====== Pupil reaction ======

[[Pupil]] reaction to light (direct and [[consensual response]]).

The [[Glasgow Coma Scale]], together with information about [[pupil]] reaction, conveys to the physician most of the clinical predictive information in [[head injury]]
((Braakman R, Gelpke GJ, Habbema JD, Maas AI, Minderhoud
JM: Systematic selection of prognostic features in
patients with severe head injury. Neurosurgery 6:362–370,
1980))
((Marmarou A, Lu J, Butcher I, McHugh GS, Mushkudiani NA, Murray GD, et al: IMPACT database of traumatic brain injury: design and description. J Neurotrauma 24:239–250,2007))
((Steyerberg EW, Mushkudiani N, Perel P, Butcher I, Lu J,
McHugh GS, et al: Predicting outcome after traumatic brain
injury: development and international validation of prognostic
scores based on admission characteristics. PLoS Med
5:e165, 2008)).

Findings demonstrate that combining these features yields more informative data than using either alone, and that a simple arithmetical score, the GCS-P, performs almost as well as more complex methods of integration.

Brennan et al., used the two largest databases on head-injured patients, the [[CRASH]] and [[IMPACT]], in which information on early GCS score, pupil findings, and late patient outcome are available for individual patients. The total numbers of patients are similar in the two databases, but there are variations in their composition. The IMPACT database is skewed toward patients with severe head injuries (81%) compared with the CRASH database (39%), yet in the CRASH database there are few people with GCS score 15. 

Brennan et al., used a [[pooled data]] set to compensate for these differences and to increase the generalizability of the findings
((Brennan PM, Murray GD, Teasdale GM. Simplifying the use of prognostic
information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended 
index of clinical severity. J Neurosurg. 2018 Jun;128(6):1612-1620. doi:
10.3171/2017.12.JNS172780. Epub 2018 Apr 10. PubMed PMID: 29631516.
)).