The Human Balancing System is made up of 3 basic components.
- Our Eyes (Oculomotor System)
- Our Inner Ears (Vestibular System)
- Our Legs/Muscles (Proprioceptive System)
This series will explore the relationship of these 3 systems and the effects it has on neck and back pain, digestive issues, headaches/migraines, balance, dizziness and vertigo, mTBI/concussion, as well as sports performance and injury recovery.
This write up continues to cover the Oculomotor (and vestibular) System and will be a basic explanation of eye movements. Look for future write ups, videos and blog posts to help explain what is happening in the brain of symptomatic people.
So far we’ve covered the basics of eye control and stability, since it is THE most important thing that we as humans can do, it was covered first.
Next up, tends to tracking of targets.
We have two types of eye movements.
These eye movements are very different and measure different parts of the brain. They do have overlapping parts, so certain findings are indicative of issues in specific areas like the brainstem and are shared by the neural integrator, and other findings are indicative of cortical (frontal, prefrontal, parietal, temporal lobe) issues.
Depending on the type of eye movement we are evaluating, and the intrusive eye movements, or lack of stillness we find tells us almost EXACTLY the place in the brain that is faulty.
In addition, we know that if you start out strong and quickly fatigue at any type of eye movement then you are metabolically compromised, meaning your blood chemistry is likely out of whack that is causing your energy production to decline rapidly throughout the testing. When we see this fatigue throughout the testing procedures, we know it’s time to run a comprehensive blood analysis searching for anemia, blood sugar dysregulation, inflammation, and other deficiencies or overloads that could be contributing to your current symptoms neurological findings.
Ok, now onto the eye movements. Let’s start with saccades. This is the layman version to keep it simple.
Remember from the previous writeups, that the VOR system is the reflexive system, meaning that the inner ear has connections to the brainstem to directly move the eyes, almost without any other signals being sent. It’s the shortest pathway and the fastest system, and therefore essentially creates the foundational pathways for all eye movements. This means that every eye movements fires into this pathway in some way whether it be for a jump to a new target, or to follow a target.
Saccades are FAST eye movements generated by the FRONTAL LOBE. The frontal lobe fires down to the brainstem that houses the Paramedian Pontine Reticular
Formation (PPRF) to the burst centers for the eyes. Parallel to this pathway is a component of the brainstem called the Superior Colliculus (SC). The SC essentially codes for the location where the eyes is going to come to rest. Example, if you recall the game Battleship, there are coordinates where the ships are located- B-1, C-3 etc– Well the SC works similar to that. Your world is essentially a grid (to your eye coordinate system) and as you move through the world, targets and objects in your environment are encoded with these markers. When your brain wants to move from the TV to the clock, you move from B2 to the right to F7. In this example we just talked about the generation of the eye movement and the jump to a new location. There are multiple other pathways involved in moving the eyes from one place to another, and we will discuss those next.
As we discussed, the frontal lobe initiates the fast eye movement, the SC codes for the new location and the PPRF is the burst center for the eyes, which determines the velocity the eyes move. In addition, the cerebellum is involved with making sure the eyes accurately arrive at the new target. The cerebellum’s role in this whole thing is making sure the eyes don’t undershoot or overshoot the target (think accuracy in a finger to nose DUI test). After the eyes hit the target they need to be able to HOLD steady on the target (coming back to the neural integrator from previous posts).
Interestingly, when we see faulty saccades, we often see suboccipital tightness which leads to headaches, migraines and vertigo. When there’s an injury to the brain (think concussion), these areas breakdown and create many of the symptoms listed above.
When we see these chronic conditions in our office including migraines, occipital neuralgia, vertigo and dizziness, post concussion syndrome, Parkinson’s and other neurodegenerative diseases, we almost always find breakdown within this saccade system, and when corrected many if not all of the symptoms reduce or resolve.
In summary, the frontal lobe signals the eyes to move, the brainstem codes for their new target and creates the burst towards the new target. The cerebellum works together with the neural integrator to make sure the eyes accurately hit the new target and hold steady on the new target.
If your eyes seem to be involved in any of your symptoms or you’ve sustained previous head injuries or concussions, please make sure to reach out and make an appointment to be evaluated. Ask for the complete neurological workup and we will design the most effective plan for you to heal, and to reduce or resolve your chronic symptoms.