Data from 235 Cases of Bell's Palsy during COVID-19 Pandemic: Were There Clusters of Facial Palsy?

Dear Editor,

Different clinical series on the prevalence of Bell's palsy (BP) in the pandemic are emerging in the literature. Some researchers [1, 2] suggest a link between facial palsy and SARS-CoV-2, although other authors [3] do not find significant differences in the incidence of facial palsy, with low rate of detection of SARS-CoV-2 viral genome in nasal swab coinciding with paralysis (2/153 BP cases). After a year of the COVID-19 pandemic, attributing to the SARS-CoV-2 virus an increase of incidence of BP cases remains unclear [4].

We present findings of investigations in incidence of BP during the COVID-19 pandemic in a population of over 530,000 people in Spain. Our research focuses on some epidemiological aspects of the temporal distribution of BP cases during the pandemic waves (Fig. 1). First, we reviewed the BP cases during 2019 (n = 137 BP) and we calculated the crude annual incidence of BP: 25.8% per 100,000 person-years in 2019, coinciding with the rate reported for a similar population in our country (24.1% per 100,000 person-years) [5]. Second, we collected 170 BP cases during 2020 and we calculated our crude annual incidence of BP during 2020: 32.07% per 100,000 person-years, higher than our rate in 2019, but in range with the very heterogeneous rates reporting in literature [5]. As interesting data, 7 patients were tested for SARS-CoV-2 by PCR in nasal swab during the BP in 2020, and only 2 resulted positive. This low rate of detection of SARS-CoV-2 viral genome among BP patients coincides with other case-series reported [3]. Finally, we explored the possibility of clusters of BP around the “peaks” of CO­VID-19 pandemic based on data from the Health Ministry of Spain over the 14-day Accumulated Incidence of COVID-19-positive cases per 100,000 inhabitants [6]. We collected 235 patients who developed a BP between March 1, 2020, and May 30, 2021. We classified them according to the 4 pandemic waves of 14-day accumulated incidence of SARS-CoV-2 per 100,000 inhabitants in Spain. As we show in the Figure 1, a similar number of cases of BP were diagnosed throughout the whole pandemic, without identifying clusters of BP during the “waves” or the “peaks.” Based on this uniform distribution of cases during the 14 pandemic months, we conclude that we have not found an increase in the incidence of BP cases in relation to the increase in the accumulated incidence of contagion by SARS-CoV-2 virus in our population.

Fig. 1

The temporal distribution of Bell's palsy cases according to the 4 pandemic “waves” of 14-days accumulated incidence of SARS-CoV-2 per 100,000 inhabitants (data from the Health Ministry of Spain [6]).

Statement of Ethics

The study design complies with the Declaration of Helsinki ethical standards.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

The study did not receive any funding.

Author Contributions

All authors have equally contributed as main authors.