Somatosensory profile of patients with haemophilia.

INTRODUCTION: Patients with haemophilia (PwH) suffer from an enhanced pain sensitivity due to repetitive joint bleedings. A comprehensive, quantitative examination of the somatosensory system has not been performed in this population to date. MATERIAL AND METHODS: Thirty patients with moderate or severe haemophilia A or B and 30 healthy controls were examined by means of Quantitative Sensory Testing to assess the function of the somatosensory system. Detection (DT) and pain thresholds (PT) were determined, amounting to a total of 13 parameters. Both knee joints and the hand as reference were examined in order to assess both joint-specific as well as general changes in the somatosensory profile. RESULTS: Analysing DT and PT, a significant main effect was found for group × stimulus interaction (P ≤ .001). Post hoc tests revealed significant differences in DT between PwH and controls for thermal stimuli across both knees (cold DT: P < .001; warm DT: P < .01) and the hand (cold DT: P < .01; warm DT: P < .05). Mechanical DT was increased in PwH at both knee joints (left knee: P ≤ .05; right knee: P ≤ .01). Furthermore, pressure PT was decreased in PwH at both knees (P ≤ .001). CONCLUSION: Haemophilic arthropathy leads to alterations of the somatosensory profile in PwH. Our results reveal initial evidence of a combination of peripheral sensitization, indicated by decreased pressure PT and mechanical DT at the knee joints, as well as general changes of the somatosensory system, shown by reduced thermal DT at affected sites and remote from these. Therefore, both mechanisms have to be considered regarding the pain management in PwH.

Validation of the digital pressure application measurement (PAM) device for detection of primary mechanical hyperalgesia in rat and mouse antigen-induced knee joint arthritis.

Several tests have been developed to obtain mechanical nociceptive withdrawal thresholds for arthritis-associated pain research in preclinical animal models, which are routinely used for testing the efficacy of antinociceptive pharmaceutical candidates. Here, we aimed to validate a recently introduced and commercially available digital pressure application measurement (PAM) device for the detection of primary mechanical hyperalgesia in a model of antigen-induced knee joint arthritis (AIA) in rats and mice. Two particular advantages of the PAM device are visual feedback control of the force increase rate and the detection of the complete threshold range. Using PAM, we were able to quantify mechanical thresholds at the knee joint in rats and mice (400 and 350 g, respectively) before and during the time course of AIA (approximately 100 g for rats and mice in the acute phase). Inter-observer agreement was generally higher when using PAM instead of an analog dynamometer. In conclusion, the digital PAM device is a suitable apparatus to detect primary mechanical hyperalgesia in experimental knee joint arthritis in rats and mice. The use of this device allows visual feedback control of the stimulus rate, thus minimizing the chances of confounding factors arising from differences in ramp speed.

Cardiovagal modulation upon postural change is altered in Huntington's disease.

BACKGROUND: Cardiac autonomic nervous system (ANS) dysfunction in Huntington's disease (HD) might affect both the sympathetic and parasympathetic branch of the ANS. RESULTS AND CONCLUSIONS: The pattern of linear heart rate variability we found in mid stage HD patients points towards a predominately reduced cardiovagal modulation compared with healthy subjects, which might influence HD patients' susceptibility for cardiovascular complications such as syncopes and cardiac arrhythmias.

Perception for ischemic pain shows similarities in adjustment disorder and major depression.

We recently described an increase of pain thresholds and tolerances for thermal and electrical pain in patients suffering from adjustment disorder (AD). Furthermore, we presented evidence that pain perception in major depressive disorder (MDD) depends on pain modality, with thresholds for ischemic pain being decreased compared to increased thermal and electrical pain thresholds. Here, we investigated perception of experimentally induced ischemic pain in 15 patients suffering from AD (subtype with depressive symptoms) and controls matched for age and sex in order to examine whether a similar pattern of modality dependent pain perception can be established. Thresholds and tolerances were assessed on both sides of the body. We found a significant decrease of ischemic pain thresholds in AD patients as compared to controls. Analogue findings have been reported for pain perception in MDD, therefore suggesting similarities with regards to pain perception in both disorders. This adds weight to the assumption that depressive symptomatology might alter pain sensitivity in this subtype of AD since symptoms are milder, yet comparable to MDD.

Increased sodium channel SNS/PN3 immunoreactivity in a causalgic finger.

The sodium channels SNS/PN3 and NaN/SNS2 are regulated by the neurotrophic factors-nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF), and may play an important role in the development of pain after nerve injury or inflammation. These key molecules have been studied in an amputated causalgic finger and control tissues by immunohistochemistry. There was a marked increase in the number and intensity of SNS/PN3-immunoreactive nerve terminals in the affected finger, while GDNF-immunoreactivity was not observed, in contrast to controls. No differences were observed for NGF, trk A, NT-3 or NaN/SNS2-immunoreactivity. While further studies are required, these findings suggest that accumulation of SNS/PN3 and/or loss of GDNF may contribute to pain in causalgia, and that selective blockers of SNS/PN3 and/or rhGDNF may provide effective novel treatments.

