Cerebrospinal fluid neuropeptides and monoaminergic transmitters in patients with trigeminal neuralgia

Exploring biomarkers in trigeminal neuralgia patients operated with microvascular decompression: A comparison with multiple sclerosis patients and non-neurological controls

BACKGROUND

Trigeminal neuralgia (TN) is a severe facial pain condition often associated with a neurovascular conflict. However, neuroinflammation has also been implicated in TN, as it frequently co-occurs with multiple sclerosis (MS).

METHODS

We analysed protein expression levels of TN patients compared to MS patients and controls. Proximity Extension Assay technology was used to analyse the levels of 92 proteins with the Multiplex Neuro-Exploratory panel provided by SciLifeLab, Uppsala, Sweden. Serum and CSF samples were collected from TN patients before (n = 33 and n = 27, respectively) and after (n = 28 and n = 8, respectively) microvascular decompression surgery. Additionally, we included samples from MS patients (n = 20) and controls (n = 20) for comparison.

RESULTS

In both serum and CSF, several proteins were found increased in TN patients compared to either MS patients, controls, or both, including EIF4B, PTPN1, EREG, TBCB, PMVK, FKBP5, CD63, CRADD, BST2, CD302, CRIP2, CCL27, PPP3R1, WWP2, KLB, PLA2G10, TDGF1, SMOC1, RBKS, LTBP3, CLSTN1, NXPH1, SFRP1, HMOX2, and GGT5. The overall expression of the 92 proteins in postoperative TN samples seems to shift towards the levels of MS patients and controls in both serum and CSF, as compared to preoperative samples. Interestingly, there was no difference in protein levels between MS patients and controls.

CONCLUSIONS

We conclude that TN patients showed increased serum and CSF levels of specific proteins and that successful surgery normalizes these protein levels, highlighting its potential as an effective treatment. However, the similarity between MS and controls challenges the idea of shared pathophysiology with TN, suggesting distinct underlying mechanisms in these conditions.

SIGNIFICANCE

This study advances our understanding of trigeminal neuralgia (TN) and its association with multiple sclerosis (MS). By analysing 92 protein biomarkers, we identified distinctive molecular profiles in TN patients, shedding light on potential pathophysiological mechanisms. The observation that successful surgery normalizes many protein levels suggests a promising avenue for TN treatment. Furthermore, the contrasting protein patterns between TN and MS challenge prevailing assumptions of similarity between the two conditions and point to distinct pathophysiological mechanisms.

Cerebrospinal fluid-contacting neurons: multimodal cells with diverse roles in the CNS

The cerebrospinal fluid (CSF) is a complex solution that circulates around the CNS, and whose composition changes as a function of an animal's physiological state. Ciliated neurons that are bathed in the CSF - and thus referred to as CSF-contacting neurons (CSF-cNs) - are unusual polymodal interoceptive neurons. As chemoreceptors, CSF-cNs respond to variations in pH and osmolarity and to bacterial metabolites in the CSF. Their activation during infections of the CNS results in secretion of compounds to enhance host survival. As mechanosensory neurons, CSF-cNs operate together with an extracellular proteinaceous polymer known as the Reissner fibre to detect compression during spinal curvature. Once activated, CSF-cNs inhibit motor neurons, premotor excitatory neurons and command neurons to enhance movement speed and stabilize posture. At longer timescales, CSF-cNs instruct morphogenesis throughout life via the release of neuropeptides that act over long distances on skeletal muscle. Finally, recent evidence suggests that mouse CSF-cNs may act as neural stem cells in the spinal cord, inspiring new paths of investigation for repair after injury.

CSF neuron-specific enolase as a biomarker of neurovascular conflict severity in drug-resistant trigeminal neuralgia: a prospective study in patients submitted to microvascular decompression

BACKGROUND

Although neurovascular conflict (NVC) is the most widely accepted cause of trigeminal neuralgia (TN), few articles have analyzed molecular and biochemical mechanisms underlying TN. In the present study, we dosed neuron-specific enolase (NSE) on serum and CSF samples of 20 patients submitted to microvascular decompression (MVD) and correlated these findings with the type of NVC.

METHODS

Blood samples were obtained preoperatively and 48 h after MVD. CSF from trigeminal cistern was intraoperatively obtained. NSE levels were measured using the Diasorin kit (LIAISON®NSE). NVC was classified as "contact" or "trigeminal nerve distortion/indentation" or "trigeminal root atrophy" based on MRI and intraoperative findings. Clinical outcome was measured by acute pain relief (APR) and Barrow Neurological Institute (BNI) scale at last available follow-up (FU; 6.40 ± 5.38 months).

RESULTS

APR was obtained in all patients. A statistically significant BNI reduction was obtained at latest FU (p < 0.0001). Serum NSE levels significantly decreased following MVD (from 12.15 ± 3.02 ng/mL to 8.95 ± 2.83 ng/mL, p = 0.001). The mean CSF NSE value was 48.94 ng/mL, and the mean CSF/serum NSE rate was 4.18 with a strong correlation between these two variables (p = 0.0008). CSF NSE level in "trigeminal root atrophy" group was significantly higher compared to "contact" (p = 0.0045) and "distortion/indentation" (p = 0.010) groups.

CONCLUSION

NSE levels seem to be related to the etiopathology and severity of NVC. A significant reduction of serum NSE levels could be related to the resolution of the NVC and clinical TN improvement.

Locus coeruleus-noradrenergic modulation of trigeminal pain: Implications for trigeminal neuralgia and psychiatric comorbidities

Trigeminal neuralgia is the most common neuropathic pain involving the craniofacial region. Due to the complex pathophysiology, it is therapeutically difficult to manage. Noradrenaline plays an essential role in the modulation of arousal, attention, cognitive function, stress, and pain. The locus coeruleus, the largest source of noradrenaline in the brain, is involved in the sensory and emotional processing of pain. This review summarizes the knowledge about the involvement of noradrenaline in acute and chronic trigeminal pain conditions and how the activity of the locus coeruleus noradrenergic neurons changes in response to acute and chronic pain conditions and how these changes might be involved in pain-related comorbidities including anxiety, depression, and sleep disturbance.

