Masseter Muscle Thickness in Individuals With Chronic Neck Pain

Ultrasonographic Measurement

Masseter muscle thickness will be assessed using the B-mode ultrasound method with a 7.5-10 MHz frequency linear probe on an ALEXUS brand ultrasound device. During measurements, participants will be positioned sitting upright, with the head in a neutral position and the jaw at rest (teeth not in occlusion). Prior to measurement, participants will be instructed to avoid activities such as intense chewing or gum chewing for the last 24 hours. The measurement point will be determined as the midpoint of the line between the zygomatic arch and the mandibular angle. The linear probe will be placed parallel to the long axis of the masseter muscle fibers, perpendicular to the skin surface, and with minimal pressure applied. The ultrasound image will clearly distinguish the skin, subcutaneous tissue, and superficial and deep fascial borders of the masseter muscle.

Visual Analog Scale (VAS)

The VAS is a one-dimensional measurement tool used to assess the intensity of pain as perceived by the individual. The scale consists of a horizontal line with endpoints defined as "0 = no pain" and "10 = unbearable pain," on which the individual marks their current pain level. Participants are asked to rate the intensity of their neck pain, and the distance from the starting point to the marked point is measured in centimeters or millimeters and scored. Higher scores indicate higher pain intensity.

Neck Disability Index - NDI

The Neck Disability Index (NDI) is a multidimensional self-report scale developed to assess the level of functional limitation associated with neck pain, covering activities of daily living. The scale consists of a total of 10 items covering pain, personal care, lifting, reading, headaches, concentration, work, driving, sleep, and recreation. Each item is scored from 0 to 5, and the total score ranges from 0 to 50. Higher scores indicate an increased level of disability related to the neck. The validity and reliability study of the 7-item questionnaire in Turkish was conducted by Emine Aslan and colleagues in 2008.

Pain Catastrophizing Scale

The Pain Catastrophizing Scale was developed to assess an individual's negative cognitive and emotional responses to their pain experience. The scale consists of three subscales: rumination (persistent thinking), magnification, and helplessness. The scale is answered using a Likert-type rating, and a total score is calculated. High scores indicate an increased tendency to catastrophize pain.

Northwick Park Neck Pain Questionnaire (NPQ)

The Northwick Park Neck Pain Questionnaire (NPQ) is a self-report measure that assesses functional impairment and symptom severity associated with neck pain. The scale consists of items covering pain, paresthesia, sleep, social life, and daily activities. Participants select the statement that best applies to them for each item. The total score reflects the level of functional impairment, with higher scores indicating greater disability and symptom severity.