Impairments in sensorimotor function have been found in association with persistent neck pain.
The cervical spine (neck) not only functions to provide mobility and stability to the head while connecting it to the relatively immobile thoracic spine; but it also plays a significant role in providing proprioceptive information to the brain to assist with balance, co-ordination and eye-sight.
I have previously written a blog about how balance is maintained, and I touched on the topic of proprioception. In this blog, when I discuss proprioception, I am specifically talking about proprioceptive input from the mechanoreceptors within the muscle spindles of the cervical spine muscles.
The cervical spine has numerous mechanoreceptors responsible for proprioceptive input. These receptors have both central and reflex connections to the vestibular, visual, and central nervous system (CNS). The interaction of the mechanoreceptor input from the upper cervical region between vision and movement of the neck is achieved through several reflex pathways. There is a particular abundance of mechanoreceptors in the sub-occipital region (the area of the neck at the base of the skull), as these muscles send and receive information to the CNS.
The cervical spine contributes to somatosensory awareness via the following mechanisms:
- Proprioception (Mechanoreceptors within the cervical spine)
- The muscles of the upper cervical spine have a significant abundance of sensory receptors in the muscle spindles which provide information to the CNS and reflex pathways.
- Eye Movement Control (Role of Cervical Spine in Occulomotor Reflex Pathways)
- There are multiple reflex pathways between the cervical spine, vestibular system, and visual system. One example of the reflex pathways is the Cervico-occular reflex (COR). This pathway works is an ocular stabilization reflex that is elicited by rotation of the neck. Cervical Afferent input from Mechanoreceptor Spindle lengthening tells the eye muscles to move at a specific rate and in a specific direction so that you can maintain eye stabilisation has your head moves.
- Balance and Postural Stability
Cervical proprioception impairment is unfortunately common in people with neck pain, which can lead to disturbances in cervical sensorimotor control / function.
The causes of altered proprioception associated with neck pain, include:
- Pain and cervical trauma i.e., Whiplash injury,
- Structural and functional changes in cervical musculature e.g., atrophy, degeneration, fatty infiltration.
- Pain and psychosocial stress
- Inflammation chemically affects the receptor sensitivity.
- Altered motor control associated with cervical facet joint or disc disease.
These are all thought to lead to a vicious cycle that continues to contribute to ongoing altered cervical proprioception.
When the cervical receptors are dysfunctional the afferent input from these receptors are altered. This functional impairment changes the integration, timing, and tuning of sensorimotor control, leading to a multitude of symptoms:
- Altered sense of cervical joint position (proprioception)
- Changes in Eye Movement Control
- Impeded Balance
- Dizziness, Unsteadiness and Lightheadedness
A 2021 Narrative Review titled “Cervical Proprioception Impairment in Neck Pain” explores 8 assessment tools used by clinicians to assess for and diagnose sensorimotor impairment in neck pain patients. These assessment tools aim to test for dysfunction in the 3 pillars: Proprioception, Eye Movement Control and Balance.
Of all the tests, cervical joint position error (JPE) is the most used and researched. Systematic reviews have shown there is consistent evidence for impaired JPE in those with idiopathic neck pain. This assessment tool (pictured) involves the use of a target and laser attached to the patient’s head.
To Perform the Joint Position Error Test, the patient stands 1m back from the target with the laser pointer pointing at the bullseye on the target. The patient then is asked to close their eyes, turn their neck in a certain direction and return to the original position. The distance from the bullseye is measured, and a measurement greater than 6.5cm is deemed significant.
The good news in all this is that there is good evidence for a tailored sensorimotor control exercise program to improve sensorimotor control and/or neck pain. Local treatment (manual therapy and local strength/stability exercises) and tailored sensorimotor control exercise prescription is suggested to be required for management. Local treatment is required to address the causes of abnormal cervical input from the receptors, such as pain and altered motor control. Eliminating pain, particularly relating to facet joint and discogenic pain, has the potential to help proprioception by treating the cause of the altered cervical mechanoreceptor input.
Persistent neck pain can have a far-reaching impact on your health and wellbeing. Therefore, it is integral that you have your symptoms thoroughly assessed with not only range of motion and strength, but also to assess for sensorimotor deficits that may need rehabilitation to improve all symptoms. At Bend + Mend, we pride ourselves in offering thorough assessment, and management options. So, if you or someone you know has been experiencing persistent neck pain, or sensorimotor dysfunction symptoms, please come see our team.
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