A case of olfactory neuroblastoma that presented with olfactory dysfunction after a COVID-19 diagnosis.

Background: Olfactory dysfunction is associated with conditions such as respiratory tract infections, trauma, sinonasal diseases, and neurodegenerative diseases. During the coronavirus disease 2019 pandemic, there was an increase in patients complaining of olfactory dysfunctions. Many studies have reported that olfactory dysfunction is associated with coronavirus disease 2019 and that the prognosis is usually favorable. Case presentation: Recently, we experienced a patient with olfactory dysfunction, which was aggravated after a coronavirus disease 2019 diagnosis. The patient had no other medical history, and their nasal endoscopic examination demonstrated no abnormal lesions. Through a psychophysical olfactory function test, the patient was diagnosed with anosmia. A paranasal sinus computed tomography demonstrated sclerotic bony changes in the cribriform plate area. A paranasal sinus magnetic resonance image study found an approximately 3.5 cm-sized olfactory neuroblastoma in the anterior cranial fossa. Conclusions: We suggest clinicians remember the possibility of underlying intracranial lesions in patients with olfactory dysfunction even during the coronavirus disease 2019 pandemic and understand the guidelines of magnetic resonance imaging when evaluating olfactory dysfunction patients. Furthermore, we recommend that clinicians pay attention to the history of olfactory dysfunction before the symptoms progress and making a coronavirus disease 2019 diagnosis.