Bell's palsy is primarily characterized by which of the following symptoms?

Bell's palsy is primarily characterized by facial paralysis, which occurs due to inflammation of the facial nerve (cranial nerve VII). This condition typically results in sudden weakness or paralysis on one side of the face, leading to a drop in the corner of the mouth, difficulty closing the eye, and challenges with facial expressions on the affected side. It can also be accompanied by symptoms such as pain around the jaw or behind the ear, increased sensitivity to sound, and changes in taste, but the hallmark symptom is the unilateral facial paralysis.

When considering the other options, paraparesis refers to weakness of the lower limbs and is not related to Bell's palsy, which affects facial muscles. Tinnitus is the perception of noise or ringing in the ears, and while it can occur with various conditions involving cranial nerves or ear problems, it is not a primary symptom of Bell's palsy. Monoplegia indicates paralysis of a single limb, which also does not apply to Bell's palsy, as the condition specifically impacts facial muscles and not arm or leg functions. Thus, the defining characteristic symptom of Bell's palsy is indeed facial paralysis.