Fact-sheet: Olfactory bulb hypoplasia - olfactory dysgenesis
Updated on 08/04/2017 at 8:28 AM
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Definition
Olfactory bulb agenesis: failure of development of the olfactory bulbs within the olfactory clefts.
Notably found in Kallmann-de Morsier syndrome, or olfactogenital syndrome = genetic disorder of embryonic development (prevalence 1/10,000, more common in girls).
Clinical features
Anosmia or hyposmia.
In the setting of Kallmann-de Morsier syndrome: delayed puberty, micropenis, malpositioned testis (inconstant), contralateral mirror movements (mirror movements of the upper limbs), cleft lip/palate, +/- hearing loss.
Laboratory findings
Hypogonadotropic hypogonadism in the setting of Kallmann-de Morsier syndrome (defective embryonic migration of GnRH-synthesizing neurons)
MRI
Shallow olfactory clefts.
Absence of the olfactory bulbs within the olfactory clefts (coronal T2- and T1-weighted images, sagittal T1-weighted images).
Morphology of the olfactory tracts within the olfactory sulci
Differential diagnosis
CHARGE syndrome (differential diagnosis of Kallmann-de Morsier syndrome) includes additional embryonic developmental anomalies (notably semicircular canal agenesis) and a polymalformative syndrome.