Bell's Palsy Linked to Stroke Risk

Pauline Anderson

May 19, 2011

May 18, 2011 — Bell's palsy (BP) may be associated with an increased risk for stroke, a new study suggests.

The relationship may relate to exposure to herpes simplex virus type 1 (HSV-1) or varicella-zoster viruses (VZVs), they speculate.

Ya-Ning Chiu, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan, and colleagues, used data from a national database to compare the risk for stroke between a group of patients with a diagnostic code of BP and found an increase in risk for stroke in these patients vs controls.

Both HSV-1 and VZVs have been linked to risk for stroke, the study authors point out. These pathogens are thought to cause inflammation, promoting atherosclerosis and vasculopathy in the cerebral vasculature. Both viruses have also been linked to BP.

"Therefore, we speculated that the increased risk of stroke after BP may be due, at least in part, to the etiological link between viral reactivation and BP and the connection between viral infection and stroke," the study authors write.

The study was published online May 6 in the Journal of Neurology, Neurosurgery, and Psychiatry.

Double the Risk

Researchers used data from Taiwan's National Health Insurance (NHI) claim database from 2000 to 2003. The study included 7506 adult patients with BP and 22,518 randomly selected age and sex controls without BP.

BP patients had to have a principal diagnosis of BP with at least 2 ambulatory visits. For a stroke, a patient had to have at least 1 hospital discharge or 2 or more ambulatory medical care visits with the principal diagnosis of stroke.

Stroke events occurred more frequently in BP patients than controls, with more than double the risk after controlling for comorbid diseases.

Table. Risk of Stroke With Bell's Palsy vs Controls

Endpoint Bell's Palsy Cohort Controls Hazard Ratio (95% CI) P
Stroke, No. (%) 300 (4.0) 356 (1.6) 2.38 (2.04 – 2.78) <.0001

CI = confidence interval

The BP cohort also tended to have more nonhemorrhagic strokes than the non-BP cohort.

Some Limitations

The study authors acknowledged that the study has limitations.

"[I]t is still possible that the BP cohort included some cases of central facial palsy incorrectly diagnosed as BP, which would increase the risk of stroke in the BP sample," they write.

"Second, due to the inherent limitation of the NHI database, information was lacking regarding the laterality of BP, brain imaging, and lifestyle risk factors, such as obesity, smoking, alcohol consumption, and physical inactivity."

Furthermore, the analysis may not have erased the confounding effects of a substantial imbalance in the distribution of vascular risk factors, such as diabetes and hypertension, between the 2 groups, the study authors added.

Because these risk factors are common in both BP and stroke, "the association between BP and stroke could be explained by common risk factors," they conclude.

'Misidentification' Major Issue

Asked for comment on these findings, Joseph Broderick, MD, professor and chair of the Department of Neurology at the University of Cincinnati Neuroscience Institute in Ohio and member of the American Academy of Neurology, said a major issue with the study is potential "misidentification" of central facial weakness related to stroke or transient ischemic attack (TIA) as weakness due to BP. 

"This is an administrative database, and the large majority of patients would be seen by primary physician not a neurologist," Dr. Broderick told Medscape Medical News in an email. General practitioners sometimes use BP as a substitute term for isolated facial weakness, he added.

This misidentification probably explains the difference in subsequent stroke risk and the higher percentage of vascular risk factors, such as diabetes, in the facial weakness cohort. 

"Once you have had a stroke/TIA, you are more likely to have a recurrent stroke than those persons without a prior history," said Dr. Broderick. "And stroke patients are more likely to have vascular risk factors than nonstroke patients."

The study authors have disclosed no relevant financial relationships.

J Neurol Neurosurg Psychiatry. Published online May 6, 2011.


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