What is Brain Herniation?

Occurrence of occupying lesions in any part of the brain to a certain extent can lead to cerebral hernia due to uneven pressure in each subcranial cavity. Common lesions that cause brain hernias are:

Du Jianxin	(Chief physician)	Department of Neurosurgery, Xuanwu Hospital, Capital Medical University
Wei Yukui	(Attending physician)	Department of Neurosurgery, Xuanwu Hospital, Capital Medical University

When there is a occupying lesion in one of the sub-cavities in the normal cranial cavity, the pressure of the sub-cavity is higher than the pressure of the adjacent sub-cavity, the brain tissue is shifted from the high pressure area to the low pressure area, and it is squeezed to the nearby physiological or non-physiological channels Some brain tissues, nerves, and blood vessels are compressed, and cerebrospinal fluid circulation is impaired to produce corresponding symptoms, which is called cerebral hernia. Cerebral hernia is caused by a sharp increase in intracranial pressure. When making a diagnosis of cerebral hernia, a rapid intravenous infusion of hypertonic drugs to reduce intracranial pressure should be performed according to the principle of treatment of increased intracranial pressure in order to alleviate the disease and gain time. When the diagnosis is made, quickly complete the preparation for craniotomy according to the condition, and remove the cause as soon as possible, such as removing intracranial hematomas or removing brain tumors.

Western Medicine Name

Brain hernia

Affiliated Department

Surgery-Neurosurgery

Disease site

head

The main symptoms

Severe headache, vomiting, drowsiness, etc.

Contagious

Non-contagious

Causes of cerebral hernia

Occurrence of occupying lesions in any part of the brain to a certain extent can lead to cerebral hernia due to uneven pressure in each subcranial cavity. Common lesions that cause brain hernias are:

Various intracranial hematomas caused by injury, such as acute epidural hematoma, subdural hematoma, and intrahematoma;

Various intracranial tumors, especially tumors located in one cerebral hemisphere and posterior cranial fossa tumors;

intracranial abscess;

Intracranial parasitic disease and various other chronic granulomas.

Congenital factors, such as hernia deformity of cerebellum. In addition, for patients with increased intracranial pressure, lumbar puncture releases too much cerebrospinal fluid, leading to an increase in the pressure difference between the intracranial compartments, which can promote the formation of cerebral hernias.

Cerebral hernia pathogenesis

Under normal circumstances, the cranial cavity is divided by the cerebral sickle and the cerebellum into separate pressure chambers with equal pressure and communicating with each other. Above the cerebellum, it is called the supraventricular cavity, and it is divided into left and right two sub-cavities, which contain the left and right cerebral hemispheres; below the cerebellum, it is called the sub-occipital cavity, which contains the cerebellum, pontine, and medullary. When the pressure in a certain cavity is increased for some reason, the brain tissue can be displaced from the high pressure area through the anatomical gap or the orifice to the low pressure area, thereby generating a brain hernia. Herniated brain tissue compresses adjacent nerves, blood vessels and other tissue structures, causing ischemia and hypoxia in the corresponding tissues, resulting in impaired tissue damage.

Cerebral hernia nerve compression or stretch

Cerebral hernias compress or stretch adjacent nerves to cause damage, and the most common oculomotor nerve injury is. The oculomotor nerve is close to the temporal lobular gyrus, and the nerve fibers that control the pupil are located on the surface of the oculomotor nerve, which is very sensitive to external forces.

Brain hernia

Displaced brain tissue compresses or pulls the brain stem, causing the brain stem to deform and distort, affecting the function of the upper and lower nerve conduction bundles and nerve nucleus groups, and impaired nerve function.

Cerebral hernia vascular changes

The arteries supplying the brain tissue are directly compressed or stretched to cause vasospasm, causing ischemia, bleeding, secondary edema and softening of bad things, venous stasis, and bleeding of Toshiba veins or nerve tissue edema.

