Concussion

Concussion was defined by a  panel of medical and neurological experts, the “Zurich Group”, at the 4th International Conference on Concussion in Sport in 2012 as “a complex pathophysiological process affecting the brain, induced by biomechanics forces'.1

Although concussions usually are caused by a blow to the head, they can also occur when the head and upper body are violently shaken. These injuries can cause a loss of consciousness, but most concussions do not. Because of this, some people have concussions and don't realise it.

The symptoms may begin immediately, or they may not develop for hours, days, weeks, or even months following the injury. The signs of a concussion may include:

 - brief loss of consciousness after the injury
 - memory problems
 - confusion
 - drowsiness or feeling sluggish
 - dizziness
 - double vision or blurred vision
 - headache
 - nausea or vomiting
 - sensitivity to light or noise
 - balance problems
 - slowed reaction to stimuli

Biomarkers

The term biomarker, refers to a broad subcategory of medical signs – that is, objective indications of medical state observed from outside the patient – which can be measured accurately and are reproducible.

Ultimately, biomarkers can be used to detect a change in the physiological state of a patient that correlates with the risk or progression of a disease/condition or with the susceptibility of a disease/condition to a given treatment. Biomarkers hold great promise for personalised medicine as information gained from diagnostic or progression markers can be used to tailor treatment to the individual for highly efficient intervention in the disease/condition process.

Imaging

a. Computed Tomography (CT) Scan

Indications for ordering a CT scan include focal neurologic examination findings, signs or symptoms of increased intracranial pressure, Glascow Coma Score (GCS) score less than 15, and seizures related to trauma. Some authors suggest that any athlete with loss of concussion (LOC) (grade 3 concussion), should have a CT scan obtained.2 This area is controversial. Athletes with a brief LOC are at no higher risk for long-term neurologic sequelae, and indications for imaging should not differ from those listed above.

CT scanning continues to be the imaging study of 'choice' in evaluating an acute head injury. Better imaging of an acute hemorrhage, speed of the methodology, and improved ability to monitor the patient are the reasons for using CT scanning rather than magnetic resonance imaging (MRI).

b. Magnetic Resonance Imaging (MRI)
MRI is the imaging study of choice for patients who have prolonged symptoms (> 7 days), or for a late change in an individual's neurologic signs or symptoms.

MRI offers a more detailed examination and possibly detects more subtle findings.

Delayed or slowly developing bleeds may be easier to detect on MRI.

c. Positron Emission Tomography (PET)

​Positron emission tomography (PET) is a medical imaging procedure that provides unique information about how an organ or system in the body is working. PET scans are mainly used to assess cancers, neurological (brain) diseases and cardiovascular (heart-related) disease. 

A PET scan involves the painless injection of a small amount of a ‘positron-emitting’ radioactive material (called a radiopharmaceutical). Images of the body are then taken using a PET scanner. The camera detects emissions coming from the injected radiopharmaceutical, and the computer attached to the camera creates two and three-dimensional images of the area being examined. 

Areas where the injected radiopharmaceutical gathers appear ‘brighter’ than normal tissues on the images.  

Almost all PET scanners today are combined with a CT scanner so that the PET images can be combined or fused with the CT images. This combines the structural information from the CT scan with the PET’s functional information and improve the accuracy of the test. 

​PET imaging can provide information about the biochemical function of the brain. As such, it is used to assess people with neurological diseases, including Alzheimer’s and Parkinson’s diseases, because the images can show areas of the brain that are functioning differently to normal.

​Specifically for TBI, it is 'early days' but there is some promise being shown in radio labelled glucose, and tracking how it is being taken up and or used in damaged tissue as opposed to surrounding healthy tissue. Similarly findings have been shown when specific radio labelled proteins have been used.

Although positron emission tomography (PET) scanning and functional MRIs (fMRIs) may be used, their clinical application in most cases of MTBI is uncertain.4-6

Neuropsychologic Testing

​​Assessment. This generally involves a neuropsychological test(s). Previous concussions, depression, anxiety, medication use, sleep disturbance or other factors can slow recovery or masquerade as concussion symptoms.
The neuropsychological test(s) will assess memory, attention, reasoning and other cognitive skills. Personality and mood tests can help the neuropsychologist understand if psychological factors are at work. Results of this evaluation will help identify ongoing cognitive impairments and specify what abilities have been most affected. Repeat testing can be useful to document improvement over time.

