To this day, imaging is deemed as the ‘gold-standard’ for analysis of all related head trauma. In the case of mTBI, a means of excluding more defined or pronounced injury such as a bleed.  

The obvious short-coming of is that this form of testing is impractical in most non- hospital related admissions. In particular in non-urban areas.  The bottom line; All imaging is grossly invasive and expensive.

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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.1. 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;

 - 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

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.2-4.


Due to the increased risk of iatrogenic malignancy when exposing pediatric patients to ionizing radiation from CT scans, researchers developed an algorithm (partially shown) to aid in the determination of which children presenting with TBI should undergo neuroimaging.  

The majority of children with mild symptoms and no dangerous mechanism of injury do not require CT evaluation and can be observed for the development of concerning signs/symptoms, such as altered mental status, intractable vomiting, or worsening symptoms.9.



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Although positron emission tomography (PET) scanning and functional MRIs (fMRIs) may be used, their clinical application in most cases of mTBI is uncertain.5-8.

References

1. Stein SC, Ross SE. Mild head injury: a plea for routine early CT scanning. J Trauma. 1992 Jul. 33(1):11-3. [Medline].
2. Ptito A, Chen JK, Johnston KM. Contributions of functional magnetic resonance imaging (fMRI) to sport concussion evaluation. NeuroRehabilitation. 2007. 22(3):217-27. 
3. 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. 
4. 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.

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

6. Ptito A, Chen JK, Johnston KM. Contributions of functional magnetic resonance imaging (fMRI) to sport concussion evaluation. NeuroRehabilitation. 2007. 22(3):217-27.            

7. 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.              

8. 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.​

9. Kuppermann N, Holmes JF, Dayan PS, et al, for the Pediatric Emergency Care Applied Research Network (PECARN). Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study. Lancet. 2009 Oct 3;374(9696):1160-70.