R. NICKBRYANMDS. JAMESZINREICHMD
Disorders of smell are uncommon in children. The most common cause of temporary anosmia is nasal obstruction associated with upper respiratory tract infections. Obstruction of the nasal airway by enlarged adenoids,1 nasal and nasopharyngeal tumors, or nasal polyps can also cause a decrease in olfactory function. Head trauma, endocrine disorders such as Addison disease and thyroid dysfunction, brain tumors, viral infections, and exposure to environmental pollution can all affect the sense of smell. Congenital anosmia has been defined as anosmia that the patient becomes aware of during childhood. The most common form of congenital anosmia is Kallmann syndrome, or olfactory dysplasia, which has an incidence of 1:10000 in men and 1:50000 in women.2 Kallmann syndrome is characterized by hypogonadotropic hypogonadism and anosmia.3 Other developmental anomalies, primarily of the midline, have been described with Kallmann syndrome, including cryptorchidism, osteopenia, obesity, mild sensorineural hearing loss, cleft lip and/or palate, metacarpal abnormalities, ichthyosis, renal agenesis, and cardiac and intracranial abnormalities.4- 6 Studies of patients with Kallmann syndrome have shown agenesis of the olfactory bulbs and tracts.7 Other congenital disorders, including holoprosencephaly, Down syndrome, Turner syndrome, and Riley-Day syndrome are associated with decreased olfaction. However, to our knowledge, complete absence of the olfactory bulb and tract has been well documented only in Kallmann syndrome. The olfactory sulci lie between the gyrus rectus and the medial orbital gyrus (Figure 3, arrowheads). The olfactory tracts are located just beneath the gyrus rectus region (Figure 4, arrows) and connect anteriorly with the olfactory bulbs and posteriorly with the anterior olfactory nucleus and the olfactory stria and trigone, which are continuous with the gray matter of the prepiriform cortex, the anterior perforated substance, and the precommissural septal area. Neuroradiologic findings in Kallmann syndrome are centered around the detection of the olfactory sulci. An earlier pneumoencephalography series by Lieblich et al4 did not find normal olfactory sulci in 4 such patients. Reported associated findings on computed tomography have been extensive calcification of the lentiform nuclei, thalami, dental nuclei, subcortical white matter, and red nuclei.8 However, it seems that surface-coil MRI imaging is the optimal technique for revealing the intricate details of the olfactory bulbs, olfactory tract, and rhinencephalon. Therefore, MRI is the preferred method to evaluate these structures in patients with anosmia. Three recent studies of the imaging findings in Kallmann syndrome have reported these findings on MRI examination: (1) absence of olfactory bulbs and tracts, (2) hypoplastic olfactory bulbs and tract, and/or (3) absence or hypoplasia of the olfactory sulci.9- 11 These findings are consistent with the MRI findings in this case, which include hypoplasia of the right olfactory sulcus with slight inferior displacement of the frontal lobe (Figure 1, arrow), as well as absence of the olfactory bulbs in their expected location (Figure 2, arrowheads).
Imaging Quiz Case 1. Arch Otolaryngol Head Neck Surg. 1998;124(3):342. doi:10.1001/archotol.124.3.340