Grey matter changes of the pain matrix in patients with burning mouth syndrome

Burning mouth syndrome (BMS) is characterized by a burning sensation in the mouth, usually in the absence of clinical and laboratory findings. Latest findings indicate that BMS could result from neuropathic trigeminal conditions. While many investigations have focused on the periphery, very few have examined possible central dysfunctions. To highlight changes of the central system of subjects with BMS, we analysed the grey matter concentration in 12 subjects using voxel‐based morphometry. Data were compared with a control group (Ct). To better understand the brain mechanisms underlying BMS, the grey matter concentration of patients was also compared with those of dysgeusic patients (Dys). Dysgeusia is another oral dysfunction condition, characterized by a distorted sense of taste and accompanied by a reduced taste function. We found that a major part of the ‘pain matrix’ presented modifications of the grey matter concentration in subjects with BMS. Six regions out of eight were affected [anterior and posterior cingulate gyrus, lobules of the cerebellum, insula/frontal operculum, inferior temporal area, primary motor cortex, dorsolateral pre‐frontal cortex (DLPFC)]. In the anterior cingulate gyrus, the lobules of the cerebellum, the inferior temporal lobe and the DLPFC, pain intensity correlated with grey matter concentration. Dys also presented changes in grey matter concentration but in different areas of the brain. Our results suggest that a deficiency in the control of pain could in part be a cause of BMS and that BMS and dysgeusia conditions are not linked to similar structural changes in the brain.     

Small fibre neuropathies

PURPOSE OF REVIEW: To summarize the recent advances in aetiology, diagnostic assessment, and treatment of small fibre neuropathies. RECENT FINDINGS: New causes of small fibre neuropathy have been recognized and advances in neurophysiologic and neuropathologic techniques for investigating small fibres have been made, increasing the interest in this field. In particular, skin biopsy proved to be a sensitive method to diagnose small fibre neuropathy. It allows the detection of subclinical abnormalities of peripheral nerve function in patients with diabetes and tongue denervation in patients with burning mouth syndrome. This technique has also been used to demonstrate the neuroprotective effect of erythropoietin in experimental models of neuropathy. Among nonconventional neurophysiologic techniques for investigating small fibres, laser-evoked potential and contact heat-evoked potential stimulators have been developed and deserve particular interest. Several trials on neuropathic pain that is a typical feature of small fibre neuropathies have been performed and guidelines have recently been published. SUMMARY: Detection of small fibre impairment allows earlier diagnosis of neuropathy and could be used as an outcome measure in future regenerative neuropathy trials. Standardization of skin biopsy can have an important impact on clinical practice and research. Further studies are needed to assess the reliability of current neurophysiologic techniques for testing small fibre function in peripheral neuropathies and the correlation with well established neuropathologic examination.     

Electroconvulsive therapy for burning mouth syndrome

Objective: Burning mouth syndrome (BMS) is an orofacial pain disorder characterized by a chronic, idiopathic burning sensation of the oral mucosa that mostly affects middle‐aged women. Although both psychological and neuropathological factors have been postulated to underlie BMS, the pathogenic mechanism of the condition remains controversial, as do the treatment strategies. Method: A single case was reported. Results: Ms A, a 66‐year‐old woman with BMS type 1, which is characterized by daily burning pain associated with circadian variation, underwent electroconvulsive therapy (ECT). After the completion of 12 ECTs, the pain markedly diminished and the pronounced ECT effect persisted over the subsequent 24‐week period of observation. Conclusion: To our knowledge, this is the first clinical report on the efficacy of ECT for treating pain associated with BMS. ECT can be considered to be an option for treating individuals with enduring and intractable intraoral burning pain.     

