Bell’s Palsy is defined as sudden paralysis of the facial nerve with no other cause identified. It occurs more commonly in those with diabetes, hypertension, as well as in those who are pregnant. It has been associated with a number of different viral infections including herpes simplex virus type 1 or HSV-1 (most commonly); herpes simplex virus type 2 (HSV-2); human herpesvirus (HHV); varicella-zoster virus (VZV); influenza B; adenovirus; coxsackievirus; Epstein-Barr virus; hepatitis A, B, and C viruses; cytomegalovirus (CMV); and rubella virus. Other diseases involving the facial nerve can be misdiagnosed as Bell’s Palsy. They include stroke, certain infections (Lyme Disease, Herpes Zoster), tumours, injury to the facial nerve, diabetic or hypertensive neuropathy of the facial nerve, inflammatory or demyelinating diseases affecting the facial nerve (multiple sclerosis, sarcoidosis). While there is still debate, the general consensus is that Bell’s Palsy is caused by inflammation of the facial nerve inside a bony canal leading to nerve injury. While causes are likely multiple, most are likely infectious with the most common being reactivation of Herpesvirus 1.
Community members of Magnetawan First Nation became concerned at the number of cases of Bell’s Palsy that were being diagnosed among their community members. They communicated their concerns to their Community Health Nurse. She did a preliminary investigation. The Zone Nursing Officer then requested the Public Health Unit of FNIH-OR to assess the situation. As a result, I visited the First Nation in July of 2010 and held a public meeting to gather more information and hear the concerns of those affected.
Since 1999, eight cases of Bell’s Palsy have been identified within Magnetawan First Nation, a community with 92 on reserve residents and 233 registered members. Four of the cases occurred between March 2009 and April 2010. Seven of the cases were diagnosed by a physician and one by a nurse practitioner. There have been no cases identified on reserve since April 2010.
There have been 3 female and 5 male cases raging in age from 26 to 69 years, with an average age of 48 years. The five oldest cases all had at least one chronic condition with three suffering from hypertension and two suffering from diabetes. The three youngest cases had no identified chronic conditions. With one exception, identified cases have occurred in the spring and fall.
In the literature the expected incidence of Bell’s Palsy is 20-35 cases per 100,000 population per year.
At this expected rate, in the on reserve population of Magnetawan FN (92), you would expect one case every 30 years. If you broaden to the registered population of Magnetawan (233), you would expect one case one case every 15 years.
Because Bell’s Palsy is not a reportable disease, there are no general statistics available on its occurrence in the surrounding area or in similar populations. Inquiries with First Nation and Inuit Health in Thunder Bay Zone, in the Emergency Department of the Parry Sound Hospital, and in the North Bay Parry Sound District Health Unit did not identify any other comparable clusters.
Suspected clusters of Bell’s Palsy have been identified and investigated in the past. The results of investigations are generally negative or inconclusive and environmental contamination, in particular, has not been identified as a possible cause. A recent Canadian investigation into a possible cluster in Toronto (Morris et al., Neuroepidemiology 2002;21:255–261) did not identify any geographic or temporal clustering suggestive of infectious etiology. They also commented on the number of neurologic symptoms not attributable to the facial nerve suggesting a substantial misdiagnosis of cases.
In conclusion, Magnetawan First Nation has been experiencing a higher than expected rate of Bell’s Palsy in the last few years, particularly in 2009. No particular demographic characteristics or possible exposures have been identified. Given the small number of identified cases and the multiple possible causes and the lack of a causal hypothesis, an epidemiologic cases control study is not likely to be helpful. For the present, the best approach is for the Community Health Nurse to be alert for new cases and to investigate any new cases aggressively for possible causes.