What causes Bell's Palsy?

Bell's Palsy is primarily caused by an injury to the facial nerve, which is cranial nerve VII. This nerve controls the muscles of facial expression, and when it is damaged, it can lead to sudden, temporary weakness or paralysis of one side of the face. The exact cause of this injury isn't always clear, but it is commonly associated with conditions that involve inflammation or swelling around the nerve.

Understanding Bell's Palsy involves recognizing that it predominantly results from the effects of viral infections, such as the herpes simplex virus, leading to inflammation of the facial nerve. Although viral infections can be one of the contributing factors over time, the immediate physiologic issue involves the direct impact on the cranial nerve itself.

Other conditions such as trauma to the spinal cord, hereditary motor neuropathy, or even infections caused by different pathogens do not specifically lead to the presentation and symptoms typical of Bell's Palsy. Therefore, the most accurate and direct cause linked to the symptoms of Bell's Palsy is indeed the peripheral nerve injury impacting the facial nerve.