painPREDICT: first interim data from the development of a new patient-reported pain questionnaire to predict treatment response using sensory symptom profiles

Objective: Sensory symptom patterns may be useful for predicting treatment response, and, thus, improve individual therapy in patients suffering from neuropathic pain (NeP). Existing screening questionnaires focus predominately on neuropathic mechanisms without consideration of nociceptive mechanisms or mixed pain states. This study aimed to develop a new questionnaire, painPREDICT, using a wide set of patient-reported descriptors potentially associated with neuropathic and nociceptive pain mechanisms, and to explore sensory symptom patterns. Methods: PainPREDICT was constructed based on exploratory (n = 27 patients) and cognitive debriefing interviews (n = 49 patients and nine physicians), across five NeP conditions. The pilot questionnaire was then administered in a non-interventional, cross-sectional, multi-center study to 840 pain patients across the US and Germany. The identification of a sensory symptom pattern was based on hybrid clustering resulting from items standardization followed by principal component analysis. Results: The final questionnaire included 20 items covering: pain intensity, location of pain, course of pain, and sensory symptoms. Most patients participating in the cross-sectional study suffered either from painful diabetic polyneuropathy (n = 330) or radiculopathy (n = 349), fewer from central pain (n = 61) or other types of NeP (n = 100). The hybrid clustering of the new questionnaire data identified three different characteristic sensory symptom profiles in patients with NeP: "Irritable nociceptors", "deafferentation pain", and "pain attacks with nociceptive component". Although some differences in the distribution of the sensory profiles were found, all profiles were represented in all NeP etiology groups. Conclusions: This study set the ground of painPREDICT and showed promising results for its use to categorize patients according to sensory symptom patterns.

Altered Metabolism in Frontal Brain Circuits in Cluster Headache

Neuroimaging studies have explored cerebral activation patterns in patients with cluster headache (CH) during attacks and have revealed activation of multiple brain areas known to belong to the general pain-processing network. However, it is still unclear which changes in brain metabolism are inherent to the shift from the ‘in bout’ to the ‘out of bout’ period. We measured cerebral glucose metabolism in 11 episodic CH patients during the cluster and again during the remission period with 18F-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) and compared these data with 11 healthy controls. ‘In bout’ compared with ‘out of bout’ scans were associated with increases of metabolism in the perigenual anterior cingulate cortex (ACC), posterior cingulate cortex, prefrontal cortex, insula, thalamus and temporal cortex. Decreases in metabolism were observed in the cerebellopontine area. Compared with healthy volunteers, hypometabolism in the patient group (‘in bout’ and ‘out of bout’) was found in the perigenual ACC, prefrontal and orbitofrontal cortex. Thus, FDG-PET in CH patients revealed ‘in bout’ activation of brain structures which are involved in descending pain control. Compared with controls, the regional brain metabolism was constitutively decreased in most of these structures, irrespective of the bout. This finding indicates a deficient top-down modulation of antinociceptive circuits in CH patients. We suggest that trigger mechanisms of CH are insufficiently controlled and thus promote the initiation of the bout period and acute attack.

A retrospective analysis of the long-term test-retest stability of pain descriptors of the painDETECT questionnaire

OBJECTIVE

PainDETECT (PD-Q) is a patient reported screening questionnaire to identify patients with neuropathic pain based on questions regarding typically sensory symptoms of neuropathic pain. The aim of the present investigation was to assess the test-retest stability of pain descriptors of the PD-Q within a time window of 1-3 weeks.

METHODS

Data sets of 74 chronic pain patients sampled in an open pain register at two visits were analyzed and compared. Patients with change of pain localization between visits were excluded from analysis. Beside conventional measures (Pearson correlation coefficient r, intraclass correlation coefficient ICC, kappa), also calculated measures known from method comparison were used.

RESULTS

The mean duration between visits was 15 days. The measures were in the range of r = 0.72-0.86, ICC = 0.71-0.86, and kappa = 0.62-0.72 for PD-Q pain descriptors (burning, prickling, mechanical allodynia, pain attacks, thermal hyperalgesia, numbness, pressure induced pain).

CONCLUSION

The individual PD-Q pain descriptors showed accurate test-retest stability as a prerequisite for use in repeated measurements (e. g. post baseline or follow up data) in clinical trials.

Duloxetine use in chronic painful conditions--individual patient data responder analysis

Background

Duloxetine has been studied in four distinct chronic pain conditions – osteoarthritis (OA), fibromyalgia, chronic low back pain (CLBP) and diabetic peripheral neuropathic pain (DPNP). These trials have involved large numbers of patients with at least moderate pain, and have used similar methods for recording pain intensity, over about 12 weeks.

Methods

Data from the trials were pooled according to painful condition, and reanalysed at the level of the individual patient and using increasing levels of pain intensity reduction (<15%, 15–29%, 30–49%, ≥50%), with different imputation methods on withdrawal.

Results

The proportion of patients recording at least 50% pain intensity reduction plateaued after 2–6 weeks in fibromyalgia, and 8–12 weeks in other conditions. The duloxetine-specific benefit [number needed to treat (NNT) for at least 50% pain intensity reduction] was fairly constant after about 2 weeks for DPNP and fibromyalgia and after about 4 or 5 weeks for OA and CLBP. In all conditions, responses were bimodal, with patients generally experiencing either very good or very poor pain relief. Last-observation-carried-forward imputation produced numerically and occasionally statistically better (lower) NNTs than use of baseline-observation-carried-forward (true response).

