Perceptual Distortions in Acute Neck Pain

Study Overview
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Brief Summary
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Research has shown that chronic pain is related to variety of perceptual distortions. Little is known on how acute pain experience influences perception, especially precision of touch. This project is aiming to test the hypothesis of pain as a process of biological value leading to improvement in tactile acuity.

Detailed Description
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This project has following goals: To test the hypothesis of pain as a process of biological value leading to improvement in tactile acuity To investigate intra-rater reliability of tests measuring perceptual distortions in pain To investigate validity of novel tests measuring perceptual distortions in pain To explore the influence of acute neck pain on left/right recognition task To explore the effect of acute neck pain on body perception

Official Title
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Perceptual Distortions in Acute Neck Pain

Conditions
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Neck Pain, Posterior, Pain, Acute

Intervention / Treatment
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* Other: Saline injection
* Other: Sham injection


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Only participants without tactile dysfunction will be included. Participants reporting availability during the days in which the research will be performed. Exclusion Criteria: current pain experience episodes of neck thoracic or lumbar pain lasting more than 24 hours within previous month history of chronic pain, i.e. pain lasting more than three-month period comorbidities affecting nervous system cardio-vascular diseases psychiatric illnesses any disease requiring systematic drug consumption diagnosed scoliosis.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Sequential Assignment
Interventional Model Description: Within-group designed study. All participants will be assessed in three different experimental conditions (control, saline injection, sham injection). The order of conditions will be counterbalanced across participants and randomly chosen.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Saline injection<br>In the saline condition, acute neck pain will be induced via 0.5 ml hypertonic (5% NaCl) saline solution. | Other: Saline injection<br>* In the saline injection condition, acute neck pain will be induced via 0.5 ml hypertonic (5% NaCl) saline bolus injection which is a commonly used model of acute pain. Saline will be injected into the right (or left) trapezius muscle at the level of C7 cervical level. Injections will be performed by a physician under ultrasound imaging guidance to ensure that each single injection will be equally placed at the same depth. The side for the pain induction will be randomised across subjects. The place of needle insertion and corresponding point on the opposite side of the body will be covered by placing a small piece of adhesive plaster to ensure blinding.<br>* Other names: Pain induced by saline injection;|
| Sham Comparator: Sham injection<br>In the sham injection condition, a real needle will be shown to the participants to imitate and produce the anticipation of a pain experience. | Other: Sham injection<br>* In the sham-injection condition (nocebo comparator), a real needle will be shown to the participants to imitate and produce the anticipation of a pain experience. A pinprick sensation will be produced by a weighted stimulus applied perpendicularly to the skin without piercing the skin. A stimulus of 512 millinewtons (mN) will be used to produce a pinprick sensation and activation of cutaneous nociceptors. Adhesive tapes covering stimulation points will also be provided. The stimuli will be applied in exactly the same spot as the real injection in previous experimental condition.<br>* Other names: Pain induced by sham injection;|
| No Intervention: Control<br>Participants in the control condition will not receive any kind of pain or pinprick sensation. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Tactile acuity measured by two-point discrimination test (TPD). | Mechanical callipers will be delicately applied to the spot just below the location where real or sham injection will be administered. Tactile stimuli will be applied until the very first blanching of the skin. Testing will be commenced with 0 mm between the two calliper's tips, and then the distance between them will be gradually increased until participants will able to verbally report that two points had been touched instead of one. Subsequently, the descending sequence will be applied until the perception of the two points disappeared. | TPD change from baseline at 30 seconds post-manipulation period (e.g. saline injection). | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Laterality judgements measured by left/right recognition application. | A set of images displaying human neck in different orientation in space will be show to participants. The goal of the task is to decide whether given picture depicts neck rotated to the left or right or flexed into left o right side. The accuracy and response time is measured. | Measured at baseline and  30 seconds after manipulation (e.g. saline injection). | 
| Sensory dissociation measured by two-point estimation task (TPE). | One tactile stimulus will be applied until the very first blanching of the skin, with a 120 mm horizontal separation between the calipers' tips. Participants will be then asked to indicate with their calipers the distance they have perceived. | Measured at baseline and  30 seconds after manipulation (e.g. saline injection). | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Tactile acuity, Tactile dysfunction, Sensory dissociation, Two-point discrimination, Perception