Dopamine regulates astrocytic IL-6 expression and process formation via dopamine receptors and adrenoceptors

Dopamine levels in the central nervous system change under pathological conditions such as Parkinson's disease, Huntington's disease, and addiction. Under those pathological conditions, astrocytes become reactive astrocytes characterized by morphological changes and the release of inflammatory cytokines involved in pathogenesis. However, it remains unclear whether dopamine regulates astrocytic morphology and functions. Elucidating these issues will help us to understand the pathogenesis of neurodegenerative diseases caused by abnormal dopamine signaling. In this study, we investigated the effects of dopamine on IL-6 expression and process formation in rat primary cultured astrocytes and acute hippocampal slices. Dopamine increased IL-6 expression in a concentration-dependent manner, and this was accompanied by CREB phosphorylation. The effects of a low dopamine concentration (1 μM) were inhibited by a D1-like receptor antagonist, whereas the effects of a high dopamine concentration (100 μM) were inhibited by a β-antagonist and enhanced by a D2-like receptor antagonist. Furthermore, dopamine (100 μM) promoted process formation, which was inhibited by a β-antagonist and enhanced by both an α-antagonist and a D2-like receptor antagonist. In acute hippocampal slices, both a D1-like receptor agonist and β-agonist changed astrocytic morphology. Together, these results indicate that dopamine promotes IL-6 expression and process formation via D1-like receptors and β-adrenoceptors. Furthermore, bidirectional regulation exists; namely, the effects of D1-like receptors and β-adrenoceptors were negatively regulated by D2-like receptors and α₂-adrenoceptors.

Cerebrospinal Fluid in Classical Trigeminal Neuralgia: An Exploratory Study on Candidate Biomarkers

Trigeminal neuralgia (TN) is a severe type of facial pain. A neurovascular conflict between cranial nerve V and a nearby vessel is the main pathophysiological mechanism, but additional factors are likely necessary to elicit TN. In this study, the primary aim was to explore differences in protein expression in the cerebrospinal fluid (CSF) of TN patients in relation to controls. Methods: Sixteen TN patients treated with microvascular decompression and 16 control patients undergoing spinal anesthesia for urological conditions were included. Lumbar CSF was collected preoperatively for the TN patients and before spinal anesthesia for the controls. A multiplexed proximity extension analysis of 91 CSF proteins was conducted using Proseek Multiplex Development 96, including biomarkers of cell communication, cell death, neurogenesis, and inflammation Results: The TN patients and the controls were of similar age, sex, and burden of co-morbidities. The TN patients exhibited higher concentrations of Clec11a, LGMN, MFG-E8, and ANGPTL-4 in CSF than the controls (q < 0.05). Conclusions: TN patients exhibited increased CSF biomarkers indicative of peripheral demyelinating injury (Clec11a), immune tolerance and destruction of myelin (LGMN), neuronal cell death (MFG-E8), and disturbances in myelin clearance (ANGPTL-8). Our findings are hypothesis-generating for candidate biomarkers and pathophysiological processes in classical TN.

Alpha and beta adrenoceptors activate interleukin-6 transcription through different pathways in cultured astrocytes from rat spinal cord

In brain astrocytes, noradrenaline (NA) has been shown to up-regulate IL-6 production via β-adrenoceptors (ARs). However, the underlying intracellular mechanisms for this regulation are not clear, and it remains unknown whether α-ARs are involved. In this study, we investigated the AR-mediated regulation of IL-6 mRNA levels in the cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol increased IL-6 mRNA levels. The phenylephrine-induced IL-6 increase was accompanied by an increase in ERK phosphorylation, and these effects were blocked by inhibitors of PKC and ERK. The isoproterenol-induced IL-6 increase was accompanied by an increase in CREB phosphorylation, and these effects were blocked by a PKA inhibitor. Our results indicate that IL-6 increases by α1- and β-ARs are mediated via the PKC/ERK and cAMP/PKA/CREB pathways, respectively. Moreover, conditioned medium collected from astrocytes treated with the α2-AR agonist dexmedetomidine, increased IL-6 mRNA in other astrocytes. In this study, we elucidate that α1- and α2-ARs, in addition to β-ARs, promote IL-6 transcription through different pathways in spinal cord astrocytes.

Increased CSF Levels of Apolipoproteins and Complement Factors in Trigeminal Neuralgia Patients-In Depth Proteomic Analysis Using Mass Spectrometry

The main cause of trigeminal neuralgia (TN) is compression of a blood vessel at the root entry zone of the trigeminal nerve. However, a neurovascular conflict does not seem to be the only etiology and other mechanisms are implicated in the development of the disease. We hypothesized that TN patients may have distinct protein expression in the CSF. In this study, lumbar CSF from TN patients (n = 17), scheduled to undergo microvascular decompression, and from controls (n = 20) was analyzed and compared with in depth mass spectrometry TMTbased quantitative proteomics. We identified 2552 unique proteins, of which 46 were significantly altered (26 increased, and 20 decreased, q-value < .05) in TN patients compared with controls. An over-representation analysis showed proteins involved in high-density lipoprotein, such as Apolipoprotein A4, Apolipoprotein M, and Apolipoprotein A1, and the extracellular region, including proteins involved in the complement cascade to be over-represented. We conclude that TN patients have distinct protein expression in the CSF compared to controls. The pathophysiological background of the protein alterations found in this study warrants further investigation in future studies. PERSPECTIVE: In this article, cerebrospinal fluid from patients with trigeminal neuralgia was analyzed using in depth shotgun proteomics, revealing 46 differentially expressed proteins compared to controls. Among these, apolipoproteins and proteins involved in the complement system were elevated and significantly over-represented, implying an inflammatory component in the pathophysiology of the disease.

CGRP Plasma Levels Decrease in Classical Trigeminal Neuralgia Patients Treated with Botulinum Toxin Type A: A Pilot Study

Objective

The aim of this study was to investigate the changes of calcitonin gene-related peptide (CGRP) plasma levels in patients with classical trigeminal neuralgia (TN) and if plasma CGRP concentrations could be used to predict the response to botulinum toxin type A (BTX-A).

