Facial palsy is the complete or partial loss of facial muscle motor function due to damage to the seventh cranial nerve. The most common type of facial palsy is Bell palsy (also known as idiopathic facial paralysis), an acute onset unilateral lower motor neuron palsy characterized by upper and lower facial muscle paralysis.

Patients with Bell palsy present with inability to close the eye, inability to raise the corner of the mouth, and often difficulty controlling saliva drainage from the affected side. This is often caused by reactivation of herpes simplex virus or herpes zoster infection.

In contrast to peripheral lower motor neuron palsy, facial palsy can be caused by an upper motor neuron lesion such as a stroke or mass lesion and typically only affects the lower portion of the face. Bilateral facial nerve palsy may be seen in the setting of infections such as Lyme disease. Findings of additional cranial neuropathies should prompt consideration of diagnoses other than Bell palsy.

Severe hypertension has been associated with facial palsy, particularly in children but also in adults. In children, there may be a substantial delay to diagnosis of hypertension; one study notes a median time of 45 days between the first symptoms of peripheral facial palsy and a diagnosis of arterial hypertension. Another study reports that adults with uncontrolled hypertension due to poor medication compliance have a higher incidence of Bell palsy.