Herniations

Transtentorial herniation may result in necrosis of the cerebral peduncle, contralateral to the expanding mass. This is what is called the Kernohan's notch (the patient will present with a hemiplegia ipsilateral to the brain mass). The figure depicts a cross section of the midbrain in a patient with an expanding mass on the left cerebral hemisphere. Notice the necrosis of the right cerebral peduncle.