Neck Pain & ….

When the neck is injured there is often a cascade of other symptoms that follow. These can include dizziness, unsteadiness, visual issues, headaches, migraines, problems with being able to focus, and of course pain.

In order to provide the most effective and sustainable care it is crucial to find out the cause and contributing factors.

Why is it that an injury to the neck can negatively affect our vision, stability, how we walk, and even how we run?

The neck is part of a complex system that allows us to move. This system is called the sensorimotor control system. The sensorimotor control system is made up of our eyes (visual system), inner ear (vestibular system), and proprioceptive system. These three systems work together to send information to the brain about the body’s position in space which allows the body to appropriately perceive, adapt, and react to our environment.

We’re going to briefly touch on each system and then discuss how these systems work together and why an injury or abnormality with one can lead to a plethora of issues that often times seem unrelated.

First the vestibular system.

The vestibular system is a sensory system and its main function is providing our brain with information about movement, head position, and spatial orientation. It does this through utilizing the inner ear, pictured on the right. The main components that collect this information are the semicircular canals, the part outlined in red in the picture on the right. The semicircular canals are arranged in a manner where they are each at a different angle, approximately 45 degrees different from each other. In these canals there are hair cells and liquid called endolymph. As we nod our head, turn our head, or tilt our head the endolymph rushes over the hair cells. Then dependent on how the endolymph interacts with the hair cells in the canals will determine the message that is then sent to the brain and other areas communicating the head’s location or movement in space based on the vestibular system.

If you have more questions on spatial orientation here is a wonderful paper put out by the FAA that dives into it. Link

Next is the visual system.

The visual system is our eyes. The visual system is extremely complicated and truly amazing. Not only does it allows us to perceive distance but it also allows us to see colors, adapt to light, and so much more. The eyes are becoming more and more involved in diagnosing and treating certain disorders because the eyes give us a direct look into how the brain is or isn’t functioning correctly.

For instance the eyes use certain strategies to control the movement of the eyes to allow us to focus on objects. Specifically, saccades and smooth pursuits. Saccades are a series of rapid eye movements that the eyes use to correct the position of our eyes on a stationary target that we are looking at, while smooth pursuits are used to track a moving target that we are looking at. In certain individuals specifically those that have suffered a traumatic neck injury or concussion the eyes can lose some of their ability to track objects whether the object is moving or stationary. Utilizing eye tracking software researchers and doctors are able to determine how the eyes are improperly functioning and whether saccades are being affected or smooth pursuit or both.

Next is the proprioceptive system.

What is the proprioceptive system?

You know how in order to determine what is going on around us we use our external senses; smell, hearing, sight, touch, and taste?

The proprioceptive system essentially does the same thing for the inside of the body but for our musculoskeletal system.

The proprioceptive system tells the brain what is going on inside the body when it comes to movement, position, and space. It does this by using mechanoreceptors. Mechanoreceptors are located inside our muscles, tendons, ligaments, and surrounding our joints.

The proprioceptive system is a combination of these sensors and the tissues these sensors are located in. They tell the brain how our musculoskeletal system is functioning and where the muscles, tendons, ligaments, and joints are in relation to each other and how they’re interacting with each other.

The proprioceptive system primarily utilizes 5 different types of mechanoreceptors and each type relays a different type of information to the brain.

The five types, what information they relay to the brain, and where they are located is in the graphic on the right.

The proprioceptive system works together with our visual system and vestibular system to allow us to move through the world smoothly and unhindered. It allows us to adjust our gait and speed when walking over a cobblestone street without thinking. It provides a soccer player with the ability to to contort their body as they jump for a header. It provides a football player with the ability to run at a full sprint and make a diving catch. It allows a gymnast to do gymnast things. While many of these movements are done consciously, all of this is able to happen due to the coordination of these three systems and the intricate details these three systems are sending to the brain and each other.

Proper functioning of the sensorimotor control system is crucial for us to be able to move through the world unhindered and without pain.

This brings us back to our original question, “How come an injury to the neck can negatively affect our vision, stability, and even how we walk?”

If you look at the different types of mechanoreceptors you’ll notice muscle spindles. Muscle Spindles perceive, evaluate, report, and calibrate the length of muscles. They also stimulate muscles that help accomplish the movement or contraction and provide input for velocity of contraction and change in velocity. Essentially muscle spindles allows our muscles to contract and relax accurately, quickly, and reliably.

SOT Muscles By Dreviscerator Frank Scali, DC, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27170669

While muscle spindles are located throughout our entire body the highest density of muscles spindles are found in a group of muscles in the upper neck called the suboccipital triangle. These muscles connect the top two vertebrae of the spine to each other and attach to the skull. While these muscles are muscles they act more like a sensory organ due to the high density of muscle spindles and the role they play with coordinating movement of the neck with the eyes and vestibular system. 