Methods

Forty-seven patients with classical TN were recruited and treated with BTX-A. A patient was considered a responder when the visual analog scale (VAS) score and number of episodes were reduced by at least 50% compared with baseline data. Matched healthy subjects with no headache history served as controls. CGRP levels were measured by the enzyme-linked immunosorbent assay.

Results

A total of 45 patients and 30 healthy controls completed the study. Plasma CGRP concentrations after treatment with BTX-A (median [interquartile range {IQR}] = 28.86 [14.75–61.23] pg/mL) were significantly lower than before treatment (median [IQR] = 55.38 [22.59–71.67] pg/mL, P &lt; 0.001). Plasma CGRP concentrations in responders after treatment with BTX-A (median [IQR] = 28.02 [12.78–57.28] pg/mL) were significantly lower than before treatment (median [IQR] = 50.57 [24.30–70.09] pg/mL, P &lt; 0.001). In nonresponders, there were no significant differences between the levels before and after treatment (P = 0.938). Age, gender, VAS score, taking/not taking carbamazepine, and the number of trigeminal nerve branches involved had no significant influence on the median difference between plasma CGRP concentrations. The concentration of CGRP before treatment was not predictive of the treatment result.

Conclusions

CGRP levels decrease significantly in patients with classical TN after treatment with BTX-A. Plasma levels of CGRP cannot be used to predict the response to BTX-A. This study indicates that CGRP is likely to be involved in the pathophysiology of classical TN. Moreover, the analgesic mechanism of BTX-A may be related to the inhibition of CGRP release.

Biomarkers in Temporomandibular Disorder and Trigeminal Neuralgia: A Conceptual Framework for Understanding Chronic Pain

In this review, we will explore the use of biomarkers in chronic pain, using the examples of two prototypical facial pain conditions: trigeminal neuralgia and temporomandibular disorder. We will discuss the main categories of biomarkers and identify various genetic/genomic, molecular, neuroradiological, and psychophysical biomarkers in both facial pain conditions, using them to compare and contrast features of neuropathic, nonneuropathic, and mixed pain. By using two distinct model facial pain conditions to explore pain biomarkers, we aim to familiarize readers with different types of biomarkers currently being studied in chronic pain and explore how these biomarkers may be used to develop new precision medicine approaches to pain diagnosis, prognosis, and management.

Antagonism of Transient Receptor Potential Ankyrin Type-1 Channels as a Potential Target for the Treatment of Trigeminal Neuropathic Pain: Study in an Animal Model

Transient receptor potential ankyrin type-1 (TRPA1) channels are known to actively participate in different pain conditions, including trigeminal neuropathic pain, whose clinical treatment is still unsatisfactory. The aim of this study was to evaluate the involvement of TRPA1 channels by means of the antagonist ADM_12 in trigeminal neuropathic pain, in order to identify possible therapeutic targets. A single treatment of ADM_12 in rats 4 weeks after the chronic constriction injury of the infraorbital nerve (IoN-CCI) significantly reduced the mechanical allodynia induced in the IoN-CCI rats. Additionally, ADM_12 was able to abolish the increased levels of TRPA1, calcitonin gene-related peptide (CGRP), substance P (SP), and cytokines gene expression in trigeminal ganglia, cervical spinal cord, and medulla induced in the IoN-CCI rats. By contrast, no significant differences between groups were seen as regards CGRP and SP protein expression in the pars caudalis of the spinal nucleus of the trigeminal nerve. ADM_12 also reduced TRP vanilloid type-1 (TRPV1) gene expression in the same areas after IoN-CCI. Our findings show the involvement of both TRPA1 and TRPV1 channels in trigeminal neuropathic pain, and in particular, in trigeminal mechanical allodynia. Furthermore, they provide grounds for the use of ADM_12 in the treatment of trigeminal neuropathic pain.

Neuromodulation via the Cerebrospinal Fluid: Insights from Recent in Vitro Studies

The cerebrospinal fluid (CSF) occupies the brain's ventricles and subarachnoid space and, together with the interstitial fluid (ISF), forms a continuous fluidic network that bathes all cells of the central nervous system (CNS). As such, the CSF is well positioned to actively distribute neuromodulators to neural circuits in vivo via volume transmission. Recent in vitro experimental work in brain slices and neuronal cultures has shown that human CSF indeed contains neuromodulators that strongly influence neuronal activity. Here we briefly summarize these new findings and discuss their potential relevance to neural circuits in health and disease.

Clinical study of cerebrospinal fluid neuropeptides in patients with primary trigeminal neuralgia

OBJECTIVES

To investigate the expression levels of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and β-endorphin in the cerebrospinal fluid (CSF) and peripheral blood of patients with primary trigeminal neuralgia (TN).

PATIENTS AND METHODS

We included 20 patients with primary TN who underwent percutaneous radiofrequency thermocoagulation and collected four types of samples from all of them: sample A: CSF samples; sample B: peripheral blood samples; sample C: peripheral blood samples collected one day before the operation; sample D: peripheral blood samples withdrawn one day after the operation. Another 20 CSF samples of patients with nervous system disease or gynecological disease were collected as a control (sample E). Samples A and B were obtained at the same time. We also evaluated the expression of CGRP, SP, β-endorphin, and VIP by visual analog scale (VAS) scores one day before and one day after the operation. In addition, heart rate (HR) at baseline and at the time of sample collection, mean arterial pressure (MAP), and all side effects of the procedure were recorded.

RESULTS

Significance were found concerning about CGRP, SP, β-endorphin, and VIP in TN patients and the controls (P<0.001). The expression of CGRP, SP, and VIP in sample A was higher than that in sample E. However, the β-endorphin level in sample A was lower than that in sample E. There was a positive correlation between sample A and B regarding the expression of CGRP, SP, β-endorphin, and VIP (P<0. 01). There was no relationship between the time of disease onset and the expression of CGRP, SP, β-endorphin, and VIP in sample A and sample B (P>0.05). No difference was detected between the neuropeptides levels in samples B and C (P>0.05). Notably, VAS in sample D was significantly lower than that in sample C (P<0.01). Finally, there was no difference between the intraoperative HR and MAP values in the studied samples.

