- Lancinating pain occasionally occurs in some people over one side of the face in the sensory distribution area (or part of the area) of the fifth or ninth nerves; this phenomenon is called tic douloureux (or trigeminal neuralgia or glossopharyngeal neuralgia).  The pain feels like sudden electrical shocks, and it may appear for only a few seconds at a time or may be almost continuous.  Often it is set off by exceedingly sensitive trigger areas on the surface of the face, in the mouth, or inside the throat - almost always by a mechanoreceptive stimulus rather than a pain stimulus.  For instance, when the patient swallows a bolus of food, as the food touches a tonsil, it might set off a severe lancinating pain in the mandibular portion of the fifth nerve.
- The pain of tic douloureux can usually be blocked by surgically cutting the peripheral nerve from the hypersensitive area.  The sensory portion of the fifth nerve is often sectioned immediately inside the cranium, where the motor and sensory roots of the fifth nerve separate from each other, so that the motor portions, which are needed for many jaw movements, can be spread while the sensory elements are destroyed.  This operation leaves the side of the face anesthetic, which in itself may be annoying.  Furthermore, sometimes the operation is unsuccessful, indicating that the lesion that causes the pain might be in the sensory nucleus in the brain stem and not in the peripheral nerves.