Kernohan's notch is a groove in the cerebral peduncle that may be caused by this displacement of the brainstem against the tentorial incisure.

The tentorial incisure is located between the tentorial edges and communicates the supratentorial and infratentorial spaces.

Its anterior border is free and concave, and bounds a large oval opening, the tentorial incisure, for the transmission of the cerebral peduncles.

Tentorial incisure (also known as the tentorial notch or incisura tentorii) refers to the anterior opening between the free edge of the tentorium cerebelli and the clivus for the passage of the brainstem.

The midbrain is pushed through the tentorial notch.

The common causes include hippocampal gyrus herniation through the tentorial notch, acute hematoma, edema following trauma, abscess, or tumor.

Supratentorial herniation is of structures normally above the tentorial notch and infratentorial is of structures normally below it.

Also, it is important to note that the anatomical size of tentorial notches vary considerably between individuals; however, very little evidence supports that a more narrow notch creates a predisposition towards Kernohan's notch.

Tentorial incisure (also known as the tentorial notch or incisura tentorii) refers to the anterior opening between the free edge of the tentorium cerebelli and the clivus for the passage of the brainstem.

In situations of tumor, hemorrhage, or edema, increased pressure within the cranial cavity, especially if the mass is in the middle fossa, can push the uncus over the tentorial notch against the brainstem and its corresponding cranial nerves.