A patient cannot differentiate sharp from dull stimulation on both sides of the face. This finding most likely indicates damage to which nerve?

• A. Facial nerve
• B. Glossopharyngeal nerve
• C. Trigeminal nerve
• D. Vagus nerve

Answer: (C)

Assessing whether a person can tell sharp from dull on the face tests the trigeminal nerve’s sensory function. This nerve carries all general somatic sensation from the face, including pain, temperature, and discriminative touch, through its three divisions. If these sensory pathways are damaged, a patient loses the ability to distinguish sharp versus dull stimuli on the face. The other nerves are responsible for different roles: the facial nerve mainly controls facial muscles (with some taste), while glossopharyngeal and vagus nerves handle sensation in the throat and visceral areas, not facial skin. So bilateral loss of sharp-versus-dull differentiation on the face points to disruption of the trigeminal nerve.