[Specificities of orofacial neuropathic pain]. / Spécificités de la douleur neuropathique oro-faciale.

Head pain and notably orofacial pain differs from spinal pain on pathophysiological, clinical, therapeutic and prognostic levels. Its high prevalence, important impact on quality of life and significant socio-economical burden justify specific study of such type of pain. Among them, neuropathic orofacial pain resulting from disease or trauma of the trigeminal nervous system is among the most difficult types of pain to diagnose and to treat. Deciphering of underlying peripheral and central mechanisms has allowed numerous conceptual, clinical and therapeutic advances, notably the role of neural and non neural cell types, such as glia, immunocytes, vascular endothelial cells or the role of trigeminal sensory complex neural circuitry reconfiguration in the development of post-traumatic trigeminal neuropathic pain. Cellular interactions within the trigeminal ganglion, allowing a better understanding of several painful dental, ocular or cephalalgic comorbidities, are also described.

Title: Spécificités de la douleur neuropathique oro-faciale. Abstract: Les douleurs de la région céphalique ­ et notamment les douleurs oro-faciales ­ diffèrent des douleurs spinales sur les plans physiopathologique, clinique, thérapeutique et pronostique. Leur prévalence élevée, leur fort retentissement sur la qualité de vie individuelle et leur impact économique et sociétal important justifient une étude spécifique. Parmi ces douleurs, les douleurs neuropathiques, résultant d'une maladie ou d'un traumatisme du système nerveux trigéminal, sont parmi les plus difficiles à diagnostiquer et à soigner. L'étude des mécanismes neurobiologiques, périphériques et centraux les sous-tendant a permis de nombreuses avancées conceptuelles, cliniques et thérapeutiques, avec, par exemple, la mise en évidence du rôle des cellules nerveuses et non nerveuses, telles que la glie, les immunocytes, les cellules endothéliales vasculaires ou le rôle de la reconfiguration de la circuiterie nerveuse au niveau du complexe sensitif trigéminal, dans la genèse des douleurs neuropathiques post-lésionnelles. Les interactions cellulaires au sein du ganglion trigéminal, susceptibles d'éclairer la compréhension de certaines comorbidités douloureuses dentaires, oculaires ou céphalalgiques, sont également décrites.

Synergistic effect of combining dual enkephalinase inhibitor PL37 and sumatriptan in a preclinical model of migraine.

OBJECTIVE: The aim of this study was to test whether a combination of sumatriptan with dual enkephalinase inhibitor PL37 would result in an additive or a synergistic effect. BACKGROUND: Combination treatment is frequently used to improve the therapeutic efficacy of drugs. The co-administration of two drugs may result in efficacy at lower doses than those needed for either drug alone, thus minimizing side effects. Here, we tested the effect of the co-administration of two drugs on cutaneous mechanical hypersensitivity (MH), a symptom often affecting cephalic regions in patients with migraine: dual enkephalinase inhibitor PL37, a small molecule that protects enkephalins from rapid degradation, and sumatriptan, a serotonin 5-HT1B/1D receptor agonist. METHODS: We investigated the effects of oral administrations of sumatriptan, PL37, or their combination on changes in cutaneous mechanical sensitivity induced by a single intraperitoneal administration of the nitric oxide donor, isosorbide dinitrate (ISDN) in male rats. Mechanical sensitivity was assessed using von Frey filaments applied to the face of animals to determine pain thresholds. Isobolographic analysis was performed to determine the nature of the interaction between sumatriptan and PL37. RESULTS: Sumatriptan as well as PL37 each produced a dose-dependent inhibition of ISDN-induced cephalic MH. Median effective dose (ED50 ) values were 0.3 and 1.1 mg/kg for sumatriptan and PL37, respectively. An isobolographic analysis of the effect of combined doses of sumatriptan and PL37 based on their calculated ED50 values demonstrated a synergistic effect of the combination on cephalic MH, with an interaction index of 0.14 ± 0.04. CONCLUSION: These results suggest that PL37 acts synergistically with sumatriptan to produce an anti-allodynic effect in a rat model of migraine. Thus, combining PL37 and sumatriptan may be a useful therapeutic strategy in the management of migraine. PLAIN LANGUAGE SUMMARY: There have been many advances in migraine treatment, but we still need more options that are effective and have few side effects. Sumatriptan is one available drug for acute treatment of migraine, but it does not work for every patient and is not suitable for some people. We tested a new drug called PL37 (that blocks enkephalinases) together with sumatriptan and the combination minimized side effects and allowed lower doses of the drugs for effective migraine treatment in an animal model.