Conclusions

Baseline-observation-carried-forward (true response), which combines the success of high levels of pain relief with the failure to experience pain relief on withdrawal of the drug is conservative and probably reflective of clinical practice experience. The distribution of effect was not normal; few patients had the average response and averages are not an appropriate descriptor for these data.

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[Placebo responders in randomized controlled drug trials of fibromyalgia syndrome : Systematic review and meta-analysis]

BACKGROUND

The superiority of true drug treatment over placebo in reducing symptoms of fibromyalgia syndrome (FMS) is small. Drug placebo treatment of functional somatic syndromes (FSS) such as FMS has been discussed. We determined the magnitude of placebo responders in drug trials with FMS patients to substantiate further research on placebo treatment of FSS.

MATERIAL AND METHODS

CENTRAL, MEDLINE, Scopus, and the databases of the U.S. National Institutes of Health and the Pharmaceutical Research and Manufacturers of America were searched for randomized, double-blind, placebo-controlled trials with a parallel design and treatment duration of ≥ 12 weeks in FMS patients from inception to 31 December 2010. The magnitude of placebo responders was assessed by the pooled estimate of patients with a 30% and 50% reduction in pain.

RESULTS

Thirty studies with 3,846 patients on placebo were included. The pooled estimate of a 30% placebo pain reduction was 30.8% (95% confidence interval (CI) 29.4-32.3%) and of a 50% placebo pain reduction was 18.8% (95% CI 17.5-20.1%). The pooled estimate of the risk ratio of 30% pain reduction by true drug versus placebo was 1.38 (95% CI 1.27-1.49). The pooled estimate of the risk ratio of 50% pain reduction by true drug versus placebo response was 1.57 (95% CI 1.36-1.81).

CONCLUSION

The magnitude of responders to placebo in drug trials of FMS is substantial. The efficacy, safety, and costs of drugs recommended for FMS therapy and open-label placebo should be compared in large multinational trials sponsored by public institutions. The English full-text version of this article is available at SpringerLink (under "Supplemental").

Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): somatosensory abnormalities in 1236 patients with different neuropathic pain syndromes

Neuropathic pain is accompanied by both positive and negative sensory signs. To explore the spectrum of sensory abnormalities, 1236 patients with a clinical diagnosis of neuropathic pain were assessed by quantitative sensory testing (QST) following the protocol of DFNS (German Research Network on Neuropathic Pain), using both thermal and mechanical nociceptive as well as non-nociceptive stimuli. Data distributions showed a systematic shift to hyperalgesia for nociceptive, and to hypoesthesia for non-nociceptive parameters. Across all parameters, 92% of the patients presented at least one abnormality. Thermosensory or mechanical hypoesthesia (up to 41%) was more frequent than hypoalgesia (up to 18% for mechanical stimuli). Mechanical hyperalgesias occurred more often (blunt pressure: 36%, pinprick: 29%) than thermal hyperalgesias (cold: 19%, heat: 24%), dynamic mechanical allodynia (20%), paradoxical heat sensations (18%) or enhanced wind-up (13%). Hyperesthesia was less than 5%. Every single sensory abnormality occurred in each neurological syndrome, but with different frequencies: thermal and mechanical hyperalgesias were most frequent in complex regional pain syndrome and peripheral nerve injury, allodynia in postherpetic neuralgia. In postherpetic neuralgia and in central pain, subgroups showed either mechanical hyperalgesia or mechanical hypoalgesia. The most frequent combinations of gain and loss were mixed thermal/mechanical loss without hyperalgesia (central pain and polyneuropathy), mixed loss with mechanical hyperalgesia in peripheral neuropathies, mechanical hyperalgesia without any loss in trigeminal neuralgia. Thus, somatosensory profiles with different combinations of loss and gain are shared across the major neuropathic pain syndromes. The characterization of underlying mechanisms will be needed to make a mechanism-based classification feasible.

The mu-opioid receptor agonist remifentanil induces acute dysphoria irrespective of its analgesic properties

Mu-opioidergic agonists are believed to induce euphoria, whereas kappa-agonists are thought to lead to dysphoria. Our study investigated mood effects of remifentanil, a mu-receptor opioid agonist, in healthy male volunteers. Moreover, we examined interactions between mood and pain. Three conditions were investigated in 21 volunteers: saline, 0.05 and 0.15 microg kg(-1) min(- 1) remifentanil. Each condition was investigated during non-painful heat and during painful heat stimulation. Mood was measured with the von Zerssen's mood scale (Bf-S score) and pain intensity using a Visual Analogue Scale (VAS). High Bf-S scores are reflecting discontent and dysphoria. Changes were tested for significance using a linear mixed model approach. Remifentanil significantly increased Bf-S scores during painful heat (+91.4%), indicating a negative mood effect, although it reduced VAS scores of painful heat intensity (-49.0%). The type of sensory stimulation (non-painful versus painful) had no effect on mood. There was no interaction between remifentanil dose and type of stimulation. Our results provide evidence for negative mood effects of remifentanil. These effects occur with and without pain. Taken into account that remifentanil reduces pain, one could have expected analgesia-related amelioration of mood instead. In clinical practice, these remifentanil effects should be considered and a comedication might be advisable.

Temperature modulated histamine-itch in lesional and nonlesional skin in atopic eczema - a combined psychophysical and neuroimaging study

BACKGROUND

Itch is the major symptom of many allergic diseases; yet it is still difficult to measure objectively. The aim of this study was to use an evaluated itch stimulus model in lesional (LS) and nonlesional (NLS) atopic eczema (AE) skin and to characterize cerebral responses using functional magnetic resonance imaging (fMRI).

