Neuropathic Orofacial Pain: Proposed Mechanisms, Diagnosis, and Treatment Considerations

By Spencer C, Gremillion H

Date: 01/2007
Journal: Dental Clinics

Purpose:

Discuss neuropathic pain causes and mechanisms

Results:

Neuropathic pain described as pain initiated or caused by a primary lesion or dysfunction in the nervous system. Summarizes neuropathic pain conditions frequently seen in dental offices.

Neuropathic orofacial pain – Spontaneous pain that is unprovoked, cannot be treated with conventional analgesics or opiods

Pathophysiology – change in excitability of primary nociceptive afferents may be single most important factor in generation & maintenance of acute chemogenic pain or chronic neuropathic pain in humans

  1. Deafferentation is defined as continuous pain after complete or partial damage to the nerve-post endo trx reported as 3-6%
  2. Demylenation-degenerative process causing loss of myelin sheath of nerves-can become areas of ectopic sites of repetitive   firing that occur spontaneously or as response to stimuli

-membrane remodeling affecting Na+ channels responsible for   ectopic repetitive firing

-Local anesthesia used as diagnostic aid-stabilize membrane

1.Trigeminal Neuralgia (TN)-causes-idiopathic, demyelinating diagnosis, trauma,

a.2-27 people per 100k

b.Most often in women over 50, usually a trigger point, report a sharp, shooting, stabbing pain that last for up to a few minutes

  1. Pre-trigeminal neuralgia (PTN)
  2. presents as a dull aching pain (toothache or sinus like pain) with a sporadic sharp component-spontaneous w/o specific trigger point, then progresses to TN

-treatment of TN is pharmacotherapy or surgery

  1. Atypical Odontalgia-constant pain with a tooth with no obvious source of local pathology
  2. most often seen around age 50,most common in maxillary molar area, and is of moderate intensity
  3. unchanging persistent pain for at least 3 months-anesthetic may or may not alleviate symptoms
  4. no defined mechanism for disorder-have used TCAs and benzodiazepenes for treatment
  5. Post-herpetic neuralgia (PHN)-persists after outbreak of herpes zoster (varicella)
  6. Virus migrates most often to dorsal root ganglion of the thoracic spine (55% of cases)
  7. 15% virus is found in cranial nerve ganglion (V and VII) and 12% in cervical distribution of spinal nerves
  8. once “triggered” condition is “shingles”-usually unilateral and can be expressed in any branch of trigeminal system
  9. Reactivation of the dormant virus
  10. when triggered virus invades nerves and ganglion causing necrotizing action (primary cause of PTN)
  11. pain may or may not be associated with area where rash was present
  12. 87% of patient with PTN experience allodynia, hyperesthesia, dysethesia, or anesthesia-describe pain as deep, aching, burning, stabbing, itching, electrical, unbearable etc.

the older the patient is at outbreak, the more likely they are to develop PTN (avg. is 1 in 5)

  1. No cure-prevention w/ vaccine, pharmacotherapy, nerve blocks, topical meds, electrical stimulation, alternative trx