Brain herniation

Brain herniation (pressure cone) is a protrusion of brain tissue. A certain area of ​​the brain is pushed out of its typical location due to the influence of various pathological processes, such as edema. Intracranial pressure increases in these lesions. There is ischemia of the brain, damage in the area of ​​the herniation, and often also oppression of vital structures in the places where the herniation pushes through.

On the surface of the brain, the border of the protrusion is visible as an indented groove. Larger or longer-lasting herniations can be congested, subsequently hemorrhagic to necrotic.

Cingular (interhemispheric) herniation
In the case of cingulate herniation, the gyrus cinguli (the gyrus surrounding the corpus calosum medially) is pushed under the falx cerebri. This typically occurs with unilateral processes in the frontal lobe. Diagnostically, it is visible both on CT and on angiography, where we refer to the signum falcis as the displacement of the anterior cerebri artery below the falx. Clinically, it usually has no noticeable symptoms. However, there may be compression or kinking of the anterior cerebri artery, subsequent ischemia deepens the symptomatology (palsy of lower limbs...)

Central herniation (transtentorial)
In central herniation, the rostral part of the brainstem and diencephalon is pushed into the tentorial opening (after the clivus). There is compression of the posterior cerebral artery and trunk arteries. It arises from a lesion in the supratentorial space. It gradually leads to rostrocaudal deterioration of brainstem functions. We distinguish the following clinical stages for this herniation:


 * 1) The diencephalon  disorder manifests itself first as symmetrical bilateral miosis  (central sympathetic disorder –hypothalamus),  followed by disturbances of consciousness according to Glasgow Coma Scale (GCS) 9–14. A pull on the pituitary stalk will cause diabetes insipidus, pyramidal irritation phenomena on the lower limb (Babinski) and a hypertonic state. In the worst case, decortication (flexion) occurs. Respiration is spontaneous with yawns and sighs, later Cheyne–Stokes breathing. This impairment is 95% reversible.
 * 2) The mesencephalon order is accompanied by bilateral mydriasis (a disorder of the parasympathetic – Edinger-Westphal nuclei) and impaired consciousness according to GCS 4–9. Decerebral rigidity appears (extension, opisthotonus).  It has a 95% mortality rate.
 * 3) Pons disorder manifests itself as loss of muscle tone = atonia, because the connection to the cerebellum does not work. The pupils are unresponsive; mydriatic. tachypnoe appears
 * 4) A disorder of the medulla, kwhich contains vital centers, is manifested by a drop in blood pressure (regulatory pressure center) and respiratory arrest (respiratory center).

Temporal herniation
Displacement of the uncus gyri hippocampi into the posterior cranial fossa is referred to as temporal herniation. It arises from rapidly expanding processes compressing the temporal lobe (epidural hematoma). The first on the wound is N. III, there is homolateral mydriasis, then contralateral hemiparesis either due to oppression of the cortex or the pyramidal tract. As long as the patient has a mydriatic pupil, it is still relatively fine, then it continues to press on the mesencephalon and bilateral mydriasis occurs. Further progression corresponds to the picture described for central herniation.

Occipital conus
An occipital conus is a herniation of the tonsils of the cerebellum through the foramen magnum. There is an oppression of the medulla oblongata .It can arise as a terminal phase of central or temporal herniation or it is during expansive processes in the posterior cranial fossa. Clinically, we find headaches, double vision (diplopia), limb weakness, coordination disorders (ataxia), and irritation phenomena. The opposition of the neck (pseudomeningeal syndrome) is also often seen. Decompensation of the condition can be sudden.

It skips the stages of deterioration and goes straight to death because the vital centers are oppressed.

Fungus cerebri
Fungus cerebri is a special type of herniation. It occurs after brain surgery, k when the edematous brain pushes into the trepanation hole and lifts the skull bones.