Radiologic imaging of sports-induced brain injuries

TBI can occur in a wide range of sports activities. Lesions are most commonly caused by impact (contact sports) or activities involving high velocity. Acute sports-related injuries are indistinguishable from head trauma sustained in other accidents. Recurring craniocerebral injuries, such as in sustained in contact sports, can lead to chronic traumatic encephalopathy (CTE). This condition is a tauopathy, which is caused by repetitive mild traumatic brain injury (mTBI). Players of contact sports, such as rugby, hockey, boxing, or American football, have an increased risk of acquiring this condition. Imaging studies play an important role in the diagnosis, management, and follow-up of sports-related TBI. CT remains valuable for the detection of intracranial hemorrhage, skull fractures, and mass effect; unfortunately this technique is less sensitive for lesions such as diffuse axonal injury (DAI). Therefore, whenever there is a discrepancy between the clinical status of a patient and the CT findings, MRI should be used. MRI is becoming increasingly important for diagnosing parenchymal damage in sports-induced injuries. New sequences, such as susceptibility-weighted imaging (SWI), are very useful to detect microhemorrhagic foci. Diffusion-weighted imaging (DWI) and especially diffusion tensor imaging (DTI) provide quantitative measurements (such as FA, MD, ADC) which can be used as biomarkers for outcome prediction. Lower fractional anisotropy (FA) and high lesion count and volume have been related to poorer functional outcome. Other useful imaging modalities are 1 H-magnetic resonance spectroscopy (1 H-MRS), functional magnetic resonance imaging (fMRI), and positron emission tomography (PET).