METHODS

Thermal modulation was performed on a histamine stimulus in randomized order on LS or NLS in rapid alternating order from 32 degrees C (warm) to 25 degrees C (cold). Subjective itch ratings were recorded. Additionally, fMRI measurements were used to analyze the cerebral processing (n = 13). Healthy skin (HS) of age-matched volunteers served as control (n = 9).

RESULTS

Mean VAS itch intensity was significantly (P < 0.0001) higher during the relative cold [55.2 +/- 8.3% (LS); 48.6 +/- 8.2% (NLS)] compared to the relative warm blocks [36.0 +/- 7.3% (LS); 33.7 +/- 7.6% (NLS)]. Compared to HS, the itch response was delayed in LS and NLS. Itch intensity was perceived highest in LS, followed by NLS and HS. For NLS, fMRI revealed at the beginning of the itch provocation a cerebral deactivation pattern in itch processing structures (thalamus, prefrontal, cingulate, insular, somatosensory and motor cortex). During the course of stimulation, the cerebral deactivation was reduced with time and instead an activation of the basal ganglia occurred. In contrast LS showed an activation instead of deactivation pattern already at the beginning of the stimulation in the above mentioned structures.

CONCLUSIONS

Moderate short-term temperature modulation led to a reproducible, significant enhancement of histamine-induced itch with the strongest effect in LS. The differences in itch perception and itch kinetics between healthy volunteers and NLS in patients point towards an ongoing central inhibitory activity patients with AE, especially at the beginning of the itch provocation.

[Trigeminal autonomic cephalgias. After initial diagnosis, consider secondary causes]

Trigeminal autonomic cephalgias (TAC) are classified as primary headache syndromes. The use of instrumental procedures including neuroimaging in the diagnostic workup of the TACs is controversially discussed in the literature. Several case reports have been previously published, reporting trigeminal autonomic cephalgias related to structural lesions. We contribute two of our own cases of symptomatic TACs and demonstrate that a "classic" clinical presentation does not preclude a symptomatic etiology. Thus, we advocate a systematic diagnostic evaluation including neuroimaging in every patient presenting with symptoms indicative of TAC for the first time.

[Pain and consciousness. Articles from the summer workshop held by the German Interdisciplinary Collaboration for Pain Therapy (DIVS) in 2005]

Six articles are presented which illustrate the activities at the summer workshop "Pain and awareness" held 27-28 May 2005 in Marienfeld by the German Interdisciplinary Collaboration for Pain Therapy (DIVS). One article on pain constructs in the mind explains the advantages of functional imaging methods: these enable characterization of partial aspects of pain processing in the brain and the mechanisms that lead to chronic states of pain syndromes. A further overview explains the influence of different drugs on pain perception and various conscious states. How back pain patients experience their illness was analyzed in a study using an explanatory model interview: somatic aspects were dominant, but in three-fourths of the patients psychological illness attributions also played a role. A summary from the perspective of religious history and theology explores how pain is interpreted and accepted in various religious communities. Another article addresses hypnosis as a complementary technique to anesthesia procedures in surgical medicine, for treating chronic pain and experimental acute pain. The last contribution deals with how people in different cultures experience pain: ethnocentric bias can lead to difficulties in communication and misjudgments when treating foreign-born patients. All in all the workshop highlighted important formative factors in pain processing in a condensed form and offered stimulating perspectives for this area of pain research and future treatment options.

Positronenemissionstomographie (PET) in der Schmerzforschung

Over the last decades, functional imaging studies have fostered our knowledge of cerebral pain processing in humans. A lively interest has been focussing on possible opioidergic mechanisms of pain transmission and modulation. Today, reliable knowledge of the in vivo distribution of opioid receptors in healthy human subjects is available from positron emission tomography (PET) studies of opioidergic neurotransmission. Gender dependent differences in receptor distribution and ligand metabolism have been demonstrated. Moreover, an increasing number of studies are reporting alterations in receptor distribution patterns in states involving painful diseases. Various acute painful challenges have also been shown to induce measurable changes in receptor availability in multiple brain areas. The perigenual anterior cingulate cortex (ACC) has been identified as one brain region with a major impact on opioidergic pain modulation. Thereby, the ACC apparently executes cortical top-down control on brainstem structures in (exogenous) pharmacological opioid analgesia. In addition, accumulating evidence suggests that non-pharmacological treatment approaches also utilize similar endogenous opioid dependent pathways to exert pain modulation. This article summarizes our current knowledge of PET studies of the opioidergic system and outlines future perspectives.

Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): Standardized protocol and reference values

The nationwide multicenter trials of the German Research Network on Neuropathic Pain (DFNS) aim to characterize the somatosensory phenotype of patients with neuropathic pain. For this purpose, we have implemented a standardized quantitative sensory testing (QST) protocol giving a complete profile for one region within 30 min. To judge plus or minus signs in patients we have now established age- and gender-matched absolute and relative QST reference values from 180 healthy subjects, assessed bilaterally over face, hand and foot. We determined thermal detection and pain thresholds including a test for paradoxical heat sensations, mechanical detection thresholds to von Frey filaments and a 64 Hz tuning fork, mechanical pain thresholds to pinprick stimuli and blunt pressure, stimulus/response-functions for pinprick and dynamic mechanical allodynia, and pain summation (wind-up ratio). QST parameters were region specific and age dependent. Pain thresholds were significantly lower in women than men. Detection thresholds were generally independent of gender. Reference data were normalized to the specific group means and variances (region, age, gender) by calculating z-scores. Due to confidence limits close to the respective limits of the possible data range, heat hypoalgesia, cold hypoalgesia, and mechanical hyperesthesia can hardly be diagnosed. Nevertheless, these parameters can be used for group comparisons. Sensitivity is enhanced by side-to-side comparisons by a factor ranging from 1.1 to 2.5. Relative comparisons across body regions do not offer advantages over absolute reference values. Application of this standardized QST protocol in patients and human surrogate models will allow to infer underlying mechanisms from somatosensory phenotypes.