Painful neuropathy in subclinical hypothyroidism: clinical and neuropathological recovery after hormone replacement therapy

We describe a 60-year-old woman complaining of severe burning feet for 3 months. A neurological examination showed absent Achilles tendon reflexes; nerve conduction study demonstrated mild sensory neuropathy, and skin biopsy revealed a length-dependent loss of intraepidermal nerve fibres. Haematological exams demonstrated a subclinical hypothyroidism and hormone replacement therapy was started. Conversely, symptomatic treatments for neuropathic pain were withdrawn after few days because of side effects. During the following months, thyroid function recovered, and the patient experienced a progressive decrease of neuropathic pain intensity. At 6- and 12-month follow-ups, nerve conduction study and clinical examination were normal, whereas skin biopsy demonstrated a complete reinnervation of the epidermis. Subclinical hypothyroidism is a possible cause of sensory neuropathy and hormone replacement therapy can prompt nerve regeneration.     

Chronic ischemic monomelic neuropathy from critical limb ischemia

OBJECTIVE: To describe the peripheral neuropathy resulting from chronic and critical arterial leg ischemia. METHODS: The authors evaluated 19 patients on entry to a gene therapy treatment trial for chronic and critical leg ischemia. Measurements included medical history, examination, neurologic symptom (NSS) and neurologic examination (NES) scores, motor and sensory nerve conduction studies, and quantitative sensory testing. The critically ischemic leg was compared with the less affected contralateral limb. RESULTS: All patients experienced pain from skin ulceration or vascular claudication, but many also had rest pain (58%), numbness (58%), burning (42%), and paresthesias (37%) in the ischemic foot that were consistent with peripheral nerve ischemia. Only three patients (16%) were free of neuropathic symptoms. The most common asymmetric neurologic signs included hypalgesia (74%), toe weakness (64%), hyperesthesia (63%), and pallanesthesia (53%) in the distal leg. NSS and NES were more abnormal in the critically ischemic leg, as were distal motor, total motor, and sensory examination subscores (p < 0.01 for each). Sural sensory potentials were reduced or absent, frequently on both sides. The symptomatic limb had reduced tibial motor amplitudes and increased thermal (cold) sensory thresholds (p < 0.01 for both) whereas the distal latencies, conduction velocities, and vibration thresholds were similar in the two legs. CONCLUSIONS: There is a predominantly sensory neuropathy associated with chronic and critical limb ischemia. Neuropathic symptoms are often obscured by the effects of ischemia on other tissues. The neurophysiologic changes suggest that the underlying pathophysiology is a distal axonopathy affecting nerve fibers of all sizes. Measures of blood flow in the leg correlate with neurologic symptom scores, examination scores, and electrophysiologic testing.     

Analysis of long-standing nociceptive and neuropathic pain in patients with post-polio syndrome

The purpose of this study was to analyze pain, both nociceptive and neuropathic, in patients with post-polio syndrome (PPS) and relate the pain to age at the initial polio infection, age at examination, to gender and disability. The study was conducted in a university hospital department. Patients with PPS were interviewed at their regular visits about pain, its character, intensity and localization. A clinical examination, including a thorough neurological examination, was performed. Data included age at time of polio infection, age at time of examination and gender. Pain intensity was measured with the VAS-scale and walking capability by the WISCI-scale. One hundred sixty-three (88 women, 75 men) patients were included in the study. Pain was present in 109 (67%). Pain was more frequently reported by women (82%) than by men (49%). 96 patients experienced nociceptive pain, 10 patients both neuropathic and nociceptive pain and three experienced pure neuropathic pain. Half of the patients with pain experienced pain in more than one body region. When neuropathic pain was present, another additional neurological disorder was diagnosed. Pain was more often found in younger patients (around 70%) than in older patients (around 50%). In summary pain is common in patients with PPS and most patients experienced nociceptive pain. Women have pain more often than men. Older patients experience pain more seldom than younger patients. Age at time of primary polio infection is important for the development of pain. When neuropathic pain is present, it is important to proceed with neurological examination to find an adequate diagnosis.     

