Temporal Summation of Pain

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(Largely summarized and quoted from Thomas Graven-Nielsen and Lars Arendt-Nielsen, Nature Reviews, Rheumatology, volume 6, 2010.)

Definition[edit]

This is the pain phenomenon whereby repeated application of the pain stimulus results in the subject experiencing a progressive increase in subjective pain. It is the “facilitated pain response to sequential stimuli of equal strength”. (Basic aspects of musculoskeletal pain: from acute to chronic pain. Lars Arendt-Nielsen,1 César Fernández-de-las-Peñas,2 and Thomas Graven-Nielsen1, J Man Manip Ther. 2011 Nov; 19(4): 186–193, available in full online at:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3201649/.)

Significance[edit]

It is believed to be an indicator of central sensitization.

Methods of induction and measurement[edit]

One method of testing is to apply pain stimuli at short intervals such as striking a part of the body 10 times at an inter-stimulus interval of two seconds. It can be induced by repeated tapping on muscle by a pressure probe. Nie found that “sequential pressure stimulation on muscle tissue with a 1-second inter-stimulus interval evokes a progressive increase in pain intensity”. (Temporal summation of pain evoked by mechanical stimulation in deep and superficial tissue. Nie H, Arendt-Nielsen L, Andersen H, Graven-Nielsen T, J Pain. 6: 348-355. 2005).

It can be measured by the temporal summation pain threshold.

It can also be assessed by measuring the nociceptive withdrawal reflexes which can be elicited by cutaneous electrical stimulation.

Potential to test for temporal summation of mechanical pressure pain with a robotic arm[edit]

A device that can be used to deliver near identical pressure stimuli and regular inter-stimulus intervals that are controlled by the operator is the Woodpecker. (For details see: https://encyclopediaoftouchbodysenseandpain.com/Woodpecker,_The.) It has settings that allow the user to select, the pressure to be applied, the number of repetitions and the inter-stimulus interval. It comes with a specialized tripod so that it can be directed at most parts of the surface of the body including such areas the myofascial trigger points as well as fibromyalgia tender points. The duration of application of pressure can be tightly controlled and monitored with this device. This is not true of hand held algometers including both spring and digital types. This standardization is highly desirable and possibly even essential for testing temporal summation. Presently, the testing of temporal summation is mainly a research tool, but if a research lab were to establish norms, then it could be used in front line clinical medicine as a diagnosis and monitoring tool for pain patients, especially chronic pain patients with central sensitization.

Mediation of temporal summation by the CNS[edit]

According to Sarlani, temporal summation is mediated by the central nervous system. (Cited in Sarlani et al. 2004)

(For a review see: Assessment of mechanisms in localized and widespread musculoskeletal pain. Thomas Graven-Nielsen & Lars Arendt-Nielsen, Nature Reviews Rheumatology 6, 599–606(2010), abstract available at: https://www.nature.com/articles/nrrheum.2010.107.)

Types of stimuli that can be used[edit]

Temporal summation of pain has been studied using many stimuli including electrical, chemical, pressure and focused ultrasound. Mechanical stimuli can be applied at regular intervals with devices such as the Woodpecker or the “computer-controlled pressure probe” described by Graven-Nielsen.

Target tissues for stimulation[edit]

Temporal summation is induced more efficiently “when stimulating muscle tissue compared with similar stimulation of the skin”. (Assessment of mechanisms in localized and widespread musculoskeletal pain. Graven-Nielsen T, Arendt-Nielsen L, Nature reviews. Rheumatology, 26 Jul 2010, 6(10):599-606.)

Role of temporal summation in fibromyalgia[edit]

A study of fibromyalgia patients by Sörensen et al., 1998 of electrode stimulation of muscles that were not spontaneously painful showed that as compared to normal controls “temporal summation after intramuscular repeated stimulation was facilitated in fibromyalgia patients.

A future study by Staud found that these patients also had facilitated temporal summation to pressure stimulation (Temporal summation of pain from mechanical stimulation of muscle tissue in normal controls and subjects with fibromyalgia syndrome. Staud R, Cannon RC, Mauderli AP, Robinson ME, Price DD, Vierck Jr CJ, Pain. 102: 87-95(2003) https://pubmed.ncbi.nlm.nih.gov/12620600/. They used force-controlled mechanical stimulation. They applied it to the “flexor digitorum muscle of the forearm in a series of brief contacts (15 stimuli, each of 1s duration, at 3 or 5s interstimulus intervals).” They applied the stimulation repeatedly. Results showed that even for normal controls there was moderate temporal summation of deep pain. However, it was “greatly exaggerated for FMS subjects and occurred at “substantially lower forces and at a lower frequency of stimulation.”

Moreover, it was associated with “painful after-sensations” of “greater in amplitude and more prolonged for FMS subjects.” These observations complement a previous demonstration that temporal summation of pain and after-sensations elicited by thermal stimulation of the skin are moderately enhanced for FMS subjects.

[Author’s comment: The question arises as to whether or not temporal summation testing should be part of the examination of fibromyalgia patients. To justify the effort and time required it would have to yield useful information. Since it is known that the epicondyles tender points have good discriminative value for FM, a protocol needs to be tested and developed. To ensure standardized testing a robotic arm called The Woodpecker could be used. Video is advised. The ideal force and duration of application of force in unknown, but a good starting point would be 1kg applied for one quarter of a second at intervals, and stopped two applications after the patient crosses over from minor discomfort to pain. This could be done for both the left and right epicondyles.]

For further perspective, see the entry Woodpecker, About the. For a graph showing force vs. time for the type of stimulation that could be used with modifications to test for temporal summation see: “Graph was created by programming the Woodpecker to alternately press and release for four seconds each.”