CONCLUSION

In primary TN patients, the blood levels of CGRP, SP, β-endorphin, and VIP were associated with those in CSF samples. There was a significant difference between the levels of the four neuropeptides in CSF and control samples. Our results also indicated that the levels of neuropeptides in blood samples can be tested for those in CSF. The disease onset and duration exerted insignificant effects on the production and release of CGRP, SP, β-endorphin, and VIP.

Risk of psychiatric disorders following trigeminal neuralgia: a nationwide population-based retrospective cohort study

Background

TN is one of the most common causes of facial pain. A higher prevalence of psychiatric co-morbidities, especially depressive disorder, has been proven in patients with TN; however, a clear temporal-causal relationship between TN and specific psychiatric disorders has not been well established. We performed a nationwide population-based retrospective cohort study to explore the relationship between TN and the subsequent development of psychiatric disorders, including schizophrenia, bipolar disorder, depressive disorder, anxiety disorder, and sleep disorder.

Methods

We identified subjects who were newly diagnosed with TN between January 1, 2000 and December 31, 2010 in the Taiwan National Health Insurance Research Database. A comparison cohort was constructed for patients without TN who were matched according to age and sex. All TN and control patients were observed until diagnosed with psychiatric disorders, death, withdrawal from the National Health Institute system, or until December 31, 2010.

Results

The TN cohort consisted of 3273 patients, and the comparison cohort consisted of 13,092 matched control patients without TN. The adjusted hazard ratio (aHR) of depressive disorder, anxiety disorder and sleep disorder in subjects with TN was higher than that of the controls during the follow-up [aHR: 2.85 (95 % confidence interval: 2.11–3.85), aHR: 2.98 (95 % confidence interval: 2.12–4.18) and aHR: 2.17 (95 % confidence interval: 1.48–3.19), respectively].

Conclusions

TN might increase the risk of subsequent newly diagnosed depressive disorder, anxiety disorder, and sleep disorder, but not schizophrenia or bipolar disorder. Additional prospective studies are required to confirm these findings.

Cerebrospinal fluid substance P-like immunoreactivity correlates with aggression in personality disordered subjects

BACKGROUND

Neurochemical studies have pointed to a modulatory role in human aggression for a variety of central neurotransmitters; some seem to play an inhibitory role, whereas others seem to play a facilitory role in the modulation of aggression. Laboratory animal studies of substance P suggest a facilitory role for this undecapeptide in the modulation of aggression, but no studies of substance P have yet been reported with regard to human aggression.

METHODS

Basal lumbar cerebrospinal fluid samples were obtained from 38 physically healthy subjects with personality disorder (PD) and substance P-like immunoreactivity was measured and correlated with measures of aggression and impulsivity.

RESULTS

The cerebrospinal fluid substance P-like immunoreactivity levels were directly correlated with a composite measure of aggression and, more specifically, with Buss-Durkee Aggression. No correlation was seen with any measure of impulsivity or of general dimensions of personality.

CONCLUSIONS

These data suggest a direct relationship between central nervous system substance P containing neural circuits and aggression in human subjects. This finding adds to the complex picture of the central neuromodulatory role of impulsive aggression in human subjects.

Cerebrospinal fluid catecholamine levels as predictors of outcome in subarachnoid hemorrhage

OBJECTIVE

Subarachnoid hemorrhage (SAH) is associated with marked sympathetic activation at the time of ictus. The purpose of this study is to determine whether early central catecholamine levels measured from cerebrospinal fluid (CSF) relate to outcome in patients with SAH.

METHODS

Observational study of consecutive SAH grade 3-5 patients who underwent ventriculostomy placement, but did not undergo open craniotomy for aneurysm obliteration. CSF samples were obtained during the first 48 h following symptom onset and assayed for catecholamine levels. Statistical analyses were performed to determine whether the levels predicted mortality by day 15 or mortality/disability by day 30.

RESULTS

For the 102 patients included, mean age was 58, and 73% were female - 21% experienced day-15 mortality, and 32% experienced mortality/disability by day 30. Early mortality was related to Hunt-Hess (H/H) grade (p < 0.001), neurogenic cardiomyopathy (NC) (p = 0.003), cerebral infarction (p = 0.001), elevated intracranial pressure (ICP) (p = 0.029), epinephrine (EPI) level (p = 0.002) and norepinephrine/3,4-dihydroxyphenylglycol (NE/DHPG) ratio (p = 0.003). Mortality/disability was related to H/H grade (p < 0.001), NC (p = 0.018), infarction (p < 0.001), elevated ICP (p = 0.002), EPI (p = 0.004) and NE/DHPG (p = 0.014). Logistic regression identified age [OR 1.09 (95% CI 1.01-1.17)], H/H grade [9.52 (1.19-77)], infarction [10.87 (1.22-100)], ICP elevation [32.26 (2-500)], EPI [1.06 (1.01-1.10)], and (inversely) DHPG [0.99 (0.99-1.00)] as independent predictors of early mortality. For mortality/disability, H/H grade [OR 21.74 (95% CI 5.62-83)], ICP elevation [18.52 (1.93-166)], and EPI [1.05 (1.02-1.09)] emerged as independent predictors. Proportional-hazards analysis revealed age [HR 1.041 (95% CI 1.003-1.08)], H/H grade [6.9 (1.54-31.25)], NC [4.31 (1.5-12.35)], and EPI [1.032 (1.009-1.054)] independently predicted early mortality.

CONCLUSIONS

CSF catecholamine levels are elevated in SAH patients who experience early mortality or disability. EPI may potentially serve as useful index of outcome in this population of patients with SAH.

Nasal sumatriptan as adjunctive therapy for idiopathic trigeminal neuralgia: report of three cases

We examine the effect of nasal sumatriptan as an adjunctive therapy in 3 patients with idiopathic trigeminal neuralgia refractory to carbamazepine (CBZ) and found that this therapy might be suitable for patients for whom the CBZ dose cannot be increased, who are under poor pain control, and who are not candidates for nerve blocks or surgery.

