As the bubble of the older generation moves through the longer life cycle, more and more older people will be falling down, probably breaking bones in the process because their balance networks have silently degraded away. What can anyone do about an elderly patient in a hospital who needs constant support? Japanese researchers have created the human assist robot. Instead of requiring one assistant per patient, which will never be possible, multiple robots could instead attach themselves to patients, mobilizing the patients to perform the variety of tasks that patients need to execute in a hospital environment. What’s so important about balance, you may ask, what does it have to do with concussions too??
The eyes motions are especially vulnerable following a concussion. Surprisingly concussions appear to accelerate aging of different systems within the brain. The latest concussion understanding is the following insight: concussions affect different control systems within the brain that self repair at different rates of healing. Concussions definitively affect the eye physiology which has been reported by both NHL players, Guillaume Latendressse and Sidney Crosby. Each player received multiple 70+ GyroStim pitch/roll/spin gyro chair treatments that appears to have reestablished their eyes to their brain vestibular system, as a component of their post concussion healing processes. So the question becomes: how does balance work in the human body? One way to appreciate balance control is to build a robot to keep somebody upright whose tendency is to fall over all the time, someone with very flawed balance capacity, the aged patient or the badly concussed patient with vertigo. Lets look at how such a robot might control balance of posture so when the robot is attached only to the legs-waist-torso portion of the patients body, what does the robot have to do to accomplish balancing a person? What does the robot have to sense to correct and maintain what we call normal upright posture? Pay attention here because this is how we will diagnose a concussion one day, by finally understanding the examining how the eyes become concussed deregulated loosing central balance control by delinking off the vestibular network.
I am sourcing from an IEEE paper entitled Human balance measurement and human posture assist robot design from Kanagawa Insititute of Technology Department of System Design Engineering by Yoshihiko Takahashi, Hideyuki Takahashi, Kouichi Sakamoto and Shinnobu Ogawa. The authors constructed a working prototype robot capable of raising a patient who happens to fall down by sensing his balance. Human balance in this scenario is sensed and detected as vertically oriented posture among a trio of sensors with strain gauges acting on two moveable artificial joints, an ankle and a waist with a foot force pad. The strain gauges help the robot judge the balance of the attached patient. The robot design had a two link design where both links are actuated and detected by DC motors and potentiometers.
Basically according to the authors, they noticed that a person keeps his balance by mainly moving the ankles and the waist to keep his balance. Hence they opted to build a two link structure and a foot. Essentially mimicking a trunk and a leg, with a manually moveable knee joint to increase flexibility of the robots posture. Both angles from ankle joints and waist joints are detected by potentiometers and the DC motors actuate or move both joints. The authors resolved the state of human balance as distinguishable according to the load on the back of the foot. The strain gauges were positioned on a 3 mm metal plate one under the tiptoe and the second under the heel, When a person inclined forward against the strain gauges, a small angle of the ankle was detected which increased as the waist also bent. until 4 degrees of ankle became the limit a person could maintain only using his ankle movement, termed as Link 1 The second strain gauge angular movement was much smaller since only minor waist bending is need to accomplish moving the center-of-gravity core using only waist bending over the foot, termed as Link 2.
The posture is detected through the strain gauge output and the potentiometer output, moving the robot through a personal computer judging the human posture to move the robot to maintain the balance of the attached patient. Assuming if the patient leaned forward the strain gauge output was negative and if the patient leaned backward the strain gauge output was positive. Link 1 was only moved in the case the angle was a small ankle and the link 1 is moved in the opposite direction of the human movement. The link 2 is moved so that the angle between the link 1 and link 2 becomes zero when ankle and waist are moved together. The control system evolved to limit the range of posture to guide the robot movement angle to the strain gauge output, balancing the tipping forward to limits on the ankle to bending back ward only a small angle, stopping any movement past the tipping limits. The established desired positions were fixed in the vertical position of the robot using 4 inputs and 2 output systems via the computer control program to control output voltage by actuating the two DC motors of link 1 and link 2. Once the comparison from the vertical was made against the two outputs of the strain gauges and the two potentiometers, the difference of the strain gauge output was calculated and the strain gauge output was obtained. The computer program compared this state depending on the positive, negative and magnitude of the strain gauge output. The final recovery movement control is made after calculating the position errors to the desired values. Control experiments were made to ensure the robot could self stabilize the patient after severe 10 degree stabilization angles were started using the link1 and link 2 with both responses converging when the links were started simultaneously, with a sampling time of 8 msec.
