Burning mouth syndrome responsive to pramipexol

Unveiling the link between chronic pain and misuse of opioids and cannabis

Over 50 million Americans endure chronic pain where many do not receive adequate treatment and self-medicate to manage their pain by taking substances like opioids and cannabis. Research has shown high comorbidity between chronic pain and substance use disorders (SUD) and these disorders share many common neurobiological underpinnings, including hypodopaminergic transmission. Drugs commonly used for self-medication such as opioids and cannabis relieve emotional, bothersome components of pain as well as negative emotional affect that perpetuates misuse and increases the risk of progressing towards drug abuse. However, the causal effect between chronic pain and the development of SUDs has not been clearly established. In this review, we discuss evidence that affirms the proposition that chronic pain is a risk factor for the development of opioid and cannabis use disorders by outlining the clinical evidence and detailing neurobiological mechanisms that link pain and drug misuse. Central to the link between chronic pain and opioid and cannabis misuse is hypodopaminergic transmission and the modulation of dopamine signaling in the mesolimbic pathway by opioids and cannabis. Moreover, we discuss the role of kappa opioid receptor activation and neuroinflammation in the context of dopamine transmission, their contribution to opioid and cannabis withdrawal, along with potential new treatments.

Salivary metabolome indicates a shift in tyrosine metabolism in patients with burning mouth syndrome: a prospective case-control study

ABSTRACT

The pathophysiology of primary burning mouth syndrome (BMS) remains controversial. Targeted analyses or "omics" approach of saliva provide diagnostic or pathophysiological biomarkers. This pilot study's primary objective was to explore the pathophysiology of BMS through a comparative analysis of the salivary metabolome among 26 BMS female cases and 25 age- and sex-matched control subjects. Secondary objectives included comparative analyses of inflammatory cytokines, neuroinflammatory markers, and steroid hormones among cases and control subjects, and among BMS patients according to their clinical characteristics. Salivary metabolome, neuroinflammatory markers, cytokines, and steroids were, respectively, analysed by liquid chromatography coupled with mass spectrometry, ELISA and protease activity assay, and multiparametric Luminex method. Among the 166 detected metabolites, univariate analysis did not find any discriminant metabolite between groups. Supervised multivariate analysis divided patients into 2 groups with an accuracy of 60% but did not allow significant discrimination (permutation test, P = 0.35). Among the metabolites contributing to the model, 3 belonging to the tyrosine pathway ( l -dopa, l -tyrosine, and tyramine) were involved in the discrimination between cases and control subjects, and among BMS patients according to their levels of pain. Among the detectable molecules, levels of cytokines, steroid hormones, and neuroinflammatory markers did not differ between cases and control subjects and were not associated with characteristics of BMS patients. These results do not support the involvement of steroid hormones, inflammatory cytokines, or inflammatory neurogenic mediators in the pathophysiology of pain in BMS, whereas the observed shift in tyrosine metabolism may indicate an adaptative response to chronic pain or an impaired dopaminergic transmission.

Burning mouth disorder and Parkinson's disease: A scoping review of the literature

BACKGROUND

Burning mouth disorder (BMD) is a complex medical condition characterized by a burning sensation in the mouth of fluctuating intensity. BMD is considered a diagnosis of exclusion, as oral burning can occur secondary to local or systemic conditions. Parkinson's disease (PD) is one such condition.

OBJECTIVE

To provide a scoping review of the literature by assessing all articles written in English that investigated the relationship between BMD and PD.

MATERIALS AND METHODS

Various databases (PubMed, Ovid, Web of Science, Science Direct and Scopus) and a search platform (EBSCOhost) were searched following similar investigative approaches. Duplicates were removed and reference lists of original studies were scrutinized for additional articles. Any decision about the inclusion/exclusion in the review was by consensus among the co-authors.

RESULTS

Twenty-five original articles and one supplemental article were included in the final review, of which 13 met the inclusion criteria. These were further divided into five categories based on the study design/article, which included Prevalence studies (n = 6), Letter to the editor (n = 1), Incidence study (n = 1), Case reports (n = 2) and Experimental studies (n = 3). Strongest data was provided by epidemiological studies, which suggest BMD and PD are poorly associated.

CONCLUSIONS

A scoping review of the existing literature does not suggest that PD patients are any more at risk of developing BMD compared to the general population. While there may be a link through the dopaminergic system as determined by imaging studies, it is unlikely that the pathogenesis of PD disease shares significant commonality with BMD.

