Bell's Palsy Linked to Stroke Risk

A new study suggests that Bell's palsy (BP) may be associated with an increased risk for stroke, possibly due to exposure to herpes simplex virus type 1 (HSV-1) or varicella-zoster viruses (VZVs).

Researchers at the National Taiwan University Hospital (Taipei) used data from Taiwan's National Health Insurance (NHI) claim database from 2000 to 2003. The study included 7,506 adult patients with BP and 22,518 randomly selected age and sex controls without BP. The BP patients had to have a principal diagnosis of BP with at least two ambulatory visits. For a stroke, a patient had to have at least one hospital discharge or two or more ambulatory medical care visits with the principal diagnosis of stroke.

The researchers found that stroke events occurred more frequently in BP patients than controls, with more than double the risk, after controlling for comorbid diseases. The BP cohort also tended to have more nonhemorrhagic strokes than the non-BP cohort. The researchers found that both HSV-1 and VZVs were linked to risk for stroke, and speculated that these pathogens are thought to cause inflammation, promoting atherosclerosis and vasculopathy in the cerebral vasculature. Both viruses have been linked to BP in previous studies. The study was published early online on May 6, 2011, in the Journal of Neurology, Neurosurgery, and Psychiatry.

"It 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,” said lead author Ya-Ning Chiu, MD, of the department of physical medicine and rehabilitation. "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.”

Bell's palsy, also known as idiopathic facial paralysis, arises from dysfunction in cranial nerve VII (the facial nerve) that results in the inability to control facial muscles on the affected side. Several conditions can cause facial paralysis, such as brain tumor, stroke, and Lyme disease; however, if no specific cause can be identified, the condition is known as Bell's palsy, named after Scottish anatomist Charles Bell. Corticosteroids have been found to improve outcomes while antiviral drugs have not, but early treatment is necessary for steroids to be effective. Most people recover spontaneously and achieve near-normal to normal functions. Many show signs of improvement as early as 10 days after the onset, even without treatment.

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