Comparative efficacy of SSRIs and amisulpride in burning mouth syndrome: a single-blind study

INTRODUCTION: Although a significant amount of evidence indicates the efficacy of some antidepressants in treating psychogenic pain and somatoform disorder, very few studies have investigated their possible therapeutic action in burning mouth syndrome (BMS). The purpose of this 8-week, single-blind study was to provide preliminary data on the efficacy and tolerability of amisulpride and the selective serotonin reuptake inhibitors (SSRIs) paroxetine and sertraline for patients with BMS. METHOD: Seventy-six patients with BMS (diagnosed according to the criteria in the literature and integrating the Diagnostic Interview Schedule-Revised for a complete psychiatric assessment), with no possible local or systemic causes and without concurrent major depression, were randomly assigned to receive amisulpride (50 mg/day), paroxetine (20 mg/day), or sertraline (50 mg/day). Efficacy assessments included a visual analogue scale (VAS) for pain intensity, the Hamilton Rating Scale for Depression (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A), and the Clinical Global Impressions scale (CGI). RESULTS: All 3 treatment regimens resulted in a significant improvement from baseline in burning mouth symptoms at week 8 as demonstrated by the quantitative (mean reduction in VAS, HAM-D, and HAM-A scores) and qualitative (percentage of responders) analyses. Amisulpride showed a shorter response latency than the SSRIs. No serious adverse events were reported, and the incidence of side effects did not differ among the 3 groups. None of the patients who received amisulpride withdrew from the trial, whereas withdrawal from the trial occurred within the first week of treatment in 11.5% of patients (N = 3) treated with paroxetine and in 21.7% of patients (N = 5) treated with sertraline. CONCLUSION: The data suggest that amisulpride and SSRIs may be effective treatments for BMS; they are equally effective and equally well tolerated in the short-term treatment of BMS. Amisulpride is associated with better compliance within the first week of treatment and with a shorter response latency in comparison with SSRIs. This finding may indicate that amisulpride is especially useful at the beginning of drug therapy of BMS. Double-blind, placebo-controlled trials are needed to further document the efficacy of amisulpride and SSRIs in the treatment of BMS.     

Pain in diabetic neuropathy case study: whole patient management

Painful diabetic peripheral neuropathy (DPN) is described as a superficial burning pain associated with other positive and/or negative sensory systems affecting the feet and lower extremities. It is one of the most commonly encountered neuropathic pain syndromes in clinical practice. Presentation may be complicated by multiple symptoms, including allodynia, hyperalgesia, other less well characterized dysesthesias, and serious disruption of social functioning and mood. Peripheral nerve function may deteriorate, which can account for patient reports of diminution of pain after several years of follow-up. Although current understanding holds that the pathogenesis of DPN is multifactorial in nature, long-term studies have shown that rigorous glycemic control is the most relevant factor in clinical intervention and can delay the onset and slow the progression of neuropathy. In addition to glycemic control, other treatment approaches must be examined in order to restore quality of life for patients experiencing painful DPN. Differential diagnosis is required to isolate DPN from other unexplained chronic pain. Neurologic testing in painful DPN is an area of active research and is used to assess the neurologic pathways giving rise to the pain, the degree of neural damage and the degree of subclinical damage. Current treatment options for DPN include mainly antidepressants and anticonvulsants, with other agents such as tramadol, dextromethorphan and memantine being employed or studied. This review article includes a case study of a patient with painful DPN to demonstrate the current management strategies for this neuropathic pain syndrome.     

Challenges in the development of novel treatment strategies for neuropathic pain

Neuropathic pain might best be considered as a collection of various pain states with a common feature, that being symptoms suggestive of dysfunction of peripheral nerves. The development of therapeutic options for the treatment of neuropathic pain is complicated significantly by several factors. Neuropathic pain may arise from widely diverse etiologies such as physical trauma, disease, infection, or chemotherapy. Symptoms indicative of neuropathic pain may also arise in individuals with no evidence of any type of nerve trauma (idiopathic). Although neuropathic pain is a substantial health care issue, it is relatively uncommon and only occurs in a small fraction (<10%) of individuals with these initiating factors. Moreover, the efficacy of treatment protocols, even against the same type of symptoms, differ depending on the underlying initiating cause of the neuropathy. Although these observations strongly suggest that there are predisposing factors that may impart susceptibility to the development of neuropathic pain, no common predisposing factors or genetic markers have been satisfactorily identified. Because of these vagaries, treatment of neuropathic pain has been based on trial and error. However, recent progress in the understanding of neurophysiologic changes that accompany peripheral nerve dysfunction indicate that regulation of ion channels that maintain membrane potentials or generate action potentials may provide an important therapeutic approach. Neuropathic pain is accompanied by increased activity of peripheral nociceptors, which is produced in part by changes in levels of specific calcium and sodium channels. The identification of sodium and/or calcium channels subtypes that are expressed almost exclusively on nocicpetors may provide a way of regulating the activity of exaggerated nociceptor function without altering other sensory modalities. Thus, the selective targeting of ion channels may represent a viable therapeutic target for the management of the neuropathic pain state, regardless of etiology.     

