What are Sub-Concussions?

By Published On: 03/08/20224.5 min read
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Sub-concussions occur when smaller-force head impacts cause brain injury without clinical signs and symptoms of concussion. This means individuals and those around them are not aware of this silent brain injury.

Sub-concussive injuries are “hidden in plain sight”, and are serious.

While individual sub-concussions do not cause concussion symptoms like dizziness, headache, nausea or vomiting, multiple sub-concussions can adversely affect memory and behaviour, as well as the ability to focus, learn and think. Critically, it can also increase the risk of Chronic Traumatic Encephalopathy (CTE). CTE is a progressive, neurodegenerative disease that leads to early-onset dementia.

In every sub-concussion, there are rotational forces present; these cause the brain to rotate inside the skull. This is associated with the tearing of tiny blood vessels and brain cells, resulting, over time, in the breakdown of the blood-brain barrier and the creation of damaging neuro-inflammation. Reducing rotational forces to the brain is essential to lower the risk of neuro-inflammation. Rezon Halos® reduces rotational forces by up to 61%.

How hard is a sub-concussive hit?

A sub-concussive hit is only a quarter to a half of the force required to cause a concussion.

And in children?

Between ages 8-12 is when peak development of the brain occurs. However, the brain continues to develop through the refinement and rearrangement of brain pathways and connections until early 20s. Axons are the tail-like structures that connect neurons in the brain and connect neurons to other cell types. These axons are coated in myelin, which improves how the electrical discharges transfer information along the axon – and this is crucial to healthy brain function.

Myelin is formed as the brain develops. Children and youths have less myelin than adults, and this is problematic because myelin protects the axon. Axons with little myelin are more exposed and prone to damage from sub-concussions. Less myelinated axons also don’t recover as well from injury as highly myelinated axons. This means children are more vulnerable to brain injury – their brains undergo noticeable changes, even if they were never diagnosed with a concussion.

The difference between concussions and sub-concussions

Concussions

A concussion is a brain injury. Also known as “mild” Traumatic Brain Injury (mTBI), it is caused by a single impact to the head and temporarily impairs brain function.

  • Concussion produces symptoms that an individual is aware of (e.g. headache, dizziness) or signs that another person can see (e.g. balance disturbances).
  • Symptoms of concussion can be physical, cognitive, and emotional, and can cause changes in sleep.
  • Concussion symptoms can be delayed, with an onset that ranges from hours to days after the concussion causing event.
  • Even after observable concussion symptoms subside, the brain takes longer to heal than the duration of observed concussion symptoms – the brain is still at risk for up to a year.
  • Concussion can cause both short- or long-term physical, cognitive, social, and emotional symptoms. These changes may lead to problems with memory, and communication, personality changes, and sleep disruption, as well as depression.
  • Concussion recovery varies, but most people appear to recover within four weeks. However, 15% – 30% of individuals develop Persistent Post-Concussion Symptoms (PPCS) and have an extended recovery time with cognitive, behavioural and emotional difficulties that can last for months to years.
  • Individuals with concussions were found to be twice as likely to die prematurely than the general population, with suicide and fatal injuries as the main causes of death.
  • An individual’s concussion history can be inaccurate by recall bias, poor detection, and misinterpretation of what concussion constitutes.

Sub-Concussions

A sub-concussion is a brain injury from a small-force impact, and displays no overt signs or symptoms of concussion.

  • Sub-concussion results from an impact of lower force than required to cause a concussion – typically a quarter to a half of the force required to cause a concussion.
  • Impacts that cause sub-concussion are 500 times more frequent than impacts that result in concussion.
  • A sub-concussion causes damage to the brain without any symptoms.
  • Multiple/repetitive sub-concussions can adversely affect memory and behaviour, as well as the ability to focus, learn and think.
  • The accumulated damage of sub-concussions (and not concussions) contributes to problems in later life such as mood, behaviour problems, and CTE (Chronic Traumatic Encephalopathy) – a progressive, neurodegenerative disease that leads to early-onset dementia.
  • Sub-concussion cannot be diagnosed in a clinical setting. However sub-concussive brain injury is detectable via sophisticated neuro imaging .
  • No safe threshold for sub-concussions has been proven.
  • While not everyone will suffer a concussion, they will typically take hundreds, and even thousands of sub-concussions in their lifetime.

Diagnosing sub-concussions

Sub-concussion is not diagnosed in a clinical setting, given the inability to yet diagnose sub-concussion with reliable testing. But sub-concussive injury is detectable.
Standard brain imaging scans (like CT in A&E departments) cannot show such small changes like sub-concussions. More sophisticated brain imaging like Diffusion Tensor Imaging (DTI) can identify the subtle changes in the brain from sub-concussive impacts. Functional Magnetic Resonance Imaging (fMRI) can show the activity of different brain areas during thinking and memory tasks.

Why sub-concussions are dangerous

Repeated sub-concussions affect brain cells and connections in the brain, damage the blood-brain barrier, and create inflammation in the brain. This means memory and attention is impaired, with mood and behaviour problems.

Sub-concussions create brain damage and can trigger life-changing, longer-term neurodegenerative consequences. That is why Rezon Halos® is focused on reducing the rotational forces of sub-concussive impacts, and protecting the brain in day-to-day activities.

Author: Judith McMinn

Image shows Judith Mcminn, Founder and CEO of Rezon, presenting about Rezon Halos® brain protection to an audience.
Judith McMinn is the CEO and Founder of Rezon. With an initial focus on protecting sports players and professional athletes from CTE (an early-onset dementia), our research found a significant and sizeable problem with brain injury for those with epilepsy, autism, balance issues, fainting, hydrocephalus, post-surgery recovery, seizures, and children on the spectrum. It is these stories of struggle and daily sacrifices, because of head impacts, that have shifted our focus. Halos® offers brain protection for every wearer.
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