Brain Herniation

Brain herniation (from Latin herniatio — protrusion, hernia) is a life-threatening complication of intracranial hypertension. In this condition, part of the brain tissue physically shifts and is pushed into narrow natural openings within the skull due to high pressure.

Etiology and pathophysiology

The cranial cavity is divided into several compartments by rigid and inextensible membranes of the dura mater. The formation of a large hematoma or significant swelling leads to a catastrophic increase in pressure in one of these compartments. Healthy brain tissue seeks an exit and shifts towards areas of lesser resistance.

The most common variant is temporal-tentorial herniation. In this case, the hook of the temporal lobe migrates into the tentorial notch of the cerebellum. The second critical variant is occipital herniation, in which the cerebellar tonsils herniate through the foramen magnum, where the brain transitions to the spinal cord.

Clinical significance

The brain tissue involved in herniation functions as a mechanical wedge. It compresses the brainstem, where life-sustaining centers for breathing, heartbeat, and vascular tone regulation are located.

Clinically, the process is characterized by rapid depression of consciousness to deep coma. A distinct feature is the dilation of the pupil on one side and abnormal extension of the limbs in response to pain. If displacement reaches the lower sections of the brainstem, inevitable respiratory arrest and death ensue. This condition is an absolute indication for emergency surgical decompression to save the patient’s life.