Peripheral facial palsy: tests
BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.
Isolated unilateral peripheral facial palsy
- Typical Bell palsy (onset over 1 to 3 days, forehead involved, rest of the neurological examination normal): no routine laboratory tests.
Laboratory tests (depending on the context)
- Lyme serology (tick exposure or erythema migrans within the last 3 months, bilateral involvement, headache or radicular pain, onset from spring to autumn)if neededLyme disease is a possible, though rare, cause of facial palsy; the absence of a recalled tick exposure does not rule it out [2]. Without erythema migrans: ELISA serology (IgM and IgG); if it is negative in the first 4 weeks and doubt persists, repeat it 4 to 6 weeks later [2]. The HAS (2025) has neuroborreliosis considered first in case of a tick bite or tick exposure in the previous 3 months, recent erythema migrans, bilateral involvement, radicular pain, headache or other unusual symptoms, or onset from spring to autumn; without erythema migrans, serology is then always indicated [3]. Erythema migrans seen by a doctor: clinical diagnosis, serology not recommended [3].
- Fasting plasma glucose (if diabetes possible, before corticosteroids)if neededDiabetes is a risk factor for Bell's palsy and a systemic cause of peripheral facial palsy that laboratory tests can identify [1]; first-line treatment is oral corticosteroid therapy [1].
At 3 weeks, if the first Lyme serology is negative and doubt persists
Do not order
- “Routine” laboratory tests (FBC, CRP, multiple serologies) for typical Bell's palsy: laboratory tests are not necessary for the diagnosis [1]
- Lyme serology in a person without symptoms after a tick bite: do not diagnose Lyme disease without symptoms [2]
- Lyme serology for erythema migrans (with or without facial palsy): not recommended, the diagnosis is clinical [3]
Child: isolated peripheral facial palsy
Laboratory tests
- Lyme serology (ELISA, confirmed by Western blot if positive or equivocal)
At 3 weeks, if the first serology is negative
- Repeat Lyme serology (follow-up decided with the parents)if neededNegative initial serology: close clinical follow-up (other causes, new neurological signs) and follow-up serology at 3 weeks, as a shared decision with the parents; in case of seroconversion, no lumbar puncture [3].
Do not order
- Lumbar puncture as first-line test for isolated unilateral facial palsy in a child without meningeal signs: not recommended; start with blood serology [3]
Sources (6)
- Dalrymple SN, Row JH, Gazewood J. Bell palsy: rapid evidence review. Am Fam Physician. 2023;107(4):415-420.
- National Institute for Health and Care Excellence (NICE). Lyme disease. Guideline NG95, avril 2018, mise à jour 17 octobre 2018.
- Haute Autorité de santé. Borréliose de Lyme et autres maladies vectorielles à tiques (MVT). Recommandation de bonne pratique, adoptée par le Collège le 13 février 2025 ; et fiche « Diagnostic d'une paralysie faciale périphérique de Lyme », février 2025.
- Lantos PM, Rumbaugh J, Bockenstedt LK, Falck-Ytter YT, Aguero-Rosenfeld ME, et al. Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease. Clin Infect Dis. 2021;72(1):e1-e48.
- Rauer S, Kastenbauer S, Hofmann H, Fingerle V, Huppertz HI, et al. Guidelines for diagnosis and treatment in neurology – Lyme neuroborreliosis (S3, Allemagne). GMS Ger Med Sci. 2020;18:Doc03.
- Heckmann JG, Urban PP, Pitz S, Guntinas-Lichius O, Gágyor I. The Diagnosis and Treatment of Idiopathic Facial Paresis (Bell's Palsy). Dtsch Arztebl Int. 2019;116(41):692-702.