Pramipexole treatment attenuates mechanical hypersensitivity in male rats experiencing chronic inflammatory pain

Opioids are commonly prescribed for pain despite growing evidence of their low efficacy in the treatment of chronic inflammatory pain and the high potential for misuse. There is a clear need to investigate non-opioid alternatives for the treatment of pain. In the present study, we tested the hypothesis that acute and repeated dopamine agonist treatment would attenuate mechanical hypersensitivity in male Long-Evans rats experiencing chronic inflammatory pain. We used two clinically available therapeutics, l-DOPA (precursor of dopamine biosynthesis) and pramipexole (dopamine D2/3 receptor agonist), to examine the functional role of dopamine signaling on mechanical hypersensitivity using an animal model of chronic inflammatory pain (complete Freund's adjuvant, CFA). We found that both acute and repeated pramipexole treatment attenuated hyperalgesia-like behavior in CFA-treated animals but exhibited no analgesic effects in control animals. In contrast, there was no effect of acute or repeated l-DOPA treatment on mechanical hypersensitivity in either CFA- or saline-treated animals. Notably, we discovered some extended effects of l-DOPA and pramipexole on decreasing pain-like behavior at three days and one week post-drug treatment. We also examined the effects of pramipexole treatment on glutamatergic and presynaptic signaling in pain- and reward-related brain regions including the nucleus accumbens (NAc), dorsal striatum (DS), ventral tegmental area (VTA), cingulate cortex (CC), central amygdala (CeA), and periaqueductal gray (PAG). We found that pramipexole treatment decreased AMPA receptor phosphorylation (pGluR1845) in the NAc and DS but increased pGluR1845 in the CC and CeA. A marker of presynaptic vesicle release, pSynapsin, was also increased in the DS, VTA, CC, CeA, and PAG following pramipexole treatment. Interestingly, pramipexole increased pSynapsin in the NAc of saline-treated animals, but not CFA-treated animals, suggesting blunted presynaptic vesicle release in the NAc of CFA-treated animals following pramipexole treatment. To examine the functional implications of impaired presynaptic signaling in the NAc of CFA animals, we used ex vivo electrophysiology to examine the effects of pramipexole treatment on the intrinsic excitability of NAc neurons in CFA- and saline-treated animals. We found that pramipexole treatment reduced NAc intrinsic excitability in saline-treated animals but produced no change in NAc intrinsic excitability in CFA-treated animals. These findings indicate alterations in dopamine D2/3 receptor signaling in the NAc of animals with a history of chronic pain in association with the anti-hyperalgesic effects of pramipexole treatment.

Restless legs syndrome affecting the head region: "restless head syndrome"

OBJECTIVE

Restless legs syndrome (RLS) is a well-established disease that has recently been shown to have variants affecting the arms, face, abdomen, and genital area. To our knowledge, there has been no study reporting on the RLS variant affecting the head region.

METHODS

The retrospective study reviewed a total of 460 patients who presented to Fırat University Medical School and were diagnosed as having RLS based on the International Restless Legs Syndrome Study Group (IRLSSG) criteria between June 2017 and January 2020. Of these, 18 patients that presented with head-related RLS symptoms (in addition to legs or arms) and four cases that presented with isolated head involvement were included in the study.

RESULTS

In 15 out of 18 (81.8%) patients, the restless head syndrome was accompanied by restless arm syndrome (RAS). In the remaining four (18.2%) patients, the disease involved the head region alone. The disease initially emerged in a single region in the body and gradually spread to one or multiple other regions in most patients and the symptoms were relieved by head rubbing. Serum iron level was low in 8 (36.4%) patients and normal in 14 (63.6%) patients. All the patients had normal cranial imaging and the symptoms were eliminated after dopaminergic therapy.

CONCLUSIONS

Although RLS typically involves the legs alone, it may also affect other body parts such as upper extremities, abdomen, face, and genital area. We propose that the novel RLS variant described in the present study could be termed "restless head syndrome."

The Role of Mesostriatal Dopamine System and Corticostriatal Glutamatergic Transmission in Chronic Pain

There is increasing recognition of the involvement of the nigrostriatal and mesolimbic dopamine systems in the modulation of chronic pain. The first part of the present article reviews the evidence indicating that dopamine exerts analgesic effects during persistent pain by stimulating the D2 receptors in the dorsal striatum and nucleus accumbens (NAc). Thereby, dopamine inhibits striatal output via the D2 receptor-expressing medium spiny neurons (D2-MSN). Dopaminergic neurotransmission in the mesostriatal pathways is hampered in chronic pain states and this alteration maintains and exacerbates pain. The second part of this article focuses on the glutamatergic inputs from the medial prefrontal cortex to the NAc, their activity changes in chronic pain, and their role in pain modulation. Finally, interactions between dopaminergic and glutamatergic inputs to the D2-MSN are considered in the context of persistent pain. Studies using novel techniques indicate that pain is regulated oppositely by two independent dopaminergic circuits linking separate parts of the ventral tegmental area and of the NAc, which also interact with distinct regions of the medial prefrontal cortex.

Dopamine agonist responsive burning mouth syndrome: Report of eight cases

BACKGROUND

Burning mouth syndrome (BMS) is characterized by burning sensation of the oral mucosa. There is a lack of effective treatment. In recent years, a special subtype of BMS has been reported, in which oral burning sensation is alleviated after chewing, speaking, or dopaminergic drug delivery. Currently, there are few reports about the subtype of BMS in China. This study was a retrospective analysis of the clinical data of BMS patients sensitive to dopamine agonist at our hospital, aiming to improve the recognition on this disease.

CASE SUMMARY

Eight patients diagnosed with dopamine agonist responsive BMS at the Liaocheng People's Hospital from January 1, 2017 to June 30, 2020 were recruited. The clinical manifestations, treatment, and prognosis were retrospectively analyzed. There were three male and five females in the eight patients. The median age was 56 years (range, 46-65 years). All the eight patients showed burning pain in the mouth. The symptoms were mild in the morning and severe in the evening, and alleviated after chewing, talking, and other oral activities. Four patients were accompanied by restless legs syndrome (RLS). Family history of RLS was positive in two patients. All patients were treated with pramipexol, and symptoms were basically relieved after 2-8 wk.

