vanshita wrote:
B
Uncal herniation
In uncal or transtentorial herniation, the innermost part of the temporal lobe, the uncus, can be squeezed so much that it goes by the tentorium and puts pressure on the brainstem (Shepherd, 2004). The tentorium is a structure within the skull formed by the meningeal layer the dura mater. Tissue may be stripped from the cerebral cortex in a process called decortication (McCaffrey, 2001). The uncus can squeeze the third cranial nerve, which controls parasympathetic input to the eye on the side of the affected nerve. This interrupts the parasympathetic neural transmission, causing the pupil of the affected eye to dilate and fail to constrict in response to light as it should, so a dilated unresponsive pupil is an important sign of increased intracranial pressure (Cornell, 1998). Cranial arteries may be compressed during the herniation (Orlando Regional Healthcare, 2004). This type of herniation can also damage the brain stem, causing lethargy, slow heart rate, respiratory abnormalities, and pupil dilation (McCaffrey, 2001). Uncal herniation may advance to central herniation