Investigation of the Relationship Between Central Sensitization and Balance in Fibromyalgia

Biodex Balance System \[Biodex Balance System SD (Biodex, Inc, Shirley, NY) (BBS)\]:The Biodex Balance System is a computer-assisted device that assesses postural stability. It measures static and dynamic balance, fall risk, and proprioception through different difficulty levels and test protocols. In our study, this system will be used to investigate the relationship between balance and central sensitization. Participants will be evaluated using the postural stability test, fall risk test, athlete single leg test, and limits of stability test protocols, and they will be trained before the testing process.

Pressure pain threshold (PPT) is defined as the minimum force applied that causes pain. This measurement is commonly used for assessing tender points and has been shown to be useful.

According to this protocol, a pressure stimulus, referred to as the test stimulus, will first be applied to the trapezius muscle to induce a pain intensity of 4 on a 10-point Numeric Rating Scale (NRS). Subsequently, a conditioning stimulus will be introduced by immersing the participant's right hand in 7°C water for 20 seconds. Following this conditioning stimulus, the same test stimulus will be reapplied to the trapezius muscle, and participants will be asked to rate their pain using the NRS. If participants are unable to keep their hands in the water for the full 20 seconds, the test stimulus will be applied immediately after hand removal. The CPM score will be calculated as the ratio of the initial NRS score to the second NRS score, multiplied by 100. Scores above 100 are considered indicative of a normal CPM response, with higher scores reflecting greater descending pain inhibition.

"Responses to induced pain indicate the presence of allodynia and hyperalgesia in FMS patients. The Slow Repetitive Evoked Pain (SREP) protocol consists of nine suprathreshold painful stimuli applied to the nail bed for five seconds each, with 30-second intervals. Painful stimulation will be administered using a pressure algometer with a 1 cm² stimulation surface. Nailbed pain stimuli are commonly used to assess pain sensitivity.~The intensity of pain perception from each SREP stimulus will be evaluated using a 10-point Numerical Rating Scale (NRS) (0 = no pain, 10 = extremely painful). The SREP sensitization index will be calculated as the difference between the final and initial pain scores.~Higher positive SREP sensitization index values indicate a greater increase in perceived pain intensity across the nine stimuli, reflecting higher pain sensitization."

"The Central Sensitization Inventory (CSI) is used by some researchers to investigate pain sensitivity through symptoms associated with central sensitization and related comorbidities. It can help determine the severity of central sensitization.~The scale was developed to detect central sensitization in patients with chronic pain and consists of two sections: Section A and Section B. For scoring purposes, only Section A is used. A score of 40 or higher out of 100 is associated with an increased likelihood of central sensitization.~This scale has been shown to be a reliable and valid tool in the Turkish population with chronic pain (test-retest reliability = 0.92, Cronbach's alpha = 0.93)"

Numeric Rating Scale (NRS) will be used to determine pain intensity during assessments. Participants will be asked to rate their pain intensity by selecting a value between 0 and 10. Higher scores are associated with increased pain severity.

Revised Fibromyalgia Impact Questionnaire (FIQ) consists of three sections: function, general, and symptoms, with a total of 21 questions. It evaluates the limitations and functional disability that occur in patients with fibromyalgia. All questions are scored on the Numeric Rating Scale (NRS), ranging from 0 to 10. As the score from the questionnaire increases, it indicates a higher level of disability related to fibromyalgia. In our study, the Turkish version of the questionnaire, which has been validated and shown to be reliable, will be used.

The S-LANSS pain score is a 7-item self-administered scale developed and validated to recognize neuropathic pain in chronic pain patients and distinguish it from nociceptive pain. It evaluates neuropathic symptoms and signs through a series of questions that help identify features like hyperalgesia, allodynia, and paresthesia, which characterize the chronic pain sensation associated with neuropathic pain. These features are often seen in fibromyalgia (FMS) pain. In our study, the Turkish version of the questionnaire, which has undergone validity and reliability testing, will be used.

"The Tampa Kinesiophobia Scale is a 17-item measure designed to assess fear of movement/re-injury. The scale evaluates fear-avoidance behaviors related to work activities, injury/re-injury concerns, and fear-avoidance parameters. It is used in the context of acute and chronic low back pain, fibromyalgia (FMS), musculoskeletal injuries, and whiplash-associated disorders.~The scale uses a 4-point Likert scoring system (1 = Strongly disagree, 4 = Strongly agree). After reversing the scores for items 4, 8, 12, and 16 (for example, if a participant selects 1 for these items, it is counted as 4; 2 is counted as 3, etc.), the total score is calculated. The participant receives a score between 17 and 68. A higher score on the scale indicates a higher level of kinesiophobia. In our study, the Turkish version of the scale, which has undergone validity and reliability testing, will be used."

"This scale is used to assess anxiety and depression symptoms and consists of 14 items (7 items for anxiety, 7 items for depression). For each subscale, scores range from 0 to 21:~* 0-7 points: No symptoms or very mild symptoms~* 8-10 points: Moderate symptoms~* 11 points or higher: Symptoms likely corresponding to a clinical diagnosis of anxiety and depression According to the 2016 diagnostic criteria for Fibromyalgia Syndrome (FMS), the presence of depression contributes to the diagnosis of FMS. The HAD scale has been shown to be a suitable tool for assessing FMS and related patient education programs.~In our study, the Turkish version of the HAD scale, which has been validated and shown to be reliable, will be used."

The SF-12 Health Survey is one of the most widely used scales for assessing health-related quality of life. In our study, the Turkish version of the SF-12, which has been validated and shown to be reliable, will be used. The scores will be calculated using an online calculation tool, and two types of scores-Physical Component Summary (PCS) and Mental Component Summary (MCS)-will be obtained.

The Fatigue Severity Scale (FSS) is a 9-item questionnaire used to assess the severity, frequency, and impact of fatigue on daily life. Each item is rated on a scale from 1 to 7. A lower score indicates a decrease in fatigue severity. In our study, the Turkish version of the scale, which has been validated and shown to be reliable, will be used.

The Timed Up and Go (TUG) test is designed to measure dynamic balance based on the time it takes for participants to stand up and walk. The patient begins by sitting on a standardized chair (height of 46 cm). During the test, the patient is asked to stand up from the chair, walk 3 meters, turn around, and return to sit back on the chair. The time taken to complete this process is measured. Lower values indicate better stability. A cut-off value of 13.5 seconds is used to identify individuals at higher risk of falling.