Brain Imaging

Occasionally neuroimaging may be required to assist in the diagnosis and ongoing management of player who has suffered a head injury.
Bleeding into or around the brain and swelling compressing it can be verified on CT or MRI and appropriate intervention instigated.
However it is important to remember that none of these studies diagnose concussion, which may be present even if there is a normal scan.
A number of new technologies are being investigated to assist in the diagnosis and management of concussion.

• CT scan initially
• Consider magnetic resonance imaging (MRI) if more prolonged recovery
• Remember, CT scan does not diagnose concussion
• Also, normal CT scan ? No concussion !!!
• Newer imaging (primarily research role)
  • Functional magnetic resonance imaging (fMRI)
  • Positron emission tomography (PET)
  • Single-photon emission computed tomography (SPECT)

And of course for most levels of sport, the sophisticated radiological techniques are not available or indeed helpful on the sideline.

• Standard CT and MRI do not show concussion, only bleeding
• Intracranial haemorrhage may be amendable to surgery, but is not concussion
• Not currently available or helpful on the sideline

Diffusion Tensor Imaging is a new technique which may be helpful in showing functional changes to normal brain activity.
It may also be able to demonstrate bio markers to assist in the diagnosis of concussion.

Diffusion Tensor Imaging (DTI)

• The standardized CAT and MRI brain scans may appear to be normal in concussion patients, but these techniques do not pick up tears in the white matter.
• White matter links areas of gray matter to produce thinking functions of the brain, such as attention and memory.
• If the white matter is damaged by a concussion, the connections get disrupted and attention and memory are affected.
• Scientists have shown white matter damage correlates with attention and memory problems.
• A new technology called DTI, or diffusion tensor imaging, uses advanced software to get more detailed information from an MRI to obtain images of the white matter damage.
• It can also be used to show “damage metabolites” or biomarkers

The circled front part of a DTI brain scan shows the most common site for tearing in the white matter in concussions.

Diffusion Tensor Imaging studies are being used to track concussion and to ultimately predict outcomes form single or multiple concussive or sub-concussive events.
Using magnetic resonance imaging (MRI), measurement of the signal attenuation from water diffusion is one of the most important contrast mechanisms. Diffusion Tensor Imaging (DTI) may be used to map and characterize the three-dimensional diffusion of water. Estimates of white matter connectivity patterns in the brain are obtained using DTI reflect nerve and brain function.

In the spectrum of mild Traumatic Brain Injury in sports, it may well be the case that a single injury can cause lasting and long-term effects, and it is also likely that the cumulative effects of multiple sub-concussive impacts lads to similar long-term consequences.

Studies like this can track both acute injury and long term functional changes following concussion or in athletes who may have suffered head injuries that were never recorded as concussions or which were sub-concussive.

Studies investigating manifestations of previous concussions in American football have used techniques such as electroencephalography(EEG) and Transcranial Magnetic Stimulation (TMS) to investigate the underlying neurobiology of long-term concussion.

TMS uses electromagnetic induction to induce weak electric currents using a rapidly changing magnetic field to cause activity in specific or general parts of the brain with little discomfort, allowing for study of the brain’s functioning and interconnections.

This study by Pearce et al using TMS demonstrates that acutely concussed Australian Football players show abnormalities in motor, cognitive and neurophysiological measures with variable rates of recovery.
These findings suggest that measuring the recovery of concussed athletes should incorporate a range of testing modalities rather than relying on one area of measurement in determining return to play.

This study by Pearce et al using TMS in retired AFL Australian Footballers is the ?rst to demonstrate differences in motor control and intracortical inhibition in players who had sustained concussions during their playing career two decades previously.

Twenty participants had played professionally at the elite level (AFL), whereas 20 sub-elite players had played at amateur levels. Both groups were compared with 20 age-, education-, and gender-matched healthy participants who had never received a concussion injury.

This study has shown, for the ?rst time, that repeat concussion injuries in AF players manifest as changes in ?ne dexterity, visuomotor reaction time, and intracortical inhibition, quanti?ed by TMS.

Moreover, these changes were observed in both retired elite and amateur players, showing that repeated concussions have long-term outcomes regardless of the level or standard of competition that a player participates in,