Computed temography of the anterior skull base in Kallmann syndrome reveals specific ethmoid bone abnormalities associated with olfactory bulb defects.

Context: Kallmannsyndrome (KS) is characterized by congenital hypogonadotropic hypogonadism (CHH) and an impaired sense of smell related to defective development of the olfactory system. Objective: The aim of the study was to use high-resolution computed tomography (CT) to detect specific abnormalities in the ethmoid bone region surrounding the olfactory bulbs in patients with KS. Patients: Thirty-seven KS patients were compared to normosmic CHH (nCHH) patients (n=15) and controls (n=30) of similar age. Design and Methods: We conducted a prospective study in a single referral center. Subjects underwent CT in bone windows with axial, coronal, and sagittal reconstructions centered on the olfactory fossa (OF) and cribriform plate (CP). We characterized the OF structure by measuring OF height, width, and surface area and a series of angles. The CP foramina were counted bilaterally. Olfactory bulb magnetic resonance imaging, performed in parallel, was compared with CT findings. Results: OF height, width, and surface area were all significantly lower in KS patients than in nCHH patients and controls (P < .0001). KS patients also had wider angles than nCHH patients and controls (P < .0001). KS subjects with olfactory bulb agenesis on magnetic resonance imaging or who harbored KAL1 mutations had the most marked changes in OF measurements and angles. Coronal OF height distinguished KS patients from controls with the best sensitivity and specificity. The mean number of CP foramina was similar in KS, nCHH, and control subjects. Conclusions: KS is associated with specific ethmoid bone abnormalities. The preserved number of CP foramina in KS patients suggests that the integrity of olfactory structures is not mandatory for their formation during fetal development or their maintenance in adult life.