Clearly the neck is extremely important when it comes to the three systems that help us coordinate our movement and maintain our balance and stability.

Fun Fact. These suboccipital muscles don’t just help coordinate movement of the neck with the eyes and the vestibular system but also have attachments directly to a protective layer that surrounds the brain. That protective layer is dura mater and while it is believed that its main function is protection of the brain and spinal cord this connection also helps the flow of cerebrospinal fluid around the brain and spinal cord when moving the head and neck.

As we’ve learned above there is a ton of information that is being collected by our eyes, inner ear, and proprioceptive system, specifically the neck. Any movement of our head and neck are going to stimulate the vestibular sensors and the sensors that are collecting information about the length of muscles and speed of contraction as we move our head. If we then open our eyes  we will also have visual input jumping into the mix. With all of this happening at once all three systems have to work together simultaneously to maintain our balance. Much of this is accomplished through the use of multiple reflexes. Here are some of them below.

Cervical-Occular Reflex - Eyes move reflexively due to changes in position of the neck it works with the VOR to help stabilize the eyes when moving the head and neck.

Vestibulo-Colic Reflex - Receives vestibular information and causes corresponding muscular contraction of neck muscles in response to the vestibular information.

Vestibulo-Occular Reflex - Eyes move reflexively while the head moves due to the information coming from the vestibular system, this reflex helps to stabilize gaze.

Cervico-Colic Reflex - Movement of the head cause neck muscles to reflexively respond to further stabilize the head based on how certain neck muscles are moving.

Vestibulo-Spinal Reflex - Movement of the head causes certain spinal and postural muscles to contract to help stabilize posture.

How do some of these reflexes work together?

“To guarantee clear vision the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) work in conjunction to stabilize the visual image on the retina. The VOR receives input from the vestibulum, responding to movements of the head in space. The COR receives input from the mechanoreceptors, mainly the muscle spindles and joint sensors, of the upper cervical spine (Hikosaka and Maeda 1973). The COR responds to movements of the head relative to the trunk.” 

Let’s again return to the original question.
"Why is it that an injury to the neck can negatively affect our vision, stability, how we walk, and even how we run?”

When the neck is injured, whether it’s sleeping wrong, sitting in an asymmetrical position, a neck injury during a concussion, straining the neck when trying to lift a heavy weight, or a neck injury due to a whiplash injury, the mechanoreceptors in the neck are no longer going to function at 100% accuracy. The level of mechanoreceptor dysfunction is most likely correlated with the level of injury.

This inaccurate message sent from the mechanoreceptors in the neck is then combined with accurate information sent from the visual and vestibular system.

Your body then has to try and direct movement, coordination, balance, and stability off of inaccurate information. This causes many of the reflexes involved in sensorimotor control to not work normally. This can then result in dizziness, visual disturbances, uncoordinated movements, and more.

When an injury to the neck occurs in damages the sensors in the neck which leads to faulty inaccurate information being combined with accurate information from the vestibular system and visual system. On top of the pain from the injury this inaccurate information exacerbates the issues by causing abnormal movement of the muscles, instability, and often times dizziness, an inability to focus, and possibly an increase for risk of injury.

We are here to help if you are suffering with neck pain, headaches, dizziness, or other issues related to a neck injury. To schedule your complimentary consultation click below.

References

1. Ischebeck, B. K., de Vries, J., van Wingerden, J. P., Kleinrensink, G. J., Frens, M. A., & van der Geest, J. N. (2017). The influence of cervical movement on eye stabilization reflexes: A randomized trial. Experimental Brain Research, 236(1), 297–304. https://doi.org/10.1007/s00221-017-5127-9

2. Ischebeck, B. K., de Vries, J., van Wingerden, J. P., Kleinrensink, G. J., Frens, M. A., & van der Geest, J. N. (2017). The influence of cervical movement on eye stabilization reflexes: A randomized trial. Experimental Brain Research, 236(1), 297–304. https://doi.org/10.1007/s00221-017-5127-9

3. Kristjansson, E., & Treleaven, J. (2009). Sensorimotor function and dizziness in neck pain: Implications for assessment and Management. Journal of Orthopaedic & Sports Physical Therapy, 39(5), 364–377. https://doi.org/10.2519/jospt.2009.2834

4. Mooti, R., & Park, H. (2022). Contribution of cervical proprioception, vision, and vestibular feedback on reducing dynamic head–trunk orientation error in the yaw direction. Frontiers in Neuroscience, 15. https://doi.org/10.3389/fnins.2021.774448

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6. Schneider, K. J., Meeuwisse, W. H., Palacios-Derflingher, L., & Emery, C. A. (2018). Changes in measures of cervical spine function, vestibulo-ocular reflex, dynamic balance, and divided attention following sport-related concussion in elite youth ice hockey players. Journal of Orthopaedic & Sports Physical Therapy, 48(12), 974–981. https://doi.org/10.2519/jospt.2018.8258

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