Diagnosis of isolated congenital anosmia using simultaneous functional magnetic resonance imaging and olfactory event‐related potentials: Our experience in six patients

Abstract

Olfactory disorders can be classified as conductive, sensorineural or due to an impairment in the olfactory central nervous system. The vast majority of olfactory dysfunction occurs as a result of upper respiratory tract infection (18%-45%), sinonasal disease (7%-56%) or head trauma (8%-20%), whereas the prevalence of primary anosmia is low (0.4%). 1 The causes of primary anosmia are syndromic and non-syndromic. Syndromic primary anosmia is usually associated with Kallmann syndrome, which is characterised by hormonal abnormalities such as hypogonadotropic hypogonadism. On a very rare occasion, a primary anosmia presents as olfactory bulb agenesis without associated syndrome. In previous studies of such cases, diagnosis is usually based on the absence of an olfactory bulb on structural MRI, rather than on objective functional measures. But recent study revealed that olfactory bulb agenesis does not necessarily mean anosmia. So we examined both structural and functional MRI and olfactory event-related potential data to diagnose isolated congenital olfactory bulb agenesis, gaining objective evidence of olfactory function.

The diagnostic value of the olfactory evaluation for congenital hypogonadotropic hypogonadism

“…However, studies have indicated the discordance of OBV and OERP. Patients with the agenesis of OB may have identifiable OERPs (27)(28)(29). Thus, the olfactory function of these patients may be underestimated for the lack of OERP test.…”

Magnetic resonance spectroscopy findings of brain olfactory areas in patients with COVID‐19‐related anosmia: A preliminary comparative study

“…2,3 Overall, olfactory disorders could be classified as conductive sensory-neural or due to a CNS impairment. 4 Until now, the basic pathogenesis of these complications remains controversial, and evidence suggests that the main pathogenesis of anosmia in the setting of COVID-19 infection can probably depend on CNS dysfunction. 5 The most important current discussions in COVID-19-related anosmia are the controversies about the biochemical basis of these pathologies, diagnosis, and treatment.…”

“…Although most of these anosmic patients will eventually improve within a few months, a considerable number of patients will develop prolonged smell loss more than 2 years after diagnosis 2,3 . Overall, olfactory disorders could be classified as conductive sensory‐neural or due to a CNS impairment 4 . Until now, the basic pathogenesis of these complications remains controversial, and evidence suggests that the main pathogenesis of anosmia in the setting of COVID‐19 infection can probably depend on CNS dysfunction 5 .…”

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“…Although most of these anosmic patients will eventually improve within a few months, a considerable number of patients will develop prolonged smell loss more than two years after diagnosis 2,3 . Overally, olfactory disorders could be classified as conductive sensory-neural or due to a central nervous system impairment 4 . Until now, the basic pathogenesis of these complications remains controversial, and evidence suggests that the main pathogenesis of anosmia can probably depend on CNS dysfunction 5 .…”