Idiopathic headache as a possible risk factor for phantom tooth pain

Single-nucleotide polymorphisms of the SLC17A9 and P2RY12 genes are significantly associated with phantom tooth pain

Phantom tooth pain (PTP) is a rare and specific neuropathic pain that occurs after pulpectomy and tooth extraction, but its cause is not understood. We hypothesized that there is a genetic contribution to PTP. We focused on solute carrier family 17 member 9 (SLC17A9)/vesicular nucleotide transporter (VNUT) and purinergic receptor P2Y12 (P2RY12), both of which have been associated with neuropathic pain and pain transduction signaling in the trigeminal ganglion in rodents. We sought to corroborate these associations in humans. We investigated gene polymorphisms that contribute to PTP. We statistically examined the association between genetic polymorphisms and PTP vulnerability in 150 patients with orofacial pain, including PTP, and 500 healthy subjects. We found that the rs735055 polymorphism of the SLC17A9 gene and rs3732759 polymorphism of the P2RY12 gene were associated with the development of PTP. Carriers of the minor allele of rs735055 and individuals who were homozygous for the major allele of rs3732759 had a higher rate of PTP. Carriers of the minor allele of rs735055 reportedly had high SLC17A9 mRNA expression in the spinal cord, which may increase the storage and release of adenosine triphosphate. Individuals who were homozygous for the major allele of rs3732759 may have higher P2RY12 expression that is more active in microglia. Therefore, these carriers may be more susceptible to PTP. These results suggest that specific genetic polymorphisms of the SLC17A9 and P2RY12 genes are involved in PTP. This is the first report on genes that are associated with PTP in humans.

Capsaicin 8% patch treatment for amputation stump and phantom limb pain: a clinical and functional MRI study

Purpose

The aim of this study was to measure the efficacy of a single 60 min application of capsaicin 8% patch in reducing chronic amputation stump and phantom limb pain, associated hypersensitivity with quantitative sensory testing, and changes in brain cortical maps using functional MRI (fMRI) scans.

Methods

A capsaicin 8% patch (Qutenza) treatment study was conducted on 14 patients with single limb amputation, who reported pain intensity on the Numerical Pain Rating Scale ≥4/10 for chronic stump or phantom limb pain. Pain assessments, quantitative sensory testing, and fMRI (for the lip pursing task) were performed at baseline and 4 weeks after application of capsaicin 8% patch to the amputation stump. The shift into the hand representation area of the cerebral cortex with the lip pursing task has been correlated with phantom limb pain intensity in previous studies, and was the fMRI clinical model for cortical plasticity used in this study.

Results

The mean reduction in spontaneous amputation stump pain, phantom limb pain, and evoked stump pain were −1.007 (p=0.028), −1.414 (p=0.018), and −2.029 (p=0.007), respectively. The areas of brush allodynia and pinprick hypersensitivity in the amputation stump showed marked decreases: −165 cm², −80% (p=0.001) and −132 cm², −72% (p=0.001), respectively. fMRI analyses provided objective evidence of the restoration of the brain map, that is, reversal of the shift into the hand representation of the cerebral cortex with the lip pursing task (p<0.05).

Conclusion

The results show that capsaicin 8% patch treatment leads to significant reduction in chronic pain and, particularly, in the area of stump hypersensitivity, which may enable patients to wear prostheses, thereby improving mobility and rehabilitation. Phantom limb pain (“central” pain) and associated brain plasticity may be modulated by peripheral inputs, as they can be ameliorated by the peripherally restricted effect of the capsaicin 8% patch.

Temporomandibular disorders and other causes of facial pain

Temporomandibular disorders and facial pain cause significant discomfort and disability for affected patients. Understanding the clinical presentation, pathogenesis, and therapy is essential in helping patients who have these problems. This article critically reviews these aspects, with an emphasis on their relationship to headache.

