Oct 9, 2020
This podcast presents, Dr. Ron Tarrel, a Neurologist with Noran Neurological Clinic, who talks about brain injuries, specifically concussions, including symptoms and when follow-up is needed.
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Mechanisms, Pathophysiology, and Testing.
When we define concussion or brain injury, it's not only about the physical damage, but interruption of the physiologic process of the brain.
Unfortunately, there is not a nice, neat set of symptoms and the phrase traumatic brain injury seems to be a catchall phrase. Different mechanisms will affect our brains differently, but not uniformly. Whiplash can cause myofascial tissue damage in the cervical spine, affecting proprioception and balance. There are blunt trauma mechanisms causing fractures and or penetrating injuries to the brain. In addition to high energy explosions, causing thermal injury as well as particulate projectile injuries; and there are shearing injuries.
Briefly the different types of mechanisms/forces that lead to injury were discussed, including a deeper dive into ballistic, penetrating blunt force, blast/explosive wave, energy/thermal and shear injuries. Additionally, Dr. Tarrel discusses items that occur on the cellular level, however per TBI outline provides a more comprehensive list of metabolic dysregulation - such as: CPP, metabolic dysfunction, inflammation, apoptosis, axonal injury.
There is a variety of cognitive tests mentioned in this podcast, including the Slums exam, the mini mental status, sac, and the Skat 5 tests. Many are used in the field for assessment and represent a quick look at a singular moment in time. These tests help diagnose injury, but have limitations in terms of prognosis. The same can be said for impact testing for kids. These tests can provide a good baseline prior to an injury which helps in future diagnosis, but does not predict risk for injury.
Is there utility for lab workup in this patient population? Currently, the community is investigating Tau proteins, which are a brain derived neurotrophic factor. These trophic proteins have to do with inflammation and breakdown of normal homeostatic tissue. It has not been determined what is actually happening when a Tau protein is released. This continues to be an ongoing area of research.
Symptoms...so let's say we have this patient...
Symptoms we are looking to investigate would be penetrating injury, skull fracture, loss of neurologic function, weakness, etc. Does the patient exhibit ataxia or disequilibrium? Are symptoms progressing? What is the level of awareness or consciousness? Signs of increased ICP or focal deficits. This patient would require an initial head CT and possibly an MRI.
When is discharge appropriate for these patients? Sometimes patients aren't able to give you specific information to look for the problem. Their complaints are generalized, and vague. You have to pay attention to these symptoms, but you might have to wait for the dust to settle and patient remains asymptomatic continue to observe for signs and symptoms.
Patients that have a loss of awareness or even vague changes should have a follow-up visit. Upon return if they are symptom free and have a negative neuro exam, further imaging would not be necessary. However, if there are symptoms, even some that seem vague like an imbalance, or "just not feeling right". Then further work up would be beneficial. A key takeaway here is that vague symptoms can challenge clinicians, but it's important to take these patients at face value.
Does follow up have to be with a neurologist? There are many neurologists that do not treat concussions. Head injuries have been a mainstay of the neurosurgery field, but also orthopedists are often sideline physicians that can specialize in concussions and would be appropriate for follow up.
Societal Pressure and Treatments.
There's a certain pressure to clear concussions early and allow individuals to resume their regular activities. However, concussion protocols call for a gradual return to activity post event. Returning too fast and trying to force the brain to work only promotes "misfires" in the brain.
Treatment starts with reduced activities; low light stimulus, decreased physical activity, and limited, if any, screen time. Then, slowly, activities can be reintroduced, one at a time like steps on a ladder. If the patient tolerates the dark room, turn on the tv and watch nonsense. If that goes well, eat dinner with family, walk around the block. Slowly add in activities. If symptoms return, the patient takes a step back down the ladder, returning to the previous activity they were able to tolerate. The length of this process all depends on the individual, their symptoms, and their personal rate of recovery.