Compromised trigemino-coerulean coupling in migraine sensitization can be prevented by blocking beta-receptors in the locus coeruleus.

BACKGROUND: Migraine is a disabling neurological disorder, characterized by recurrent headaches. During migraine attacks, individuals often experience sensory symptoms such as cutaneous allodynia which indicates the presence of central sensitization. This sensitization is prevented by oral administration of propranolol, a common first-line medication for migraine prophylaxis, that also normalized the activation of the locus coeruleus (LC), considered as the main origin of descending noradrenergic pain controls. We hypothesized that the basal modulation of trigeminal sensory processing by the locus coeruleus is shifted towards more facilitation in migraineurs and that prophylactic action of propranolol may be attributed to a direct action in LC through beta-adrenergic receptors. METHODS: We used simultaneous in vivo extracellular recordings from the trigeminocervical complex (TCC) and LC of male Sprague-Dawley rats to characterize the relationship between these two areas following repeated meningeal inflammatory soup infusions. Von Frey Hairs and air-puff were used to test periorbital mechanical allodynia. RNAscope and patch-clamp recordings allowed us to examine the action mechanism of propranolol. RESULTS: We found a strong synchronization between TCC and LC spontaneous activities, with a precession of the LC, suggesting the LC drives TCC excitability. Following repeated dural-evoked trigeminal activations, we observed a disruption in coupling of activity within LC and TCC. This suggested an involvement of the two regions' interactions in the development of sensitization. Furthermore, we showed the co-expression of alpha-2A and beta-2 adrenergic receptors within LC neurons. Finally propranolol microinjections into the LC prevented trigeminal sensitization by desynchronizing and decreasing LC neuronal activity. CONCLUSIONS: Altogether these results suggest that trigemino-coerulean coupling plays a pivotal role in migraine progression, and that propranolol's prophylactic effects involve, to some extent, the modulation of LC activity through beta-2 adrenergic receptors. This insight reveals new mechanistic aspects of LC control over sensory processing.

Enhanced pain facilitation rather than impaired pain inhibition in burning mouth syndrome female patients.

BACKGROUND: Deficient endogenous pain modulation has been implicated in the development and exacerbation of chronic orofacial pain. To date, relatively little is known regarding the function of the endogenous pain modulation in patients with burning mouth syndrome (BMS). This case-control study investigated endogenous pain modulation in women with BMS. METHODS: Conditioned pain modulation (CPM) was assessed upon temporal summation (TSP) of thermal pain. Forty female subjects, 20 BMS patients and 20 age-matched control subjects, were included in a 2 session-protocol. Mechanical and thermal pain thresholds were measured on the forearm and hand. TSP was obtained using repetitive laser-evoked thermal stimuli applied on the non-dominant hand, at an intensity yielding to moderate pain. During TSP, CPM was produced by immersing the contralateral foot in a water bath at painful cold (8 °C) temperature. In control conditions, the foot was immersed in a water bath at not painful (30 °C) temperature. RESULTS: BMS was not associated with any impairment in thermal as well as mechanical extracephalic pain thresholds. TSP and CPM efficacy were similar in BMS patients and control subjects. However, BMS patients exhibited enhanced extracephalic heat hyperalgesia. CONCLUSION: This study reveals that there is no impairment of endogenous pain inhibition mechanisms in BMS patients, but rather an increase in pain facilitation.

GABAA and Glycine Receptor-Mediated Inhibitory Synaptic Transmission onto Adult Rat Lamina IIi PKCγ-Interneurons: Pharmacological but Not Anatomical Specialization.

