Maxfacts

Classification of facial pain syndromes

Idiopathic (unknown cause) facial pain makes up a significant proportion of oral and maxillofacial practice. In 1994 the International Association for the Study of Pain revised its classification of chronic pain. This now includes:

• Dental-type pain
• Odontalgia (toothache!)
• Pulpitis (inflammation of the dental pulp)
• Periapical periodontitis and dental abscess
• Atypical odontalgia (toothache, in the absence of detectable dental disease)
• Cracked tooth syndrome
• Glossodynia (also known as ‘burning mouth syndrome’ or oral dysaesthesia)
• Trigeminal herpes zoster and postherpetic neuralgia
• Trigeminal neuralgia (tic douloureux)
• Glossopharyngeal neuralgia (affecting tongue and throat)
• Secondary neuralgia (from central nervous system lesions)
• Temporomandibular joint (jaw joint) pain dysfunction syndrome
• Rheumatoid arthritis of the temporomandibular joint

Idiopathic facial pain is a very real entity and not just a manifestation of psychological problems, although they are sometimes associated. All forms should remain a ‘diagnosis of exclusion’ (that is, all other causes of facial pain, notably arising from the teeth, sinuses, neuralgias and headaches should be considered and if necessary investigated). A thorough medical history and examination needs to include examination of the cranial nerves. In selected cases CT or MRI scans may be necessary to exclude serious pathology. This is important as vague pain can on occasion be a symptom of a life-threatening disease, particularly when conventional treatments fail. Periodic reassessment is also advisable for this reason. Occasionally some forms of idiopathic facial pain (for example, oral dysaesthesia ) are associated with deficiencies in iron, vitamin B₁₂ or folic acid.

Aetiology

It has been suggested that facial-pain symptoms may be interrelated and form part of a whole body pain syndrome involving the neck, back, abdomen and skin. Adverse life events, ‘stress’ and impaired coping ability are the strongest known associated factors.

The aetiology of idiopathic facial pain is (by definition) unknown - the physiology of pain is very complicated. In temporomandibular joint pain dysfunction syndrome evidence suggests that stress-induced inflammation within and around the joint can cause local production of various chemicals, including free radicals, which results in pain and in possibly destructive changes to the joint. Some of these chemicals may also develop in muscles and teeth, accounting for the different anatomical locations for pain. Neuropeptides have been demonstrated within the temporomandibular joint capsule. Free radicals, in addition to causing pain, may also have an effect on the synovial fluid (lubricating fluid in the joint), impairing its lubricating ability and resulting in adhesions across the joint. Other pain mediating agents (including 15-hydroxyeicosatraeinoic acid, 15-HETE, and ‘substance P’, a neuropeptide) have been identified. It has been suggested that these chemicals may be present in other nerve endings, which may help to account for dental-type pain in the absence of obvious dental disease (odontalgia; see below).

Atypical facial pain

This is pain which does not fit into any other diagnostic categories (such as diseases of the teeth, sinuses, ear, jaw joint, etc.). It is essentially a diagnosis of exclusion.

Atypical facial pain is often characterised by its bizarre and inconsistent nature. Symptoms may be related to those of atypical odontalgia (see below) which, it has been suggested, is a localised variant of atypical facial pain. It may be described as an intense, deep, constant burning or aching pain. It is usually difficult to localise the pain. As a rule of thumb, organic pain (due to infection, trauma, tumours, nerve irritation etc.) does not cross the midline of the face. Despite the severity of the symptoms, patients are not kept awake at night by the pain. Other symptoms (such as dysaesthesia (distorted sensation), paraesthesia (lack of sensation), tingling and numbness may be experienced. There has to be careful assessment to make sure there is no underlying disease such as multiple sclerosis or tumours. Similar to temporomandibular joint pain dysfunction syndrome, stress, anxiety and depression are often associated with atypical facial pain.

Trigeminal neuralgia

Trigeminal neuralgia (tic douloureux) is described as ‘a painful unilateral affliction of the face, characterised by brief electric shock-like (lancinating) pains, limited to the distribution of one or more divisions of the trigeminal nerve’. Typically it occurs in middle aged and elderly patients. The second and third divisions of the trigeminal nerve (mainly in the region of the upper and lower jaws) are usually affected. Episodes may occur occasionally or frequently over several weeks to months, often followed by pain-free intervals. Patients describe the pain as like a sudden electric shock, frequently triggered by trivial stimuli of the face, such as with washing, shaving, chewing and talking. It may also occur spontaneously.

Other facial pain syndromes

Odontalgia

• Short-lasting diffuse pain resulting from dentinoenamel (dental enamel) defects and evoked by local stimuli.
• Sharp or dull, mild to moderate pain lasting less than a second to minutes.

Pulpitis

• Pain resulting from pulpal inflammation, that is evoked by local stimuli.
• Sharp, dull ache, or throbbing pain, moderate to severe, lasting minutes or hours, with episodes that may continue for several days.

Periapical periodontitis and abscess

• Severe throbbing pain arising from the periodontal tissues.
• Continuous, mild to intense aching, especially after hot or cold stimuli, that may last a few minutes to several hours.

Atypical odontalgia

• Severe throbbing pain in the tooth without major pathology.
• Often described as severe continual throbbing in teeth and gingivae (gums). It may vary from mild to intense pain, especially with hot or cold stimuli. It may be widespread or well localised, frequently precipitated by a dental procedure and may move from tooth to tooth. It may last a few minutes to several hours.
• Atypical odontalgia may be a symptom of psychosis or depression, and there is often excessive concern with oral hygiene.

Glossodynia and sore mouth (also known as ‘burning mouth syndrome’ or ‘oral dysaesthesia’)

• Burning pain in the tongue or mucous membranes.
• Burning, tender, nagging pain, usually constant, but may be variable, and increasing in intensity from morning to evening; occasionally associated with iron, vitamin B₁₂ or folate deficiency.

Cracked tooth syndrome

• Brief sharp pain in a tooth, due to cusp (grinding surface) flexion and ‘microleakage’.
• Moderate pain on biting that lasts a few seconds.

Trigeminal herpes zoster

• Acute herpetic infection in the cranial nerve V (the trigeminal nerve).
• Burning, tingling pain with occasional lancinating components felt in the skin. Pain may precede or follow herpetic eruptions and last from one week to several weeks.
• Spontaneous permanent remission is common, although the condition may progress to chronic (postherpetic) neuralgia (see below).

Postherpetic neuralgia

• Chronic pain with skin changes in the distribution of the cranial nerve V following acute herpes zoster.
• Burning, tearing, itching dysaesthesia and crawling dysaesthesias in skin of affected areas of moderate intensity; exacerbated by mechanical contact. May last for several years, spontaneous subsidence is not uncommon.

Secondary neuralgia from central nervous system lesions

• Pains in the distribution of one or more branches of the cranial nerve V resulting from a recognised lesion (such as a tumour, multiple sclerosis, aneurysm (swelling of an artery wall)).
• May be indistinguishable from trigeminal neuralgia (see above) or be a constant, severe dull pain.

Glossopharyngeal (affecting tongue and throat (pharynx)) neuralgia

• Sudden, severe, brief stabbing recurrent pains in the distribution of the glossopharyngeal nerve.
• Sharp, stabbing bouts of severe pain felt deep in throat or ear, often triggered by touch or swallowing and by ingestion of cold fluids. Episodes may interfere with eating and can last for weeks to several months and subside spontaneously. Recurrence is common.
• Needs to be distinguished from Eagle’s syndrome (caused by an elongated or misshapen styloid process (a pointed piece of bone just below the ear), and/or calcification of the stylohyoid ligament).