Falls are a leading cause of injury and death among adults and a significant public health issue.

In 2009, 2.2 million nonfatal fall injuries occurred among older adults in Australia that required treatment in emergency departments and more than 581,000 of these patients were hospitalized. In the same year, over 19,000 older adults died from unintentional fall injuries making falls the fifth leading cause of death in adults. This may not be on your priority list as a younger adult, but is still something important to consider earlier in life as far as having a preventative strategy in place. Regardless of age and falls, various conditions such as whiplash/concussion, diabetes, visual impairments and vestibular disorders can play havoc with your balance and postural system and even lead to symptoms such as visual vertigo, motion intolerance and dizziness.

Given these scary statistics, Dr. Yazbek has invested in Phyiosensing, which is the gold standard in the quantitative assessment, treatment and management of dizziness, balance and postural disorders.
It is a balance and pressure plate using stabilometry and baropodometry in a single plate. Stabilometry quantifies the variations of centre of pressure and oscillations in the support base. Baropodometry is the study of static and dynamic foot pressures or plantar pressure using a foot pressure plate.

Phyiosensing comprises of 11 assessment protocols that are aimed at quantifying return to work, post motor vehicle accident, head and neck injury (concussion or whiplash associated disorders) and provides an in depth falls risk assessment. Combined with an exhaustive chiropractic/neurological examination, Physiosensing may also be used as a diagnostic tool for those who have unexplained balance and postural disorders.

The most common causes of loss of balance and postural control are:

  • impaired physical functioning
  • diabetic neuropathy
  • concussion and whiplash injury
  • visual impairments
  • obesity
  • vestibular disorders
  • osteoporosis and
  • polypharmacy. (Polypharmacy refers to the use of “too many” medications but may be necessary in the older population with multiple pathologies).

Falls studies have determined that taking 4+ drugs is associated with an increased incidence of falls. In light of existing evidence, careful and regular medication reviews are advised to reduce the effect of polypharmacy on injurious falls. A recent Australian hospital–based study including 204 patients over 60 years found that drug to drug interactions along with the number of fall-risk-increasing drugs and the total number of drugs were significantly associated with falls among the frail elderly. Prescriptions for older patients, therefore, should be individualized and subject to frequent periodic reviews, while consistently striving to minimize the total number and amount of medications consumed by the patient.

In order to understand the balance and postural system, we need to understand that our body requires three major senses to maintain postural equilibrium in space. They include (refer to figure 1):

  1. Vision
  2. Vestibular
  3. Somatosensory

Some key points to mention:

  • The information gathered from eyes open on a firm surface involves 70% of the information coming from the somatosensory system, 20% vestibular and 10% vision
  • Information gathered from eyes open on an unstable surface involves 70% vestibular, 20% vision, 10% somatosensory systems

It becomes quite clear that this change in sensory weighting and depending on which sub-system (vision, somatosensory or vestibular) is injured or underperforming, rehabilitation may involve manipulating the brain’s input of one or more of these systems to aid in compensatory recovery.

 

Figure 1

Navigating the world with the use of only one sensory modality is ambiguous!

Whilst it is obvious that vision (one of our special senses) provides us with a spatial map of the world which includes information determining ‘what’ and ‘where’ we see, to orient our posture to the external world. Somatosensory and vestibular senses require some explanation into their roles regarding balance and postural control.

Let’s consider a few questions:

Using vision alone, can you differentiate between:

  • Tilting your head to the right as opposed to tilting the whole body and head to the right?
  • A room rotating to your left as opposed to rotating yourself to your right with the room fixed?
  • Moving your eyes to the left as opposed to turning your head to the right with the eyes fixed straight ahead?
  • Bending your head forwards as opposed to falling towards the ground?

Using vestibular sense alone:

  • Could you differentiate between head tilt to the left on a stationary trunk as opposed to whole body translation to the right with head fixed over the feet?

You would be right in thinking that we need quality input from all three sources in order to accurately ascertain the relationship between the internal and external environment.

