New-onset Bell palsy and Lyme disease

Evidence

Lyme disease is caused by the spirochete Borrelia burgdorferi, which is transmitted by black-legged ticks in eastern North America. It is characterized by 3 stages: early, early disseminated, and late disseminated disease. Lyme disease is on the rise in both Canada and the United States. Recent statistics in Canada show a 6-fold increase in the number of reported cases between 2009 and 2015, with most local cases occurring in Ontario, Quebec, and Nova Scotia.¹ In the United States, Lyme disease cases are concentrated in the northeastern states and the upper Midwest.² Lyme disease is slightly more common in men (56% of reported cases) in Canada, and there is a bimodal distribution by age with high incidence in adults aged 45 to 74 years and in children aged 5 to 9 years.¹ The most common presenting symptoms are an erythema migrans rash (74.2%) and arthritis (35.7%). However, Bell palsy is not rare—it has been found in 8.2% of reported cases in Canada.¹

There are 2 reasons why it is important to consider Lyme disease when a person presents with Bell palsy. First, it is easy to miss: people with facial palsy caused by Lyme disease can present without any other sign or symptom, and idiopathic Bell palsy might be the first diagnosis that comes to mind. If left undetected, it could lead to early or late disseminated Lyme disease, which is more difficult to treat. Second, one could do harm by treating it as idiopathic Bell palsy. Administering corticosteroids is the routine treatment and, because Bell palsy has been linked to viral infections, it is sometimes treated with antivirals as well.³ But antivirals will not help, and a recent study found worse long-term outcomes associated with corticosteroid use in acute Lyme disease facial palsy.⁴

Bottom line

Lyme disease can be difficult to diagnose, but because of the rising incidence in Canada it is important to maintain a high index of suspicion. Laboratory diagnosis is a 2-step process.⁵ In this case, the emergency physician ordered the screening ELISA (enzyme-linked immunosorbent assay) for your patient. If the ELISA result is equivocal or positive, order a Western blot. A positive Western blot result confirms the diagnosis.⁵ Lyme disease should be considered in any patient with a new onset of Bell palsy. Current treatment recommendations for early disseminated Lyme disease with central nervous system involvement include ceftriaxone and doxycycline.⁶ For this patient, you order a Western blot, extend his prescription of doxycycline to complete a full 21-day course, arrange follow-up, and reassure him that most Lyme disease facial palsies resolve.