The temporomandibular articulation is composed of bilateral, diarthrodial, temporomandibular joints (TMJs). The TMJ and its associated structures play an essential role in guiding mandibular motion and distributing stresses produced by everyday tasks, such as chewing, swallowing, and speaking.

The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area. The nerve is divided into three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3); their cell bodies are located in the trigeminal ganglia and they make connections with second-order neurons in the trigeminal brainstem sensory nuclear complex.

Herpes zoster (HZ), is a distinctive syndrome caused by reactivation of varicella zoster virus (VZV). This reactivation occurs when immunity to VZV declines because of aging or immunosuppression. Postherpetic neuralgia (PHN), defined as pain persisting more than 3 months after the rash has healed (the virus reactivates and travels along the sensory nerves to the skin, causing the distinctive prodromal pain followed by eruption of the rash) is a debilitating and difficult to manage consequence of HZ.

Tension-type headache (TTH) is the most common form of headache. It can be categorized into three subtypes according to the International Classification of Headache Disorders based on headache frequency: (1) infrequent episodic TTH (<12 headache days/year), (2) frequent episodic TTH (12-180 days/year), and (3) chronic TTH (>180 days/year).

Glossopharyngeal neuralgia (GPN) is a pain syndrome characterized by unilateral sharp pain in the sensory distribution of the ninth cranial (glossopharyngeal) nerve. The pain usually comes as an acute attack and lasts from a few seconds to a few minutes. Patients usually describe the pain as lancinating, stabbing, shooting, and electric shock–like; it is felt in the ear, throat, posterior part of the tongue, soft palate, and lower lateral and posterior parts of the pharynx. Sometimes a painful feeling of pressure or burning that lasts for several minutes follows the pain attacks. Between the paroxysms of pain these patients remain pain free, but triggering of pain by swallowing and speech makes them extremely disabled, resulting in severe weight loss.