Opioidergic changes in the pineal gland and hypothalamus in cluster headache: A ligand PET study

Using PET with the opioidergic ligand [11C]diprenorphine, the authors demonstrate decreased tracer binding in the pineal gland of cluster headache patients vs healthy volunteers. Opioid receptor availability in the hypothalamus and cingulate cortex depended on the duration of the headache disorder. Therefore, the pathophysiology of cluster headache may relate to opioidergic dysfunction in circuitries generating the biologic clock.

Schwerwiegende Risiken und Komplikationen der epiduralen Neurolyse nach Racz

Racz's minimal invasive epidural catheter procedure, also known as "epidural neuroplasty" is not only utilized in patients suffering from failed spine surgery ("failed back surgery syndrome") but also increasingly applied to non-surgical back pain patients to prevent chronification or deterioration. Its hypothesized principle of action is local epidural lysis of adhesions, neurolysis of vertebral nerve roots and local lavage of proinflammatory mediators by repeated injection of local anesthetics, corticosteroids, hyaluronidase and hypertonic saline solution. However adverse events are well known to occur in epidural neuroplasty. Complications of epidural neuroplasty are due to the procedure itself or due to specific drugs-related side effects. Unintended dural puncture, administration of the drugs to the subarachnoid or subdural space, catheter shearing, infection and severe hemodynamic instability during application are most commonly observed adverse events. Complications related to the procedure itself occur immediately, while complications relating to drug administration show later onset. Within this context, we report a case of severe meningitis with neurologic sequelae in a patient who received Racz catheter-treatment for unspecific low-back pain and provide an overview of the literature on other potential severe complications. As a consequence, we recommend that the Racz catheter procedure as yet should be restricted to controlled clinical trials with rigorous inclusion- and exclusion criteria.

The effect of mirtazapine in patients with chronic pain and concomitant depression

OBJECTIVE

To evaluate the safety, tolerability and efficacy of mirtazapine in patients with the primary diagnosis of chronic pain and concomitant depression in an open post-marketing surveillance study.

RESEARCH DESIGN AND METHODS

594 patients with a primary diagnosis of at least one chronic pain syndrome (minimum duration of 3 months) and the diagnosis of concomitant depression, appropriately made by a neurologist or psychiatrist, were recruited at psychiatric and/or neurological outpatient facilities throughout Germany. The primary efficacy parameter was pain at baseline and endpoint using a patient self-assessment scale. Secondary analyses were performed at baseline, week 1 (day 7 +/- 2), week 4 (day 28 +/- 4) and at endpoint (day 42 +/- 4 or early termination) and included safety and tolerability assessments. Investigators rated the severity of different potential co-morbidities (including depression) with a four-step rating scale (not present, mild, moderate, severe).

RESULTS

594 patients were enrolled and treated with mirtazapine (mean daily dose of 34.5 +/- 10.4 mg at study endpoint). A statistically significant (p < 0.0001; one sample sign test) reduction of pain from baseline to endpoint was found for the overall population. The percentage of patients free of pain or with only moderate pain increased significantly, irrespective of patients' age or pain syndromes. Furthermore, we found a substantial improvement from baseline to endpoint regarding co-morbidities such as sleep disturbance, irritability and exhaustion. The number of adverse events was low (<7%; n = 37), with fatigue (n = 13) and weight gain (n = 11) occurring most frequently. No previously-unknown side effects occurred. One hundred and six patients (18%) discontinued mirtazapine during the study. The main reason was lack of efficacy (6%, n = 33), which may be a reflection of sub-optimal response to the anti-depressant or analgesic effect of the drug, but no appropriate rating scale was used to clarify this question. Only a small number of patients stopped the drug due to adverse events (3%; n = 15). At study endpoint, the majority of physicians and patients rated the overall efficacy and tolerability of mirtazapine as good or very good. Most patients (80%) continued the therapy after 6 weeks.

CONCLUSIONS

Despite the limitations of an open observational study, our findings suggest that mirtazapine is a safe and well-tolerated drug for use in daily clinical practice. It still remains unclear whether the reduction of pain, the enhancement of the depressed mood or the combination of both effects led to these results. Nevertheless, our data point to a potential beneficial effect of mirtazapine in the treatment of patients with pain and concomitant depression. However, more systematic research, including placebo-controlled studies, and further empirical testing are necessary.

[Pain and neuroborreliosis]

Pain is one of the presenting symptoms in acute neuroborreliosis. Classically, acute neuroborreliosis--also known in Europe as Bannwarth's syndrome--is a combination of radicular pain, cranial neuritis and peripheral radiculitis and inflammatory changes of the CSF. The prognosis following antibiotic therapy is favorable. At least in its early stages, however, the diagnosis neuroborreliosis might be missed or mistaken. Thus, targeted assessment of typical signs is needed to expedite examination of the CSF which then permits definitive diagnosis.

Changes of Cerebrovascular Response to Visual Stimulation in Migraineurs After Repetitive Sessions of Somatosensory Stimulation (Acupuncture): A Pilot Study

OBJECTIVES

To evaluate the effect of repetitive somatosensory stimulation (acupuncture) on cerebrovascular response in migraineurs by functional transcranial Doppler.

