Olfactory Bulb Signal Abnormality in Patients with COVID-19 Who Present with Neurologic Symptoms

Abstract

BACKGROUND AND PURPOSE: Unique among the acute neurologic manifestations of Severe Acute Respiratory Syndrome coronavirus 2, the virus responsible for the coronavirus disease 2019 (COVID-19) pandemic, is chemosensory dysfunction (anosmia or dysgeusia), which can be seen in patients who are otherwise oligosymptomatic or even asymptomatic. The purpose of this study was to determine if there is imaging evidence of olfactory apparatus pathology in patients with COVID-19 and neurologic symptoms. MATERIALS AND METHODS: A retrospective case-control study compared the olfactory bulb and olfactory tract signal intensity on thin-section T2WI and postcontrast 3D T2 FLAIR images in patients with COVID-19 and neurologic symptoms, and age-matched controls imaged for olfactory dysfunction. RESULTS: There was a significant difference in normalized olfactory bulb T2 FLAIR signal intensity between the patients with COVID-19 and the controls with anosmia (P ¼ .003). Four of 12 patients with COVID-19 demonstrated intraneural T2 signal hyperintensity on postcontrast 3D T2 FLAIR compared with none of the 12 patients among the controls with anosmia (P ¼ .028). CONCLUSIONS: Olfactory bulb 3D T2 FLAIR signal intensity was greater in the patients with COVID-19 and neurologic symptoms compared with an age-matched control group with olfactory dysfunction, and this was qualitatively apparent in 4 of 12 patients with COVID-19. Analysis of these preliminary finding suggests that olfactory apparatus vulnerability to COVID-19 might be supported on conventional neuroimaging and may serve as a noninvasive biomarker of infection. ABBREVIATIONS: COVID-19 ¼ coronavirus disease 2019; OB ¼ olfactory bulb; SARS-CoV-2 ¼ Severe Acute Respiratory Syndrome coronavirus 2 S evere Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the coronavirus disease 2019 (COVID-19) pandemic, may produce a broad range of acute neurologic symptoms that involve both the CNS and the peripheral nervous system, including stroke, 1 meningitis, encephalitis, Guillain-Barré syndrome, and acute necrotizing hemorrhagic encephalopathy. 2 Unique among these acute neurologic manifestations is chemosensory dysfunction (anosmia or dysgeusia), which can be seen in patients who are otherwise oligosymptomatic or even asymptomatic. A single-institution report from the United States that involved 1480 patients with COVID-19

COVID-19 Imaging: What We Know Now and What Remains Unknown

“…Large vessel occlusions have been seen in patients with COVID-19, which is unsurprising given the prothrombotic effects of the underlying infection. Anosmia, a common presenting symptom, was shown to be associated with T2 hyperintensity and volume loss in the olfactory bulb on MRI, but it remains unclear whether these imaging findings relate to direct viral involvement or post-inflammatory changes (115,116). A recent report of olfactory epithelial biopsy highlighted its disruption, suggesting that direct neural invasion was not the primary culprit in anosmia (117).…”

Pathophysiology and Imaging Findings of COVID-19 Infection: An Organ-system Based Review

“…Neurologic imaging manifestations are protean and may be related to direct SARS-CoV-2 CNS infection or the sequela of COVID-19 infection and associated therapy, including hypoxemic injury, cytokine release syndrome, mechanical ventilation, or extracorporeal membrane oxygenation ( 71 ) ( 72 ). A common presenting clinical symptom is anosmia ( 73 ), with imaging showing increased T2/FLAIR signal of the olfactory bulb on MRI ( Figure 5 A, B). PRES (posterior reversible encephalopathy syndrome) with and without hemorrhage ( Figure 5 C,D) has also been identified as a neurologic manifestation of COVID-19 infection ( 74 ) ( 75 ).…”

Reply:

“…Thus, it was not only in our study 1 that a relationship between anosmia and apparent alteration of the MR image was observed in patients with COVID-19 even if other MR imaging sequences have been performed and analyzed. [4][5][6] Our obligation is to present to the scientific community what we believe as an interpretation of a possible lesion demonstrated by the imaging. Obviously, we agree that there is always the risk of seeing what we want to see and not seeing what we do not want to see.…”