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is defined as a Glasgow Coma Score (GCS) of 13-15, although some authorities believe a GCS of 13 should be considered moderate (GCS 9-12). A GCS of 15 is completely normal. You lose one point if: you only open your eyes when told to (rather than spontaneously), your best verbal response is confused rather than oriented, or your best motor response is a localized response to pain rather than obeying commands to move. Concussion is a subset of mild traumatic brain injury defined by the American Academy of Neurology as “a trauma-induced alteration in mental status that may or may not involve loss of consciousness”. In addition, concussion typically refers to the rapid onset of short- lived impairment in neurologic function. However, the symptoms may take minutes to a few hours to start after the trauma and they may not be “short-lived”. Concussion is limited to cases where x-rays of the skull and CT of the head are normal.


Among patients who present to a hospital with a GCS of 15, the CT will be abnormal in roughly 5% of cases, while a GCS of 13 is associated with abnormalities on CT of 30%.


The first question that must be answered after a brain injury is whether the person has bled or is continuing to bleed inside the skull. Typically, this is determined by CT of the head. Symptoms that continue to get worse are a strong indication for a CT to look for bleeding. The Canadian CT head rule requires a CT if there is: a GCS of <15 two hours after the trauma, suspicion of


Symptoms that continue to get worse are a strong indication for a CT to look for bleeding


a skull fracture, two or more episodes of vomiting, age greater than 65, amnesia of longer than 30 minutes before the trauma, significant trauma (falling more than 3 feet (1m) or 5 stairs), any neurologic deficit, seizure or an increased risk of bleeding.


Determining whether a CT of the head is required is very complicated and the individual should be evaluated by a physician soon after any significant head trauma. The definition of concussion is a bit vague and the frequency of concussion is difficult to determine. Many cases of concussion are never documented because the person does not seek medical care. I found one estimate of concussion in the United States at 1.75 million per year. I also found estimates of concussion due to sports in the USA up to 3.8 million per year. This suggests the total incidence could be several million per year in the US alone.


Sports with the highest risk of concussion are American football, ice hockey, European football (soccer), boxing and rugby. Athletes in these sports have a risk of concussion of up to 20% per year. Non- sports causes of concussion tend to be motor vehicle accidents, falls, occupational and recreational accidents and assaults. Concussions are most common between the ages of 15-34 (active) and in the elderly (falls).


Symptoms


The classic symptoms of concussion are confusion and amnesia that start within a few minutes of the trauma. Loss of consciousness does NOT have to occur and is relatively rare in sports-related concussions. The


person typically cannot remember the traumatic event but they may also not remember events before or after the injury. Sometimes they ask the same question several times because they do not remember asking the question or the answer.


Other symptoms include headache, dizziness (vertigo or imbalance), lack of awareness of surroundings, nausea and vomiting. Later the person may develop mood and cognitive disturbances, sensitivity to light and/or noise and sleep disturbances. Most of my patients who have suffered a concussion complain of sensitivity to screens (phone, tablet, computer, TV) and florescent lights.


Seizures can occur after concussion but they are relatively rare in mild traumatic brain injury and 50% occur within 24 hours of the trauma. You should not dive for a month after a concussion or mild traumatic brain injury because of the risk of seizure. If a person has a seizure, their risk of developing post traumatic epilepsy increases four-fold to almost 25%. Seizures are relatively common after more severe head trauma. In the case of severe head trauma, diving should be avoided until the risk of seizure declines (one to three years, depending on the severity of the injury). Everyone who suffers a significant head trauma should be observed for 24 hours, as most serious problems will become apparent during that time period.


Post-trauma


Most people who suffer a concussion will completely recover in less than two weeks. Testing of motor function or cognitive function after a person has recovered from a concussion is standard. However, some recent research conducted at the University of Alberta, where they tested both motor and cognitive function at the same time, found abnormalities in almost everyone who had EVER suffered a concussion. This suggests that most people who suffer a concussion are left with a small amount of damage.


The data is not great but it seems likely that repeat trauma results in greater damage and a higher risk of long term problems. Boxers with more than 20 professional fights (and presumably a lot of concussions) frequently have significant neurological problems.


Post-traumatic headaches are relatively common but there are many possible causes other than the injury, including psychogenic, psychosocial, sociocultural, base rate misattribution, chronic pain, compensation, litigation and malingering.


The risk of developing epilepsy is double for five years after mild traumatic brain injury when the person did NOT have a seizure soon after the injury. The risk is higher if the person had a seizure. Fifty percent of the seizures will occur within one year of the injury and 80% within two years. Post-traumatic vertigo (world spinning dizziness) can occur after concussion but appears to be relatively rare.


Other cranial nerve injuries also can occur with a frequency of around 0.3% (3 per 1,000) and include: changes in taste, smell, double vision, facial pain and occipital neuralgia.


Chronic traumatic encephalopathy seems to occur after repeated head trauma (20% of professional boxers). The risk dying from a neuro- degenerative disease was three times higher than the general population for retired National Football League players and the risk of dying from Alzheimer’s disease was four times higher.


Post-concussion syndrome is the persistence of symptoms longer than two weeks after a concussion. It is common, controversial, and interesting, so I will review it in the next column.


Diving After a Concussion


The return to sports, including diving, after a concussion is controversial and the recommendations are based on consensus rather than evidence. It seems fairly clear that the risk of a future concussion is increased after every concussion. It also seem clear that athletes who return to play while they still have symptoms of a concussion have an increased risk of another concussion with more serious and persistent symptoms. I will look at this problem in greater detail in the next column but as a minimum you should not return to sports and diving until ALL of the signs and symptoms from the concussion have resolved and any soft tissue damage has completely healed. At a minimum you should wait for a month due to the risk of seizures.


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