Reader response: Loss of smell in COVID-19 patients: MRI data reveals a transient edema of the olfactory clefts
Luigi AngeloVaira, Maxillofacial Surgeon, Biomedical Science Department, PhD School of Biomedical Science, University of Sassari (Sassari, Italy)
GiacomoDe Riu, Maxillofacial Surgeon, Maxillofacial Surgery Department, University Hospital of Sassari (Sassari, Italy)
Submitted October 11, 2020
We read with interest the article by Eliezer et al.1 The authors investigated MRI findings of COVID-19 patients with loss of sense of smell, finding complete olfactory cleft obstruction in the early stages of the disease in 19 patients, which disappeared 1-month follow-up in 12 cases. The study the olfactory bulb volume showed no significant differences between COVID-19 patients and healthy controls. On this basis, the authors concluded that the olfactory cleft obstruction is the main mechanism underlying the olfactory dysfunction in COVID-19 patients.
Based on our clinical2,3 and radiological4 data, we agree with the authors that the loss of smell in COVID-19 patients is probably linked to inflammatory phenomena at the level of the olfactory epithelium and not to an involvement of the bulb. This hypothesis is supported by the complete regression of the dysfunction within few weeks in most cases3 and the lack of association with a poor prognosis and other signs of central nervous system involvement.2 Moreover, we have recently published the histopathological findings on olfactory epithelial samples taken from a patient with long-term anosmia following COVID-19. The examination revealed a massive destruction of the olfactory epithelium with evidence of mild chronic inflammatory infiltration.5 All these findings reinforce the conclusions proposed by the authors in the article, which however presents the bias of not being able to exclude an involvement of the olfactory bulb as only a volumetric analysis was carried out. Furthermore, it would have been interesting to use COVID-19 patients without olfactory disturbance and not only healthy subjects as controls. In this way, it would be possible to understand the radiological differences between patients who develop or do not develop olfactory disorders during COVID-19.
Disclosure
The authors report no relevant disclosures. Contact journal@neurology.org for full disclosures.
References
Eliezer M, Hamel AL, Houdart E, et al. Loss of smell in COVID-19 patients: MRI data reveals a transient edema of the olfactory clefts. Neurology 2020 Epub Sep 11.
Vaira LA, Hopkins C, Petrocelli M, et al. Do olfactory and gustatory psychophysical scores have prognostic value in COVID-19 patients? A prospective study of 106 patients. J Otolaryngol Head Neck Surg 2020;49:56.
Vaira LA, Hopkins C, Petrocelli M, et al. Smell and taste recovery in coronavirus disease 2019 patients: a 60-day objective and prospective study. J Laryngol Otol 2020;134:703–709.
Lechien JR, Michel J, Radulesco T, et al. Clinical and radiological evaluations of COVID-19 patients with anosmia: preliminary report. Laryngoscope 2020 Epub Jul 17.
Vaira LA, Hopkins C, Sandison A, et al. Olfactory epithelium histopathological findings in long-term COVID-19 related anosmia. J Laryngol Otol 2020 [in press].
We read with interest the article by Eliezer et al.1 The authors investigated MRI findings of COVID-19 patients with loss of sense of smell, finding complete olfactory cleft obstruction in the early stages of the disease in 19 patients, which disappeared 1-month follow-up in 12 cases. The study the olfactory bulb volume showed no significant differences between COVID-19 patients and healthy controls. On this basis, the authors concluded that the olfactory cleft obstruction is the main mechanism underlying the olfactory dysfunction in COVID-19 patients.
Based on our clinical2,3 and radiological4 data, we agree with the authors that the loss of smell in COVID-19 patients is probably linked to inflammatory phenomena at the level of the olfactory epithelium and not to an involvement of the bulb. This hypothesis is supported by the complete regression of the dysfunction within few weeks in most cases3 and the lack of association with a poor prognosis and other signs of central nervous system involvement.2 Moreover, we have recently published the histopathological findings on olfactory epithelial samples taken from a patient with long-term anosmia following COVID-19. The examination revealed a massive destruction of the olfactory epithelium with evidence of mild chronic inflammatory infiltration.5 All these findings reinforce the conclusions proposed by the authors in the article, which however presents the bias of not being able to exclude an involvement of the olfactory bulb as only a volumetric analysis was carried out. Furthermore, it would have been interesting to use COVID-19 patients without olfactory disturbance and not only healthy subjects as controls. In this way, it would be possible to understand the radiological differences between patients who develop or do not develop olfactory disorders during COVID-19.
Disclosure
The authors report no relevant disclosures. Contact journal@neurology.org for full disclosures.
References