Three groups were compared: PLWH with chronic pain, PLWH without chronic pain and healthy controls. Pain modulation was assessed through mechanical temporal summation (TS), heat TS at three different temperatures: 46, 48, and 50°C, and CPM with pressure pain thresholds as test stimuli, and cold pressor as conditioning.
The authors found that mechanical TS was significantly greater in PLWH with chronic pain as compared to the PLWH without chronic pain or controls. Similarly, PLWH with chronic pain also had significantly more wind-up than both other groups at temperatures of 46 and 48 °C in the heat TS paradigm, though not at 50°C. Interestingly, both groups of PLWH showed no significant CPM effect, while the controls did. Controls significantly differed in their CPM effect from PLWH.
PLWH with chronic pain had significant correlation between average pain severity and mechanical TS.
These changes in pain modulation may signal vulnerability for developing chronic pain in PLWH, however more mechanistic research in this field is warranted.
Medoc’s AlgoMed was used in the CPM paradigm, and Medoc’s TSA-II was used for the heat TS paradigm.
Citation: Owens, Michael A., Romy Parker, Rachael L. Rainey, Cesar E. Gonzalez, Dyan M. White, Anooshah E. Ata, Jennifer I. Okunbor, Sonya L. Heath, Jessica S. Merlin, and Burel R. Goodin. “Enhanced facilitation and diminished inhibition characterizes the pronociceptive endogenous pain modulatory balance of persons living with HIV and chronic pain.” Journal of neurovirology 25, no. 1 (2019): 57-71.
Link to the abstract: https://www.ncbi.nlm.nih.gov/pubmed/30414048
Gulf War Illness (GWI) is presented by a number of health symptoms, among them pain complaints and gastro-intestinal (GI) issues in returning veterans who have served in the Persian Gulf War.
A study by Zhou et al. from 2018 utilizing Medoc’s TSA-II used QST and compared between veterans suffering from GWI with GI complaints (GWI+GI), veterans with GWI without GI complaints, and healthy veterans. The experimental pain tests comprised of: Heat Pain Threshold, Cold Pressor Threshold, Ischemic Pain Threshold and Ischemic Pain Tolerance. Veterans with GWI+GI had significantly lower heat pain thresholds and cold pressor thresholds as compared to healthy veterans and veterans with GWI but no GI symptoms. There was no significant difference between healthy veterans and veterans with GWI but no GI symptoms. For the ischemic pain threshold and tolerance test both GWI veterans groups reached their respective levels before the healthy veterans. Moreover, average daily abdominal pain in GWI+GI veterans was significantly correlated with the experimental pain measures. These findings of increased pain sensitivity and their connection to GI symptoms in GWI veterans may point to convergence of visceral and somatic pain pathways, authors hypothesize.
Source: Zhou, Q., Verne, M. L., Zhang, B., & Verne, G. N. (2018). Evidence for somatic hypersensitivity in veterans with Gulf war illness and gastrointestinal symptoms. The Clinical journal of pain, 34(10), 944-949.
Picture source: Wikimedia Commons, U.S. DOD
This question motivated Levy et al. to investigate the endogenous inhibition efficiency of the trigeminal and extra-trigeminal areas of the face, neck, and arm in healthy volunteers. Two TSA devices were used to allow thermal test and conditioning stimulation within these areas. CPM was tested in three different zones; 1) forehead (V1) and cheek (V3), 2) cheek and neck (C4), and 3) neck and arm (C7). Additionally, spatial summation of pain (SSP) and temporal summation (TS) of pain were tested on all four areas.
Interestingly, the forehead was found to be least sensitive to heat pain, requiring the highest temperature to reach a VAS 5-6 pain rating. The only configuration that yielded a significant CPM response, was the neck and arm set-up, which did not involve any of the trigeminal sites. Spatial summation of pain was elicited in all four sites, and post-hoc analysis showed less spatial summation of pain in the forehead as compared to the other regions. Temporal summation of pain did not differ significantly between sites.
This study showed inefficient pain modulation in trigeminal, as compared to extra-trigeminal areas. These findings could point to a possible factor in the etiology of pain syndromes involving the trigeminal area.
To study CPM with two thermodes, you no longer need two TSAs, Our new TSA2, comes with standard dual-thermode abilities, allowing for advanced thermal stimulation protocols, with one portable device!
For the article abstract:
Medoc Ltd. will exhibit at The 7th International Congress on Neuropathic Pain (NeuPSIG 2019), the international forum that provides the latest research and developments in understanding the mechanisms, assessment, prevention and treatment of neuropathic pain.
The conference will be held this year on May 8-11 in London, and will focus on Diabetic Neuropathic Pain and Chemotherapy-induced Peripheral Neuropathic Pain.
Join our MINI Symposium:
“The use of Quantitative Sensory Testing in pharma-sponsored analgesic clinical trials: insights from recent trials” by Roi Treister. May 10th 12:45 at the Buckingham Room
Attend the QST Workshop with Medoc devices:
Hands-On workshop with leaders in the pain study field. May 10th 15:30-18:30 at the Windsor Suite
You’re welcome to visit us at our Booth #202
Thermal Quantitative Sensory testing (QST) is routinely performed in various diabetes clinics around the world to monitor for small fiber abnormalities.
QST testing may detect subclinical neuropathy and hence, treatment may be adjusted in time.
QST identifies the better surgical skin graft technique:
In a recent article published in the International Journal of Surgery, authors reported the use of a wide array of QST (quantitative sensory testing) techniques to identify which of three surgical flap techniques is the least damaging to sensory nerve function of the donor site.
Diabetic neuropathy is one of the most common complications seen in patients suffering from diabetes worldwide, with rates of neuropathies seen in up to 50% of diabetic patients (Gordois et al., 2003a; Gordois et al., 2003b). Medoc has been developing different tools which, with the use of thermal and vibratory stimuli, are able to evaluate the type and level of impairment in different nerve fibers. (more…)