MR-IMAGING OF KALLMANN SYNDROME, A GENETIC DISORDER OF NEURONAL MIGRATION AFFECTING THE OLFACTORY AND GENITAL SYSTEMS

PURPOSE: We report the MR findings in nine patients with clinical and laboratory evidence of Kallmann syndrome (KS), a genetic disorder of o lfactory and gonadal development. In patients with KS, cells that norm ally express luteinizing hormone-releasing hormone fail to migrate fro m the medial olfactory placode along the terminalis nerves into the fo rebrain. In addition, failed neuronal migration from the lateral olfac tory placode along the olfactory fila to the forebrain results in apla sia or hypoplasia of the olfactory bulbs and tracts. Patients with KS, therefore, suffer both reproductive and olfactory dysfunction. METHOD S: Nine patients with KS underwent direct coronal MR of their olfactor y regions in order to assess the olfactory sulci, bulbs, and tracts. A 10th patient had MR findings of KS, although the diagnosis is not yet confirmed by laboratory tests. RESULTS: Abnormalities of the olfactor y system were identified in all patients. In particular, the anterior portions of the olfactory sulci were uniformly hypoplastic. The olfact ory bulbs and tracts appeared hypoplastic or aplastic in all patients in whom the bulb/tract region was satisfactorily imaged. In two (possi bly three) patients, prominent soft tissue in the region of the bulbs suggests radiographic evidence of neurons that have been arrested befo re migration. CONCLUSIONS: Previous investigators of patients with KS used axial MR images to demonstrate hypoplasia of the olfactory sulci but offered no assessment of the olfactory bulbs. In the present study we used coronal images to show hypoplasia of both olfactory sulci and bulbs. In addition, we found what we believe to be the radiologic cor relate of arrested neuronal migration in KS.