Expression of TRPM8 in the distal cerebrospinal fluid-contacting neurons in the brain mesencephalon of rats

Background

It has been shown that distal cerebrospinal fluid-contacting neurons (dCSF-CNs) exist near the ventral midline of the midbrain aqueduct and also in the grey matter of the inferior third ventricle and the fourth ventricle floor in the superior segment of the pons. The dCSF-CNs communicate between the cerebrospinal fluid (CSF) and the brain parenchyma and may participate in the transduction and regulation of pain signals. The cold sensation receptor channel, TRPM8 is involved in analgesia for neuropathic pain, but whether the TRPM8 receptor exists on dCSF-CNs remains unknown. However, there is preliminary evidence that TRPM8 is expressed in dCSF-CNs and may participate in the transmission and regulation of sensory information between brain parenchyma and cerebrospinal fluid (CSF) in rats.

Methods

Retrograde tracing of the cholera toxin subunit B labeled with horseradish peroxidase (CB-HRP) injected into the lateral ventricle was used to identify dCSF-CNs. A double-labeled immunofluorescent technique and laser scanning confocal microscopy were used to identify the expression of TRPM8 in dCSF-CNs. Software Image-Pro Plus was used to count the number of neurons in three sections where CB-HRP positive neurons were located in the mesencephalon of six rats.

Results

The cell bodies of CB-HRP-positive dCSF-CNs were found in the brain parenchyma near the midline of the ventral Aq, also in the grey of the 3V, and the 4V floor in the superior segment of the pons. In the mesencephalon their processes extended into the CSF. TRPM8 labeled neurons were also found in the same area as were CB-HRP/TRPM8 double-labeled neurons. CB-HRP/TRPM8 double-labeled neurons were found in 42.9 ± 2.3% of neurons labeled by TRPM8, and all CB-HRP-labeled neurons were also labeled with TPRM8.

Conclusion

This study has demonstrated that the cold sensation receptor channel, TRPM8, is localised within the dCSF-CNs of the mesencephalon. TRPM8 acts as receptor of dCSF-CNs for sensation transmission and pain regulation.

Substance P expression in the distal cerebrospinal fluid-contacting neurons and spinal trigeminal nucleus in formalin-induced the orofacial inflammatory pain in rats

The distal cerebrospinal fluid-contacting neuron (dCSF-CN) is a peculiar type of neuron whose body is in the parenchyma of the brain and processes extend into cerebrospinal fluid (CSF) in the cavity of the ventricle in the central nervous system. Because most of the dCSF-CNs are found in the dorsal raphe nucleus (DR) of the brainstem, we presume these neurons relate to pain modulation. Many experiments have demonstrated that substance P (SP) plays an important role in the development of pain and hyperalgesia. To explore whether the dCSF-CNs modulated the orofacial inflammatory pain in rats, we examined behavioral changes with the orofacial formalin test and SP-expression in the dCSF-CNs and spinal trigeminal nucleus (STN) with dual immunohistochemical labeling for light microscopy or immunoelectron microscopy. It is revealed that 2h after 2.5% formalin injection SP-expression in the dCSF-CNs and STN is upregulated significantly, which may be considered an important role for nociceptive processing.

Trigeminal neuralgia: for one nerve a multitude of treatments

Trigeminal neuralgia (TN) is reputed to be one of the most painful conditions in human experience. Thus, many treatments, both medical and surgical, have been developed for this relapsing and remitting, paroxysmal stabbing or electrical, facial pain syndrome. The likely etiology in many cases is vascular compression of the trigeminal nerve root entry zone, leading to focal demyelination and aberrant neural discharges. MRI may disclose neurovascular contact, although not with sufficient sensitivity or specificity to substitute for careful clinical diagnosis. In treating TN, antiepileptic drugs are superior to traditional analgesics. Carbamazepine is the first choice drug. Additional drugs for which there is evidence of efficacy include oxcarbazepine, baclofen, gabapentin, lamotrigine and phenytoin. Many patients eventually experience tachyphylaxis or may not tolerate effective doses. Surgical options include: microvascular decompression; balloon compression; radiofrequency thermocoagulation or glycerol rhizotomies; and subcutaneous alcohol branch blockade. Stereotactic gamma knife radiosurgery is a further option. Motor cortex stimulation and transcranial magnetic stimulation, although having shown initial promise for trigeminal neuropathic pain, seem to be ineffective for classical TN. The choice of drug, whether or when to operate, and which procedure to choose should be individualized to the particular needs and conditions of the patient.

Bronchial asthma as neurogenic paroxysmal inflammatory disease: do some antiepileptic drugs have antiasthmatic properties?

Bronchial asthma is an inflammatory disease, and neurogenic inflammation may play important role in asthma mechanisms. But asthma also is an inflammatory disease with paroxysmal clinical picture. It is known that migraine and trigeminal neuralgia also are inflammatory diseases with paroxysmal clinical picture, and neurogenic inflammation plays important role in their mechanisms. Antiepileptic drugs are highly effective in pharmacotherapy of migraine and trigeminal neuralgia, and these drugs completely prevent attacks of migraine and trigeminal pain in great majority of cases. Due to this it is possible that some antiepileptic drugs may be highly effective in pharmacotherapy of asthma. Bronchial asthma can be considered as peripheral paroxysmal and inflammatory disease with definite central neurogenic mechanism. It is also possible that some antiepileptic drugs can suppress inflammatory processes in asthma through the central neural influence, like in therapy of migraine and trigeminal neuralgia.

Cerebrospinal fluid biomarkers in primary headache disorders

OBJECTIVE

The object of this review is to examine the published literature for cerebrospinal fluid laboratory measures of primary headache disorders to identify biomarkers and provide recommendations for future biomarker discovery.

BACKGROUND

Biomarkers may distinguish deviation from a normal state, provide insight into mechanisms of pathophysiology, quantify the degree of change, discriminate what may be clinically overlapping disorders, and allow monitoring and/or selection of specific treatment. High-throughput, discovery technologies fuel the ability to reveal more biomarkers than past hypothesis-driven studies. DESIGN OR METHODS: Publications were identified in PubMed, ISI web of knowledge (both Web of Science and BIOSYS), and SciFinder, using the key words for cerebrospinal fluid (CSF) and migraine, headache, or biomarkers. Additional references were sought from the papers identified in these searches. Data were assessed relating to all primary headache types for clinical and scientific methods and results.