CONCLUSION

Dopamine agonist responsive BMS is a special subtype of BMS, which is alleviated after oral activities. Dopamine receptor agonist is an effective treatment.

Orofacial pain in 1916 patients with early or moderate Parkinson disease

This article reports the largest epidemiological study of orofacial pain prevalence in patients with Parkinson disease to date.

Introduction:

Several studies have reported that some types of orofacial pain are more common in patients with Parkinson disease (PD) than the general population.

Objectives:

In this study, we aimed to investigate the prevalence of self-reported orofacial pain in a larger group of patients with PD than has been previously studied.

Methods:

We analysed data from 1916 participants with PD in a cross-sectional study recruited to the UK Parkinson's Pain Study who had detailed assessments of pain, motor, and nonmotor symptoms. The King's Parkinson's Pain scale was used to quantify different subtypes of pain.

Results:

A total of 139 (7.3%) patients reported the presence of some form of orofacial pain. Burning mouth syndrome was reported in 32 (1.7%), whereas chewing pain was found in 38 (2.0%) and grinding pain in 78 (4.0%). Orofacial pain was significantly more common in females (10.4%) than males (5.9%). Multiple logistic regression analysis showed a significant association between orofacial pain and pain severity, neuropathic pain, and oral motor and nonmotor dysfunction.

Conclusion:

In our study, population cohort of early patients with PD found prevalence of orofacial pain conditions similar to that in the general population.

Antinociceptive effects of rotigotine-loaded microspheres and its synergistic interactions with analgesics in inflammatory pain in rats

Rotigotine-loaded microspheres (RoMS) are sustained-release formulations with prolonged anti-Parkinson's effects. Given that pain is a non-motor symptom of Parkinson's disease, this study investigated the antinociceptive effects of RoMS and their synergistic effects with analgesics on inflammatory pain. A model of inflammatory pain was prepared by intraplantarly injecting male Sprague-Dawley rats with carrageenan. The antinociceptive effects of RoMS, acetaminophen, and tramadol, both alone and in combination, were evaluated using the hind paw withdrawal latency in the hot plate test and Randall-Selitto test. The rotigotine concentrations in serum and tissues were assayed using ultra-performance liquid chromatography-tandem mass spectrometry. Isobolographic analysis was performed to evaluate the nature of the interactions of RoMS with acetaminophen or tramadol. The results showed that hind paw withdrawal latency to thermal and mechanical stimuli was significantly increased on day 3 and 7 after administered RoMS. Rotigotine could be detected in serum and tissues 3 and 7 days after an intramuscular injection of RoMS. However, the rotigotine concentration fell the detection limit of the assay on day 14 after administration. RoMS produced synergistic antinociceptive effects in the inflammatory pain model when RoMS is combined with acetaminophen or tramadol. These findings suggest that RoMS can relieve inflammatory pain in rats. Furthermore, the combination of RoMS with acetaminophen or tramadol produces synergistic antinociception, which may be clinically worthy because combination therapies may reduce the drug doses required for antinociception.

Sheth M, Viswanath O, Urits I. Chronic Pain Treatment Strategies in Parkinson's Disease

Neurological disorders, including Parkinson’s disease (PD), have increased in prevalence and are expected to further increase in the coming decades. In this regard, PD affects around 3% of the population by age 65 and up to 5% of people over the age of 85. PD is a widely described, physically and mentally disabling neurodegenerative disorder. One symptom often poorly recognized and under-treated by health care providers despite being reported as the most common non-motor symptom is the finding of chronic pain. Compared to the general population of similar age, PD patients suffer from a significantly higher level and prevalence of pain. The most common form of pain reported by Parkinson’s patients is of musculoskeletal origin. One of the most used combination drugs for PD is Levodopa-Carbidopa, a dopamine precursor that is converted to dopamine by the action of a naturally occurring enzyme called DOPA decarboxylase. Pramipexole, a D2 dopamine agonist, and apomorphine, a dopamine agonist, and Rotigotine, a dopamine receptor agonist, have showed efficacy on PD-associated pain. Other treatments that have shown efficacy in treating pain of diverse etiologies are acetaminophen, Nonsteroidal anti-inflammatory drugs (NSAIDs), and cyclooxygenase-2 (COX-2) inhibitors. Opioids and opioid-like medications such as oxycodone, morphine, tramadol, and codeine are also commonly employed in treatment of chronic pain in PD. Other opioid related medications such as Tapentadol, a central-acting oral analgesic with combined opioid and noradrenergic properties, and Targinact, a combination of the opioid agonist oxycodone and the opioid antagonist naloxone have shown improvement in pain. Anticonvulsants such as gabapentin, pregabalin, lamotrigine, carbamazepine and tricyclic antidepressants (TCAs) can be trialed when attempting to manage chronic pain in PD. The selective serotonin and noradrenaline reuptake inhibitors (SNRIs) also possess pain relieving and antidepressant properties, but carry less of the risk of anticholinergic side effects seen in TCAs. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been shown in multiple studies to be effective against various types of PD associated pain symptoms. Massage therapy (MT) is one of the most common forms of complementary and alternative medicine. Studies have shown that pressure applied during MT may stimulate vagal activity, promoting reduced anxiety and pain, as well as increasing levels of serotonin. In a survey study of PD patients, rehabilitative therapy and physical therapy were rated as the most effective for pain reduction, though with only temporary relief but these studies were uncontrolled. Yoga has been studied for patients with a wide array of neurological disorders. In summary, PD pathology is thought to have a modulating effect on pain sensation, which could amplify pain. This could help explain a portion of the higher incidence of chronic pain felt by PD patients. A treatment plan can be devised that may include dopaminergic agents, acetaminophen, NSAIDs, opioids, antidepressants, physical therapies, DBS and other options discussed in this review. A thorough assessment of patient history and physical examination should be made in patients with PD so chronic pain may be managed effectively.

