Distraction by a cognitive task has a higher impact on electrophysiological measures compared with conditioned pain modulation.

BACKGROUND: Conditioned pain modulation (CPM) evaluates the effect of a painful conditioning stimulus (CS) on a painful test stimulus (TS). Using painful cutaneous electrical stimulation (PCES) as TS and painful cold water as CS, the pain relief was paralleled by a decrease in evoked potentials (PCES-EPs). We now aimed to compare the effect of CPM with cognitive distraction on PCES-induced pain and PCES-EP amplitudes. METHODS: PCES was performed using surface electrodes inducing a painful sensation of 60 (NRS 0-100) on one hand. In a crossover design healthy subjects (included: n = 38, analyzed: n = 23) immersed the contralateral hand into 10 °C cold water (CS) for CPM evaluation and performed the 1-back task for cognitive distraction. Before and during the CS and 1-back task, respectively, subjects rated the pain intensity of PCES and simultaneously cortical evoked potentials were recorded. RESULTS: Both CPM and cognitive distraction significantly reduced PCES-EP amplitudes (CPM: 27.6 ± 12.0 µV to 20.2 ± 9.5 µV, cognitive distraction: 30.3 ± 14.2 µV to 13.6 ± 5.2 µV, p < 0.001) and PCES-induced pain (on a 0-100 numerical rating scale: CPM: 58 ± 4 to 41.1 ± 12.3, cognitive distraction: 58.3 ± 4.4 to 38.0 ± 13.0, p < 0.001), though the changes in pain intensity and PCES-amplitude did not correlate. The changes of the PCES-EP amplitudes during cognitive distraction were more pronounced than during CPM (p = 0.001). CONCLUSIONS: CPM and cognitive distraction reduced the PCES-induced pain to a similar extent. The more pronounced decrease of PCES-EP amplitudes after distraction by a cognitive task implies that both conditions might not represent the general pain modulatory capacity of individuals, but may underlie different neuronal mechanisms with the final common pathway of perceived pain reduction.

[Unsuccessful pain treatment over 6 years of a thoracic radiculopathy caused by an unrecognized Tarlov cyst]. / 6 Jahre erfolglose Schmerztherapie bei thorakaler Radikulopathie durch eine unerkannte Tarlov-Zyste.

This article presents a case of unsuccessful pharmaceutical and invasive pain treatment for 6 years without any adequate diagnostics in a female suffering from unilateral thoracic radiculopathy (Th8, right) leading to severe disability and unemployment. The origin was an undetected Tarlov cyst. After resection of the cyst the pain and other complaints disappeared (follow up: 8 months) without need for further pain medication. This case underlines the necessity of adequate diagnostics ahead of long-term pain treatment. Thoracic Tarlov cysts are very uncommon but should be included in the differential diagnosis because curative treatment may be possible.

[Botulinum toxin A injections in neuropathic pain : A post-hoc subgroup analysis of patients with peripheral nerve injury]. / Botulinumtoxin-A-Injektionen bei neuropathischem Schmerz : Eine Post-hoc-Subgruppenanalyse bei Patienten mit peripherer Nervenverletzung.

The randomized controlled trial (RCT) presented in this article showed significant relief in neuropathic pain following subcutaneous injections of botulinum toxin A over 24 weeks compared to placebo. This result was confirmed in a novel post-hoc analysis of the subgroup of 46 patients with peripheral nerve injury. Relevant adverse effects did not occur during the RCT.

Olfactory disorders in childhood: A comparative study of olfaction in children with adenoid hyperplasia versus a control group and the postoperative effects of adenoidectomy with respect to olfactory ability.

PURPOSE: Hyposmia in childhood is poorly characterized. The "U-Sniff Test", validated for children with anosmia, can be used to objectify olfactory impairment but has not been used to distinguish between hyposmia and normosmia. Therefore, we investigated children with enlarged adenoids with respect to hyposmia, its correlation with adenoid size, and the sensitivity of questionnaires to predict olfactory impairment. METHODS: In a prospective comparison, olfaction was assessed by "U-Sniff Test" (score 0-12; <8 hyposmia) in 41 children (5-18 years) with adenoid hyperplasia and compared with 196 children without any respiratory affection (control) after exclusion of previous SARS-Cov2-infection from December 2020 to December 2021. ENT-related complaints were collected using a self-designed questionnaire. We were able to include 13 children in a follow-up examination to compare preoperative performance in the "U-Sniff Test" with postoperative outcome after adenoidectomy. STATISTICS: chi-square-test (p < 0.05), odds-ratio, Spearman's rho, ROC-, cluster analysis. RESULTS: Severe hyposmia was present in 36.6% of children with adenoid-hyperplasia compared to 3.1% of the control-group. Adenoid-children scored significantly more often between 8 and 10 points (58.5%) than the control (31.6%; p < 0.01). Adenoid size and olfactory performance correlate significantly (r: 0.83; CI -0.89 … -0.72). Hyposmia in the adenoid group is characterized predominately by loss of the odors banana, butter and rose. None of children with hyposmia or parents reported impaired olfactory performance. Postoperatively, olfactory function improved significantly in 85% of cases (p 0.01, SD ± 1.71, Δ3.54points). CONCLUSION: Questionnaires are insufficient to detect hyposmia in this cohort. In contrast, the "U-Sniff Test" detects even reduced olfactory performance without reaching the cut-off value, which represents the majority of test results in the adenoid group. Therefore, we recommend the classification of moderate hyposmia (8-10 points) to be included for our study population.

Conditioned pain modulation using painful cutaneous electrical stimulation or simply habituation?

BACKGROUND AND AIMS: Cold pressor test was recently reported to significantly reduce painful cutaneous electrical stimulation (PCES)-induced pain and corresponding evoked potentials (PCES-EPs), but whether this reduction is an effect of conditioned pain modulation (CPM) remains unknown. To what extent these findings are confounded by habituation is also unknown. We thus compared the effect of CPM and habituation on PCES-induced pain and PCES-EPs and analysed whether increased attention by a random change of electric stimulation would intensify this possible habituation effect. METHODS: Three custom-built concentric surface electrodes were used to induce a pain intensity of 60 on a 0-100 numerical rating scale (NRS) among 29 healthy subjects (age 20-35y, 16 females). PCES-EPs (including P0N1 and N1P1 amplitudes, N1 latencies) were assessed over Cz. Group A received 14 min of electrical stimulation with constant intensity followed by 14 min of electrical stimulation with variable intensities, group B vice versa. Afterwards, subjects perceived cold-water pain (10 °C) contralaterally as conditioning stimulus to assess CPM. Statistical analysis was conducted with ANOVA and t-test. RESULTS: In both groups, N1 latencies remain unchanged, but the intensity of PCES-induced pain (12 ± 17%; p < 0.01) and N1P1 amplitudes of PCES-EPs (10 ± 16%; p < 0.05) decreased significantly during the 14-min PCES with constant current intensity. CPM also significantly reduced pain ratings (36 ± 19%; p < 0.001) and amplitudes (37.2 ± 15.8%), p < 0.001). A significant decline of P0N1 amplitudes occurred only during CPM (18 ± 61%; p < 0.001). CONCLUSION: We found a significant effect of habituation on PCES-induced pain and PCES-EPs, although the effect of CPM was significantly larger and could not be explained by habituation alone. SIGNIFICANCE: Painful cutaneous electrical stimulation leads to moderate habituation of pain and evoked potential amplitudes, but the conditioned pain modulation effect using this method is significantly larger, which might indicate a different mechanism in central processing.