METHODS

Changes of cerebral blood flow velocity in the right posterior and left middle cerebral arteries were measured by functional transcranial Doppler during visual stimulation (flickering light over 57 seconds) in 10 migraineurs before and after 10 acupuncture sessions. The same stimulation paradigm was performed in 10 control subjects. Cerebral blood flow velocity data were analyzed with a previously validated technique based on automated stimulus-related averaging. To evaluate the clinical effect of the treatment, a headache diary monitored the frequency and intensity of the migraine attacks. A positive treatment effect was defined as a reduction of at least 50% in the attack frequency or the mean headache intensity (or both).

RESULTS

Before treatment, migraineurs showed overshooting cerebral blood flow velocity changes at the beginning and at the end of the stimulation and a delayed decline to baseline compared with control subjects. After treatment, this response pattern was significantly diminished (P</=.05) in those who benefited from treatment (n = 6). Those who did not benefit from treatment (n = 4) showed a significantly (P</=.05) more marked alteration of the cerebral blood flow velocity pattern.

CONCLUSIONS

Data indicate that repetitive somatosensory stimulation (acupuncture) might positively influence the abnormal cerebrovascular response in migraineurs. In a subgroup of migraineurs, however, the dysfunction of the cerebrovascular system might deteriorate under the treatment.

[3H]-nociceptin ligand-binding and nociceptin opioid receptor mrna expression in the human brain

Following the cloning of the novel nociceptin opioid receptor (NOP(1)) and the identification of its endogenous ligand orphanin FQ/nociceptin the distribution and functional role of the NOP(1) receptor system have been studied mainly in the rodent CNS. In the present study the regional distribution and splice variant expression of the NOP(1) receptor was investigated in the adult human brain using [(3)H]-nociceptin autoradiography, NOP(1) reverse transcriptase PCR and mRNA in situ hybridization. Ligand binding revealed strong expression of functional NOP(1) receptors in the cerebral cortex and moderate signals in hippocampus and cerebellum. Interestingly, the NOP(1) receptor specific ligand was also strongly bound in the human striatum. A matching pattern of mRNA expression was observed with high amounts of NOP(1) mRNA in the prefrontal and cingulate cortex as well as in the dentate gyrus of the hippocampus. mRNA levels in the Ammon's horn and cerebellar cortex were moderate and low in the striatum. A considerable expression of N-terminal NOP(1) splice variant mRNAs was not detectable in the human brain by means of in situ hybridization. This suggests that functional NOP(1) receptors in the human brain are encoded by N-terminal full length NOP(1) transcripts. The present data on the anatomical distribution of nociceptin binding sites and NOP(1) receptor mRNA contribute to the knowledge about opioid receptor systems in the human brain and may promote the understanding of function and pharmacology of the orphanin FQ/nociceptin receptor system in the human CNS.

Different modes of manual acupuncture stimulation differentially modulate cerebral blood flow velocity, arterial blood pressure and heart rate in human subjects

The psychophysiological effect of different modes of manual acupuncture stimulation was investigated in 12 healthy, right handed, male subjects (mean age 29). The cerebral blood flow velocity (CBFV) in both middle cerebral arteries, arterial blood pressure (BP), heart rate (HR) and the perceived intensity of the stimulation were monitored while an acupuncture needle in the right dorsal thenar muscle (point Hegu, Li 4) was repetitively rotated with either high frequency (4-8 Hz) and low amplitude (hf-la) or low frequency (1-2 Hz) and high amplitude (lf-ha). Response patterns induced by hf-la and 1f-ha [corrected] stimulation differed significantly (P < 0.05) as tested by Student's t-test: (1), 1f-ha [corrected] stimulation was perceived as more intense and induced a more marked right hemispheric CBFV increase; (2), while hf-la stimulation lead to a slight decrease of BP and HR, lf-ha stimulation induced an initial pressor response (increase of BP, decrease of HR) and a more marked long term decrease of BP. Data indicate that the mode of manual acupuncture stimulation has a differential effect on the perceived stimulation intensity, the cerebral activation and the cardiovascular reflex response.

Increase in GABAergic Cells and GABA Levels in the Spinal Cord in Unilateral Inflammation of the Hindlimb in the Rat

The effects of chronic peripheral inflammation on spinal cord gamma-aminobutyric acid (GABA) were examined in the rat. Following the injection of complete Freund's adjuvant in the left hindlimb footpad an increased number of immunoreactive cells occurred in ipsilateral laminae I - III of the dorsal horn from L3 to L5. GABA-immunoreactive cells were more numerous than contralaterally 1 week after the onset of the inflammation, reached maximal numbers after 3 - 4 weeks, and declined thereafter. Differences from control sides were statistically significant except at week 6. GABA levels in homogenates of the ipsilateral lumbar enlargement were increased significantly at 4 weeks. Since increases in GABA occurred in the spinal cord zone of projection of the nerves supplying the inflamed foot, the central response is surmised to result from the increased nociceptive input arriving from the periphery. However, the transmission from primary axons to GABA interneurons is not likely to be monosynaptic since profiles containing glutamate decarboxylase or GABA immunoreactivity are known to be predominantly presynaptic, and rarely postsynaptic, to primary afferent endings in electron micrographs in the rat. The findings support the function attributed to spinal GABA in modulating nociceptive input at segmental level.

