## 8 Imaging  
Imaging is commonly used for diagnosis and screening and can reveal important findings in athletes with stingers [9; 10; 47]. However, the absence of definitive recommendations or guidelines makes imaging indications a controversial subject [48]. A study by [PERSON] and [PERSON] on expert opinion and controversies mentioned that the findings of imaging were not always clear [18]. A recent modified Delphi consensus study with the Cervical Spine Research Society by [PERSON] et al. showed a super majority (69.9%) of spine surgeons agreed that athletes who experience first-time stingers and symptoms lasting from seconds to less than 5 min need no imaging studies [10]. This contrasts with the old consensus of considering imaging for symptoms that last longer than one hour [18]. [PERSON] et al. also showed that a super majority (84.5%) of surgeons agreed that further consideration, including imaging, is indicated if the symptoms persist for more than 5 min or if athletes have more than one episode of stingers, regardless of the duration of symptoms [10]. Essential imaging included cervical radiographs with anterior, posterior, lateral flexion/extension, and odontoid views, as well as MRI [5; 6; 18]. CT scan was reported as an alternative for those who cannot perform MRI [5; 6; 18]. Single-photon emission computed tomography (SPECT) was also reported to facilitate the diagnosis of an occult cervical vertebra fracture [8].  
Chronic stingers are believed to result from degenerative anatomical changes in the cervical spine [5; 19; 24; 25]. Hence, imaging can possibly identify those at risk of sustaining stingers based on changes observed in the imaging. [PERSON] et al. described the Torg-Pavlov ratio to confirm and screen for stingers (Figure 3A) [7]. The Torg-Pavlov ratio is determined by dividing the distance from the midpoint of the posterior aspect of the vertebral body to the nearest point on the corresponding spino-laminar line by the anteroposterior width of the vertebral body on a plain radiograph [7]. According to [PERSON] et al., 95% of all reported cases had a Torg-Pavlov ratio of <0.8 [7]. However, a very low positive predictive value for asymptomatic athletes makes this measurement insufficient for screening [49]. The role of MRI in screening is also a recent novel development. While studying the changes in the sub-axial space for chronic stingers, [PERSON] et al. determined the mean sub-axial cervical space available for the cord (MSCSAC) [19]. MSCSAC is the average of the values determined by subtracting the sagittal cord diameter from the disc-level spinal canal diameter between C3 and C6 [19] (Figure 3B) and is a better alternative to the classic Torg-Pavlov ratio [19]. This novel measurement has a sensitivity of 80% and a negative predictive value of 0.23 for stingers when 5.0 mm was used as a cut-off. When a cut-off value of 4.3 mm was used, MSCSAC had a 96% specificity with a 13.25 positive likelihood ratio. [PERSON] et al. also found that these measurements are 20% more accurate than the classic Torg ratio [19]. Other novel measures used to objectively identify cervical spinal canal stenosis are cord-to-canal area ratio (Figure 4A), which is the ratio of transverse cord area to transverse canal area, and cord compression ratio (Figure 4B), which is the ratio of sagittal to axial cord diameter (a/b in Figure 4B) [27]. These measures are highly predictive of individuals at risk for cervical spine injury after minor trauma and can indirectly predict those at risk for chronic stingers.