Association between Chronic Pain and Alterations in the Mesolimbic Dopaminergic System

Chronic pain (pain lasting for >3 months) decreases patient quality of life and even occupational abilities. It can be controlled by treatment, but often persists even after management. To properly control pain, its underlying mechanisms must be determined. This review outlines the role of the mesolimbic dopaminergic system in chronic pain. The mesolimbic system, a neural circuit, delivers dopamine from the ventral tegmental area to neural structures such as the nucleus accumbens, prefrontal cortex, anterior cingulate cortex, and amygdala. It controls executive, affective, and motivational functions. Chronic pain patients suffer from low dopamine production and delivery in this system. The volumes of structures constituting the mesolimbic system are known to be decreased in such patients. Studies on administration of dopaminergic drugs to control chronic pain, with a focus on increasing low dopamine levels in the mesolimbic system, show that it is effective in patients with Parkinson’s disease, restless legs syndrome, fibromyalgia, dry mouth syndrome, lumbar radicular pain, and chronic back pain. However, very few studies have confirmed these effects, and dopaminergic drugs are not commonly used to treat the various diseases causing chronic pain. Thus, further studies are required to determine the effectiveness of such treatment for chronic pain.

An overview of pain in Parkinson's disease

Pain is a common non-motor symptom of Parkinson's disease (PD) and the prevalence of pain among PD patients varies because of the disease stage, co-morbidities, and evaluating tools. Risk factors for pain in PD include an early age of onset, long disease duration, motor complications, concomitant depressive symptoms, female gender, and associated medical conditions. In patients with PD, pain can be classified as musculoskeletal pain, chronic body pain (central or visceral), fluctuation-related pain, nocturnal pain, orofacial pain, pain with discolouration/oedema/swelling, and radicular/neuropathic pain; musculoskeletal pain as the most common type. Potential underlying mechanisms include a disruption of peripheral nociception and alterations in central pain threshold/processing. Genetic polymorphisms in genes that confer pain susceptibility might also play a role in the occurrence of pain in PD. In advanced stage of patients with PD, polyneuropathy could occur in patients using high dosage of levodopa. Pain often correlates to other non-motor symptoms of PD, including depression, sleep, and autonomic symptoms. Dopaminergic drugs, non-dopaminergic medications, botulinum toxin, deep brain stimulation, and physiotherapy have shown some benefits for certain types of PD-related pain. An increased awareness of pain as a common non-motor symptom of PD provides further insights into sensory system dysregulation in this disease. In this review, we aim to summarizes the clinical features of pain in patients with PD and emphasize the latest evidence of pain related to levodopa treatment.

An updated review on pathophysiology and management of burning mouth syndrome with endocrinological, psychological and neuropathic perspectives

Burning mouth syndrome (BMS) is a chronic oro-facial pain disorder of unknown cause. It is more common in peri- and post-menopausal women, and sex hormone dysregulation is believed to be an important causative factor. Psychosocial events often trigger or exacerbate symptoms, and persons with BMS appear to be predisposed towards anxiety and depression. Atrophy of small nerve fibres in the tongue epithelium has been reported, and potential neuropathic mechanisms for BMS are now widely investigated. Historically, BMS was thought to comprise endocrinological, psychosocial and neuropathic components. Neuroprotective steroids and glial cell line-derived neurotrophic factor family ligands may have pivotal roles in the peripheral mechanisms associated with atrophy of small nerve fibres. Denervation of chorda tympani nerve fibres that innervate fungiform buds leads to alternative trigeminal innervation, which results in dysgeusia and burning pain when eating hot foods. With regard to the central mechanism of BMS, depletion of neuroprotective steroids alters the brain network-related mood and pain modulation. Peripheral mechanistic studies support the use of topical clonazepam and capsaicin for the management of BMS, and some evidence supports the use of cognitive behavioural therapy. Hormone replacement therapy may address the causes of BMS, although adverse effects prevent its use as a first-line treatment. Selective serotonin reuptake inhibitors (SSRIs) and serotonin and noradrenaline reuptake inhibitors (SNRIs) may have important benefits, and well-designed controlled studies are expected. Other treatment options to be investigated include brain stimulation and TSPO (translocator protein 18 kDa) ligands.