Temporomandibular disorders and headache

Headache is a common symptom, but when severe, it may be extremely disabling. It is assumed that patients who present to dentists with headache often are diagnosed with a temporomandibular disorder (TMD), although many may have migraine. TMD as a collective term may include several clinical entities, including myogenous and arthrogenous components. Because headache and TMD are so common they may be integrated or separate entities. Nevertheless, the temporomandibular joint (TMJ) and associated orofacial structures should be considered as triggering or perpetuating factors for migraine. This article discusses the relationship between the TMJ, muscles, or other orofacial structures and headache.

Neuropathic orofacial pain: proposed mechanisms, diagnosis, and treatment considerations

The most common reason patients seek medical or dental care in the United States is due to pain or dysfunction. The orofacial region is plagued by a number of acute, chronic, and recurrent painful maladies. Pain involving the teeth and the periodontium is the most common presenting concern in dental practice. Non-odontogenic pain conditions also occur frequently. Recent scientific investigation has provided and explosion of knowledge regarding pain mechanisms and pathways and an enhanced understanding of the complexities of the many ramifications of the total pain experience. Therefore, it is mandatory for the dental professional to develop the necessary clinical and scientific expertise on which he/she may base diagnostic and management approaches. Optimum management can be achieved only by determining an accurate and complete diagnosis and identifying all of the factors associated with the underlying pathosis on a case-specific basis. A thorough understanding of the epidemiologic and etiologic aspects of dental. musculoskeletal, neurovascular, and neuropathic orofacial pain conditions is essential to the practice of evidence-based dentistry/medicine.

Headache may be a risk factor for complex regional pain syndrome

We investigated whether headache and family history of headache are risk factors for complex regional pain syndrome (CRPS) or not. Twenty-three CRPS patients and 69 healthy persons were interviewed whether or not they suffered from headache and had first-degree family history of headache. A headache sufferer was defined as a person who regularly suffered from headache for more than 2 days per month. Headache after an occurrence of CRPS (headache after an injury or operation in case of CRPS after an injury or operation) was excluded and just headache before an occurrence of CRPS was included. If a first-degree family had a regular headache, she or he was regarded as a headache sufferer regardless of the frequency of headache. Of the 23 patients with CRPS, 12 (52.2%) had suffered from headache before an occurrence of CRPS. Of the 69 healthy persons, 18 (26.1%) suffered from headache. Significant differences between patients and healthy persons were found. Of the 23 patients with CRPS, eight (34.8%) had a first-degree family history of headache. Of the 69 healthy persons, ten (14.5%) had a first-degree family history of headache. Significant differences between patients and healthy persons were found in a family history. The results suggest that headache and a first-degree family history of headache are risk factors for CRPS. To determine whether or not headache and first-degree family history of headache are risk factors for CRPS, further prospective studies with larger patient numbers should be carried out.

Atypical Odontalgia: A Review of the Literature

OBJECTIVE

To review previous reports of cases of atypical odontalgia to examine its epidemiological and clinical characteristics and to explore the etiology and pathophysiology of the disease.

BACKGROUND

Atypical odontalgia is one of many painful conditions that affect the oral cavity and is often overlooked in the differential diagnosis.

METHODS

A search of the literature was performed for all cases of atypical odontalgia reported from 1966 to the present.

RESULTS

The typical clinical presentation of atypical odontalgia that has been reported involves pain in a tooth in the absence of any sign of pathology; the pain may spread to areas of the face, neck, and shoulder. The existing literature suggests that this condition occurs in 3% to 6% of the patients who undergo endodontic treatment, with high female preponderance and a concentration of cases in the fourth decade of life. Deafferentation seems to be the most likely mechanism to initiate the pain, but psychological factors, alteration of neural mechanisms, and even an idiopathic mechanism have been implicated. Not all reported cases were preceded by trauma to the teeth or gums. The treatment of choice is a tricyclic antidepressant, alone or in combination with a phenothiazine. The outcome is usually fair, with many patients obtaining complete relief from pain. Especially in the absence of overt pathology, particular attention should be paid to avoiding any unnecessary and potentially dangerous dental intervention on the teeth.

CONCLUSION

Atypical odontalgia is surprisingly common, of uncertain origin, and potentially treatable.

