GAP Australasian-Dentist Issue 80 Jul-Aug 19

Category AustrÀlÀsiÀn Dentist 73 involves the trigeminal nerve distribution but does not fit criteria for other cranial neuralgias. Àhe diagnosis is made by the report of continuous daily pain affecting the face and/or mouth for more than two hours per day without an obvious cause or mechanism. Patients are frequently misdiagnosed, or attribute their pain to a previous event, such as a dental procedure. Epidemiology At 0.03%, the estimated prevalence of PÀFP in the general population is far lower than that of trigeminal neuralgia (0.3%). 6 Àhe incidence is unknown. PÀFP mainly affects adults, and is rare in children. Clinical case studies indicate both sexes are affected, but most patients are middle to older aged women. 7 Postulated risk factors include female sex, anxiety or depression, chronic widespread pain and a history of multiple surgical procedures. 3 Clinical features PÀFP is usually poorly localised and of a deep, aching, pressing quality. Àt is typically, but not always, unilateral. Àhe pain is of moderate to severe intensity, but this often fluctuates. At onset, the nasolabial and jaw areas are often affected. Àhe pain does not follow dermatomal patterns and may spread elsewhere in the craniocervical regions. Patients often relate onset of pain to trauma or a dental procedure, such as root canal treatment or tooth extractions, but the pain may occur without any preceding injury. Àhe clinical examination and diagnostic work-up (e.g. laboratory findings and medical imaging studies) are usually unremarkable. Patients may report subjective feelings of altered sensation, but the pain is not associated with objective findings such as sensory loss, or other features of neuropathy such as allodynia and hyperalgesia. Cold weather, psychological stress, fatigue and dental treatment may aggravate the symptoms. PÀFP may be comorbid with other pain conditions associated with central sensitisation, such as chronic widespread pain and irritable bowel syndrome. Àt is not unusual for patients with PÀFP to also complain of headaches and neck and back pain. Psychological factors and psychiatric symptoms have been associated with PÀFP and are common among patients with the condition, but the existence of a causal link between psychological factors and PÀFP is contentious. 8 Anxiety and depression scores are commonly high in PÀFP patients, particularly those reporting high pain intensity. 9 Àherefore, psychological screening tests should be considered. 10 Pathophysiology Current opinion is that PÀFP is unlikely to be a single clinical entity. Àt appears that both biological and psychological factors are involved. Àn some patients PÀFP may be truly neuropathic, possibly related to a minor surgical procedure or a peripheral nerve injury in the orofacial region that cannot be locally demonstrated; in other patients the condition may be a focal manifestation of abnormal central nervous system processing and central sensitisationwithout an obvious aetiology. PÀFP and a related condition that is now termed painful posttraumatic trigeminal neuropathy (PP ) may form a continuum. Àt is possible that PÀFP is induced by relatively insignificant trauma compared with PP , which follows more obvious and significant trauma to the peripheral nerves. As compared to PÀFP, positive or negative sensory changes associated with neuropathy, such as allodynia, hyperaesthesia or hypoaesthesia, are more prominent features of PP . Àhe term persistent dentoalveolar pain (PDAP; previously termed atypical odontalgia, phantom tooth pain, dental causalgia) has been applied to a continuous pain localised to one or more teeth, or a tooth socket after extraction, in the absence of any usual orodental cause. PDAP may be considered a more localised subform of PÀFP, although the mean age at onset is younger and it occurs more equally among men and women. However, as there is a history of trauma in many cases, usually dental procedures, PDAP is more likely a subform of PP . Potential risk factors for PDAP after endodontic treatment include extended duration of preoperative pain, female sex, presence of other chronic pain problems and a history of painful treatment in the orofacial region. 11 Given that most patients with PÀFP are either perimenopausal or menopausal women, and the known effect of oestrogen in other orofacial pain conditions, hormonal factors may be associated with the condition. 12 Àhe association between PÀFP and certain psychiatric comorbidities, particularly depression, anxiety and high catastrophising, is well documented, but a direct aetiological link remains uncertain. 13 Àhe prevalence of psychiatric symptoms in patients with PÀFP requires further study. Ànderscoring the biological aspect, recent studies using quantitative sensory testing and brain imaging have been able to demonstrate specific central nervous system sensory abnormalities in patients with PÀFP. Àt appears that hypofunction of dopaminergic pathways in the basal ganglia may contribute to PÀFP and other related clinical pain conditions. 14 About 20% of patients with PÀFP show neurophysiological signs of trigeminal neuropathy compatible with subclinical neuropathic pain. Oral sensory abnormalities, in most cases thermal hypoaesthesia, have been shown in most patients, but 25% of patients with PÀFP have normal findings in neurophysiological and thermal quantitative sensory testing studies. 9, 15, 16 Current evidence supports the concept that, in most patients, PÀFP is a subclinical trigeminal neuropathic pain that may arise from a minor, partial nerve trauma, pure peripheral small fibre neuropathy or a more central trigeminal system lesion. 17 Differential diagnoses PÀFP is essentially a diagnosis of exclusion. Daily or near daily headaches are extremely common presentations in clinical practice. Primary headache disorders including chronic migraine, cluster headache and hemicrania continua may be confused with PÀFP. Careful medical and dental history taking, physical examination, laboratory studies and imaging studies are required to rule out more common causes of continuous orofacial pain. Both extraoral (cranial nerve, head and neck) and intraoral (teeth and oral soft tissue) examinations are needed to rule out local abnormalities and other sources of pain. As they are by far the most common causes of orofacial pain, orodental disease and myogenous temporomandibular disorders should be ruled out. Ànderlying primary or metastatic malignancy, diabetes, hypothyroidism, vitamin and folate deficiencies, oral infection, sinus infection and postherpetic neuralgia have been associated with continuous neuropathic-type pain and need to be ruled out. Demyelinating disease (either peripheral or central), connective tissue disease and other chronic pain disorders should also be considered. Dental imaging including periapical and panoramic views is required to rule out dentoalveolar causes of pain. CÀ or M of the face, jaw and brain do not generally demonstrate any relevant abnormalities and are only indicated if the history and examination suggest a need (e.g. positive neurological signs). Treatment considerations Àheabsenceofanyclearpathophysiological basis for PÀFP precludes establishment of a treatment protocol. 13, 18 Ào date, there are no definitive curative therapies for PÀFP; and, in addition, chronic pain is considered a disease entity where management rather n aÀ