Functional neurology is one of many specialties within chiropractic. Postdoctoral training in neurology takes place in the course of 3 years, leading to examinations certifying the doctor of chiropractic (DC) as a Diplomate of the American Chiropractic Neurology Board. Within chiropractic neurology, there are also the subspecialty colleges of childhood developmental disorders, brain injury rehabilitation, electrodiagnostics, vestibular rehabilitation, and neurochemistry, each of which requires approximately 2 additional years of training.
Functional neurology developed within the chiropractic profession for a couple of reasons. The original premise of chiropractic was that (1) spinal misalignments called subluxations impinge spinal nerves, causing an imbalance in nerve output to the body, resulting in an unhealthy body and disease; and (2) subluxations were “removed” by spinal “adjustments.” This was one hypothesis of many on health and disease put forth in the late 19th century. Today, nearly all chiropractors use a type of spinal manual therapy known as adjustments and are among the world’s most highly trained in these skills. In addition, prescription pharmaceutical products and surgery are not therapeutic options for chiropractors; this has resulted in the development of approaches such as functional neurology.
Although modern chiropractic has set aside the notion of spinal subluxations as the cause of disease, chiropractic neurologists use spine and extremity manipulation differently to send afferent input to specific areas of the brain, taking advantage of the fact that proprioception is one of the main inputs to the brain and one of the triumvirate of balance, proprioception, and visual sensory information sources that the brain uses for primary survival. A hallmark of human evolution is that the brain has developed very sophisticated systems to know where it is in space to prevent falls, a leading cause of accidental human death. This requires continuously updated and very accurate maps of both internal and external environments. A great deal of this map localization and updating occurs through proprioception because the primary way the brain knows where its body’s parts are is through muscle spindle activity—one of many types of proprioception. Thus, the muscular system has both sensory and motor functions.
Chiropractic functional neurology uses the principles of Sherrington’s 1932 Nobel Prize–winning theory known as the central integrated state. This refers to a nerve’s ability to “fire” being the sum of all its activating and inhibiting inputs. It also relies on modern understandings of the importance of accurate visual, vestibular, proprioceptive, and cortical integration in neurodevelopment, neurotrauma, and neurodegeneration. Because many nervous system abnormalities have no ablative or organic pathology, they are termed functional lesions. It is the nonablative basis of functional lesions that can make them amenable to improvement through the unique applications of chiropractic functional neurology.
The nervous system was once considered fixed after childhood, but now we know it is capable of remarkable change. The brain and nervous system are “plastic” and can be shaped or modified by sensory, motor, or cognitive experiences where temporal- and spatial-summative neural activation can be used to rewire and reprogram the nervous system. Repetitively firing a pair of neurons produces neurotransmitters in the “talking” neuron. This increases receptor expression for that neurotransmitter on the “listening” neuron. The “listening” neuron also sends neurotrophic growth factors back to the “talking” neuron, further promoting stability of the connection. Nerve cells can also grow new connections to different neurons using synaptogenesis and can perhaps use neuronal migration to extend to more distant areas. This is how humans learn any new skill and why “practice makes perfect.”
For example, an adult with retained primitive reflexes may have developed attention-deficit/hyperactivity disorder owing to impaired connectivity in the frontal lobe, such that they cannot inhibit the impulse to have their attention drawn to a distracting object. However, if inhibition of primitive reflexes can be reintegrated, even as an adult, a greater prefrontal cortical inhibition can be built that can have a positive effect on focus and attention. Another example might be someone with anxiety disorder and “migraine” resulting from inability of the eyes to maintain fixation on a target. The patient does not recognize the cause, but because putting the fovea of the retina accurately on a visual target is a primary survival skill, when the eyes cannot fixate on a target, the limbic system can become overactive because the brain recognizes that it keeps losing its visual targets. Every time the eyes jump to a target, the brain turns off vision, a phenomenon known as saccadic masking. We are literally blind in that moment. If this is happening constantly, one of the brain’s primary survival functions is impaired, and the brain knows it. At the same moment, head position- and velocity-sensing nerves in the brainstem are also turned off. Add this loss of position sense to the saccadic masking, and the limbic system can go into overdrive, resulting in high anxiety. Furthermore, the spinal postural, cephalomotor, and extraocular muscles of the vestibulo-ocular reflex (VOR) all fatigue when they are constantly activated by the eyes constantly trying to regain a target. If the VOR is constantly activated because the eyes do not hold a target, this fatigues the nerves and muscles to the point of lactic acidosis and exhaustion, and extraocular muscle fatigue is a common source of head pain. The combined result is a patient with anxiety disorder and “migraine.” These are 2 examples of functional brain lesions not necessarily caused by ablative injury or disease.
The 2 cases in this issue of the journal demonstrate the effect that functional lesions can have on the nervous system. For example, Dr Swingen’s patient deteriorated to the point where she had to forego school and return home just to be able to rest and to hopefully recuperate. Although “rest” has historically been the main approach to concussion, today, greater emphasis is placed on active treatment to help the brain recover. In this case, the patient sustained damage to brainstem neurons where integration for gaze stability and for eye movements occurs. Neuron populations that control “pulse” and “step” activities that propel the eyes to a target and then hold the eyes fixed on that target all had to be retrained using finely tuned exercises directed at very specific neuron populations in the brainstem, cerebellum, and cortex that control these activities. With graded application of vestibular and ocular motor strategies, metabolic capacity of the nerves and muscles was restored, which can be seen in the posttreatment video nystagmography (VNG). A very important point to note here is that VNG findings are thought to be permanent and, thus, the ability to show changes on VNG is quite unique and remarkable. In the end, the unique exercises that produced the VNG changes also proved to be the key in the patient’s fast recovery once the correct therapies were introduced.
In the second case, Dr Boothby follows a patient through years of integrated health care, much of which included graded therapeutics to avoid overstimulation. This eventually allowed the patient to go from needing hip replacement to having fairly normal hip function. In the course of care, Dr Boothby noted that the patient developed ratcheting head movements suggesting a “broken VOR” and so referred him to a chiropractic neurologist who provided very specific vestibular rehabilitation to rebuild metabolic capacity in the system. Because the vestibular system is integral to postural stabilization in advance of volitional movement, when the vestibular system is not functioning well, it can impair gait as well as joint motion and function, all of which are central issues in this case, with the end result being that the patient no longer needed hip replacement; again, quite remarkable.
Today, people know their blood pressure and cholesterol numbers, but how many know the speed, latency, and accuracy of their saccades? Because saccades are such an effective measure of brain function, it is prudent to use brain tests of saccades and other parameters to determine whether the brain is working well. These tests also document resolution of developmental delay, resolution of concussion from mild traumatic brain injury, or resolution of symptoms of cognitive decline with aging. All these and more have shown themselves to be amenable, in many cases, to chiropractic functional neurology.
Biography
Russell Margach, DC, is a 1985 cum laude graduate of the University of Western States, where he earned his doctor of chiropractic (DC) degree. He began his studies of chiropractic neurology with the Carrick Institute in 2010 and completed that training in 2013. He went on to complete subspecialty fellowships in childhood developmental disorders (2012–2013) and brain injury rehabilitation (2013–2014). Dr Margach is also the principal author of the State of Oregon’s Board of Chiropractic Education’s white paper, which resulted in the specialty practices and examinations of functional neurology being added to the scope of practice for qualified DCs in Oregon. He is also a clinical research peer reviewer for the Journal of the American Osteopathic Association and Elsevier’s Clinical Biomechanics.