Other important aspects of recovery include a normal sleep wake cycle and adequate pain control. In a normal sleep wake cycle with adequate sleep, CSF is turned over twice as fast as nonopioid treatment. Opioids are good pain relievers, but also serve as a mood and energy suppressants. They are good medications when used appropriately. Non-opioid medications include, Tylenol, aspirin, if bleeding risk is low, and gabapentin. Gabapentin has been found to be a good baseline medication for TBI patients.
There is a mental health component to traumatic brain injuries. Those with underlying depression are more likely to develop severe symptoms post a TBI event.
Traumatic Brain Injury: Brain Dysfunction resulting from some external force
- Incidence rates of 1/6 to 3.8 million in sports in the US annually.
--As you might imagine, there is a lot of physics and chemistry behind our understanding of concussion and the forces that lead to head injury.
- BALLISTIC: Ballistic injury generally refers to projectiles and their flight. Factors that influence the severity of ballistic injury include force speed and the direction of impact.
- PENTRATING INJURY: Penetrating injury is just that. An injury that pierces and enters the skull directly causing direct tissue destruction along with the penetrating forces.
- BLUNT FORCE INJURY: Blunt force injury is also direct physical force to the skull/head but without penetration
Impact of any kind not only triggers direct forces on the brain tissue itself, but there are complex cellular and molecular processes that lead to further dysfunction, neuronal dysfunction and cell death. There are multiple factors that contribute to this severity of injury that go beyond the initial impact.
The generally accepted formula for concussion is that it takes 90-100G's; the force of a object accelerating with gravity to cause brain/axonal injury. That can be equated to hitting a wall at approximately 20 miles/per hour. However, that does not determine the severity of injury of which multiple other factors play into.
1. Is "whiplash" a common
culprit in concussion?
Yes, to the idea that whiplash can cause concussive like symptoms. 100's and 100's of patients who suffered mechanical whiplash injuries who developed other changes including cognitive changes that would not necessarily relate to simple cervical spinal or spinal muscular injury. That is where the notion of shearing injury comes in and I will come back to that in a moment but I can also tell you that it works both ways. Patients with myofascial injury often develop a sense of dizziness or imbalance or vertigo. You can often tell the difference between true vestibular dysfunction, vertigo, and the feeling of dysequilibrium (some people use words like rafting or floating, etc.) or the sense of uncontrollable movement within their environment. There is a myofascial syndrome in which the normal resting length of muscles is affected related directly to, for instance, the neck injury. We have proprioceptive information from our spinal column to our brain which, based on normal resting length of muscle and muscle tension, provides information to our brain telling us when we are safe and stable within our environment. With soft tissue injury, specifically myofascial injury, injury to the muscle tissue and the fascial tissues which surround muscles individually and in groups, the resting length of muscle and fascial tension can change related to microscopic tearing or shearing of muscle fibers, inflammation and the body's own protective response which is for muscles to splint or spasm, or tighten up around an area of injury. This then leads to different proprioceptive information registered by the brain and one can get the feeling that he/she are off balance, floating, rafting, whatever because the normal resting length of our muscles in various positions has been altered in response to the injury and based on that, your brain believes your neck is in a position that is not. And the individual feels "off" in whatever way.
That same kind of shearing injury that we discussed affecting the spinal column, muscular and myofascial tissues also affects the brain and specifically the white matter or nerve tracts of the brain. Neurons have 2 specific components to them in regards to the delivery of information. First there are the dendrites which are nerve tracts that bring electrical signals to the nerve cell body and then long tails known as axons that take information away from the cell body, all in the white matter of our brain, not the thinking controlling cortical gray matter. These axons and dendrites live in a sort of ground substance in the brain and when forces are exerted on the brain tissue itself, just like the muscles and connective tissues around the spine, you can have a shearing injury that causes stretch and tearing to those tissues. This will necessarily affect normal transmission of electrical information from our cortex down to the spinal cord and information coming in from the body to the brain. So in other words, our thoughts and our commands coming out of our brain as well as how we register information coming into our brain is distorted because there is literally derailing of the information traveling in either direction. Obviously, how our brain interprets our world around us, our position in it, and how our brain organizes thoughts and responses to information can all be affected. This is believed the level of injury that causes some of the more subtle yet more confusing and difficult-to-treat symptoms that occur with a complex head injury.