Increased cold and heat pain thresholds influence the thermal grill illusion in schizophrenia.

BACKGROUND: Patients with schizophrenia show decreased sensitivity towards clinical and experimental painful conditions. To date, the exact underlying mechanisms are not completely understood. One method to examine central integrative processes of pain perception is the thermal grill illusion (TGI), in which interlacing cold and warm bars create the illusion of a painful sensation. METHODS: In 18 unmedicated patients with acute paranoid schizophrenia, cold and heat pain thresholds (CPT/HPT) as well as the perception of the TGI were examined and compared to 18 matched controls. In addition, symptom scales were obtained in order to relate pain perception to psychopathology. RESULTS: CPT and HPT were significantly increased in patients compared to controls. In the range of TGI stimuli that were perceived painful by controls, patients did not indicate painful sensations, instead the stimulus response curve of TGI pain perception was shifted towards higher stimulus intensities, i.e., greater temperature differentials between cold and warm bars. This increase was comparable to that seen in CPT and HPT. There was no association with psychopathology for any pain parameter. CONCLUSIONS: CPT and HPT, as well as temperature differentials for the perception of the TGI were increased in patients with schizophrenia as compared to controls. Similar to visual illusions, in which reduced contrast sensitivity has been shown to alter the perception of illusions, the discriminatory somatosensory deficit, which is reflected in higher CPT and HPT as well as the previously reported increased warmth perception thresholds, might account for the attenuation of TGI in patients.

The role of proinflammatory cytokines in the generation and maintenance of joint pain.

The proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) not only promote and maintain inflammation, they also contribute to the generation and maintenance of inflammatory pain by acting at nociceptive nerve cells. A large proportion of dorsal root ganglion (DRG) neurons express TNF receptors and receptor units for stimulation with IL-6. In the rat model of antigen-induced arthritis (AIA), neutralization of TNF-alpha by etanercept and infliximab reduced inflammation-evoked mechanical hyperalgesia at the inflamed knee joint. This treatment also attenuated the infiltration of macrophages into the DRGs usually observed during the acute phase of AIA. Intra-articular application of etanercept reduced the responses of C-fibers to mechanical stimulation of the inflamed joint but did not influence responses to stimulation of the normal joint. Finally, in cultured DRG neurons TNF-alpha increased the proportion of neurons that express the TRPV1 receptor and may thus contribute to the generation of inflammation-evoked thermal hyperalgesia.

Calcium-activated potassium channel SK1- and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors.

Calcium-activated potassium ion channels SK and IK (small and intermediate conductance, respectively) may be important in the pathophysiology of pain following nerve injury, as SK channels are known to impose a period of reduced excitability after each action potential by afterhyperpolarization. We studied the presence and changes of human SK1 (hSK1)- and hIK1-like immunoreactivity in control and injured human dorsal root ganglia (DRG) and peripheral nerves and their regulation by key neurotrophic factors in cultured rat sensory neurones. Using specific antibodies, hSK-1 and hIK-1-like immunoreactivity was detected in a majority of large and small/medium-sized cell bodies of human DRG. hSK1 immunoreactivity was decreased significantly in cell bodies of avulsed human DRG (n = 8, surgery delay 8 h to 12 months). There was a decrease in hIK1-like immunoreactivity predominantly in large cells acutely (<3 weeks after injury), but also in small/medium cells of chronic cases. Twenty-three injured peripheral nerves were studied (surgery delay 8 h to 12 months); in five of these, hIK1-like immunoreactivity was detected proximally but not distally to injury, whereas neurofilament staining confirmed the presence of nerve fibres in both regions. These five nerves, unlike the others, had all undergone Wallerian degeneration previously and the loss of hIK1-like immunoreactivity may therefore reflect reduced axonal transport of this ion channel across the injury site in regenerated fibres, as well as decreased expression in the cell body. In vitro studies of neonatal rat DRG neurones showed that nerve growth factor (NGF) significantly increased the percentage of hSK1-positive cells, whereas neurotrophin 3 (NT-3) and glial cell line-derived neurotrophic factor (GDNF) failed to show a significant effect. NT-3 stimulated hIK1 expression, while NGF and GDNF were ineffective. As expected, NGF increased expression of the voltage-gated sodium channel SNS1/PN3 in this system. Decreased retrograde transport of these neurotrophic factors in injured sensory neurones may thus reduce expression of these ion channels and increase excitability. Blockade of IK1-like and other potassium channels by aminopyridines (4-AP and 3,4-DAP) may also explain the paraesthesiae induced by these medications. Selective potassium channel openers are likely to represent novel therapies for pain following nerve injury.