Mechanical allodynia (pain to normally innocuous tactile stimuli) is a widespread symptom of inflammatory and neuropathic pain. Spinal or medullary dorsal horn (SDH or MDH) circuits mediating tactile sensation and pain need to interact in order to evoke mechanical allodynia. PKCγ-expressing (PKCγ+) interneurons and inhibitory controls within SDH/MDH inner lamina II (IIi) are pivotal in connecting touch and pain circuits. However, the relative contribution of GABA and glycine to PKCγ+ interneuron inhibition remains unknown. We characterized inhibitory inputs onto PKCγ+ interneurons by combining electrophysiology to record spontaneous and miniature IPSCs (sIPSCs, mIPSCs) and immunohistochemical detection of GABAARα2 and GlyRα1 subunits in adult rat MDH. While GlyR-only- and GABAAR-only-mediated mIPSCs/sIPSCs are predominantly recorded from PKCγ+ interneurons, immunohistochemistry reveals that ~80% of their inhibitory synapses possess both GABAARα2 and GlyRα1. Moreover, nearly all inhibitory boutons at gephyrin-expressing synapses on these cells contain glutamate decarboxylase and are therefore GABAergic, with around half possessing the neuronal glycine transporter (GlyT2) and therefore being glycinergic. Thus, while GABA and glycine are presumably co-released and GABAARs and GlyRs are present at most inhibitory synapses on PKCγ+ interneurons, these interneurons exhibit almost exclusively GABAAR-only and GlyR-only quantal postsynaptic inhibitory currents, suggesting a pharmacological specialization of their inhibitory synapses.

Dual enkephalinase inhibitor PL37 as a potential novel treatment of migraine: evidence from a rat model.

The dual enkephalinase inhibitor PL37, a small molecule that protects enkephalins from rapid degradation, has demonstrated analgesic properties in animal pain models and in early human clinical trials. This study tested the antimigraine potential of PL37 on cutaneous mechanical hypersensitivity affecting cephalic regions in migraineurs. Using behavioural testing and c-Fos immunoreactivity in male rats, we investigated the effects of single (oral or intravenous) and repeated oral administration of PL37 on changes in cutaneous mechanical sensitivity and sensitization of the trigeminocervical complex induced by repeated administration of the nitric oxide donor, isosorbide dinitrate. In naïve rats, single or repeated administration of PL37 or vehicle had no effect on cephalic mechanical sensitivity. However, single oral PL37 treatment effectively inhibited isosorbide dinitrate-induced acute cephalic mechanical hypersensitivity. Single intravenous but not oral PL37 administration inhibited chronic cephalic mechanical hypersensitivity. Daily oral administration of PL37 prevented cephalic mechanical hypersensitivity and decreased touch-induced c-Fos expression in trigeminocervical complex following repeated isosorbide dinitrate administration. These data reveal the therapeutic potential of the dual enkephalinase inhibitor PL37 as an acute and prophylactic treatment for migraine. Protecting enkephalins from their degrading enzymes therefore appears to be an innovative approach to treat migraine.

Chronic facial inflammatory pain-induced anxiety is associated with bilateral deactivation of the rostral anterior cingulate cortex.

Patients with chronic pain, especially orofacial pain, often suffer from affective disorders, including anxiety. Previous studies largely focused on the role of the caudal anterior cingulate cortex (cACC) in affective responses to pain, long-term potentiation (LTP) in cACC being thought to mediate the interaction between anxiety and chronic pain. But recent evidence indicates that the rostral ACC (rACC), too, is implicated in processing affective pain. However, whether such processing is associated with neuronal and/or synaptic plasticity is still unknown. We addressed this issue in a chronic facial inflammatory pain model (complete Freund's adjuvant model) in rats, by combining behavior, Fos protein immunochemistry and ex vivo intracellular recordings in rACC slices prepared from these animals. Facial mechanical allodynia occurs immediately after CFA injection, peaks at post-injection day 3 and progressively recovers until post-injection days 10-11, whereas anxiety is delayed, being present at post-injection day 10, when sensory hypersensitivity is relieved, but, notably, not at post-injection day 3. Fos expression reveals that neuronal activity follows a bi-phasic time course in bilateral rACC: first enhanced at post-injection day 3, it gets strongly depressed at post-injection day 10. Ex vivo recordings from lamina V pyramidal neurons, the rACC projecting neurons, show that both their intrinsic excitability and excitatory synaptic inputs have undergone long-term depression (LTD) at post-injection day 10. Thus chronic pain processing is associated with dynamic changes in rACC activity: first enhanced and subsequently decreased, at the time of anxiety-like behavior. Chronic pain-induced anxiety might thus result from a rACC deactivation-cACC hyperactivation interplay.