RESULTS

Fifty-five out of 82 biomarkers were found from 55 publications, though none have been validated for clinical utility. Data for site (ventricular, cervical, lumbar) and timing of CSF collection, headache state, and diagnostic description were patchy, and controls were often poorly defined. Most routinely performed CSF measurements were within normal limits. Most levels of pain-related molecules were reduced, and concentrations of most neurotransmitters, neuropeptides, proteins, and small molecules were increased. Though few studies assessed the specificity of biomarkers for primary headaches, it is clear that there are differences in CSF biomarkers between migraine, cluster headache, tension-type headache, and trigeminal neuralgia.

CONCLUSIONS

The high proportion (67%) of biomarkers identified from laboratory measures tested thus far predicts that many more biomarkers will be identified for primary headaches when more candidates are evaluated. In order to discover and evaluate more biomarkers, especially those that may have clinical application for headache management, 3 recommendations are encouraged: prospective design of care-independent studies; evaluation of more clinical variables; and evaluation of substantially more candidates by using discovery-based research methods. Outlines of approaches to pursue these aims are proposed.

Sumatriptan alleviates pain in patients with trigeminal neuralgia

OBJECTIVES

Arterial compression of the trigeminal root may lead to trigeminal neuralgia. 5-HT1B/1D receptor agonists may inhibit vasodilation and inflammation near the irritated trigeminal root. A recent study showed attenuation of mechanical allodynia by a 5-HT1A receptor agonist in a rat model of trigeminal neuralgia. The present study examined the effectiveness of a 5-HT1A/1B/1D receptor agonist, sumatriptan, on pain relief in patients with trigeminal neuralgia.

METHODS

The study was conducted in 15 patients with idiopathic trigeminal neuralgia. The patients had been suffering from painful paroxysms for at least 1 month. Each patient was injected with 1 mL of saline subcutaneously (placebo), followed 15 minutes later with subcutaneous sumatriptan (3 mg in 1 mL saline). This was followed the next day by oral sumatriptan (50 mg twice daily) for 1 week.

RESULTS

The visual analog scale did not change after saline, but significantly decreased after subcutaneous sumatriptan. Both 1 week after oral sumatriptan and 1 week after discontinuation of the drug, visual analog scale scores resulted in a significant decrease from the baseline. Adverse events after subcutaneous sumatriptan occurred in 4 patients: fatigue in 4 and nausea in 2. Side effects from the oral medication appeared in 4 patients: fatigue in 2, nausea in 1 and chest discomfort in 1. These side effects subsided soon after discontinuation of sumatriptan.

CONCLUSIONS

Our results indicate that subcutaneous injection followed by oral administration of sumatriptan produces prompt and continuous analgesia in patients with trigeminal neuralgia.

Subcutaneous sumatriptan for refractory trigeminal neuralgia

BACKGROUND

Mechanical compression of the trigeminal root by an artery is thought to cause trigeminal neuralgia. The 5-HT(1B/1D) receptor agonist may inhibit neurogenic inflammation and vasodilation near the irritated trigeminal root.

OBJECTIVE

To examine the effectiveness of a 5-HT(1B/1D) receptor agonist, sumatriptan, on a paroxysmal pain in trigeminal neuralgia.

METHODS

Twenty-four patients with trigeminal neuralgia refractory to previous treatment were randomized to receive subcutaneously either 3 mg (1 mL) of sumatriptan or 1 mL of saline placebo. Following a 7-day period, patients crossed over to receive the alternative treatment. Paroxysmal pain triggered by touching or moving the face was assessed with VAS before and 15 minutes after the treatment. Patients used a descriptive scale to pain-grade outcome, and asked to note whether the pain returned and how long after therapy it recurred.

RESULTS

Subcutaneous sumatriptan, but not placebo, significantly decreased VAS from 8.3 +/- 2.1 to 2.4 +/- 3.0 cm (mean +/- SD). The number of patients who described their pain as moderately or slightly better was 20 in the sumatriptan group and 1 in the placebo group. The effect of subcutaneous sumatriptan persisted for a median period of 7.9 hours (range: 1-20 hours).

CONCLUSIONS

Subcutaneous sumatriptan produced prompt analgesia without serious adverse reactions in patients with trigeminal neuralgia refractory to previous treatment.

Drug therapy of trigeminal neuralgia

Trigeminal neuralgia is a chronic pain syndrome of still unestablished origin. Its diagnosis depends on clinical grounds. Drug therapy initially helps a great majority of patients. The choice of drugs is quite large, but truly effective compounds with a tolerable side effect profile remain few. Carbamazepine (or oxcarbazepine) and lamotrigine appear to be the most effective, followed by baclofen. Several patients require further nonpharmacological treatment for which no evidence-based recommendation is possible. In the future, neuromodulation may be brought to bear, as in other chronic pain syndromes.

Bronchial asthma as neurogenic paroxysmal inflammatory disease: a randomized trial with carbamazepine

PURPOSE

Based on the assumption that bronchial asthma has not only inflammatory, but also certain neurogenic paroxysmal mechanism and pathophysiological links with other non-epileptic paroxysmal inflammatory diseases--migraine and trigeminal neuralgia, we decided to investigate efficacy of antiepileptic drug carbamazepine in patients with moderate persistent or severe asthma.

METHODS

Sixty-three patients completed randomized double-blind, placebo-controlled trial.

RESULTS

Stable remission was achieved after carbamazepine treatment in 25 patients in active group (n=33). No significant improvement was registered in patients of placebo group (n=30). Following open-label treatment shows high and stable antiasthmatic efficacy of carbamazepine monotherapy.

CONCLUSIONS

Carbamazepine showed high efficacy in therapy of moderate persistent or severe bronchial asthma. Antiasthmatic activity of carbamazepine can be considered as influence on neurogenic mechanisms of asthma. We suppose that it is possible to use carbamazepine for therapy of bronchial asthma in clinical practice.

