophic hypogonadism and anosmia or h yposmia. Most cases have been recorded among men. It is a genetic diso rder with a specific gene location on the X chromosome. The cells that normaly express luteinizing hormone-releasing hormone or LHRH fail to migrate the olfactory placode to the forebrain. The lateral projectio ns of the olfactory placode also fail to induce development of the olf actory bulbs and tracts. Material and methods : The aim of this study was to compare the MRI appearence of the olfactory sulci, the olfactor y bulbs and frontal lobe between groups. The first reference group was composed of 20 subjects and the second group of 18 patients suffering from Kallmann syndrome. For all studies we used a 1,5 T magnet system (Signa GE). We performed two sagittal and coronal T1-weighted sequenc es in spin echo (TR = 600 ms, TE = 12 ms) with interleaved 3 mm slices and a 14 cm field of view. Results : In the first group, the two olfa ctory bulbs were always seen on coronal slices just behind the crista galli measuring 2 to 3,2 mm transversally. On sagittal slices, in 60 % of the cases two bulbs were seen (3 mm laterally of the pituitary sta lk) and in the other 40 % only one bulb was seen. The length of the bu lb has been measured between 6 and 11 mm. We noticed a plat frontal lo be in 85 % of the cases. In the second group the olfactory bulbs were never visible among the 18 patients suffering from Kallmann syndrome. The hypoplasic sulci were hardly visible and their size was less or eq ual to 1 cm and the frontal lobe was triangular in 80 % of the cases. One patient had hypoplasia of corpus callosum. Conclusion : MRI is hel pful tool to demonstrate abnormalities of the olfactory system which a re always present among patients suffering from Kallmann syndrome. MRI can also show, at the same time, a possible associated brain abnormal ity.