Postnatal development of inner lamina II interneurons of the rat medullary dorsal horn.

ABSTRACT: Pain processing in young mammals is immature. Despite the central role of the medullary dorsal horn (MDH) in processing orofacial sensory information, the maturation of the neurons within the MDH has been largely overlooked. Combining in vitro electrophysiological recordings and 3D morphological analysis over the first postnatal month in rats, we investigated the age-dependent development of the neurons within the inner lamina II (IIi) of the MDH. We show the lamina IIi neuronal population transition into a more hyperpolarized state, with modification of the action potential waveform, and a shift from single spiking, at early postnatal ages, to tonic firing and initial bursting at later stages. These physiological changes are associated with a strong structural remodelling of the neuronal morphology with most of the modifications occurring after the third postnatal week. Among the lamina IIi neuronal population, the subpopulation of interneurons expressing the γ isoform of the protein kinase C (PKCγ+) are key elements for the circuits underlying facial mechanical allodynia. How do they develop from the rest of the lamina IIi constitute an important question that remained to be addressed. Here, we show that PKCγ+ interneurons display electrophysiological changes over time comparable with the PKCγ- population. However, they show a distinctive increase of the soma volume and primary branches length, as opposed to the PKCγ- population. Together, our data demonstrate a novel pattern of late postnatal maturation of lamina IIi interneurons, with a spotlight on PKCγ+ interneurons, that may be relevant for the development of orofacial sensitivity.

Improved potency of pyridin-2(1H)one derivatives for the treatment of mechanical allodynia.

Mechanical allodynia, a painful sensation caused by innocuous touch, is a major chronic pain symptom, which often remains without an effective treatment. There is thus a need for new anti-allodynic treatments based on new drug classes. We recently synthetized new 3,5-disubstituted pyridin-2(1H)-one derivatives. By substituting the pyridinone at the 3-position by various aryl/heteroaryl moieties and at the 5-position by a phenylamino group, we discovered that some derivatives exhibited a strong anti-allodynic potency in rats. Here, we report that varying the substitution of the pyridinone 5-position, the 3-position being substituted by an indol-4-yl moiety, further improves such anti-allodynic potency. Compared with 2, one of the two most active compounds of the first series, eleven out of nineteen newly synthetized compounds showed higher anti-allodynic potency, with two of them completely preventing mechanical allodynia. In the first series, hit compounds 1 and 2 appeared to be inhibitors of p38α MAPK, a protein kinase known to underlie pain hypersensitivity in animal models. Depending on the substitution at the 5-position, some newly synthetized compounds were also stronger p38α MAPK inhibitors. Surprisingly, though, anti-allodynic effects and p38α MAPK inhibitory potencies were not correlated, suggesting that other biological target(s) is/are involved in the analgesic activity in this series. Altogether, these results confirm that 3,5-disubstituted pyridine-2(1H)-one derivatives are of high interest for the development of new treatment of mechanical allodynia.

Characteristics of pain in patients with pituitary adenomas: A cross-sectional study.

BACKGROUND: This study determines the prevalence and particularities of headache and pain with neuropathic characteristics (NC) in a large French group of patients with pituitary adenoma (PA). METHODS: Analysis of validated self-administered questionnaires, radiological characteristics and treatment strategies of PA was performed. RESULTS: Of the 221 sent questionnaires, 146 could be used for statistical analysis, 50% of which were completed by women. Among responders, 58.9% had pain: 30.1% migraine, 15.7% pain with NC and 13.1% other types of pain. Migraine was more common in patients with PA than in the general population (30.1% vs. 21.3%, p = .010) and attacks received appropriate treatment for less than 20% of these patients. Furthermore, the prevalence of chronic migraine was much higher than in the general population (6.8% vs. 2.2%, p = .003). Neuropathic pain was also more frequent in PA patients than in the general population (15.8% vs. 6.9%, p < .001). Neuropathic pain was most often located in the extremities and was frequently described as an 'electric shock', 'numbness', or 'pins-and-needles'. Multivariate analyses linked migraine to younger age, anxiety, pain with NC, and a visible tumour on MRI, regardless of its invasiveness or secretory nature. CONCLUSIONS: Migraine headaches and neuropathic pain are more frequent and disabling in PA patients than in the general population. Both types of pain are comorbid in PA patients and are poorly treated. Migraine is associated with the presence of a tumour. Thus, biological mechanisms of this relationship need to be characterized to design optimal treatments for these individuals. SIGNIFICANCE: Migraine headaches and neuropathic pain are more common in PA patients than in the general population and are generally poorly treated. A systematic screening for migraine should be done by physicians in daily practice to provide adequate therapeutics.