[Investigations on the effect of acupuncture on affective and sensory components of pain in patients with different stages of chronic pain]

OBJECTIVES

The aim of the study was to investigate the effects of acupuncture on the affective and sensory experience of pain in chronic pain patients. Furthermore, the study tried to estimate the therapeutical benefit of acupuncture in relation to the stage of chronic pain according to the Mainz pain staging system for chronic pain (MPSS).

METHODS

Patients with chronic pain syndromes who received acupuncture treatment answered a standardized pain questionnaire before and after treatment. The questionnaire included the visual-analogue-scale for the intensity of pain, the pain perception scale for the assessment of affective and sensory components of pain perception, and addressed the patients to the three stages of chronic pain (MPSS).

RESULTS

From April 1997 to October 1999, patients (n = 165) suffering from chronic headache and facial pain syndromes (23%), spine associated pain syndromes (48%) or other pain conditions (29%) were subsequently included. Treatment with acupuncture showed a more pronounced reduction of the affective assessment than of the sensory assessment of pain. These effects were particularly pronounced in patients assigned to stage 3 of chronic pain (MPSS).

CONCLUSIONS

Acupuncture in patients with high-stage chronic pain syndromes preferentially influences the affective dimension of pain perception. For the estimation of the overall clinical outcome of acupuncture treatment, a differentiation between affective and sensory components of pain is recommended.

Expression of GABA(B1) and GABA(B2) mRNA in the human brain

GABA(B) receptors are widely expressed in the CNS. The distribution of the recently cloned GABA(B1) receptor is highly concordant with GABA(B) ligand binding sites, but experiments with transfected cell lines indicate that GABA(B1) has to heterodimerize with GABA(B2) to gain the functionality of a native GABA(B) receptor. Using in situ hybridization we investigated the expression of GABA(B1) and GABA(B2) mRNAs in the human brain. Both transcripts were detectable in prefrontal cortex, hippocampus and cerebellum with no apparent mismatch. A distinct expression of GABA(B1) was detected in putative Bergmann glia. In the human striatum GABA(B1) mRNA was expressed in moderate amounts, whereas the GABA(B2) mRNA signal was not clearly above background. According to our data, the current concept on GABA(B) receptor composition needs re-evaluation, at least for certain brain structures.

Altered cerebrovascular response pattern in interictal migraine during visual stimulation

A dysbalance of the cerebrovascular response during functional activation of the brain has been postulated as a factor in the pathophysiology of migraine. To determine the dynamic pattern of the cerebrovascular response in migraineurs compared with a control group, changes of the cerebral perfusion during cerebral activation were studied with high temporal resolution by functional transcranial Doppler sonography (fTCD). The cerebral blood flow velocity (CBFV) in the right posterior cerebral artery (PCA) and the left middle cerebral artery (MCA) was measured simultaneously during visual stimulation in 19 interictal migraineurs and in 19 age- and sex-matched control subjects. Data were analysed with a previously validated technique based on automated stimulus-related averaging of the CBFV. The MCA migraineurs exhibited a steady increase of CBFV during the stimulation, while normal subjects showed a habituation of the CBFV response. The lack of habituation in migraineurs was significantly (P < or = 0.05) more pronounced across patients with a high attack frequency (> or = 4 per month) compared with migraineurs with a low attack frequency (< 4 per month). In the PCA, compared with normal subjects, migraineurs showed significantly (P < or = 0.05) stronger CBFV changes at the beginning and after the end of stimulation, with a slower decline to baseline. Data are in accordance with electrophysiological findings in migraineurs. It is assumed that a lack of habituation of the cerebrovascular response in migraineurs might contribute to a disturbance of the metabolic homeostasis of the brain that might induce migraine attacks.

Dose-dependent regional cerebral blood flow changes during remifentanil infusion in humans: a positron emission tomography study

BACKGROUND

The current study investigated dose-dependent effects of the mu-selective agonist remifentanil on regional cerebral blood flow (rCBF) in volunteers using positron emission tomography (PET).

METHODS

Ten right-handed male volunteers were included in a 15O-water PET study. Seven underwent three conditions: control (saline), low remifentanil (0.05 microg x kg(-1) x min(-1)), and moderate remifentanil (0.15 microg x kg(-1) x min(-1)). The remaining three participated in the low and moderate conditions. A semirandomized study protocol was used with control and remifentanil conditions 3 or more months apart. The order of low and moderate conditions was randomized. Cardiovascular and respiratory parameters were monitored. Categoric comparisons between the control, low, and moderate conditions and a pixelwise correlation analysis across the three conditions were performed (P < 0.05, corrected for multiple comparisons) using statistical parametric mapping.

RESULTS

Cardiorespiratory parameters were maintained constant over time. At the low remifentanil dose, significant increases in relative rCBF were noted in the lateral prefrontal cortices, inferior parietal cortices, and supplementary motor area. Relative rCBF decreases were observed in the basal mediofrontal cortex, cerebellum, superior temporal lobe, and midbrain gray matter. Moderate doses further increased rCBF in mediofrontal and anterior cingulate cortices, occipital lobe transition, and caudal periventricular grey. Significant decreases were detected in the inferior parietal lobes. These dose-dependent effects of remifentanil on rCBF were confirmed by a correlation analysis.

CONCLUSION

Remifentanil induced dose-dependent changes in relative rCBF in areas involved in pain processing. At moderate doses, rCBF responses were additionally detected in structures known to participate in modulation of vigilance and alertness. Insight into the mechanisms of opioid analgesia within the pain-processing neural network may lead to a better understanding of antinociception and opioid treatment.

