Burning Mouth Syndrome Case Studies

RULE-OUT OTHER NEUROPATHIC AND IDIOPATHIC CAUSES OF FACIAL PAIN Clinicians involved in the orofacial pain field should not encounter particular difficulties to make a differential diagnoses between PDAP and other neuropathic facial pain conditions, simply relying on the clinical history. Burning mouth syndrome has a characteristic clinical presentation that is easy to differentiate with PDAP (36). Persistent idiopathic facial pain (PIFP) is still an “ill-defined” entity and there is not enough data to consider or not PDAP as a localized form of this condition. The differential diagnosis relies on topographic features as PIFP manifests with poorly localized, diffuse pain on the face, while PDAP is characterized by intra-oral well-localized pain in the dento-alveolar region (17). Trigeminal neuralgia (TN) has a
characteristic clinical presentation that should be easily recognized.
However, some cases of PDAP may share some features with TN. If PDAP pain is constant without exacerbation, trigeminal neuralgia diagnosis is automatically excluded. In PDAP cases characterized by constant pain with exacerbations, the clinician may be in doubt with a trigeminal neuralgia type II diagnosis (Burchiel classification) (60). Durham et al., from qualitative data derived from PDAP patients interviews (case-series, level of evidence 4), suggest that the clinician should not rely on pain descriptors, as PDAP pain exacerbations may be described as stabbing or electric-like by some patients. Authors highlights two key differences between PDAP and TN that can be helpful in such cases. First, TN attacks usually follow an anatomical line that correspond to the direction of a trigeminal nerve branch, while PDAP pain exacerbations tend to be localized in one spot. Second, TN attacks duration are usually much shorter in duration
(seconds), than PDAP pain exacerbations (minutes or hours) (11).

RULE-OUT INTRACRANIAL LESIONS Persistent facial pain that is refractory to various treatment may create some suspicion of an intracranial lesion that is somehow interfering with the trigeminal nerve pathways (20). Ogutcen-Toller et al., (case-series, level of evidence 4) found that 7 out of 38 patients (18%) with different clinical presentations of chronic facial pain, had structural lesions impinging on the trigeminal nerve, detected with a brain MRI (61). Nixdorf et al., report the anecdotal experience (level of evidence 5), that 5% to 10% of PDAP patients have an intracranial structural lesion as cause of the pain. The authors affirm they order brain MRI for all of their PDAP patients (29). It would be interesting to develop an experimental study to test this claim and have a rationale to prescribe brain images for patients with PDAP.

RULE-OUT MYOFASCIAL PAIN Masticatory myalgia has been found in 50%-55% of PDAP patients (35) (37) (43). Furthermore, trigger point of the superficial masseter, temporalis and digastric muscles can refer pain to the teeth. Pain stemming from these trigger point may be felt in the teeth only, with the muscle of origin being painless, unless properly palpated (6). For these reasons, without a proper examination, some cases of myofascial pain of masticatory muscles may be misdiagnosed as PDAP. We could only find a case-control study by Baad-Hansen et al., (level of evidence 3) that analyzed differences between PDAP and myofascial pain patients in a scientific fashion. Authors found that pain description, psychologic profile and presence of clicking sound cannot differentiate between the two conditions. Only few factors reached a statistically significant difference between the two groups (p<0.05). Dental traumas were reported more frequently from PDAP patients as pain onset related events (83% vs 15%); PDAP patients had a longer average pain duration before diagnosis (7.7 years vs 4.5 years); jaw opening without pain was higher in PDAP patients (47mm vs 37 mm); PDAP patients had lesser painful spot upon muscle palpation (5.6 vs 10.5); PDAP patients always felt intra-oral pain, compared with only 23% of myalgia patients and finally myofascial pain patients reported pain exacerbation upon yawning in 60% of the cases, compared with only 12% of PDAP patients (43). These differences may be helpful for the differential diagnosis between PDAP and myofascial pain. However, when it comes to treatment, clinicians have to take into account the frequent co-existence of these conditions and address them both.