Five Predictors Affecting the Prognosis of Patients with Severe Odontogenic Infections.

Background: Dental cellulitis management is no longer a simple procedure, as more and more patients are needing long-time hospitalization, several surgeries and intensive care follow-up. This prospective study seeks to highlight criteria that can split patients with severe odontogenic infection into two groups: those with simple evolution and those for whom complex management is necessary. Methods: In this observational study, all patients considered with a severe odontogenic infection (which necessitated hospital admission, intravenous antibiotics and general anaesthesia) were enrolled between January 2004 and December 2014 from Clermont-Ferrand University Hospital (France). They were split into two groups: those who needed one surgical intervention with tooth extraction and collection drainage combined with probabilistic antibiotic to treat infection and those who need several surgeries, intensive care unit follow-up or tracheotomy to achieve healing. Results: 653 patients were included, of which 611 (94%) had one surgery, 42 (6%) had more than one surgery before healing. Penicillin allergy (p < 0.001), psychiatric disorders (p = 0.005), oropharyngeal oedema (p = 0.008), floor oedema (p = 0.004), fever (p = 0.04) and trismus (p = 0.018) on admission were the most relevant predictors of complex evolution. A conditional inference tree (CTREE) illustrated the association of prognostic factors and the need of multiple surgery. Conclusions: Besides clinical symptoms of severity, complications of severe odontogenic infection are predicted by measurables and objectives criteria as penicillin allergy, mandibular molar, C-reactive protein level, psychiatric disorders and alcohol abuse. Their specific association potentialize the risks. IRB number: CE-CIC-GREN-12-08.

Ketamine-Magnesium for Refractory Chronic Cluster Headache: A Case Series.

OBJECTIVES: To evaluate the safety and efficacy of ketamine-magnesium combination to reduce attacks in a series of patients with refractory chronic cluster headache (rCCH). BACKGROUND: Refractory chronic cluster headache (CCH) is a rare but highly debilitating condition that needs new treatment options. A previous publication reported that a single infusion of ketamine-magnesium combination was effective in 2 patients with rCCH. METHODS: The treatment was proposed to consecutive patients with rCCH seen in 2 French hospitals between November 2015 and February 2020 and who were resistant to at least 3 preventive treatments. They received a single ketamine infusion (0.5 mg/kg over 2 hours) combined with magnesium sulfate (3000 mg). The main outcome was a comparison of the number of daily attacks 2 weeks prior to the ketamine-magnesium infusion and 1 week after (on days 7 and 8). The second outcome was the percentage of responders (patients with ≥50% reduction in the frequency of daily attacks). Safety was assessed by the recording of adverse events during infusion. Descriptive statistics are presented as mean ± standard deviation. RESULTS: Seventeen patients (14 men), with an age of 35.2 ± 8.1 years, were included. They presented with CCH for 6.6 ± 4.3 years. The number of daily attacks decreased from 4.3 ± 2.4 before treatment to 1.3 ± 1.0 after treatment (difference: -3.1 (95% CI: -4.5 to -1.6), P < .001). Seventy six percent (13/17) were responders. Transient and mild sedation was reported by 7/17 patients (41.2%). CONCLUSIONS: The ketamine-magnesium combination seems an effective and well-tolerated therapy for rCCH. Placebo-controlled studies should be conducted to further confirm these findings.

High Prevalence of Headaches During Covid-19 Infection: A Retrospective Cohort Study.

