Adverse Events of Special Interest (AESI) and related risks: facial palsy/Bell

Definition: Peripheral facial nerve palsy is the partial (paresis) or complete (paralysis) loss of function of some or all the structures innervated by the facial nerve (cranial nerve VII). It is also classified by the temporal course of its development, depending on whether it is acute (minutes to days), subacute (days to weeks) or chronic (months or more). 

Diseases: This can be seen in the context of many conditions, including infections such as otitis media with or without cholesteatoma, rubella, Lyme borreliosis, herpes virus reactivation, influenza, and HIV infection. It can also be associated with traumatic injuries, malignancy, and autoimmune disorders, as well as in the context of hormonal changes during pregnancy (1). 

Approximately half of all cases of acute peripheral facial nerve palsy are idiopathic, for which no specific cause can be found. In the remaining half of cases, a specific cause can be determined, including infection (viral, bacterial, mycoplasma, mycobacteria, spirochetes, tick-borne zoonoses), cancer, neurological/neuromuscular junction, autoimmune/endocrine disorders, trauma, drug toxicity, hereditary disorders; diabetes, prediabetes; hypertension; migraine; and psychological factors (1).

Medications: There are no medications associated with peripheral facial nerve palsy.

Vaccines: The only proven association of Bell's palsy with a vaccine is with influenza vaccine administered intranasally with E. coli heat labile toxin (Nasalflu®, Berna Biotech) (2). The MMR vaccine has been temporarily associated with the onset of facial paralysis (3).

Sources:

• Barbara Rath, Jane Gidudu, Helen Anyoti, Brigid Bollweg, Patrick Caubel, Yeoung-Hwang Chen, et al. Facial nerve palsy including Bell's palsy: Case definitions and guidelines for collection, analysis, and presentation of immunization safety data, Vaccine, Volume 35, Issue 15, 2017, Pages 1972–1983, ISSN 0264–410X. https://doi.org/10.1016/j.vaccine.2016.05.023.
• SPEAC - Work Package: WP2 Standards and tools V1.0 – February 15th, 2021 Authors: Barbara Law Nature: Report | Diss. level: Public https://brightoncollaboration.us/wp-content/uploads/2021/03/SPEAC_D2.5.2.1_Facial-Nerve-Palsy-CaseDefinition-Companion-0_format12067-1.pdf.
• Ministry of Health. Manual de vigilância epidemiológica de eventos adverses pós-vacinação [electronic resource], 2020. http://bvsms.saude.gov.br/bvs/publicacoes/manual_vigilancia_epidemiologica_eventos_vacinacao_4ed.pdf.