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Nerves involved in the resizing of the pupil connect to the pretectal nucleus of the high midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus neurons send axons to neurons of the Edinger-Westphal nucleus whose visceromotor axons run along both the left and right oculomotor nerves .
A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation.
Purtscher's retinopathy was first characterized in 1910 and 1912 as a syndrome of sudden blindness after head trauma, [7] with patches of hemorrhage and whitening of the retina in both eyes. [3] Later, it was discovered to occur after other types of trauma , such as chest trauma, and is associated with several non-traumatic systemic diseases. [ 3 ]
For more than 100 years, clinicians have evaluated the pupils of patients with suspected or known brain injury or impaired consciousness to monitor neurological status and trends, checking for pupil size and reactivity to light. [3] In fact, before the advent of electricity, doctors checked a patient’s reaction to light using a candle.
The Neurological Pupil index, or NPi, is an algorithm developed by NeurOptics, Inc., that removes subjectivity from the pupillary evaluation. A patient's pupil measurement (including variables such as size, latency, constriction velocity, dilation velocity, etc.) is obtained using a pupillometer, and the measurement is compared against a normative model of pupil reaction to light and ...
The sign is considered ominous because it is commonly associated with a distortion of the brain stem that can cause serious dysfunction evidenced by abnormal posturing and failure of the pupils to constrict in response to light. [1] Midline shift is often associated with high intracranial pressure (ICP), which can be deadly. [1]
[5] [6] In a comprehensive review of 62 studies comprising 998 children, 504 of whom were abused, RH were found in 78% of cases of abusive head trauma (AHT) versus 5% of the cases of non-abusive head trauma. In a child with head trauma and RH, the odds ratio that this is AHT is 14.7 (95% CI 6.39, 33.62) and the probability of abuse is 91% ...
In transcalvarial herniation, the brain squeezes through a fracture or a surgical site in the skull. [7] Also called "external herniation", this type of herniation may occur during craniectomy, surgery in which a flap of skull is removed, the protruding brain region preventing the piece of skull from being replaced during the operation. [1]