Up-regulation of metabotropic glutamate receptor 3 mRNA expression in the cerebral cortex of monoarthritic rats

Metabotropic glutamate receptors (mGluR) have been shown to play a role in the modulation of acute and inflammatory pain. Additionally, we have recently detected time-dependent changes in the mRNA expression of several mGluR subtypes in thalamic nuclei of monoarthritic (MA) rats. In the present study, mGluR1, -3, -4, and -7 subtype mRNA expression was analyzed by in situ hybridization with radioactively labelled oligonucleotide probes in cerebral cortical regions of normal and MA rats at 2, 4, and 14 days of the disease. The mGluR1, -4, and -7 mRNAs were at background level in normal rats and did not change in MA animals. In contrast, mGluR3 mRNA expression was abundant in normal rats and was significantly increased in cortical areas of MA rats at all time points. Higher changes were detected bilaterally at 4 days, predominantly in layers IV/V, in the motor, primary, and secondary somatosensory cortices (average increases of 50-75%), but maximum rises occurred in the contralateral cingulate cortex (+138%). No changes were detected in the auditory cortex. The present data show an up-regulation of mGluR3 mRNA expression in the motor, somatosensory, and limbic cortices of MA rats. This possibly reflects the occurrence of central mechanisms counteracting the increased transmission of nociceptive input arising from the inflamed paw and the impaired motor behavior of these rats. Changes in the cingulate cortex may be related to the motivational-affective component of nociception.

Phantom limb pain in the human brain: unraveling neural circuitries of phantom limb sensations using positron emission tomography

Pain and other phantom limb (PL) sensations have been proposed to be generated in the brain and to be reflected in activation of specific neural circuits. To test this hypothesis, hypnosis was used as a cognitive tool to alternate between the sensation of PL movement and pain in 8 amputees. Brain activity was measured using positron emission tomography. PL movement and pain were represented by a propagation of neuronal activity within the corresponding sensorimotor and pain-processing networks. The sensation of movement was significantly (corrected for multiple comparisons) related to activity in the supplementary motor area and the primary sensorimotor cortex. The sensation of a painful PL posture activated the same brain areas but was weaker and less extended in the supplementary motor area. In contrast to the sensation of movement, pain was significantly related to activity in the thalamus, anterior cingulate, and lateral prefrontal cortex. Subjectively rated PL pain sensation correlated positively to activations in the anterior and posterior cingulate. These findings provide evidence that PL sensations are produced by the same central nervous processes that underlie the experience of the body when it is intact and that the corporeal awareness of PL pain is encoded in a thalamocortical network.

Expression of metabotropic glutamate receptors mRNA in the thalamus and brainstem of monoarthritic rats

Evidence for the involvement of metabotropic glutamate receptors (mGluR) in sensory processing has been emerging. Additionally, the differential distribution of distinct mGluR subtypes mRNA in particular thalamic nuclei of normal rats suggests that they could be involved in the processing of somatosensory information. In the present study, mGluR1, 3, 4 and 7 mRNAs expression was investigated by in situ hybridisation in selected brainstem and thalamic nuclei of adult monoarthritic rats at different time points of the disease (2, 4 and 14 days). Monoarthritic rats displayed behavioural and physical signs of painful arthritis at all time points. At 2 days of monoarthritis the mGluR1 mRNA expression was decreased mainly in the ventrobasal complex (VB) and in the posterior thalamic nuclei (Po) contralateral to the inflamed joint. The mGluR4 mRNA expression was also reduced, but minimum values were found at 4 days of monoarthritis, when no changes could be found in mGluR1 mRNA expression. At 14 days, mGluR4 mRNA expression was similar to controls, while mGluR1 mRNA was again reduced. Similar decreases of mGluR7 mRNA expression in the VB and Po were found at all time points, while mGluR3 mRNA expression was bilaterally increased in the reticular thalamic nucleus (Rt). In the brainstem no changes could be found in the expression of any mGluR subtype mRNA. The reduced expression of mGluR1, 4 and 7 transcripts in VB and Po, and the increases of mGluR3 mRNA in the Rt may contribute to counteract the increased noxious input arising from the periphery.

Reduction of benzodiazepine receptor binding is related to the seizure onset zone in extratemporal focal cortical dysplasia

PURPOSE

Comparison of regional reduction of GABA receptor binding and seizure onset zone in patients with extratemporal epilepsy due to focal cortical dysplasia.

METHODS

Two patients with frontal lobe epilepsy who remained seizure free after partial frontal lobe resection were investigated with magnetic resonance imaging, positron emission tomography (PET) with 18F-fluoro-deoxy-glucose (FDG) and 11C-flumazenil, subdural EEG-video recordings, and postoperative benzodiazepine (BDZ)-receptor autoradiography.

RESULTS

The area of reduced BDZ-receptor binding as documented by preoperative flumazenil-PET and postoperative BDZ-receptor autoradiography corresponded to the seizure onset zone and was smaller than the interictal hypometabolism documented by FDG-PET.

CONCLUSION

Flumazenil-PET is a useful tool for localization of the epileptogenic zone in patients with extratemporal epilepsy caused by focal cortical dysplasia. Neuronal distribution of BDZ-receptor density confirms in vivo flumazenil-PET findings. The regional reduction of BDZ-receptor binding in focal cortical dysplasia seems to be confined to the seizure onset zone and not to the extent of dysplastic cortex.

6-O-(2-[18F]fluoroethyl)-6-O-desmethyldiprenorphine ([18F]DPN): synthesis, biologic evaluation, and comparison with [11C]DPN in humans

6-O(2-[18F]fluoroethyl)-6- -desmethyldiprenorphine ([18F]DPN) was developed and biologically evaluated. Results of animal experiments, binding studies in vivo, and a human PET study are reported and compared with those of [11C]DPN.

