DESCRIPTION

An acute, largely idiopathic, peripheral (lower motor neuron) facial nerve palsy; Bell palsy is the most common cause of spontaneous unilateral facial paralysis resulting in the inability to voluntarily move the facial muscles of the affected side. It is associated with edema and compression of cranial nerve VII (CN VII).

EPIDEMIOLOGY

• No race, geographic, or gender predominance
• Affects all ages; highest incidence in patients ages 15 to 45 years
• Occurs with equal frequency on the left and right sides of the face

ETIOLOGY AND PATHOPHYSIOLOGY

• Inflammation of CN VII causes edema of the perineurium. Subsequent compression results in degeneration of the nerve and damage to surrounding intraneural vasculature.
• Viral etiology is suspected to be the most common cause due to activation of latent herpes virus in cranial nerve ganglia.
• Increased risk in pregnancy may be due to hypercoagulability causing thrombosis of surrounding intraneural vasculature, relative immunosuppression, and pregnancy related fluid retention

RISK FACTORS

• Pregnancy: increased risk seen in patients with chronic hypertension, maternal obesity, and severe preeclampsia
• Immunosuppression
• Diabetes mellitus
• Upper respiratory infection with viruses
• Chronic hypertension
• Obesity
• Extremes of temperature (1)