The effects of a dopamine agonist (apomorphine) on experimental and spontaneous pain in patients with chronic radicular pain: A randomized, double-blind, placebo-controlled, cross-over study

Background

Although evidence suggests that dopaminergic systems are involved in pain processing, the effects of dopaminergic interventions on pain remains questionable. This randomized, double blinded, placebo-controlled, cross-over study was aimed at exploring the effect of the dopamine agonist apomorphine on experimental pain evoked by cold stimulation and on spontaneous pain in patients with lumbar radicular (neuropathic) pain.

Methods

Data was collected from 35 patients with chronic lumbar radiculopathy (18 men, mean age 56.2±13 years). The following parameters were evaluated before (baseline) and 30, 75 and 120 minutes subsequent to a subcutaneous injection of 1.5 mg apomorphine or placebo: cold pain threshold and tolerance in the painful site (ice pack, affected leg) and in a remote non-painful site (12°C water bath, hand), and spontaneous (affected leg) pain intensity (NPS, 0–100).

Results

One-hundred and twenty minutes following apomorphine (but not placebo) injection, cold pain threshold and tolerance in the hand increased significantly compared to baseline (from a median of 8.0 seconds (IQR = 5.0) to 10 seconds (IQR = 9.0), p = 0.001 and from a median of 19.5 seconds (IQR = 30.2) to 27.0 seconds (IQR = 37.5), p<0.001, respectively). In addition, apomorphine prolonged cold pain tolerance but not threshold in the painful site (from a median of 43.0 seconds (IQR = 63.0) at baseline to 51.0 seconds (IQR = 78.0) at 120 min, p = 0.02). Apomorphine demonstrated no superiority over placebo in reducing spontaneous pain intensity.

Conclusion

These findings are in line with previous results in healthy subjects, showing that apomorphine increases the ability to tolerate cold pain and therefore suggesting that dopaminergic interventions can have potential clinical relevance.

Refractory burning mouth syndrome: clinical and paraclinical evaluation, comorbiities, treatment and outcome

BACKGROUND

Burning Mouth Syndrome (BMS) is a chronic pain condition characterized by persistent intraoral burning without related objective findings and unknown etiology that affects elderly females mostly. There is no satisfactory treatment for BMS. We aimed to observe the long-term efficacy of high velanfaxine doses combined with systemic and topical administered clonazepam in a particular subgroup of BMS patients who do not respond to current clinical management.

RESULTS

Eight (66.1 ± 6.2 years old females) out of 14 BMS patients fulfilled the inclusion criteria and were treated with venlafaxine (300 mg/d) and clonazepam (5 mg/d) for 35.4 ± 12.1 (mean ± SD) months. The average duration of the symptoms at baseline was 4.3 ± 1.4 years and the overall mean daily pain intensity score was 8.6 ± 1.3 (VAS); pain was in tongue and within the oral mucosa, accompanying by oral and facial dysesthesia. In five patients tasting was abnormal. All patients had positive history of concomitant primary headache. The average score of Hamilton Rating scale for Anxiety and Depression was 21 ± 4.2, and 26.1 ± 2.9, respectively. Previous ineffective treatments include anticonvulsants and anti-depressants. All patients responded (more than 50% decrease in VAS) after three months treatment (mean VAS 3.2 ± 2.2) with no remarkable adverse events.

CONCLUSION

BMS deserves bottomless psychiatric evaluation and management when current available treatments fail. Treatment with venlafaxine combined with topical and systemic clonazepam may be effective in refractory BMS cases but further investigation in a large-scale controlled study is needed to confirm these results.

Pharmacological therapies for pain in Parkinson's disease - a review paper

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by the loss of dopamine containing cells in the substantia nigra, with pain being one of the most common, yet frequently misunderstood symptoms. The prevalence of pain in PD populations ranges from 40-85% and is usually categorized under the following types: i) musculoskeletal pain ii) radicular and neuropathic pain iii) dystonia-related pain iv) akathitic pain and iv) central parkinsonian pain. Areas covered: The aim of this literature review was to document and present the common and uncommon pharmaceutical therapies that treat and/or alleviate these types of pain in PD. The PubMed database was searched with keywords: "Parkinson's disease", "Pain", and "Pharmacological Therapies". Research articles involving randomized, controlled trials were included as well as case studies and qualitative studies. Expert commentary: Given the increased prevalence of pain in PD populations, there is a need for a clear understanding of the types of pain treatments available and how they can be best combined to fit the specific needs of each patient.

A diagnostic and therapeutic approach to primary burning mouth syndrome

Primary burning mouth syndrome (BMS) is an oral mucosal disorder that is characterized by a chronic and often debilitating intraoral burning sensation for which no localized or systemic cause can be found. BMS most commonly affects postmenopausal women. The pathophysiology of primary BMS is not well understood. Diagnosing BMS can prove to be challenging. BMS patients can also pose a therapeutic challenge to clinicians who are consulted to evaluate these patients. Most commonly used therapies include tricyclic antidepressants, α-lipoic acid, clonazepam, and cognitive-behavioral therapy. Clinical judgment, patient counseling, and monitoring of pain are important. Further research is required to assess the effectiveness of serotonin and newer serotonin-noradrenalin reuptake inhibitors.

