Accurately diagnose the cause of neuropathic pains occuring in the trigeminal region such as atypical odontalgia, phantom tooth pain, burning mouth syndrome.
Chronic Trigeminal Neuropathy Symptoms
- Pain that is continuous or burning
- Pain that does not have a clinically or radiographically evident pathologic basis in the periphery, the ganglion, or CNS
- Pain that is is generated by non-painful stimuli or is spontaneous.
According to the International Association for the Study of Pain, neuropathic pain, by definition, is “pain initiated or caused by a primary lesion or dysfunction in the nervous system.” The pain is often described as aching and burning, varying in intensity from moderate to severe. Additionally, it can present with associated symptoms such as sensory loss, weakness, and dysesthesia.
5 Steps for Testing Chronic Trigeminal Neuralgia
While there is no imaging method or histologic analysis that can show you a “dysfunctional nerve,” there is a 5 step process that you can follow when you suspect trigeminal neuropathy.
1. Rule-out Local Pathology
A thorough clinical exam and high quality radiographs/MRIs are needed to rule out local pathology. The dentist would begin by first testing for infections and inflammation as the source of the pain using radiographs and probing.
2. Conduct Cold Testing
Conduct cold testing to see if the tooth pain sensations are long-lasting. One of the criteria that is commonly used to “prove” irreversible pulpitis is that pain lingers for 10 seconds after cold testing a tooth.
3. Rule out Tooth Fractures
Conduct tooth loading and radiographic analysis to rule out tooth fractures. Although a complete fracture can be detected, incomplete fractures are difficult to spot. Three ways to detect hairline tooth fractures are staining, removing restorations, and examining the tooth.
4. Conduct Neuropathic Pain Questionnaires
Nociceptive and neuropathic pains are similar. Dentists should collect pain history and ask a set of neuropathic pain questions about the onset, character, severity, duration, pattern and location of the pain to differentiate between nociceptive and neuropathic pain.
5. Map & Test the Allodynia Zone
Evaluate the pain site for mechanosensitivity testing using allodynia mapping to confirm you have a neuropathic pain problem and proven a focal point on the mechano-sensitive allodynia map.
Next, test the allodynia zone by conducting gingival cold testing to confirm the nerve is hyperactive, and to see if treatment reduces hyperactivity. Then, conduct an anesthetic challenge test in the area of allodynia to see if the pain can be blocked or reduced substantially with an anesthetic.
Expected Results for Chronic Trigeminal Neuropathy Diagnosis
- There is continuous pain
- The pain is moderate in intensity (3 to 5 out of 10 on the Visual Analogue Scale)
- The pain is focal in location
- In cases of persistent dental pain, there is usually a buccal gingival allodynia
- The patient is typically 30-years-old or more and female >>> male
- The pain is most commonly located in the posterior teeth
- The pain is sometimes increased by stress and shows a late afternoon increase pattern
- If allodynia exists on the gingiva, it will show a prolonged pain on cold stimulation challenge
- If allodynia exists on the gingiva, and it is not 100% centralized, pain will decrease by 50% with a topical anesthetic challenge.
The 5-step diagnostic process should be performed systematically anytime a patient is suspected of having chronic trigeminal neuropathic pain. As a baseline, this work-up would likely include that the patient undergoes:
- Cold testing for pulpal non-vitality
- Periapical radiographic examination for apical change
- A panoramic radiograph looking for other maxillofacial diseases
- A head and neck examination looking for other potentially causative diseases
- A cranial nerve examination assessing for allodynia and hyperalgesia
- If clenching induced tooth pain is suspected, use an occlusal adjustment/orthotic device to reduce loading on the tooth
- If there is an allodynic zone, perform cold and anesthetic challenges on the intraoral pain site
If all else fails, order an MRI examination of the head to rule out pathology affecting the trigeminal nerve, and if clinical history suggests psychopathology or a mood disorder (e.g., depression, anxiety), order a behavioral health assessment. These two tests are not required in many cases, but would be indicated if the pain does not respond to treatment in a reasonable time frame.
Your index of suspicion for all deadly diseases, including cancer, should elevate when you are dealing with any patient with a history of prior cancer, when dealing with a patient with exposure to risk factors (e.g. smoking), or when the pain disorder is not within the expected sites or age group of the commonly affected.
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This article was produced by the Herman Ostrow School of Dentistry of USC’s Online Master’s Degree in Orofacial Pain and Oral Medicine.