The "keyhole": a sign of herniation of a trapped fourth ventricle and other posterior fossa cysts

When a cystic structure in the posterior fossa increases in size, the accompanying increase in pressure may cause it to herniate upward through the tentorial hiatus. In our experience this happens most commonly with a dilated trapped fourth ventricle secondary to infection or intraventricular hemorr...

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Bibliographic Details
Published in:American journal of neuroradiology : AJNR 1987-05, Vol.8 (3), p.473-477
Main Authors: Wolfson, BJ, Faerber, EN, Truex, RC, Jr
Format: Article
Language:English
Subjects:
Biological and medical sciences
Brain Diseases - diagnosis
Brain Diseases - diagnostic imaging
Brain Diseases - etiology
Case Reports
Cerebral Hemorrhage - complications
Cerebral Ventricles - pathology
Cerebral Ventriculography
Cranial Fossa, Posterior - diagnostic imaging
Cranial Fossa, Posterior - pathology
Cysts - complications
Cysts - diagnosis
Cysts - diagnostic imaging
Dandy-Walker Syndrome - complications
Female
Hernia - complications
Hernia - diagnosis
Hernia - diagnostic imaging
Humans
Infant
Infant, Newborn
Investigative techniques, diagnostic techniques (general aspects)
Male
Medical sciences
Nervous system
Radiodiagnosis. Nmr imagery. Nmr spectrometry
Skull - diagnostic imaging
Tomography, X-Ray Computed
Ultrasonography
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Summary:When a cystic structure in the posterior fossa increases in size, the accompanying increase in pressure may cause it to herniate upward through the tentorial hiatus. In our experience this happens most commonly with a dilated trapped fourth ventricle secondary to infection or intraventricular hemorrhage. However, herniation of an arachnoid cyst or a Dandy-Walker malformation through the tentorium may also occur. When herniation occurs, the cystic structure assumes a "keyhole" configuration, indicating that it is trapped and that surgical intervention is necessary. Five cases are presented that illustrate this point, including two patients with dilatation of the fourth ventricle secondary to hemorrhage, two patients with Dandy-Walker malformation, and one patient with an arachnoid cyst.
ISSN:0195-6108
1936-959X