Oculomotor testing in functional neurology

16 November 2020

According to Dr. Glen Zielinski, DC, DACNB, FACFN, oculomotor testing is by far the most effective means to quantify the functionality of the entire brain. He uses it in every patient that he sees in his clinic.

But before we dive into oculomotor testing, let’s shortly introduce the concept of functional neurology and Dr. Zielinski’s clinical practice.


What is functional neurology?

Functional neurology is a small but growing multidisciplinary field that focuses on rehabilitation of neurological dysfunction through myriad forms of neurostimulation, without the use of pharmacy or surgery.

In Dr. Zielinski’s practice Northwest Functional Neurology in Oregon, US, they focus on the rehabilitation of traumatic brain injury and post-concussion syndromes.

They see a broad variety of patients, but all have some component of direct vestibular dysfunction in common or their issues are such that they can activate and improve function by way of targeted vestibular stimulation.


Components of neurorehabilitation

While appropriate vestibular function may be a necessary component of neurorehabilitation, it is far from enough according to Dr. Zielinski:

Our therapies need integration between systems that localize the individual in space, including eyes, proprioception, and vestibular networks. They must then feed forward into higher cognitive networks for building environmental context, executive function, and emotional regulation. This takes us far beyond the vestibular system, and into the various aspects of the cerebellum, the brainstem, the frontal and parietal lobes, the basal ganglia, the dorsal and ventral visual streams, and much more. Proper neurorehabilitation thus requires being able to quantify functionality of the entire brain to create precise protocols of exercises that can enhance plasticity in impaired structures and restore integration between networks. Oculomotor testing is by far the most effective means to quantify the functionality of these systems in a way that leads to actionable treatment plans and outcome assessments.


The eyes are the window to the brain

In Dr. Zielinski’s practice, they use oculomotor testing, such as gaze, saccade, smooth pursuit and optokinetic testing in every patient they see. He explains:

The eyes have been described as the window to the soul. In reality, they provide the best functional window to the brain. The eyes are the only system that activates the entire brain. By assessing functionality in all these systems, not only whether they work or not, but also how symmetrical their output may be, and ratios of fatigability, a functional snapshot of the brain’s critical systems can be obtained. Therapies can be derived from this data, and the central consequences of these therapies can be assessed almost in real time.


Comprehensive neurological examination

With oculomotor testing as the central tool, Dr. Zielinski’s staff take every patient through a comprehensive assessment:

We use balance platform posturography, video head impulse testing with the EyeSeeCam system to quantify the function of all vestibular canals, and a full VOG profile with VisualEyes™. This information provides us with a great deal of clinical utility that guides our physical and neurological examination. The most important thing in neurological rehabilitation is being able to objectively assess function within integrated systems. Oculomotor testing removes subjective bias from the equation. It keeps us very honest, because if we select the correct intervention, findings improve. There is nowhere for us to hide from the data if we do not.


Saccades tell the true story

Traditionally, several types of oculomotor tests have been used to quantify vestibular function, such as nystagmus generated with caloric irrigation.

According to Dr. Zielinski, caloric weakness or directional preponderance can be used to show a lesion in the vestibular receptors or within the vestibular nerve, but they are not enough:

Often, the ranges of normal seen within these tests are far too broad to determine whether a finding is normal for the individual patient. We see post-concussion syndrome patients all the time that have received comprehensive vestibular testing and were told that everything was within normal limits, but they are not. For example, a patient with a 5% right lateral caloric weakness may seem normal within the parameters of caloric testing, but when combined with a 10% increase in right saccade latencies, omnipause intrusions in right saccade phase plots, 10% hypometria of right saccade accuracy, and a 10% increase in anti-saccade directional error, a picture begins to emerge that implies functional pathology within the left dorsolateral prefrontal cortex, the left front striatal system, and the right cerebellar dorsal vermis. A 10% decrease in right anterior canal VOR function on vHIT testing may also be present, which can further implicate the left midbrain and right vestibular system. All these findings may be within normal ranges in and of themselves, but when viewed through a functional neuroanatomical lens, a picture of precise dysfunction can start to emerge that demonstrates what is not normal for the individual.


About Dr. Glen Zielinski

Dr. Glen Zielinski is a Chiropractic Physician and Board-Certified Functional Neurologist. He received his doctorate in chiropractic from Parker University in Dallas, Texas. He completed his neurology training with the Carrick Institute for Clinical Neuroscience, and became board certified as a Chiropractic Neurologist by the American Chiropractic Neurology Board in 2003. He was appointed as an Assistant Professor of Neurology with the Carrick Institute later that year. He was awarded a fellowship from the American College of Functional Neurology in 2010. He is fellowship-trained in Traumatic Brain Injury Rehabilitation, Vestibular Rehabilitation, Movement Disorder Rehabilitation, Childhood Neurodevelopmental Disorder Rehabilitation, and Clinical Neurochemistry. Dr. Zielinski has lectured for thousands of hours on Functional Neurology to chiropractic, medical, osteopathic, and naturopathic physicians throughout North America and Europe. He has qualified hundreds of doctors throughout the world to sit for board examination in Functional Neurology. Dr. Zielinski founded Northwest Functional Neurology in Lake Oswego, Oregon, in 2006. His practice focuses on severe traumatic brain injuries, post-concussion syndrome, movement disorders, disorders of gait and balance, and disorders of childhood neurological development.

Charlotte Ellemose Sonne
Charlotte Ellemose Sonne is a Master of Linguistics and Communication (cand.ling.merc.), having graduated from Aarhus University in 2004. Before joining Interacoustics, Charlotte's working experience included, among other, a seven year stay at DONG Energy (now Ørsted) as a Language Specialist.
Reviewed by Dr. Glen Zielinski, DC, DACNB, FACFN

Published: 16 November 2020
Modified: 20 June 2023


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