Bilateral dilating pupils and coma in cerebral compression, and misconception about uncus herniation.
- 1Department of Neurological Surgery, The University of Chicago, United States.
Abstract
Background
Uncus herniation is a concept believed to cause bilaterally dilated pupils and deterioration of consciousness in cerebral compression and high intracranial pressure. This study indicates that the concept is based on assumptions and is misleading.Methods
Without new animal experiments, data were obtained from our previous National Institutes of Health- supported laboratory experiments on cerebral compression in cats caused by extradural balloons, and in rats caused by virus-induced brain tumors. The experiments in cats were conducted before the Institutional Animal Care and Use Committee requirement. The status of uncus herniation in humans was studied through a literature review.Results
As cerebral compression increased in cats, cerebral microvessels circulation diminished and gradually stopped in the entire brain, including the brainstem. Simultaneously, pupils became dilated and fixed, and vital signs gradually stopped. Similar microvessel alterations occurred in rats when drowsiness and coma occurred. Sequential in vivo arterial injections of vital dyes confirmed gradual cerebral microvessel obstruction. Postmortem examination revealed no uncus herniation. Light and electron microscopy revealed severe ischemic changes in the entire brain.Conclusion
In cerebral compression, bilateral dilating pupils and coma represent diminishing and arresting cerebral circulation in the entire brain. Uncus herniation may or may not occur in humans. When it does, it is associated, but not the cause, and may produce unilateral pupil dilation and local symptoms.
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BibTeX
@article{hekmatpanah2026bilateral,
title = {{Bilateral dilating pupils and coma in cerebral compression, and misconception about uncus herniation.}},
author = {Javad Hekmatpanah},
journal = {Surgical neurology international},
year = {2026},
month = oct,
doi = {10.25259/sni_651_2026},
url = {https://europepmc.org/article/MED/42974530},
note = {CC BY-NC-SA},
}
RIS
TY - JOUR
TI - Bilateral dilating pupils and coma in cerebral compression, and misconception about uncus herniation.
AU - Javad Hekmatpanah
PY - 2026
DA - 2026/10/09
JO - Surgical neurology international
DO - 10.25259/sni_651_2026
UR - https://europepmc.org/article/MED/42974530
AB - Background Uncus herniation is a concept believed to cause bilaterally dilated pupils and deterioration of consciousness in cerebral compression and high intracranial pressure. This study indicates that the concept is based on assumptions and is misleading.Methods Without new animal experiments, data were obtained from our previous National Institutes of Health- supported laboratory experiments on cerebral compression in cats caused by extradural balloons, and in rats caused by virus-induced brain tumors. The experiments in cats were conducted before the Institutional Animal Care and Use Committee requirement. The status of uncus herniation in humans was studied through a literature review.Results As cerebral compression increased in cats, cerebral microvessels circulation diminished and gradually stopped in the entire brain, including the brainstem. Simultaneously, pupils became dilated and fixed, and vital signs gradually stopped. Similar microvessel alterations occurred in rats when drowsiness and coma occurred. Sequential in vivo arterial injections of vital dyes confirmed gradual cerebral microvessel obstruction. Postmortem examination revealed no uncus herniation. Light and electron microscopy revealed severe ischemic changes in the entire brain.Conclusion In cerebral compression, bilateral dilating pupils and coma represent diminishing and arresting cerebral circulation in the entire brain. Uncus herniation may or may not occur in humans. When it does, it is associated, but not the cause, and may produce unilateral pupil dilation and local symptoms.
SN - 2229-5097
SN - 2152-7806
ER -