Bell's palsy (idiopathic peripheral facial palsy) is the most common cause of facial palsy, which is related to the inflammation of the facial nerve, possibly induced by herpesvirus reactivation. Its first-line treatment comprises corticosteroids, antiviral therapy and physiotherapy. In most severe cases (grade IV to VI on House-Brackmann scale), facial motricity may remain altered or develop synkinesis or post-paralytic spasm, thus tremendously affecting quality of life. To avoid potential complications, surgical facial nerve decompression could be proposed. To date, however, there are no means to predict if Bell's palsy will evolve with any complications or if the patient will recover entirely. Thus, the invasive facial nerve decompression is equally proposed to subjects who will develop the consequences as well as to subjects able to restore without surgical treatment. This study proposes to search for prognostic blood biomarkers related to the Bell's palsy recovery pattern. Adult patients with severe Bell's palsy will be proposed to have a blood sampling for proteomic analysis in the early stage of the disease. Then 125 biomarkers on a Peptiquant™ kit will be analysed by mass spectrometry, and prognostic biomarkers will be selected regarding to the clinical recovery of Bell's palsy