Now notice some very important differences here with reality. First the robot does not move, the feet are attached so the patient links into the robot attaching with the feet, legs and waist. The system is capable of detecting and righting a tilting person say over a bed or a bath without the need for an attendant to stabilize him from falling into a hot bath. But we’re not talking about a moving robot that walks over to to the bath and leans the person over say to wash their hair. Now a whole different complexity is introduced with the friction of the floor, the center of gravity of both the patient with the robot. Things jump into the third dimension X Y Z. But in terms of educating the appreciation of what we do with normal balance is to make a huge appreciation for what we do automatically. So back to concussions with an attached robot to our body. What can we learn from controlling such a robot? I think lots more, here goes.
When we age and slowly lose our balance finesse we tend to sway more, is it because our balance is off, but what about our eyes what about the acuity does that figure into the degradation of the aging of balance? The answer will no doubt surprise you, yes, the acuity matters. So as we lose the fine details of vision the relationship of things like the peripheral perception of the horizon are also off. Our bodies adjust to this as we age but not enough. So where does concussions come into all of this? Balance control is subtly without our conscious appreciation off following a concussion. Our eye motion system, how we pivot our eyes, how we actually fix and hold onto a gazed object is no longer smooth, we make significant tracking errors which become delinked into our combined vestibular system. Concussed people, like Guillaume Latendresse use the term “…I felt like I was in a fog.” If I understand their description, that ‘fog’ is the visual aspect of the delinked vestibular-ocular component that has not recovered its normal equilibrium. The robot of control has lost the potentiometer swiftness and accuracy of our brain control program that is running our torso leg ankle foot meshlink. That is the reason eye linked balance is such an important measurement to make by comparing baseline to altered eye specific balance control after a concussion.
What is the evidence for eye movement dysfunction following concussion? Significant observations have been reported by the Christchurch Brain Research Group from New Zealand profiling the eyes oculomotor functioning incorporating several cortical and sub-cortical structures as well as the cerebellum. The group has reported these eye control networks are susceptible to concussive impact injuries, causing deficits of volitional saccades, sequences of memory-guided saccades and self-paced saccades, while reflexive saccades remain unaffected.
Dr Laura Balcer,a professor of neurology and ophthalmology from the University of Pennsylvania School of Medicine has observed that, ..” eye movement provides a window into overall brain function,” emphasizing that, “Fifty percent of the brain’s pathways are devoted to vision.” A 1976 test originally designed as an occulomotor test for eye/learning evaluation called the King-Devick is based on the subtle, constant vibration in the eyes, called saccadic movements, which allow them to focus on specific spots has now been adapted to test the post concussion effects on eye control. Published in 2011 the journal Neurology, the King-Devick test consists of a person reading a row of single-digit numbers arrayed on a page. Some numbers appear in a straight line from left to right, and other numbers are arranged in a staggered fashion across the page. The time it takes a person to recite the numbers after a head trauma is compared to a baseline timing before any head trauma. The study administered to a group of 39 boxers and martial arts participants before sparring matches. After a nine-minute bout, the athletes were retested and the time it took to complete the test was logged then compared to the baseline before the sparring match. Some athletes suffered a concussion took on average six seconds longer to complete the test. The results were even longer if a loss of consciousness occurred with the concussion. The King-Devick test was compared to a longer more comprehensive test called the Military Acute Concussion Evaluation (MACE) as a comparison. The tests although preliminary are pointing to a quick easy to use sideline assessment of evaluating concussion by testing eye function. Since eye function is affected so too is balance function linked with eye function, somewhere in that 50% of the brain’s pathways.