Motor Imagery Ability and Cervical Discogenic Pain

Background: The purpose of the study was to examine the motor imagery ability and its association with pain, functional status, neck awareness and depression levels in individuals with cervical discogenic pain (CDP).

Methods: Sixty individuals aged between 18-65 were included in the study. Demographic data was recorded, pain and disability were evaluated using Visual Analogue Scale (VAS) and Neck Disability Index (NDI), motor imagery ability using Kinesthetic and Visual Imagery Questionnaire-20 (KVIQ-20) and mental chronometry. Grip strength, cervical muscle endurance, upper limbs functionality, neck awareness and depression levels were assessed using hydraulic hand dynamometer, cervical muscle endurance tests, Upper Extremity Functional Index-15 (UEFI-15), Fremantle Neck Awareness Questionnaire (FreNAQ), and Beck Depression Inventory (BDI), respectively.

Motor imagery (MI) is defined as the cognitive representation of a body movement without the actual movement. MI depends on both kinesthetic - which require sensory-motor knowledge- and visual strategies - which require visual knowledge of the movement imagined. Kinesthetic MI is the ability to visualize a movement simulation to perceive its direction, speed, and magnitude. This ability requires the activation of neurocognitive mechanisms that underlie the design and execution of voluntary movement. Visual motor imagery occurs through internal or external visual imagery. Internal visual imagery involves visualizing a movement from ones own perspective, while external visual imagery involves seeing a movement from a third persons perspective. Neuroimaging studies revealed that the parts of the brain activating during MI were similar to those which activate while a movement was actually performed. Therefore, activating joint and muscle receptors by MI may increase corticomotor excitability. Moreover, it was demonstrated that subcortical structures were activated through excitability of presynaptic interneurons by MI, i.e. without activating alpha-motor neurons. Activation through MI ensures continuity of movement and improves the quality of desired movements, playing a key role in enhancing motor function and performance.

Individuals with cervical disc pathologies exhibit a reduced fiber density along the corticospinal tract. Functional magnetic resonance imaging studies have shown increased activation in the primary motor and premotor cortices and a loss of activation in the sensory cortex. These changes are related to the severity of the disc pathology. Besides, it was reported that prolonged compression in the cervical spine might lead to atrophy in the sensorimotor cortex and thalamus, giving rise to a functional reorganization, usually result in maladaptive neuroplasticity. Chronic pain, a common finding in cervical disc pathologies, may affect the perception of painful body parts and MI performance, as well as impaired somatotopic representation. In addition to cortical changes, the gradual processing of stimuli by mirror neurons, which generate motor movements, is considered a significant component of learning by imitation and observation. This process forms an important part of MI and is thought to be impaired in individuals with chronic pain. They highlighted that evaluating the MI ability of an individual with chronic neck pain was important for revealing the mental imagery performance.

In individuals with chronic neck pain, it was revealed that the severity of pain and the functional and psychosocial problems caused by the pain, were related to executive functions and working memory. They discovered that MI depends on executive functions. Interference tasks significantly affect the timing of MI. Therefore, it is believed that pain-related symptoms will also negatively impact MI skills. In the literature, studies have demonstrated positive effects of MI training on pain, disability, and fear of movement in individuals with chronic pain. However, it is suggested that factors related to MI ability should be further investigated. Therefore, the purpose of the study was to examine the relationships between MI ability and pain, functional status, neck awareness and depression levels in individuals with cervical discogenic pain (CDP).

Eligibility Criteria:
Inclusion Criteria:

* Aged 18 to 65 years with cervical disc herniation, who were suffered from neck pain lasting for at least 3 months,
* Had a resting pain between 3-7 according to the Visual Analog Scale;
* Could follow the instructions of a physiotherapist.

Exclusion Criteria:

* The individuals with disk degeneration without cervical disk herniation, cervical stenosis and cervical spondylosis were excluded.
* In addition, individuals who had a history of spinal tumor or head trauma, had a spinal deformity or congenital malformation, had a cervical instability and cervical artery dysfunction, underwent any cervical surgery in the preceding 6 months, musculoskeletal disorders and neuromuscular diseases in the upper extremity and shoulders (rotator cuff tear, very severe myofascial pain syndrome, cervical facet joint pain, carpal tunnel disease, etc.)
* Who were not able to follow the instructions of the therapist were excluded from the study.