Small-fiber sensory neuropathies: Clinical course and neuropathology of idiopathic cases

We describe the clinical features, natural history, and neuropathology of 32 patients presenting with “burning feet”, for whom no specific cause was identified. All had neuropathic pain in the feet and morphological abnormalities of cutaneous innervation in skin obtained using punch biopsy. Most (29) had an abnormal sensory examination. All had normal strength, proprioception, tendon reflexes, and nerve conductions. Two clinical patterns were apparent, based on natural history and spatial distribution of cutaneous denervation. Most (28) patients presented with neuropathic pain initially restricted to the feet and toes but extending more proximally to involve the legs and hands with time. Intraepidermal nerve fiber (IENF) density was most severely reduced distally, with more normal IENF densities in skin from proximal sites. In contrast, a minority (4) presented with the abrupt onset of generalized cutaneous burning pain and hyperesthesia. In these patients, IENF densities were reduced in skin from both proximal and distal sites. Absolute IENF densities in calf skin were reduced below the lower limit of normal (5th percentile) in 26 (81%). Of the 6 who underwent sural nerve biopsy, 4 had selective loss of small myelinated and/or unmyelinated axons and 2 had normal histology and fiber densities despite reduced IENF densities in skin biopsy specimens. Punch skin biopsy from proximal and distal sites is a useful means of assessing these distinctive patients and may provide further insight into pathophysiology.     

Histamine-induced itch converts into pain in neuropathic hyperalgesia.

Physiologically, itch and pain are transmitted in separate specific peripheral C-units and central afferent pathways. Some neuropathic pain patients with intact but sensitized (irritable) primary C-nociceptors have spontaneous pain, heat hyperalgesia, static and dynamic mechanical hyperalgesia. The question was whether cutaneous histamine application induces pain in these patients. For comparison histamine was applied into normal skin experimentally sensitized by capsaicin. Histamine application in the capsaicin-induced primary or secondary hyperalgesic skin did not change the intensity and quality of capsaicin pain. Itch was profoundly inhibited. Conversely, histamine application in neuropathic skin induced severe increase in spontaneous burning pain but no itch. In neuropathies irritable nociceptors may express histamine receptors or induce central sensitization to histaminergic stimuli so that itch converts into pain.     

Deep Brain Stimulation for Neuropathic Pain

Objectives. To determine whether deep brain stimulation is an effective treatment for neuropathic pain of varied etiology. Material and Methods. Thirty‐four patients with intractable neuropathic pain were prospectively studied using visual analog scores, McGill Pain Questionnaire, and Quality of Life Questionnaires (EUROQOL EQ‐5D VAS, and SF‐36 v‐2). Patients had either deep brain stimulation of either the periventricular gray or ventroposterolateral nucleus of the thalamus, or both. Results. Seventy‐six percent of patients underwent permanent implantation. Overall reduction of pain intensity was 54%. The burning component of pain improved by 77%. Health‐related quality of life improved by 38%. Conclusions. Deep brain stimulation is an effective treatment for neuropathic pain. The factors that influence outcome, including etiology and site of stimulation, are discussed.     