Not only limbs in atypical restless legs syndrome

Restless legs syndrome (RLS) typically affects the limbs, but the involvement of other body parts has also been reported. In this essay, we critically review all literature reports of atypical RLS cases with unusual localizations. Applying the updated diagnostic criteria of the International restless legs syndrome study group (IRLSSG), which also consider symptoms localized outside of the lower limbs, a few of these atypical cases reported in the previous literature resulted in a definitive diagnosis of RLS. We also discuss the relationship between RLS and burning mouth syndrome (BMS) or restless genital syndrome (RGS). We conclude clinical sleep specialists should be aware of unusual RLS localizations because they respond to the usual treatment for RLS. All the IRLSSG diagnostic criteria should be applied in every suspected case, in order to establish a correct diagnosis of this disabling but treatable condition.

Chronic Orofacial Pain: Burning Mouth Syndrome and Other Neuropathic Disorders

Chronic orofacial pain is a symptom associated with a wide range of neuropathic, neurovascular, idiopathic, and myofascial conditions that affect a significant proportion of the population. While the collective impact of the subset of the orofacial pain disorders involving neurogenic and idiopathic mechanisms is substantial, some of these are relatively uncommon. Hence, patients with these disorders can be vulnerable to misdiagnosis, sometimes for years, increasing the symptom burden and delaying effective treatment. This manuscript first reviews the decision tree to be followed in diagnosing any neuropathic pain condition, as well as the levels of evidence needed to make a diagnosis with each of several levels of confidence: definite, probable, or possible. It then examines the clinical literature related to the idiopathic and neurogenic conditions that can occasion chronic orofacial pain, including burning mouth syndrome, trigeminal neuralgia, glossopharyngeal neuralgia, post-herpetic neuralgia, and atypical odontalgia. Temporomandibular disorders also are examined as are other headache conditions, even though they are not neurologic conditions, because they are common and can mimic symptoms of the latter disorders. For each of these conditions, the paper reviews literature regarding incidence and prevalence, physiologic and other contributing factors, diagnostic signs and symptoms, and empirical evidence regarding treatments. Finally, in order to improve the quality and accuracy of clinical diagnosis, as well as the efficiency with which effective treatment is initiated and delivered, criteria are offered that can be instrumental in making a differential diagnosis.

Ilex paraguariensis Promotes Orofacial Pain Relief After Formalin Injection: Involvement of Noradrenergic Pathway

Background:

Drinking mate or chimarrão, a hot infusion of Ilex paraguariensis (ILEX) leaves, is a common habit in Southern South America that has a social and almost ritualistic role. It has been used as a stimulant beverage in South America and analgesic in regions of Argentina for treatment of headache and others painful inflammatory conditions such as arthritis and rheumatism.

Objective:

The aim of this study was to evaluate the pharmacological activity of I. paraguariensis infusion (ILEX) on orofacial nociception model induced by formalin, and study its mechanism of action.

Materials and Methods:

The analgesic effect of ILEX was assessed through writhing test, paw formalin test, paw edema induced by carrageenan, and orofacial pain induced by formalin. To study the action mechanism of ILEX, opioidergic, dopaminergic, nitrergic, and adrenergic pathways were investigated.

Results:

The high-performance liquid chromatography analysis of ILEX infusion revealed caffeine and theobromine. The treatment with ILEX reduced the number of writhing. However, it was effective neither in the formalin paw test nor in the paw edema induced by carrageenan. Different from formalin paw test, ILEX was able to reduce the orofacial reactivity to formalin in 31.8% (70.4 ± 2.5 s; first phase), and 20% (127.3 ± 18.9 s; second phase). The analgesic effect of ILEX results from the modulation of noradrenergic pathways since prazosin (α₁-adrenoceptor antagonist, 0.15 mg/kg; intraperitoneal) reversed the analgesic effect of ILEX.

Conclusions:

The present report demonstrates that analgesic effect of ILEX in orofacial formalin test is due mainly to modulation of noradrenergic pathways.

SUMMARY

Ilex paraguariensis (ILEX) has been used as a stimulant beverage in South America and analgesic in regions of Argentina for the treatment of headache and others painful inflammatory conditions such arthritis and rheumatism.

The aim of this study was to evaluate the pharmacological activity of ILEX on orofacial nociception model induced by formalin, and study its mechanism of action.

ILEX reduced the number of writhing and orofacial reactivity to formalin in mice. However, it was effective neither in the formalin paw test nor in the paw edema induced by carrageenan.

The analgesic effect of ILEX results from the modulation of noradrenergic pathways.

Abbreviation Used: ILEX: Infusion of Ilex paraguariensis, NSAIDs: Nonsteroidal anti-inflammatory drugs, L-NOARG: L-NG-nitro-arginine, UV: Ultraviolet, i.p.: Intraperitoneal, NOS: Nitric Oxide Synthase, ANOVA: Analysis of variance, S.E.M.: Standard error of mean, HPLC: High-performance liquid chromatography, NO: Nitric Oxide, v.o.: Oral route, DCQ: dicaffeoylquinic acid, BMS: Burning mouth syndrome, PBS: Phosphate-buffered saline.