Treatment. A neuropsychologist will provide psychoeducation, teaching patients about common concussion symptoms and normal recovery patterns. For cases in which patients develop an abnormal focus on their symptoms or other problems, cognitive behavioral therapy can help.
In more serious cases, neuropsychologists may suggest a rehabilitation program. In this kind of treatment, patients practice memory, reasoning and other cognitive skills to retrain the brain, just like they might undergo rehab for a physical injury. The treatment may consist of computerised training at the neuropsychologist’s office and focused practice at home.

Detailed neuropsychologic testing is employed more often at the professional level and in research in athletes with MTBI.

When evaluating an athlete's performance on the neuropsychologic tests, it is best to compare results with the athlete's previous tests.

The National Hockey League (NHL), National Football League (NFL), Major League Baseball (MLB) as well as many college teams are utilising limited neuropsychologic testing to document the possible prolonged effects of presumed minor head injuries and to assist the clinician in determining possible retirement issues.

Neuropsychologic testing is indicated in cases of complex concussions.3

Transcranial Magnetic Stimulation (TMS) 

TMS is a well established non-invasive technique to objectively measure the central nervous system (Hallett, 2000) in both health and disease (Pearce and Morris, 2011). TMS comes in two forms: repetitive TMS (rTMS) which is used as a therapeutic device for psychological disorders such as depression; and single pulse TMS which is used by neurologists and neurophysiologists to diagnose neurological conditions including Parkinson’s disease, motor neurone disease, acquired brain injury (e.g. stroke) and traumatic brain injury (Kobayashi and Pascual-Leone, 2003)

Single-pulse TMS generates electrical impulses in the nerves going to the targeted muscles in the arm or hand which is recorded by an EMG (Electromyography), taped over the muscle to be measured (Pearce et al, 2000)

Each TMS pulse is unique to the individual, and changes in the concussed athlete or individual, making it an effective objective test of concussion and readiness to return to play (Pearce et al, 2014, 2015). 

TMS has been used in Australia to measure concussion in Australian football players (current and retired) and also recently in Rugby Union (Pearce et al, 2014).

1. Consensus Statement on Concussion in Sport-the 4th International Conference on Concussion in Sport Held in Zurich, November 2012. Clinical Journal of Sport Medicine. 2013;23(2):89-117.​ Paul McCrory et al.

2. Stein SC, Ross SE. Mild head injury: a plea for routine early CT scanning. J Trauma. 1992 Jul. 33(1):11-3. [Medline].

3. McCrory P, Johnston K, Meeuwisse W, et al. Summary and agreement statement of the 2nd International Conference on Concussion in Sport, Prague 2004. Br J Sports Med. 2005 Apr. 39(4):196-204.

4. Ptito A, Chen JK, Johnston KM. Contributions of functional magnetic resonance imaging (fMRI) to sport concussion evaluation. NeuroRehabilitation. 2007. 22(3):217-27. 
5. Henninger N, Sicard KM, Li Z, et al. Differential recovery of behavioral status and brain function assessed with functional magnetic resonance imaging after mild traumatic brain injury in the rat. Crit Care Med. 2007 Nov. 35(11):2607-14. 
6. Kirov I, Fleysher L, Babb JS, et al. Characterizing 'mild' in traumatic brain injury with proton MR spectroscopy in the thalamus: Initial findings. Brain Inj. 2007 Oct. 21(11):1147-54.

​Hallett M. Transcranial magnetic stimulation and the human brain. Nature 406:147-50, 2000.
Kobayashi M, Pascual-Leone A. Transcranial magnetic stimulation in neurology. Lancet Neurol 2(3):145-56, 2003.
Pearce AJ, Corp DT, Davies CB, Major BP, Maller JJ. Second time around: Corticospinal responses following repeated sports-related concussions within the same season. A transcranial magnetic stimulation study. Journal of Acute Disease 3(3):186-93, 2014.
Pearce AJ, Morris M. Exercise as therapy in neurological conditions. In. Clinical exercise: a case-based approach: Elsevier Publishing. ; 2011, pp. 68-83.
Pearce AJ, Thickbroom GW, Byrnes ML, Mastaglia FL. The corticomotor representation of elite racquet sport athletes. Exp Brain Res 130:238-43, 2000.
Pearce AJ, Hoy K, Rogers MA, Corp DT, Davies CB, Maller JJ, Fitzgerald PB. Acute motor, neurocognitive and neurophysiological change following concussion injury in Australian amateur football. A prospective multimodal investigation. J Sci Med Sport 18:500-6, 2015.
Pearce AJ, Hoy K, Rogers MA, Corp DT, Maller JJ, Drury HG, Fitzgerald PB. The long-term effects of sports concussion on retired Australian football players: A study using Transcranial Magnetic Stimulation. J Neurotrauma 31:1-7, 2014.