Secondary Impact Syndrome: Symptoms & Complications

Instructor: Joshua Bowles

Joshua is a Sports Medicine and Athletic Training Instructor and has a Master's degree in Kinesiology.

In this lesson, we will discuss the brain injury known as Secondary Impact Syndrome. We will cover how this condition can occur and what the symptoms and complications from this injury look like.


Anyone who has ever watched a football game or a hockey game has seen a few big hits. Some of those big hits probably resulted in an injury known as a concussion, which is a mild traumatic brain injury that involves a blow or violent movement of the brain. And although concussions are a given from time to tine with collision sports, there are more serious brain conditions. Concussions are a precursor condition that can lead to Secondary Impact Syndrome, a rare but often very serious secondary condition.

Traumatic Brain Injury

When it comes to the brain, no injury is more publicized right now than concussions. And while concussions are serious in their own right, many individuals heal properly and return to normal activity when they follow sound medical advice.

Secondary Impact Syndrome, sometimes referred to as Second Impact Syndrome or SIS for short, is a traumatic brain injury that occurs when a second or multiple blows have occurred to the brain before the brain is able to fully heal properly from the concussion. When this occurs the brain swells rapidly. Unlike most other areas of the body when swelling occurs, the body is able to compensate for the swelling by the skin or other tissues stretching out.

The brain is encased inside the skull, which does not expand like most other areas. If the brain swells too much inside the skull it can have catastrophic results. Secondary Impact Syndrome is often fatal for many individuals or leaves them with serious disabilities.


Symptoms of Secondary Impact Syndrome are similar to symptoms of a concussion but are often worse. The most common symptoms that mirror concussion symptoms include:

  • nausea
  • severe headaches
  • trouble focusing
  • loss of memory.

The most serious symptoms of Secondary Impact Syndrome include:

  • loss of eye movement
  • respiratory failure
  • unconsciousness
  • death


Because Secondary Impact Syndrome causes intracranial edema, swelling within the cavity of the skull, possibly leading to a potential rupture of the blood vessels in the brain known as intracranial hemorrage; complications are likely to occur leaving the individual with some form of impairment, even in the best of conditions.

Due to the serious nature of this injury, Secondary Impact Syndrome is classified in the medical community as a medical emergency, meaning the treatment for this injury must be immediate to provide the individual the best possible chance to recover.

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