The answer lies in the anatomy of the innervation of the iris. Pupillary dilation is mediated by the sympathetic division of the autonomic nervous system. (Hypothalamus --> ciliospinal centre (at levels T1-2) in the spinal cord --> preganglionic... read more
Pupil dilation is itself not indicative of brain injury. Pupil dilation is a normal response to darkness, and occurs as part of the fight or flight response. The size of the pupil is under the control of the sympathetic nervous system. read more
Brain Injury or Disease Pressure that builds inside your brain after a head injury, stroke, or tumor can damage the muscles in your iris that normally make your pupils open and close. One or both of your pupils can become fixed in the dilated position and can’t react to light. read more
Traumatic brain injury (TBI) is a common and often devastating condition with a wide spectrum of severity. At the most severe end of the spectrum a fixed and dilated pupil (FDP) in a comatose patient has long been recognised as both a Âneurosurgical emergency and a grave prognostic sign. read more