Burning mouth syndrome: Clinical description, pathophysiological approach, and a new therapeutic option

INTRODUCTION

Burning mouth syndrome is defined as scorching sensation in the mouth in the absence of any local lesions or systemic disease that would explain that complaint. The condition responds poorly to commonly used treatments and it may become very disabling.

METHODS

We prospectively analysed the clinical and demographic characteristics and response to treatment in 6 cases of burning mouth syndrome, diagnosed at 2 tertiary hospital headache units.

RESULTS

Six female patients between the ages of 34 and 82 years reported symptoms compatible with burning mouth syndrome. In 5 of them, burning worsened at the end of the day; 4 reported symptom relief with tongue movements. Neurological examinations and laboratory findings were normal in all patients and their dental examinations revealed no buccal lesions. Each patient had previously received conventional treatments without amelioration. Pramipexol was initiated in doses between 0.36mg and 1.05mg per day, resulting in clear improvement of symptoms in all cases, a situation which continues after a 4-year follow up period.

CONCLUSIONS

Burning mouth syndrome is a condition of unknown aetiology that shares certain clinical patterns and treatment responses with restless leg syndrome. Dopamine agonists should be regarded as first line treatment for this entity.

Comorbid Functional Shoulder Pain and Zolpidem Dependence Treated with Pramipexole

Pramipexole is a dopamine agonist with higher affinity for D3 receptors. Treatment with pramipexole in clinical conditions such as restless legs syndrome, fibromyalgia, and parkinsonism has been found to significantly improve measures of pain and sleep along with the other symptoms. There is no research data available that explores the usefulness of pramipexole in somatoform/functional pain syndromes. We report a case of a 65-year-old male with bilateral functional shoulder pain associated with insomnia and zolpidem dependence effectively treated with pramipexole.

Painful Mouth and Moving Tongue: Syndrome or Casual Association?

This study presents a case series with a clinical syndrome characterized by burning pain in the mouth area and choreic movements of the tongue. This symptom complex is chronic and it predominantly affects elderly women. Pathophysiology of this entity is uncertain. Many of the patients had been treated with dopaminergic blocking agents previously, and therefore it could be a peculiar tardive syndrome. Similarities with other conditions involving pain and abnormal movements affecting the same anatomical area are highlighted.

Disorders of the oral cavity in Parkinson's disease and parkinsonian syndromes

Awareness of nonmotor symptoms of Parkinson's disease is growing during the last decade. Among these, oral cavity disorders are, although prevalent, often neglected by the patients, their caregivers, and physicians. Some of these disorders include increased prevalence of caries and periodontal disease, sialorrhea and drooling, xerostomia, orofacial pain, bruxism, and taste impairment. Though many of these disorders are not fully understood yet and relatively few controlled trials have been published regarding their treatment, physicians should be aware of the body of evidence that does exist on these topics. This paper reviews current knowledge regarding the epidemiology, pathophysiology, and treatment options of disorders of the oral cavity in Parkinson's disease patients.

Dopaminergic modulation of neuropathic pain: analgesia in rats by a D2-type receptor agonist

Experimental studies have shown that dopaminergic mechanisms can modulate both nociception and chronic pain perception, but such property is not exploited pharmacologically at the clinical level. We have previously shown that levodopa produces D2-receptor-mediated antiallodynic effects in rats with peripheral mononeuropathy. Here, we test the effects of a D2-type receptor (D2R) agonist, quinpirole, on neuropathic pain in rats. Allodynic responses to cooling and light touch were measured in the hind limbs of rats with chronic constriction injury of one sciatic nerve. Single intraperitoneal injection of quinpirole (1 mg/kg) totally inhibited cold and tactile allodynic responses for over 3 and 48 h, respectively. At that dose, quinpirole had no effect on nocifensive responses to heat. Lumbar intrathecal injection of quinpirole produced short-term inhibition of the responses to cold and tactile stimuli, suggesting that spinal mechanisms may contribute to the antiallodynic activity of quinpirole. Chronic subcutaneous infusion of quinpirole by implanted Alzet pumps (0.025 mg/kg·day) provided a slowly progressing inhibition of cold and tactile allodynic responses, which re-emerged after the pumps were removed. These experiments show the involvement of dopaminergic systems in the modulation of chronic allodynias and provide experimental support for proposing the use of D2R agonists for neuropathic pain relief.

Alterations in pain response are partially reversed by methylphenidate (Ritalin) in adults with attention deficit hyperactivity disorder (ADHD)

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is characterized by dysregulation of sensory processing and neurobiology of dopamine. Although cumulative evidence suggests that dopamine is involved in pain processing, pain perception in ADHD subjects and the effect of dopamine agonists such as methylphenidate (MP, Ritalin) on it have rarely been studied.

AIMS

The aims of this study were to (1) psychophysically assess sensitivity to pain in ADHD subjects as compared to controls and (2) examine the effects of MP on pain response in ADHD subjects.

METHODS

Thirty subjects with ADHD and 30 age- and gender-matched controls participated in a preliminary trial. Pain threshold, intensity, and tolerance in response to cold pain stimulation were measured for both groups (ADHD with no treatment). In addition, the ADHD group was reassessed following a single dose of MP treatment.

