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Head Injury
Published in Ian Greaves, Keith Porter, Jeff Garner, Trauma Care Manual, 2021
Ian Greaves, Keith Porter, Jeff Garner
Apart from the GCS, assessment of pupillary size and reactivity is vital remembering that a difference of up to 1 mm (one size) between pupils is seen in up to 20% of the healthy population. The significance of pupillary inequality must be assessed in the context of the patient’s condition more generally: unequal pupils may also be due to local trauma resulting in a traumatic mydriasis, exposure to pharmacological agents, previous surgery or a Horner’s syndrome caused by trauma to the sympathetic chain at any level from the hypothalamus to the cervicothoracic cord, making the unaffected pupil appear dilated. Bilateral absence of the pupillary light reflex with dilated pupils is a very poor prognostic sign; however, this does depend on the underlying injury (extradural vs. subdural) and the duration of its presence.32 Examination must specifically exclude the lateralizing signs of the herniation syndromes.
Miscellaneous
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The pupillary light reflex constricts the pupil in response to light, through the innervation of the iris sphincter muscle. This is the result of the neuroanatomical pathways described below. Pupillary light reflex is used to assess the brain stem function. Abnormal pupillary light reflex can be found in optic nerve and oculomotor nerve damage, brain stem lesions and in use of medications such as barbiturates.
SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
The abducens nerve innervates the lateral rectus muscle of the eye exclusively; the sole effect of damage to this nerve is that the patient is unable to abduct (laterally deviate) the eye. Ptosis results from lesion of occulomotor nerve. Pupillary light reflex tests function of optic and occulomotor nerves.
Contrast Acuity and the King-Devick Test in Huntington’s Disease
Published in Neuro-Ophthalmology, 2020
Ali G. Hamedani, Tanya Bardakjian, Laura J. Balcer, Pedro Gonzalez-Alegre
The pupillary light reflex is a polysynaptic reflex arc that involves retinal photoreceptor activation and ganglion cell depolarisation; conduction through the optic nerve, chiasm, and tract; signalling across the pretectum to the Edinger-Westphal nucleus; and pupillary constriction via the third cranial nerve. Consequently, it can be affected by abnormalities at either the afferent or efferent level. In both symptomatic and presymptomatic patients with autosomal dominant Alzheimer’s disease, subtle differences in pupillary light reflex have been identified19, consistent with the cholinergic deficit observed in that disease. We did not observe any differences in pupillary function in HD, which may help to explain why the benefit from cholinesterase inhibitors for cognitive function or chorea in HD has been minimal.32 Because pupillometry was performed under scotopic (dark-adapted) conditions using mixed-wavelength white light, afferent activation was driven primarily by rod photoreceptors, and subtle cone or intrinsically photosensitive retinal ganglion cell dysfunction may not have been captured using this method. Future studies of pupillometry in HD would benefit from both photopic (light-adapted) and scotopic testing at different ranges of light wavelength.
Static and dynamic pupil characteristics in pseudoexfoliation syndrome and glaucoma
Published in Clinical and Experimental Optometry, 2020
Kemal Tekin, Hasan Kiziltoprak, Mehmet Ali Sekeroglu, Esat Yetkin, Serdar Bayraktar, Pelin Yilmazbas
Glaucoma is an optic neuropathy characterised by progressive and chronic loss of retinal ganglion cells and their axons. Analysis of pupillary light reflex is one way to assess the integrity of afferent visual pathways and abnormalities in pupillary light reflex usually present as a relative afferent pupillary defect.1995 The relative afferent pupillary defect might be observed in the conditions of asymmetrical retinal or optic nerve diseases including glaucoma. Measurement of pupillary response via infrared pupillography was introduced by Lowenstein and Loewenfeld,1958 and the recent developments in automated pupillometry devices have enabled quantitative, objective, non‐invasive, and repeatable measurements of pupil diameter in addition to the pupillary kinetics.2018 Various studies have shown that primary open‐angle glaucoma is associated with impairments in pupillary responses by using automated pupillometry.2011 It is also well known that pupillary changes such as poor mydriasis, due to the iris infiltration and fibrosis, are associated with PES.
Case report: neuroimaging analysis of pediatric ADHD-related symptoms secondary to hypoxic brain injury
Published in Brain Injury, 2019
Additionally, the assessment of the pupillary light reflex is used to suggest the brain’s condition. By shining a light into an eye at a time, afferent signals of an eye are sent to the ipsilateral pretectal nucleus in the midbrain. From the pretectal nuclei, contralateral and ipsilateral projections reach the Edinger-Westphal nuclei also in the midbrain. These neurons synapse onto the ciliary ganglia via the oculomotor nerve, and the post-ganglionic projections innervate the iris sphincter muscles to contract the iris. Because of the description of the patient’s right pupil as ‘sluggish’ and more dilated than the left pupil, damage to the patient’s left pretectal nuclei is suggested and would be consistent with the left-sided nature of the abnormalities noted on the MRI DTI and the PET. The suspected areas involve the neurons of the Edinger-Westphal nuclei and the projections of the pretectal nuclei.