When does uncal herniation occur?
A)The hippocampal gyrus shifts from the middle fossa through the tentorial notch into the posterior fossa.
B)The diencephalon shifts from the middle fossa straight downward through the tentorial notch into the posterior fossa.
C)The cingulate gyrus shifts under the falx cerebri.
D)A cerebellar tonsil shifts through the foramen magnum.

Question

Quizplus · Accepted Answer

Uncal herniation (i.e., hippocampal herniation, lateral mass herniation) occurs when the uncus or hippocampal gyrus (or both) shifts from the middle fossa through the tentorial notch into the posterior fossa. This shift results in the compression of the ipsilateral third cranial nerve (CN), impairing parasympathetic function. When the diencephalon shifts from the middle fossa straight down through the tentorial notch it is termed a central herniation. Cingulate gyrus shift occurs when the gyrus shifts under the falx cerebri. A cerebellar tonsil shift occurs in an infratentorial herniation.

When Does Uncal Herniation Occur