- DESTRUCTIVE WAVEFORCE
Blast/Explosive wave, energy/thermal,
There are different mechanisms of blast injury created by the release of energy that can involve a wave of energy or heat and sometimes objects. One type of explosive device releases a "blast wave" causing the sudden release of expanding force emitting a pressurized energy impulse traveling out in all directions from the explosive center. These types of bombs affect air and fluid filled tissues especially, causing these tissues to burse (like a balloon filling up too fast). Thermal blasts will dramatically overheat objects in its wake (living and not). Finally, bombs can contain particles (e.g. shrapnel or nails, etc.) that can cause penetrating injury throughout a large circumferential area.
- Cellular and molecular changes
- Vascular autoregulation
- Metabolic dysfunction
- Axonal injury
The pathophysiologic changes introduced by traumatic forces into a living organ, specifically the brain, then cause secondary changes in the autoregulatory mechanisms in the brain that support maintenance of blood flow, intracranial pressure, perfusion pressure, oxygenation and energy availability and utilization. Brain injury triggers a cascade of cellular processes and disruption of that homeostasis, which leads to neural dysfunction and death and are the secondary forms of injury after trauma.
Our brains thrive on a very
exacting and delicate balance of energy and information going in
and energy and information going out And if you introduce anything
that alters that balance, it will lead to further brain
- Psychological changes
- Perceptual disturbance
- Alteration of sleep/wake cycles
- Sensory disturbances
- Environmental sensitivities
- Diagnostic Imaging
- CT or MRI initial image modality of choice
- Laboratory Testing
- Theoretical biomarkers but nothing that has been borne out.
- Cognitive Testing
1. Standardized evaluation
tools such as the SAC, SCAT5, Westmead, ImPACT for concussion may
have limited validity, especially if there is no baseline test.
Thorough Neurologic Examination
Although generally there are no hard findings.
- Activity Restrictions
- Functional Retraining
- Return to ADL's
- Return to work
- Return to sport
1. This is a BIG one.
According to a paper in Pediatrics 2015 by Thomas et al, there was
no added benefit in strict rest after concussion. This was a small
study. Are there other papers or ongoing research to support
2. In the McCrory P. et al. Consensus statement on concussion in sport—the 5th
international conference on concussion in sport held in Berlin, October 2016. Br J Sports Med. 2017; 51 : 838-847 advocates for a 6 step progressive re-introduction with 24 hours in between
RISKS OF RECURRENCE
- Recurrent injuries = cumulative and more permanent
- Pain management, sleep, psych, light exercise, etc.
- STATE HIGH SCHOOL SPORT ASSOCIATIONS
1) Centers for Disease Control and Prevention Guideline on the Diagnosis and Management of Mild Traumatic Brain Injury Among Children
JAMA Pediatr. 2018 November 01
2)Blast-Related Traumatic Brain Injury: Current Concepts and Research Considerations
Daniel W Bryden, Jessica I Tilghman, and Sidney R Hinds, II
3) A Review of the Molecular Mechanisms of Traumatic Brain Injury
Asma Akbar Ladak, Syed Ather Enam, Muhammad Talal Ibrahim
4) Management of acute moderate and severe traumatic brain injury
5) Concussion Diagnosis and Management Best Practices
NCAA Sport Science Institute
6) NFLPA Concussion Game Day Checklist Return-To-Participation Protocol
7) Traumatic Brain Injury Information Page
National Institute of Health
8) Management of Concussion and Mild Traumatic Brain Injury: A Synthesis of Practice Guidelines
Archives of Physical Medicine and Rehabilitation
9) Prevalence and Epidemiology of Combat Blast Injuries from the Military Cohort 2001 - 2014
10) Pathophysiology of Traumatic Brain Injury
Thanks for listening.