Have you ever tried reading in a moving car, shortly noticing the feelings of nausea? You can’t see yourself moving but you feel yourself moving. What if your neck pain was due to a mismatch between the brain’s interpretation of head motion via the canals of the vestibular system versus movement related information of the joints and muscles of the neck? The brain must receive incoming information from both these two systems that represent the actual kinematics (linear and angular rotation and velocity) of movement. Sometimes the ongoing perception of stiffness can be purely due to a mismatch.

This sensory ambiguity is what may lead to neck and low back stiffness, vertigo, dizziness and nausea.

What is the role of the foot in standing balance and control?

As the only contact point between the body and the ground, our feet and upper neck (somatosensory organs) play a critical role in the way in which our body controls and reacts to every upright movement. With 26 bones, 33 joints, 19 muscles and 107 ligaments the human foot is a fascinating and complex biomechanical structure. But the functional importance of the foot does not stop at pronation and supination. With thousands of plantar receptors, the foot is also a proprioceptive-rich structure, containing thousands of small nerves that are sensitive to every subtle movement we make.

Our ability for standing balance and postural control is all initiated through stimulation of these nerves on the bottom of the foot.
With small nerve receptors sensitive to stimuli such as texture, vibration, pressure and skin stretch, the skin on the bottom of the foot is unique when compared to skin on the top of the foot or the lower leg.

In the foot we have two sizes of nerves – small and large – with the smaller nerves being found in the bottom of the foot. Because of the smaller diameter, these plantar nerves are able to send signals faster to the Central Nervous System, creating faster response times.

These smaller nerves also play an important role in quiet stance and upright stability. If you think about our daily routine of putting on socks and shoes each morning, do you ever wonder what this is doing to the input of the plantar nerves? As soon as we put on socks, orthotics or shoes we block these highly sensitive small nerves on the bottom of the foot.

80% of our plantar proprioceptors are sensitive to vibration!

Any blocking or skewing of input to the plantar nerves causes a delay in response time and creates a greater reliance on the slower, large nerves found in the ankle and lower leg. Although this shift in proprioceptive feedback is subtle and doesn’t quite result in us falling – it still has a negative impact on the way in which our foot controls and reacts to the demands of human movement. The flow on effect of this is that the higher systems i.e. the vestibular and visual systems, upregulate their sensitivity.

What role does the vestibular system play?

The vestibular system involves small organs located within the inner ear, that respond to both linear and angular acceleration of the head and send information back to the brain and spinal cord. This information provides both conscious and subconscious information regarding head position relative to gravity and visual surroundings. It also has a role is enabling us to make rapid head motions whilst maintaining upright posture (vestibulo-spinal) and maintain a stable point of visual focus (vestibulo-ocular). We take balance and postural control for granted until will develop an acute pathology or a significant reduction in input from one or more of these systems. It would not be ideal if you were to be running and seeing double vision of the world whilst your head bobs up and down!

We know the foot plays a role in balance and control but the somatosensory system applies to the entire musculoskeletal framework! However, we cannot rely on our ankles and feet to maintain upright stance in all situations. We use an ankle strategy for small disturbances on a firm, flat support surface when the feet act as a small pendulum. We use a hip strategy when standing on a narrow support surface (beams), compliant or tilting support surfaces (foam, tilt boards), when stance in narrow (one foot standing or tandem stance,) or when our body’s position must be corrected quickly. The Vestibular system is not required to correct ankle strategy but important for hip strategy. People with peripheral vascular disease (diabetes) cannot use an ankle strategy and rely on hip strategy during standing on small flat surface which is inefficient.

What about patients with unilateral vestibular loss? 

Patients will have a tendency to either side bend or rotate their whole body and or head towards the same side of object motion.

What about patients with bilateral vestibular loss?

Patients with bilateral vestibular hypofunction (BVH), when standing on an inclined surface, will orient balance and control to that of the surface (somatosensory) as the vestibular system is hypo-functioning, thereby throwing themselves further into disequilibrium.