OBJECTIVES: To document the prevalence of new headaches in patients with Covid-19 infection and the potential association with other neuro-sensorial symptoms (anosmia and ageusia). The persistence of these symptoms 1 month after recovery was also documented. BACKGROUND: Headaches are a very common symptom of viral infections. Surprisingly, early Chinese studies reported a relatively low prevalence (12-15%) of headaches associated with Covid-19. METHODS: All the patients with laboratory-confirmed or chest-CT-confirmed Covid-19 infection, diagnosed between February 27th and April 15th , 2020 in the dedicated laboratory of Clermont-Ferrand University Hospital were followed for 1 month after recovery. RESULTS: A total of 139 consecutive patients (mean [SD] age, 48.5 [15.3] years; 87 women [62.6%]) were interviewed 1 month after disappearance of fever and dyspnea (semi-structured phone interview). Overall, 59.0% (82/139) of people with Covid-19 had mild disease, 36.7% (51/139) had severe disease, and 4.3% (6/139) had critical illness. Eighty-two (59.0%; 95% CI: 50.3 to 67.3) reported new headaches during the acute phase and 3.6% (5/139) had persistent headaches 1 month after fever and dyspnea remission. Anosmia and ageusia were also very common, occurring in 60.4% (84/139) and 58.3% (81/139) of the patients, respectively. These 2 symptoms persisted in 14.4% (20/139) and 11.5% (16/139) of Covid-19 patients 1 month after recovery. Headaches were neither clearly associated with anosmia, nor with ageusia, and were not associated with disease severity (ie, requiring hospitalization or intensive care unit). CONCLUSION: This specific study highlights the high prevalence of new headaches during Covid-19 infection in French patients. Further studies are needed to refine the characterization of patients with Covid-19-associated headaches.

Recent advances in our understanding of the organization of dorsal horn neuron populations and their contribution to cutaneous mechanical allodynia.

The dorsal horns of the spinal cord and the trigeminal nuclei in the brainstem contain neuron populations that are critical to process sensory information. Neurons in these areas are highly heterogeneous in their morphology, molecular phenotype and intrinsic properties, making it difficult to identify functionally distinct cell populations, and to determine how these are engaged in pathophysiological conditions. There is a growing consensus concerning the classification of neuron populations, based on transcriptomic and transductomic analyses of the dorsal horn. These approaches have led to the discovery of several molecularly defined cell types that have been implicated in cutaneous mechanical allodynia, a highly prevalent and difficult-to-treat symptom of chronic pain, in which touch becomes painful. The main objective of this review is to provide a contemporary view of dorsal horn neuronal populations, and describe recent advances in our understanding of on how they participate in cutaneous mechanical allodynia.

PKCγ interneurons, a gateway to pathological pain in the dorsal horn.

Chronic pain is a frequent and disabling condition that is significantly maintained by central sensitization, which results in pathological amplification of responses to noxious and innocuous stimuli. As such, mechanical allodynia, or pain in response to a tactile stimulus that does not normally provoke pain, is a cardinal feature of chronic pain. Recent evidence suggests that the dorsal horn excitatory interneurons that express the γ isoform of protein kinase C (PKCγ) play a critical role in the mechanism of mechanical allodynia during chronic pain. Here, we review this evidence as well as the main aspects of the development, anatomy, electrophysiology, inputs, outputs, and pathophysiology of dorsal horn PKCγ neurons. Primary afferent high-threshold neurons transmit the nociceptive message to the dorsal horn of the spinal cord and trigeminal system where it activates second-order nociceptive neurons relaying the information to the brain. In physiological conditions, low-threshold mechanoreceptor inputs activate inhibitory interneurons in the dorsal horn, which may control activation of second-order nociceptive neurons. During chronic pain, low-threshold mechanoreceptor inputs now activate PKCγ neurons that forward the message to second-order nociceptive neurons, turning thus tactile inputs into pain. Several mechanisms may contribute to opening this gate, including disinhibition, activation of local astrocytes, release of diffusible factors such as reactive oxygen species, and alteration of the descending serotoninergic control on PKCγ neurons through 5-HT2A serotonin receptors. Dorsal horn PKCγ neurons, therefore, appear as a relevant therapeutic target to alleviate mechanical allodynia during chronic pain.

Pyridin-2(1H)one derivatives: A possible new class of therapeutics for mechanical allodynia.