Sensory and affective components of orofacial pain: is it all in your brain?

In this paper, we shall review several chronic orofacial pain conditions with emphasis on those that are essentially refractory to treatment. We shall present a review of current and past literature that describes the various pain phenomena as well as their underlying central mechanisms. New data concerning refractory pain will be used to underscore the importance of central processing of pain, with particular emphasis on neuropsychological and cognitive function and capacity that may play important roles in pain processing and maintenance of the pain state. Further, neurophysiological data showing that the anterior cingulate cortex (ACC) and other structures in the brain may play key roles in modulation of chronic pain will also be discussed. Although peripheral triggering events surely play an important role in initiating pain, the development of chronic and, in particular, refractory pain may depend on changes or malfunctions in the central nervous system. These changes may be quite subtle and require sophisticated approaches, such as functional MRI, to study them, as is now being done. New findings obtained therefore may lead to more rational and reliable treatment for orofacial pain.

Intrathecal lithium reduces neuropathic pain responses in a rat model of peripheral neuropathy

We tested the ability of lithium (Li(+)) to block heat hyperalgesia, cold allodynia, mechanical allodynia and mechanical hyperalgesia in rats experimentally subjected to painful peripheral neuropathy. Chronic constrictive injury (CCI) to the sciatic nerve induced persistent hyperalgesia and allodynia. Intrathecal injection of Li(+) (2.5-40 micromol) into the region of lumbar enlargement dose-dependently reduced heat hyperalgesia, cold allodynia and mechanical allodynia for 2-6 h after injection, but had no effect on mechanical hyperalgesia. Li(+) had no significant effect on responses from control and sham-operated animals. Intrathecal injection of myo-inositol (2.5 mg) significantly reversed both the anti-hyperalgesic and anti-allodynic effect of Li(+). These findings suggest that intrathecal Li(+) suppresses neuropathic pain response in CCI rats through the intracellular phosphatidylinositol (PI) second messenger system in spinal cord neurons. Lithium (Li(+)) has already found widespread clinical application; these results suggest that its therapeutic utility may be extended to include treatment of neuropathic pain syndromes resulting from peripheral nerve injury.

Phantom tooth pain: a diagnosis of exclusion

This case report addresses the difficult diagnosis of phantom tooth pain (PTP). This is a syndrome of persistent pain in the teeth and oral structures following pulp extirpation, extraction, or rarely, an inferior alveolar nerve block. The incidence of this often misdiagnosed condition is estimated to be 3% of the population undergoing pulp extirpation, and is similar to phantom limb pain. The diagnosis of PTP is discussed here as a diagnosis of exclusion, after numerous interventions. Various treatment modalities are outlined and the use of non-traditional pharmacological approaches for pain reduction are discussed.

Is phantom tooth pain a deafferentation (neuropathic) syndrome? Part I: Evidence derived from pathophysiology and treatment

Phantom tooth pain is a syndrome of persistent pain or paresthesia in teeth and other oral tissues that may follow dental or surgical procedures such as pulp extirpation, apicoectomy, tooth extractions, or exenteration of the contents of the maxillary antrum. It can also occur when nerves are injured after trauma to the face or even after routine inferior alveolar nerve blocks if the needle pierces the nerve sheath. In the case of tooth extraction, the pain is found in the edentate area. After periodontal surgery, pain or paresthesia is located in the gingiva. The incidence of phantom tooth pain after extirpation may be as high as 3% of cases. Clinically, phantom tooth pain is similar in many essential characteristics to deafferentation pain syndromes also known as phantom pain syndromes. A limitation to this taxonomy is the lack of definitive information with respect to the pathophysiology of deafferentation pain in the trigeminal nerve. This article amplifies previous clinical descriptions of phantom tooth pain. Current concepts in the pathophysiology of neuropathic pain are reviewed as they pertain to phantom tooth pain. Treatments are described that use three routes of drug administration: oral, nerve blocks by injections, and intranasal applications. Reasons are discussed for the high rates of morbidity after dental and neurosurgery in attempts to treat phantom tooth pain.