RESULTS

The ADHD subjects "without MP" in comparison with controls displayed significantly shorter cold pain threshold (2.8 ± 2.1 vs. 5.8 ± 2.5 seconds, respectively, P < 0.001) and cold tolerance (21.8 ± 22.3 vs. 62.8 ± 59.8 seconds, respectively P < 0.001). No differences in pain intensities between the groups were found. Following MP treatment, both cold threshold and tolerance in the ADHD subjects increased significantly compared to those with no treatment (3.6 ± 2.5 seconds, P = 0.011, and 46.4 ± 53.3 seconds, P < 0.001, respectively).

CONCLUSIONS

These results suggest that adults with ADHD are more sensitive to pain compared with controls and that MP may exert antinociceptive properties in these subjects. Randomized, controlled trials are warranted to verify these findings.

Dopamine transporter genotype dependent effects of apomorphine on cold pain tolerance in healthy volunteers

The aims of this study were to assess the effects of the dopamine agonist apomorphine on experimental pain models in healthy subjects and to explore the possible association between these effects and a common polymorphism within the dopamine transporter gene. Healthy volunteers (n = 105) participated in this randomized double-blind, placebo-controlled, cross-over trial. Heat pain threshold and intensity, cold pain threshold, and the response to tonic cold pain (latency, intensity, and tolerance) were evaluated before and for up to 120 min after the administration of 1.5 mg apomorphine/placebo. A polymorphism (3′-UTR 40-bp VNTR) within the dopamine transporter gene (SLC6A3) was investigated. Apomorphine had an effect only on tolerance to cold pain, which consisted of an initial decrease and a subsequent increase in tolerance. An association was found between the enhancing effect of apomorphine on pain tolerance (120 min after its administration) and the DAT-1 polymorphism. Subjects with two copies of the 10-allele demonstrated significantly greater tolerance prolongation than the 9-allele homozygote carriers and the heterozygote carriers (p = 0.007 and p = 0.003 in comparison to the placebo, respectively). In conclusion, apomorphine administration produced a decrease followed by a genetically associated increase in cold pain tolerance.

Dopa responsive burning mouth syndrome: restless mouth syndrome or oral variant of restless legs syndrome?

Burning mouth syndrome (BMS) is an oral dysesthesia presenting as a burning sensation of the tongue and other oral and perioral mucosae. A painful symptomatology in different bodily regions (extraoral) may also be a common feature in patient with BMS. The management of BMS is challenging and there is no clear guideline for the management of idiopathic BMS. Herein, we describe a group of patients (5 patients) in whom symptoms of BMS responded to levodopa. In parallel, four patients fulfilled the criteria for restless legs syndrome (RLS). Family history of RLS was positive in two patients. We reviewed the literature and noted a marked overlap between BMS and RLS. Overlaps were noted in epidemiological profiles, pattern of clinical features and even in neurophysiological observations (alterations in the striatal dopaminergic system). We suggest that a subset of patients with BMS may be a phenotypic variant of RLS and a trial of dopaminergic drugs should be given in patients with BMS who has a history suggestive of RLS or in a patient who do not show a response to usual therapies for BMS.

Burning mouth syndrome in Parkinson's disease: dopamine as cure or cause?

Burning mouth syndrome has been reported as being more common in Parkinson’s disease patients than the general population. While the pathophysiology is unclear, decreased dopamine levels and dopamine dysregulation are hypothesized to play a role. We report a patient with Parkinson’s disease who developed burning mouth syndrome with carbidopa/levodopa. Our patient had resolution of burning mouth symptoms when carbidopa/levodopa was replaced with a dopamine agonist. Based on our patient’s clinical course, in conjunction with earlier studies assessing the relationship between burning mouth syndrome and Parkinson’s disease, we discuss a potential role for dopamine in burning mouth syndrome in Parkinson’s disease.

Burning mouth syndrome and secondary oral burning

Burning mouth syndrome is a complex disorder of unclear etiology that is most prevalent in perimenopausal women. It is often accompanied by dysguesia and subjective xerostomia. Recent evidence implicates both central and peripheral neuropathies, possibly representing a phantom pain syndrome in some patients. Ensuring that the patient's oral burning is not secondary to some other local or systemic factor is central to appropriate management. Current standard therapies include clonazepam, paroxetine, and cognitive behavioral therapy, and several promising new alternatives are described.

Burning mouth syndrome

Burning mouth syndrome (BMS) is a chronic condition characterized by burning of the oral mucosa, with or without dysgeusia and xerostomia, in the setting of no underlying systemic disease or identifiable abnormalities on physical examination or laboratory testing. BMS disproportionately affects postmenopausal women. The pathophysiology of the disease is unknown; no single treatment has proven universally successful. In light of these shortcomings, having a practical approach to the evaluation and management of patients with BMS can improve both patient quality of life and physician satisfaction.

Burning mouth syndrome

Burning mouth syndrome (BMS) is a chronic disease characterized by burning of the oral mucosa associated with a sensation of dry mouth and/or taste alterations. BMS occurs more frequently among postmenopausal women. The pathophysiology of the disease is still unknown, and evidence is conflicting; although some studies suggest a central origin, others point to a peripheral neuropathic origin. The efficacy of some medications in the treatment of BMS suggests that the dopaminergic system may be involved.