Concussion has been a big topic over the past two years or so and it has certainly featured in a couple of posts on this website. There is a lot about it that is still poorly understood.

There is a very helpful review article in the Seminars in Neurology journal written by Meeryo, Chloe and Giza, titled "Diagnosis and Management of Acute Concussion". It is available in full text for free on Medscape (which is also free to sign up with).



The article goes through pathophysiology as it is currently understood, looking at metabolic explanations for the basis of concussion. It then reviews the assessment and diagnosis of concussion and takes a fairly balanced view of the variety of resources available, from a simple history and examination to sideline tests such as the Maddock's Questions and the components of the SCAT and MACE tools and to pen-and-paper and computer based neuropsychiatric testing. It also comments on some of the CT and MRI imaging developments. Finally, the article goes through the pros and cons of the available management options, including the graded return to competition and cognitive restructuring.

Notably, the article does not discuss controversies such as the second impact syndrome or chronic traumatic encephalopathy.

Some of the interesting snippets that I took from this review were:

• There is a lot about the metabolic disturbances that may be associated with concussion that we don't yet fully understand and N-Acetylaspartate was completely new to me.
• The Balance Error Scoring System (BESS) score has a lot of problems, including wide inter-rater variability, sub-optimal sensitivity and specificity and confounding due to other injuries and a learning effect. It has also been suggested that balance recovers before the cognitive and behavioural deficits associated with concussion.

• The Modified BESS (mBESS) score, which uses only the firm ground portion of the full BESS, has no published sensitivity or specificity values.
• SCAT is on its third version, SCAT3, having modified some of the testing elements. It is made up of a composite of other scores, such as the mBESS, the Graded Symptom Checklist and the Standardised Assessment of Concussion (SAC). These individual scoring tests are said to have good sensitivity, specificity and validation, but I'm not sure that a false negative rate of up to 1 in 5 or false positive of 1 in 10 to 1 in 4 (for the SAC) are particularly reassuring.
• There is a SCAT3 for children, but the sensitivity and specificity values are untested.
• The ImPACT group now recommends that baseline testing is no longer required as the data registry that they have is now so large that it provides an adequate normative reference group. However, a study that used the CogState/Axon test as the control found that using a baseline reference provided better sensitivity and specificity values than a normative group. That said, I'm a bit unclear as to what makes the CogState/Axon test the reference standard as most of the literature on the CogState/Axon seems to come from either Cogstate itself or third party users.
  
• Reaction time assessment would seem to be a useful tool, especially as it appears that post concussion abnormal RT values return to normal pre-concussion values after the somatic, cognitive and behavioural symptoms resolve. There may, however, be some issues around a learning effect.
• There is increasing evidence that prolonged therapeutic inactivity after concussion may have worse outcomes than permitting a sub-symptomatic level of activity.

If you wanted to get an overview of the current thinking on concussion, this is a good article to start with. And now might be a good time to do just that, given that current and former American gridiron (NFL) players were recently awarded a pooled compensation of about US$1billion for concussion suffered during professional competition (though the NFL denies a link between concussion and neurological deficit).

Posts on concussion on the Rollcage Medic site