<Emphasis Type="Italic">Trachyspermum ammi</Emphasis> 10 % topical cream versus placebo on neuropathic pain,a randomized,double-blind,placebo-controlled trial

A four-week, double-blind, randomized, placebo-controlled trial was conducted to assay the effectiveness of Ajwain 10 % (Trachyspermum ammi Sprague) topical cream on neuropathic pain. Intervention encompassed Ajwain 10 % and placebo creams. Ninety-two patients who specifically mentioned daily and nocturnal burning feet were randomly assigned to receive one of those interventions. Presence and decline in patients’ numbness, tingling and allodynia were also evaluated. Major outcome measure was alteration in feet burning intensity (final week versus baseline week) regarding to a visual analog scale on a 0–10 cm scale (0 being "no pain", 10 being "worst pain"). Significant reduction in feet burning scores as well as numbness, tingling and allodynia were found in Ajwain group compared to placebo. This trial examining a cream of Ajwain essential oil versus placebo revealed the significance difference between two groups. This medicament can be a good candidate for the alleviation of feet burning, a neuropathic complication.     

Benign Multiple Sclerosis: Does it exist?

Although the definition of benign multiple sclerosis (BMS) remains controversial, it is generally applied to a subgroup of MS patients showing little disease progression, with minimal disability decades after disease onset, and is based mainly on changes in motor function. Recent studies, however, reveal that deterioration of cognitive function, fatigue, pain, and depression also occur in BMS patients, causing negative impact on work and social activities, despite complete preservation of motor function. Using conventional MRI techniques, lesion load observed in BMS is similar to levels in other disease subtypes; however, newer quantitative MRI techniques show less tissue damage, as well as greater repair and compensatory efficiency following MS injury. Currently accepted criteria for BMS diagnosis may cause overestimation of true prevalence, underscoring the need for routine monitoring of nonmotor symptoms and imaging studies. Clearly, the definition of BMS currently applied in clinical practice requires reassessment.     

Pain threshold and pain recovery after experimental stimulation in patients with burning mouth syndrome

The aim of the present study was to examine pain threshold and pain recovery in patients with burning mouth syndrome (BMS) and matched no-pain controls. Twenty female patients diagnosed with BMS without organic gross changes were enrolled in the study. Twenty control subjects were chosen from age-matched healthy female volunteers. We compared the thermal pain threshold using heat beam dolorimeter on the finger and tongue between patients and controls. Warm (at 50 degrees C for 5 s), cold (at 0 degrees C for 30 s) and mechanical (stimulation by electric tooth brush for 15 s) stimulation was applied to the tongue for both groups. Participants were asked to rate the subjective pain using a visual analogue scale (VAS). Although there was no significant differences between patients and controls in terms of the threshold on the finger, the threshold on the tongue was significantly higher in patients than in controls. We suggest there were peripheral dysfunction at the tongue, and/or central dysfunction in patients with BMS. Among the three types of stimulation, the patients perceived significantly the highest pain from the mechanical stimulation for the first 5 min after the stimulation. Furthermore, when patients with BMS perceived some pain, they continued to complain of the pain longer and more intricately than the controls. This indicates that the pain of the patients is strongly affected not only at a sensory component but also at an affective/motivational component than the controls. However, we should be cautious of simply advancing psychogenic theory in this etiology.     

Spinal Cord Stimulation Has Comparable Efficacy in Common Pain Etiologies

Objectives. The probability of success with spinal cord stimulation (SCS) depends largely on appropriate patient selection. Here, we have assessed the predictive value of pain etiology as it relates to pain relief with SCS as part of a prospective multicenter clinical trial. Methods. Sixty‐five subjects with chronic and intractable pain tested an epidural SCS system. Subjects reported pain ratings (visual analog scale) with stimulation off and stimulation on at scheduled follow‐up visits for up to 18 months after activation of the system. Visual analog scale scores were averaged and stratified by dominant pain etiologies, comprising failed back surgery syndrome, complex regional pain syndrome, and a subgroup of subjects with miscellaneous other pain etiologies. Results. More than 70% of subjects in each subgroup had successful outcomes during the temporary trial period and similar percentages of subjects from each etiology subgroup subsequently went on to permanent implantation. After permanent implantation, all subgroups reported more than 50% pain relief, on average, at each follow‐up time point. No predictive value of pain etiology was observed. Conclusions. Spinal cord stimulation is an effective therapy for neuropathic pain arising from a variety of causes. Failed back surgery syndrome, complex regional pain syndrome, and pain of other etiologies responded equally well to SCS.     

