Traumatic deafferentation (TD) is defined as a continuous pain following complete or partial damage to a peripheral nerve. The pain is described as a continuous, burning numbness and often pulling pain. The trauma is usually quite obvious (e.g., after facial trauma, root canal therapy or wisdom tooth removal or after the placement of dental implants) but may occur with minor traumas, such as crown preparation. It must be emphasized there is not necessarily a relationship between poorly executed surgical techniques and the initiation of dysesthesia. It may occur following the most perfect procedure if there is predisposition or if sensitization occurs. The discomfort can be self limiting, depending on nerve regeneration. Campbell has described persistent pain following root canal therapy and apicoectomy in approximately five percent of patients. This may be attributed to the nerve damage and central sensitization or peripheral neural changes. Elies studied patients after mandibular dental implants and reported 17% developed persistent sensory change or pain. Other TD clinical characteristics include associated hyperalgesia and allodynia and a local temperature change. Thermographic studies reveal abnormal thermograms in all patients, some being hot in the pain distribution and some cold. None are normal. Graff-Radford et al have described a hypothesis for these temperature changes that may be helpful in choosing treatment or understanding the pain mechanism. TD may be further divided based on a nerve-block effect. If sympathetic nerve block (stellate ganglion block) vs. somatic (sensory) nerve block is effective, the TD is defined as sympathetically maintained vs. sympathetically independent.
Female patients in their forties predominate in TD. The reason for this is undetermined. It is clearly not a psychological issue. There are various ways to manage TD and often combining therapy is required. The management strategies will be summarized under topical applications, procedures, pharmacology and behavioral therapy.
The use of topical therapies has not been well studied. There is some evidence that capsaicin (Zostrix) applied regularly will result in desensitization and pain relief. The recommended dose is five times per day for five days, then three times per day for three weeks. If the patient can not withstand the burning produced by the application, the addition of topical local anesthetic, either 5% lidocaine or EMLA is useful.
Neural blockade is very effective in differentiating sympathetically maintained pain from sympathetically independent pain. It may also be effective in controlling sympathetically maintained pain if used regularly. It is recommend that up to six blocks be received, repeated about a week apart, provided an additive effect is seen. Radiofrequency gangliolysis may be considered in patients with significant reduction in pain that does not persist.
Tricyclic antidepressants: It is well documented that tricyclic antidepressants are effective in many pain problems. Medications listed in Table 1 may also be helpful.
Following the behavioral evaluation, management is directed at the factors that may impact treatment and determining the most appropriate interventions. Consideration should be given to the following factors: 1) behavioral or operant; 2) emotional; 3) characterological; 4) cognitive; 5) side effects; 6) medication use and 7) compliance. Therapy should intervene at two levels. First, the physical medicine techniques or pharmacology may be changed, and secondly, behavioral techniques may be incorporated, such as cognitive and behavioral management techniques, relaxation, biofeedback and psychotherapeutic and psychopharmacological interventions.
Pain associated with a neural mechanism involving the trigeminal nerve is called trigeminal neuralgia. It is suggested that the intermittent sharp electric pain, also called tic douloureux, maintain the term trigeminal neuralgia and other pains associated with the trigeminal system should be defined either by the mechanism or clinical presentation. The term "atypical" should be avoided at all costs. Rather in cases where the clinician can not make a diagnosis, the term "idiopathic" may be entertained, and the patient should receive further workup to finalize a treating diagnosis. Generally, trigeminal neuralgias are well managed. It is imperative that all treatment options be considered and, if needed, combined.
