Effect of Visio-Vestibular Exercises on Pain, Function, Balance, and Reaction Time in Chronic Neck Pain

Neck pain is defined by the International Association for the Study of Pain (IASP) as pain felt in the area between the occiput and the first thoracic vertebra. Neck pain is a multifactorial disorder and is a major problem in modern society. In 2016, among 154 conditions, low back and neck pain had the highest healthcare expenditure in the United States with an estimated $134.5 billion. In 2012, neck pain was responsible for 25.5 million Americans being absent from work, missing an average of 11.4 days. In 2017, the global age-standardized prevalence and incidence rates of neck pain were 3551.1 and 806.6 per 100,000, respectively.

The cervical spine, especially the upper cervical spine, is the most mobile part of the vertebral column. The highly developed proprioceptive system provides neuromuscular control to the mobile cervical spine and allows efficient utilization of vital organs in the head through unique connections to the vestibular and visual systems. In people with neck pain, disturbances in afferent input from the cervical region may be a possible cause of symptoms such as dizziness, imbalance and visual disturbances, as well as signs of altered postural stability, cervical proprioception and head and eye movement control. For neck pain patients with minimal sensorimotor proprioceptive impairments, conventional treatment approaches may be sufficient. However, clinical experience and research suggest that significant sensorimotor proprioceptive impairments in the cervical spine may be an important factor in the maintenance, relapse or progression of various symptoms in patients with neck pain.

The postural control system includes all sensorimotor and musculoskeletal components involved in the control of 2 important behavioral goals: postural orientation and postural balance. Postural orientation is the relative positioning of body segments relative to each other and to the environment; postural balance is the state in which all forces acting on the body tend to keep the body in a desired position and orientation (static balance) or to move it in a controlled manner (dynamic balance). Postural control provides a stable body platform for efficient execution of goal-directed movements. The somatosensory, vestibular and visual systems are subsystems that provide sensory input to the postural control system.

The Somatosensory System encompasses all mechanoreceptive information from the periphery that leads to the perception of pain, temperature, touch and proprioception. In particular, the proprioceptive system of the cervical spine is highly developed thanks to the large number of mechanoreceptors from the γ-muscle spindles in the deep segmental upper cervical muscles. The γ-muscle spindle system serves as the last common pathway for the regulation of muscle stiffness required for various neuromuscular performances. The dense network of mechanoreceptors in the soft tissues in this region not only controls the movements of each joint, but more importantly, through direct neurophysiological connections to the vestibular and visual systems, informs the Central Nervous System about the orientation of the head relative to the rest of the body. Somatosensory information from the cervical region is the only region with such direct access to the senses of balance and vision.

The Vestibular Subsystem is specifically designed to maintain adequate postural tone in the trunk and limb muscles to ensure overall balance during posture and movement. Neck, eye, trunk and limb muscle reflexes have evolved to meet these requirements. Specialized mechanoreceptors in the semicircular canals become sensitive during changes in the speed of movement, i.e. angular velocity, and specialized mechanoreceptors in the otolith systems of the utricular and saccular maculae provide information about the position and velocity of the head relative to the direction of gravitational forces. Sensory information from the vestibular system is integrated via the vestibular nerve in all the nuclei that make up the vestibular nuclear complex and in the cerebellum.

The Visual Subsystem plays a dominant role in the guidance of movements and this is reflected by the fact that when there is a mismatch between somatosensory inputs and vision, the visual version of events usually prevails. The visual postural system consists of 3 different eye movement systems: the smooth pursuit system, the saccadic system and the optokinetic system. The smooth pursuit system stabilizes images of smoothly moving targets on the fovea with slow eye movements. The saccadic system is responsible for rapid and small movements of both eyes simultaneously when changing a fixation point. The optokinetic system stabilizes images on the entire retina when the entire visual field moves (e.g. when walking).

The aim of the study was to improve pain, function, balance and reaction times in people with chronic neck pain by stimulating and improving the components that provide input to the central nervous system (proprioceptive, visual, vestibular) through manual therapy and exercise.