What about age related decline in balance and postural control?

It is known that as we age, brain function significantly declines and coupled with that, is the accelerated degeneration of the inner hair cells that mediate balance and postural control. There is a large association between falls risk and VOR suppression deficits. As mentioned earlier, VOR is the ability to maintain a stable fixed gaze whilst turning the head rapidly. Deficient VOR may lead to unsteadiness, dizziness and altered postural equilibrium. VOR suppression is the ability to turn the head and eyes within the same plane whilst focussing on a moving target. Both VOR and VOR suppression are impaired in the elderly.

Can eye movements regulate balance and postural tone? You bet!

It is interesting to note that chronic BVH patients are more stable and spend less energy to control their posture with visual tasks that require fixation, smooth eye tracking and rapid eye burst movements. This may be due to a need for for stability by up-weighting other redundant (visual) control mechanisms. BVH patients have poor postural control in the total absence of visual cues and this supports the idea that visual detection of body sway is one mechanism used by the BVH patients to improve their posture stability. Strong improvement of BVH patients’ posture stability was observed during fixation of a visual target, pursuit with slow eye movements, and saccades, whereas the postural performance of the control group was less affected by the different visual conditions. The present findings strongly suggest that the pathways which mediate eye movement control learn to better predict and use feedback mechanisms which are involved and over-used in a compensatory sensorimotor substitution process. On the other hand, when the BVH patients are in dual-task conditions (walking whilst performing mental arithmetic), they shift to a more automatic mode of posture control that also contributes to improved postural performance. This completely opposite to the healthy population.

In both young and old females it was found that fixed backgrounds and stationary gaze fixations reduced postural sway more than oscillating backgrounds and smooth eye tracking. This suggests that the visual system is a very important contributor to balance and postural control. Physiosensing can provide objective biomechanical data that can highlight the difference between standing balance and postural control while incorporating static eye gaze versus dynamic eye movement. Vision guides postural adjustments and we cannot refrain from visual tracking in an environment just to maintain balance and postural control because our ability to manoeuvre ourselves during high visual streams (walking in a crowd full of people) would not be possible.

To conclude, it is imperative that the visual, somatosensory and vestibular systems work in collaboration so that there is no mismatch of information resulting in improvements in balance and postural control.

We are excited to be offering Physiosensing services at The Chiro Hub as part of our comprehensive consultations. To make a booking, click here. To discuss your symptoms and specialised needs, call for a complimentary phone consult with Dr. Yazbek on (02) 93172288.

References:

  1. Splichal, Dr Emily. Barefoot Strong: Unlock the Secrets to Movement Longevity (p. 6). BookBaby. Kindle Edition.
  2. Lacour M, Dosso NY, Heuschen S, Thiry A, Van Nechel C, Toupet M. How Eye Movements Stabilize Posture in Patients With Bilateral Vestibular Hypofunction. Front Neurol. 2018 Sep 18;9:744.
  3. Srulijes K, Mack DJ, Klenk J, Schwickert L, Ihlen EA, Schwenk M, Lindemann U, Meyer M, Srijana KC, Hobert MA, Brockmann K, Wurster I, Pomper JK, Synofzik M, Schneider E, Ilg U, Berg D, Maetzler W, Becker C. Association between vestibulo-ocular reflex suppression, balance, gait, and fall risk in ageing and neurodegenerative disease: protocol of a one-year prospective follow-up study. BMC Neurol. 2015 Oct 9;15:192.
  4. Thomas NM, Bampouras TM, Donovan T, Dewhurst S. Eye Movements Affect Postural Control in Young and Older Females. Front Aging Neurosci. 2016 Sep 16;8:216. eCollection 2016.
  5. Fall Risk Factors in Mid-Age Women: The Australian Longitudinal Study on Women’s Health.
  6.  kandel & Schwartz. Principles of Neural Science. 5th edition, 2012.

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