Use of Functional MRI in a Patient Diagnosed with COVID-19 Experiencing Olfactory and Gustatory Symptoms

March 2021

Researchers recently reported on the case of a 25-year-old woman who was diagnosed with COVID-19 via positive results on polymerase chain reaction assay and chest computed tomography (CT). Although the patient’s anosmia and ageusia symptoms improved following a conservative course of treatment, she reported experiencing cacosmia and cacogeusia. Subsequent physical, endoscopic, and CT evaluation produced normal results. The patient was prescribed a treatment regimen that included multivitamins, zinc, and olfactory training. The symptoms persisted for 3 months, and the patient was referred for neurologic evaluation.

Results from magnetic resonance imaging (MRI) of the patient’s brain were normal, with no structural or signal abnormalities observed in the olfactory bulbs and sulci. Functional MRI (fMRI) was used to generate blood oxygen level–dependent (BOLD) activation maps, which were fused to T1-weighted multiplanar images. The treating clinicians reported finding “absent activation in the region of the orbitofrontal cortex [OFC], while the right uncus/piriform cortex demonstrated strong BOLD signal.”

In their discussion of this case, the researchers noted that although the sense of smell seems to be more affected than the sense of taste in patients with COVID-19, a study published in 2020 reported “alteration in smell (dysosmia, hyposmia, and anosmia) and taste (dysgeusia, hypogeusia, and ageusia) was estimated to affect 52.7% and 43.9%, respectively, of patients recovered from COVID-19 infection.”

Other studies using fMRI have found a pattern of BOLD activation of primary and secondary olfactory areas in normal individuals. Among patients with COVID-19 and olfactory dysfunction, there is growing evidence suggesting the involvement of the OFC, which is where the secondary and tertiary olfactory and gustatory cortex areas are located. The researchers wrote that this evidence includes a study that reported “hypometabolism of OFC using fluorodeoxyglucose positron emission tomography” and another that found “right OFC hyperintensity on brain MRI with frontal electroencephalography abnormalities” in patients infected with COVID-19.

In their conclusion, the researchers noted that this is the first published report on the use of fMRI in a patient with symptoms of cacosmia and cacogeusia following COVID-19 infection, and that these findings could indicate that “central olfactory pathway impairment, mainly involving OFC, may be involved in the underlying etiology of persistence of olfactory and gustatory symptoms in patients after COVID-19 infection.”

Source

Ismail II, Gad KA. Absent blood oxygen level–dependent functional magnetic resonance imaging activation of the orbitofrontal cortex in a patient with persistent cacosmia and cacogeusia after COVID-19 infection. JAMA Neurol. Published online January 22, 2021. doi:10.1001/jamaneurol.2021.0009.

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