Segmental hypersensitivity and spinothalamic function in spinal cord injury pain

The mechanisms underlying central pain following spinal cord injury (SCI) are unsettled. The purpose of the present study was to examine differences in spinothalamic tract function below injury level and evoked pain in incomplete SCI patients with neuropathic pain below injury level (central pain) versus those without such pain. A clinical examination, quantitative sensory testing and magnetic resonance imaging (MRI) were performed in 10 SCI patients with below-level pain and in 11 SCI patients without neuropathic pain. Patients with and without pain had similar reductions of mechanical and thermal detection thresholds below injury level. SCI patients with central pain had sensory hypersensitivity in dermatomes corresponding to the lesion level more frequently than SCI patients without pain, but this may in part be explained by the exclusion of at-level spontaneous pain in the pain-free group. The rostral-caudal extent of the lesion measured by MRI did not differ between the two patient groups, and there were no statistically significant differences in any of the predefined areas of interest on the axial plane images. This study suggests that neuronal hyperexcitability plays a key role in central SCI pain and furthermore - in contrast to previous findings - that loss of spinothalamic functions does not appear to be a predictor for central neuropathic pain in spinal cord injury.     

Correlations between EEG and clinical outcome in chronic neuropathic pain: surgical effects and treatment resistance

Chronic neuropathic pain may require a neurosurgical treatment, but for reasons that have not been fully explored yet, a significant number of patients do not benefit from the intervention. We compared the resting EEG of 15 healthy controls to the EEG of 23 chronic neuropathic pain patients before and 12 months after treatment by the central lateral thalamotomy (CLT). A patient subgroup had a high (n = 14, pain relief (PR) ≥ 50%) and another subgroup a low (n = 9, PR < 50%) postoperative PR. EEG spectral power and source localization of the high PR patients were normalized postoperatively. In contrast, low PR patients showed postoperative maintenance of insular, cingulate and prefrontal overactivities, and their frustration values were positively correlated with cingulate and prefrontal activity. These findings demonstrate a normalizing effect of CLT on cortical activity and suggest that treatment resistance is associated with a frustration-based dynamics.     

Successful use of gabapentin in acute pain management following burn injury: a case series

Pain after burn injury has multiple qualities, including neuropathic and hyperalgesic elements. This element of the burn patients' pain experience is frequently difficult to manage and contributes significantly to their suffering. The onset may be either immediate or delayed. Gabapentin has established efficacy in the reduction of burn-induced hyperalgesia and allodynia in animal and human experimental burn models. This article reports a case series of six patients who, following admission to hospital with burn injury, described burning dysesthesia at either the injury or graft donor site. These patients were prescribed gabapentin in addition to standard analgesia. The use of gabapentin resulted in a rapid reduction in the severity of the neuropathic element of the pain. The medication was well tolerated, with no severe adverse reactions. Conclusions. This case series introduces the use of gabapentin as a potentially important therapy in the management of neuropathic pain following burn injury. Further research is required to define the use of gabapentin in this specific setting.     

Managing pain and comorbid depression: A public health challenge.

Many millions of Americans suffer chronic medical conditions complicated by both depression and pain. Chronic pain disorders may be classified as being caused by one or more mechanisms, such as nociceptive (inflammatory), neuropathic (peripheral and central), and myofascial, each associated with a complex substrate of neurophysiologic changes. Specific treatment approaches have been developed for different pain mechanisms. Because all pain sensation is personal and subjective, all pain is affected to some degree by emotional states, and, therefore, by psychosocial factors. Major depression commonly complicates chronic pain and adds to impairment and disability. There is evidence that patients with depression occurring after the onset of chronic pain have the same rates of affective disorders in family members as in the general population, and significantly lower rates than in families of patients with major depression alone. This suggests that it is the stress of living with chronic pain, not personal or family predisposition, that causes depression in these patients. Optimal treatment includes treatment of both pain and depression, together with a focus on symptom control and functional restoration.