METHODS

[18F]DPN was obtained by 18F-fluoroethylation of 3-O-trityl-6-O-desmethyldiprenorphine and subsequent deprotection in good radiochemical yields (23% +/- 7%; 100 min; 37 TBq/mmol). Binding of [18F]DPN to mu, kappa, and delta opioid receptors was shown by autoradiography studies on rat brain slices. Quantification of cerebral opioid receptor binding in men was performed by spectral analysis of a dynamic PET scan (25 frames, 90 min) after intravenous application of 63 MBq [18F]DPN (36 GBq/micromol) and correction for metabolites.

RESULTS

[18F]DPN shows high affinity to opioid receptors. Parametric images (impulse response function at 60 min) of this human study showed a binding pattern of [18F]DPN equal to that of a control group (n = 9 healthy volunteers) after administration of [11C]DPN.

CONCLUSION

The advantage of the longer half-life of 18F will allow extended scanning periods, more flexible interventions (e.g., displacement studies), and DPN to be available to PET centers without an on-site cyclotron.

Axotomy of the sciatic nerve differentially affects expression of metabotropic glutamate receptor mRNA in adult rat motoneurons

Previous studies indicated that axotomy exposes motoneurons to glutamatergic excitotoxic stress and protection from glutamatergic overactivation might be crucial for survival. Depending on the experimental model and the subtype involved, activation of metabotropic glutamate receptors (mGluRs) may either enhance excitotoxicity or exert protective effects. To investigate a possible involvement of mGluRs in neuronal rescue mechanisms after axotomy we have monitored the distribution of mGluR mRNA with in situ hybridization in adult rat motoneurons 1, 2, 3, and 4 weeks after sciatic nerve transection. Motoneurons in sham-operated control animals expressed mGluR 1, 4, and 7 mRNA. The mGluR1 mRNA signal was reduced to 49.6+/-6.9% as compared to the contralateral side 2 weeks after axotomy and 31.2+/-8.3% after 4 weeks. The mGluR4 signal declined to 22.1+/-5.1% after 1 week and 10.2+/-1.6% after 2 weeks, remaining stable thereafter. During the entire observation period the mRNA for mGluR7 was not significantly altered. Axotomy did not change the overall number of motoneurons on the ipsi- or contralateral side. The differential regulation of mGluR subtypes may be part of an adaptive cell program that helps to rescue adult motoneurons from excitotoxic cell death during the stress induced by peripheral denervation.

Autoradiographic distribution of mu-, delta- and kappa 1-opioid stimulated [35S]guanylyl-5'-O-(gamma-thio)-triphosphate binding in human frontal cortex and cerebellum

Opioid receptors are known to couple to G-proteins and to inhibit adenylyl cyclase. Receptor activation of G-proteins can be measured by agonist-stimulated [35S]guanylyl-5'-O-(gamma-thio)-triphosphate (GTP gamma S-) binding in brain sections to localize neuroanatomically functional coupling of receptors to intracellular signal transduction mechanisms. In the present study the selective mu-, delta- and kappa 1-opioid agonists DAMGO ([D-Ala2,N-Me-Phe4, Gly-ol5]-enkephalin), DPDPE ([D-Pen2,5]-enkephalin) and enadoline (CI-977) were used to stimulate [35S]GTP gamma S-binding in human brain sections of frontal cortex and cerebellum. In human frontal cortex mu- and delta- opioid stimulated [35S]GTP gamma S-binding was evenly distributed throughout the gray matter, while kappa(1)-opioid stimulated [35S]GTP gamma S-binding was detected predominantly in lamina V and VI. In the cerebellar cortex stimulated [35S]GTP gamma S-binding revealed functional coupling of mu- and kappa 1-opioid receptors in the molecular layer.

Differential distribution of metabotropic glutamate receptor subtype mRNAs in the thalamus of the rat

L-Glutamate (L-Glu) is present in most excitatory synapses of the mammalian brain, acting on several receptor subtypes. Height different genes encoding metabotropic glutamate receptors (mGluRs) subtypes have been described (mGluR1-8), having a distinct distribution in the brain. In the present study, the distribution of mGluR1, 3, 4, 5 and 7 mRNAs was determined in 20 thalamic nuclei of adult rats by performing in situ hybridisation with subtype-specific 35S-labelled oligonucleotide probes. High expression of mGluR1 mRNA mainly occurred in midline nuclei such as the centromedial/centrolateral (CM/CL) nuclei, parafascicular and submedius nuclei, and in the ventroposteromedial (VPM) and posterior (Po) nuclei. In contrast, mGluR5 mRNA was more uniformly distributed at weak to moderate levels, except in the reuniens nucleus where a strong signal was detected. The mGluR3 mRNA was highly expressed in the reticular thalamic nucleus and almost not detectable in any other thalamic region. Additionally, mGluR3 mRNA was found not only in neurones but also in putative glial cells. The mGluR4 mRNA was abundant in most thalamic nuclei, with prominent expression in the CM/CL, Po and ventrobasal complex (VPM and ventroposterolateral, VPL). Finally, mGluR7 transcripts were found evenly distributed throughout the thalamus at moderate levels, the highest signal being detected in the paraventricular thalamic nucleus, VPM, VPL and Po. This differential distribution of mGluR subtypes in the rat thalamus may contribute to the heterogeneity of glutamate effects on thalamic neurones. The mGluR1, mGluR4 and mGluR7 receptors may be involved in the processing of somatosensory information because they are expressed in nuclei that receive direct sensory input.