**3. COVID-related facial palsy**

The SARS-CoV-2 (COVID-19) infection pandemic has been a major public health issue worldwide. Recent studies have shown that it has an effect on other pathologies such as neurological syndromes [21, 51, 52]. COVID-19 as well as facial palsy disrupts the daily life of our society. Those diseases provoke anguish to those who suffer it due to possible functional and esthetic sequels [21, 51]. Literature has suggested a possible link between COVID-19 and facial palsy, the coronavirus neurotropic nature [21]. The COVID-19 ability to infect different cell types is determined by the ACE2 receptors. The ACE2 inhibitors are located at the endothelial cells of the blood-brain barrier. The binding between ACE2 and COVID-19 allows it to enter the central nervous system [52, 52, 55], even facial palsy has been proposed as the first and only COVID-19 symptom [54, 56].

The COVID-19 incidence has increased along the pandemic development, and some studies focus on the vaccine trial as facial palsy cause [21]. Although, other authors do not find significant differences in the incidence of facial palsy [57], the incidence in pregnant women increases due to the physiological pregnancy stress. This is why they could be more susceptible to neurotropic invasion by the virus [52]. It has been reported an unusual amount of children, a cluster of six, that features facial palsy between March 23 and April 26, 2020 [58]. Despite the low incidence, the bilateral facial palsy case was reported as an asymptomatic COVID-19 [59]. Later, other bilateral facial palsy studies related to COVID-19 were presented [60, 61].

Authors hypothesize in their works that Bell's palsy may be a neuro-COVID-19 manifestation. Nevertheless, a few authors have claimed that there is not enough evidence to establish a clear cause between the two conditions [21, 52, 56, 57]. Other researchers compile the online databases about COVID-19 and facial palsy, and they concluded that COVID-19 increases the number of neurological deceases and pointed out that SARS-CoV-2 infection may be an underlying etiology in patients with COVID-19, and facial palsy can be the first COVID-19 manifestation [62, 63].