Predictors of clinical pain intensity in patients with fibromyalgia syndrome

Central changes in pain processing have been previously reported in patients with fibromyalgia syndrome. These changes include decreased thresholds to mechanical and thermal stimuli (allodynia) and central sensitization, both of which are fundamental to the generation of clinical pain. Therefore, psychophysical measures of central pain processing may be useful predictors of clinical pain intensity of fibromyalgia syndrome patients. Previous studies of fibromyalgia syndrome patients have shown statistically significant correlations of psychophysical test results with clinical pain intensity. The tests used to characterize this important relationship were dependent on spinal cord pain mechanisms and included temporal summation of pain or wind-up and wind-up after-sensations. Particularly, the magnitude of wind-up after-sensations appeared to be one of the best predictors for clinical pain intensity of fibromyalgia syndrome patients (27%). Furthermore, the combination of tender point count, negative affect, and wind-up after-sensations accounted for approximately 50% of the variance in clinical pain intensity of fibromyalgia syndrome patients. Therefore, wind-up after-sensations, tender point count, and negative affect not only seem to represent relevant pain mechanisms but also strongly emphasize their importance for fibromyalgia syndrome pain.

Predictors of clinical pain intensity in patients with fibromyalgia syndrome

Central changes in pain processing have been previously reported in patients with fibromyalgia syndrome. These changes include decreased thresholds to mechanical and thermal stimuli (allodynia) and central sensitization, both of which are fundamental to the generation of clinical pain. Therefore, psychophysical measures of central pain processing may be useful predictors of clinical pain intensity of fibromyalgia syndrome patients. Previous studies of fibromyalgia syndrome patients have shown statistically significant correlations of psychophysical test results with clinical pain intensity. The tests used to characterize this important relationship were dependent on spinal cord pain mechanisms and included temporal summation of pain or wind-up and wind-up after-sensations. Particularly, the magnitude of wind-up after-sensations appeared to be one of the best predictors for clinical pain intensity of fibromyalgia syndrome patients (27%). Furthermore, the combination of tender point count, negative affect, and wind-up after-sensations accounted for approximately 50% of the variance in clinical pain intensity of fibromyalgia syndrome patients. Therefore, wind-up after-sensations, tender point count, and negative affect not only seem to represent relevant pain mechanisms but also strongly emphasize their importance for fibromyalgia syndrome pain.

Monoaminerge Transmitter in der Zerebrospinalflüssigkeit von Patienten mit akuten, chronischen und episodischen Schmerzen

BACKGROUND AND STUDY PURPOSE

Pain and depression share similar neurobiological characteristics, and it is a common clinical observation that pain and depression may coincide in the same patient. They also appear to influence each other in the process of chronification. Furthermore, there is a complex coupling of pain and depression by monoaminergic transmitter system.

PATIENTS AND METHODS

On the basis of these findings, norepinephrine (NE), epinephrine (E), dopamine (DOP), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and vanillylmandelic acid (VMA) concentrations were determined in the cerebrospinal fluid (CSF) in patients with acute (20), chronic (27), and episodic pain syndrome (44) in a prospective study. The biochemical parameters were correlated to self-assessment pain and depression scores. The control group consisted of 13 pain-free patients with diseases affecting the muscular system.

RESULTS

Patients with chronic and episodic pain syndromes had significantly more depressive and psychovegetative symptoms compared to patients with acute pain. In patients with acute pain, DOP was significantly higher than in controls and chronic and episodic pain patients. In addition DOP was positively correlated to self-assessment pain score (p*<0.05). In patients with chronic and episodic pain, NE and 5-HIAA were positively correlated to the duration of disease and were significantly lower than in the control group. In neither of these two groups could significant correlations be established between these parameters and pain or depression self-assessment scores. In all groups, positive correlations were seen between the neurotransmitter and their metabolites.

CONCLUSION

The pathological decrease of NE and 5-HIAA in the CSF points to the crucial role of noradrenergic and serotonergic transmitter systems in the generation, modulation, and perpetuation of chronic and episodic pain syndromes. It indicates that antidepressants are effective drugs in these diseases. However, a discriminative neurochemical pattern between pain and depression could not be established. The demonstration of polyvalent correlations between different neurotransmitters is indicative of complex neurobiological coupling between cortical, limbic, and hypothalamic neuronal networks on the one hand and the nociceptive descending system on the other hand in the genesis of pain and depression.

The distributions and signaling directions of the cerebrospinal fluid contacting neurons in the parenchyma of a rat brain

Many studies have been made on the distributions of CSF contacting neurons (CSF-CNs) in the parenchyma of the brain with horseradish peroxidase (HRP) or autoradiographics. A significant amount of data has shown that both HRP and autoradiographical substances could pass freely through the spaces of ependyma into the parenchyma of the brain. It is therefore possible that the results were not exact. We found that CB-HRP was a dependable tracer to CSF-CNs and studied the distributions and the signaling directions of cerebrospinal fluid contacting neurons (CSF-CNs) in the parenchyma of the brain with the cholera toxin subunit B with horseradish peroxidase (CB-HRP) tracing combined with transmission electron microscopy. The results were as follows: (1) CSF contacting tanycytes existed not only in the wall of the third ventricle (3V), but also in the walls of the lateral ventricle (LV), the fourth ventricle (4V) and the central canal (CC) of the spinal cord. (2) Some CSF contacting glia cells were observed in the lateral septal nucleus (LS). (3)The distal CSF-CNs in the parenchyma were found in LS, the anterodorsal thalamic nucleus (AD), the supramammillary nucleus (SuM), the dorsal raphe nucleus (DR), the floor of 4V and the lateral superior olive (LSO), but they were mainly found in DR and divided into groups A and B. (4) Axon terminals labeled by CB-HRP were found in the cavity of the brain ventricle. (5) The synaptic relationships between the neurons were labeled by CB-HRP in DR and no-labeled by CB-HRP in the parenchyma. Both synapses Gray I and II were found. It was significant that the presynaptic elements were formed by the neurons no-labeled CB-HRP and the postsynaptic elements labeled CB-HRP. Our results suggested firstly that the signaling directions of CSF-CNs in DR were only from the parenchyma to CSF.