Mechanical Allodynia (MA), a frequent chronic pain symptom caused by innocuous stimuli, constitutes an unmet medical need, as treatments using analgesics available today are not always effective and can be associated with important side-effects. A series of 3,5-disubstituted pyridin-2(1H)-ones was designed, synthesized and evaluated in vivo toward a rat model of inflammatory MA. We found that the series rapidly and strongly prevented the development of MA. 3-(2-Bromophenyl)-5-(phenylamino)pyridin-2(1H)-one 69, the most active compound of the series, was also able to quickly reverse neuropathic MA in rats. Next, when 69 was evaluated toward a panel of 50 protein kinases (PK) in order to identify its potential biological target(s), we found that 69 is a p38α MAPK inhibitor, a PK known to contribute to pain hypersensitivity in animal models. 3,5-Disubstituted pyridin-2(1H)-ones thus could represent a novel class of analgesic for the treatment of MA.

Whole-body reversible neuropathic pain associated with right parieto-temporal operculum single inflammatory lesion in a patient with multiple sclerosis: A case report.

BACKGROUND: The posterior insula and the medial parietal operculum (PIMO) are part of the pain network. Pain can be induced by direct stimulation of the PIMO, but the clinical consequence of lesions in this brain area is not well known. CASE REPORT: We report the case of a patient with multiple sclerosis who presented a relapse characterized by isolated widespread neuropathic pain. The MRI displayed a single new inflammatory lesion in the juxta cortical white matter of the opercular region. This lesion was extended to the parietal operculum and was associated with the pain syndrome. The patient was treated with high-dose intravenous methylprednisolone, and the pain disappeared progressively. Diffusion-tensor MRI showed that some of the fibres passing through the lesion ended in the PIMO. CONCLUSION: Based on diffusion-tensor MRI we hypothesize that the partial disconnection from afference to the PIMO can lead to widespread neuropathic pain. SIGNIFICANCE: Most of the data concerning the functional role of the PIMO come from stereoelectroencephalography in presurgical evaluation of epilepsy, or from functional imaging (PET or fMRI). There is, however, very few data on the consequences of the lesion of the PIMO. Here, we report the first case of a transient widespread pain syndrome associated to a single, small and reversible inflammatory lesion of the PIMO. Thus, this case highlights the key role of the PIMO in spatial perception of pain.

Increased cerebral responses to salient transitions between alternating stimuli in chronic migraine with medication overuse headache and during migraine attacks.

INTRODUCTION: In a previous study exploring central pain modulation with heterotopic stimuli in healthy volunteers, we found that transitions between sustained noxious and innocuous thermal stimulations on the foot activated the "salience matrix". Knowing that central sensory processing is abnormal in migraine, we searched in the present study for possible abnormalities of these salient transitional responses in different forms of migraine and at different time points of the migraine cycle. METHODS: Participants of both sexes, mostly females, took part in a conditioned pain modulation experiment: Migraineurs between (n = 14) and during attacks (n = 5), chronic migraine patients with medication overuse headache (n = 7) and healthy volunteers (n = 24). To evoke the salience response, continuous noxious cold or innocuous warm stimulations were alternatively applied on the right foot. Cerebral blood oxygenation level dependent responses were recorded with fMRI. RESULTS: Switching between the two stimulations caused a significant transition response in the "salience matrix" in all subject groups (effect of the condition). Moreover, some group effects appeared on subsequent post-hoc analyses. Augmented transitional blood oxygenation level dependent responses in the motor cortex and superior temporal sulcus were found in two patient groups compared to healthy controls: chronic migraine with medication overuse headache patients and migraineurs recorded during an attack. In chronic migraine with medication overuse headache patients, salience-related responses were moreover greater in the premotor cortex, supplementary motor area, lingual gyrus and dorso-medial prefrontal cortex and other "salience matrix" areas, such as the anterior cingulate and primary somatosensory cortices. CONCLUSION: This study shows salience-related hyperactivation of affective and motor control areas in chronic migraine with medication overuse headache patients and, to a lesser extent, in episodic migraine patients during an attack. The greater extension of exaggerated blood oxygenation level dependent responses to unspecific salient stimuli in chronic migraine with medication overuse headache than during a migraine attack could be relevant for headache chronification.