Ratings of experimental pain and pain-related negative affect predict clinical pain in patients with fibromyalgia syndrome

Patients with fibromyalgia syndrome (FMS) report chronic pain related to abnormal sensitivity of muscles that is reflected by so-called tender points (TP). TP represent areas of abnormal mechanical pain thresholds that have only shown a minor correlation with clinical pain of FMS patients and seem to be better suited for predicting distress. Pain-related negative affect (PRNA), abnormal temporal summation of second pain (termed wind-up or WU), and abnormal WU decay are frequently present in FMS patients. WU and WU decay can provide measures of central sensitization, which may contribute to clinical FMS pain. We therefore investigated the role of WU, WU decay, TP count, and PRNA as predictors of clinical pain in FMS subjects.Fifty-five FMS subjects rated their clinical pain at entry into the study using a visual analogue scale (VAS). After a TP evaluation, all subjects received two trials of thermal WU and WU decay testing. Hierarchical regression analysis demonstrated that the combination of PRNA ratings, TP count, and WU decay ratings predicted 49.7% of the variance of clinical pain in FMS. This model demonstrates independent relationships of biological and psychological factors to clinical pain and underscores the important role of abnormal peripheral and central pain mechanisms for FMS. Therefore, the combination of PRNA, TP count, and WU decay may provide an excellent measure for future clinical studies of FMS patients.

An immunocytochemical investigation of human trigeminal nucleus caudalis: CGRP, substance P and 5-HT1D-receptor immunoreactivities are expressed by trigeminal sensory fibres

5-HT1D (but not 5-HT1B)-receptor immunoreactivity (i.r.) can be detected on trigeminal fibres within the spinal trigeminal tract of the human brainstem. The present study used immunohistochemical and morphometric techniques to determine the proportions of trigeminal fibres expressing substance P, CGRP or 5-HT1D-receptor immunoreactivities. Co-localization studies between 5-HT1D-receptor and substance P- or CGRP-i.r. were also performed. Brainstem material was obtained with consent (four donors) and the total number of immunoreactive fibres within the trigeminal tract was estimated using random field sampling. A greater proportion of fibres (>1 microm diameter) expressed CGRP-i.r. (80 +/- 6%) compared with substance P-i.r. (46 +/- 7%) or 5-HT1D-receptor-i.r. (25 +/- 1%). 5-HT1D-receptor-i.r. was co-localized on some CGRP- or substance P-i.r. fibres. This suggests that 5-HT1D-receptors can regulate the release of CGRP and substance P and may be relevant to the clinical effectiveness of 5-HT1B/1D-receptor agonists in the treatment of migraine and other cranial pain syndromes.

Substance P content in the cerebrospinal fluid and fluid perfusing cerebral ventricles during elicitation and inhibition of trigemino-hypoglossal reflex in rats

The aim of this study was to establish whether tooth pulp and periaqueductal central gray (PAG) stimulation affects the release of substance P (SP) into the fluid perfusing the cerebral ventricles in rats. The content of substance P in the cerebrospinal fluid and fluid perfusing cerebral ventricles was determined during incisor pulp stimulation with electrical impulses inducing nociceptive trigemino-hypoglossal reflex and then during inhibition of the reflex by stimulation of PAG. Perfusion of the cerebral ventricles was carried out using artificial cerebrospinal fluid (aCSF). SP-like immunoreactivity (SP-LI) was determined in the samples by radioimmunoassay. Samples were collected in four groups: first group-cerebrospinal fluid (CSF); second group-aCSF perfusates without stimulation; third group-aCSF perfusates during incisor pulp stimulation; fourth group-aCSF perfusates during incisor pulp stimulation and simultaneous inhibition of trigemino-hypoglossal reflex by PAG stimulation. It was shown that incisor pulp stimulation led to the increased release of SP-LI into the fluid perfusing cerebral ventricles. Stimulation of PAG reduced the release of SP-LI into the cerebro-ventricular system to the values obtained before the tooth pulp stimulation. The results indicate that PAG significantly inhibits the release of SP-LI into the rat cerebral ventricular system and may be involved in the inhibition of trigemino-hypoglossal reflex.

The neuropharmacology of centrally-acting analgesic medications in fibromyalgia

As demonstrated above, the anatomy and neuropharmacology of the pain pathways within the CNS, even to the level of the midbrain, are extraordinarily complex. Indeed, discussions of the effects of these agents on the neuropharmacology of the thalamus, hypothalamus, and cortex were excluded from this review owing to their adding further to this complexity. Also, the dearth of data regarding FMS pain pathophysiology necessitated a relatively generic analysis of the pain pathways. As mentioned in the introduction, the current thought is that central sensitization plays an important role in FMS. However, we see in this chapter that the behavioral state of central sensitization may be a result of alterations in either the ascending systems or in one or more descending systems. Studies to assess the presence or relative importance of such changes in FMS are difficult to perform in humans, and to date there are no animal models of FMS. Accepting these limitations, it is apparent that many drugs considered to date for the treatment of FMS do target a number of appropriate sites within both the ascending and descending pain pathways. The data regarding clinical efficacy on some good candidate agents, however, is extremely preliminary. For example, it is evident from the present analysis that SNRIs, alpha 2 agonists, and NK1 antagonists may be particularly well suited to FMS, although current data supporting their use is either anecdotal or from open-label trials [114,149]. Other sites within the pain pathways have not yet been targeted. Examples of these include the use of CCKB antagonists to block on-cell activation or of nitric oxide synthetase antagonists to block the downstream mediators of NMDA activation. Efficacy of such agents may give considerable insight into the pathophysiology of FMS. Finally, as indicated previously, FMS consists of more than just chronic pain, and the question of how sleep abnormalities, depression, fatigues, and so forth tie into disordered pain processing is being researched actively. Future research focusing on how the various manifestations of FMS relate to one another undoubtedly will lead to a more rational targeting of drugs in this complex disorder.

NK1 (substance P) receptor antagonists--why are they not analgesic in humans?

Tachykinin NK1 receptor antagonists have failed to exhibit efficacy in clinical trials of a variety of clinical pain states. By contrast, in preclinical studies in animals NK1 receptor antagonists have been shown to attenuate nociceptive responses sensitized by inflammation or nerve damage, although they exhibit little effect on baseline nociception. Other agents with this profile of activity in animal tests, typically nonsteroidal anti-inflammatory drugs (NSAIDs), are analgesic in humans. Thus, NK1 receptor antagonists appear able to block behavioural responses to noxious and other stressful sensory stimuli at a level detectable in animal tests but fail to provide the level of sensory blockade required to produce clinical analgesia in humans.