Cerebral hernia cerebrospinal fluid circulation disorder

The cerebrospinal fluid around the midbrain is the only way for cerebrospinal fluid circulation. The cerebellar notch hernia can compress the cerebrospinal fluid around the midbrain, causing cerebrospinal fluid to flow back to the curtain.

Brain Hernia Changes Out of Brain Tissue

Hernia out of the brain tissue can be congested, bleeding or edema due to blood circulation disorders, which can increase the pressure on adjacent tissues. ^[1]

Brain hernia classification

According to the location of the brain hernia: Brain hernia is divided into the following three common types:

Cerebral herniation

The hippocampal gyrus and hook gyrus of the temporal lobe on the screen are moved to the subchapter through the cerebellar notch, or the cerebellar vermiform part and the anterior cerebellum are herniated from the subchamber;

Cerebellar tonsillar hernia

Push the cerebellar tonsil and medulla through the foramen magnum into the spinal canal;

Cerebral hernia

The buckle on one side of the hemisphere was squeezed into the contralateral cavity through the inferior sickle hole.

Cerebral hernia staging

According to the development law of cerebral hernia, it can be divided into three stages:

Cerebral hernia precursor stage (early stage of cerebral hernia)

Refers to the stage before the formation of cerebral hernia, which is caused by the increase of intracranial pressure and the increase of cerebral hypoxia.

Cerebral hernia Compensation period

Cerebral hernias have been formed and the brain stem is oppressed, but the body can still barely sustain life through a series of regulatory compensatory effects.

Cerebral hernia

The brainstem continues to be stressed, compensatory functions are exhausted, and functional failure occurs.

Clinical manifestations of cerebral hernia

Cerebral herniation

1. Symptoms of increased intracranial pressure: severe headache and frequent vomiting, more severe than before hernia, and irritability.

2. Change of consciousness: manifested as drowsiness, shallow coma or even coma, and slow or disappeared to external stimuli.

3 Pupil changes: The pupils on the two sides are not the same, the pupils on the sick side are slightly reduced at the beginning, and the light reaction is slightly dull. Later, the pupils on the sick side are gradually enlarged and slightly irregular, and the direct and indirect light reactions disappear, but the pupils on the opposite side are still normal This is due to the oppression of the affected side of the oculomotor nerve. In addition, the affected side may also have drooping eyelids, exophthalmos, and so on. If the brain hernia continues to develop, bilateral pupil dilation and photoresponse disappear, which is caused by dysfunction caused by compression of the nucleus of the oculomotor nerve in the brain stem.

4 Dyskinesia: Mostly occurs on the opposite side of the dilated pupil, manifested as reduced or disappeared voluntary movement of the limbs. The continued development of cerebral hernia spreads the symptoms to both sides, causing the limbs to lose muscle strength or intermittent head and neck reclining, the limbs are straight, the back of the body is overextended, and the angle of the arch is reversed. Characteristic manifestations of severe impairment.

5. Disturbance of vital signs: changes in blood pressure, pulse, breathing, and temperature. In severe cases, blood pressure may rise and fall, breathing may suddenly and slowly, sometimes flushing, sweating, sometimes pale, sweat closed, body temperature may be as high as 41 or below 35 without rising, and finally breathing Stopped, finally blood pressure dropped, cardiac arrest and died.

Cerebral hernia foramen magnum

Patients often only have severe headaches, repeated vomiting, vital signs disturbances, neck stiffness, pain, late changes in consciousness, no pupil changes, and sudden respiratory arrests occur earlier.

Cerebral hernia

Causes the softening and necrosis of the brain tissue on the compressed side of the cerebral hemisphere on the diseased side, and the symptoms of paresis and dysuria of the contralateral lower limbs.

Cerebral hernia diagnosis

Medical history and clinical signs: Ask whether there is a history of cranial hypertension or the cause of the transition from chronic cerebral hernia to acute cerebral hernia. Patients with increased intracranial pressure who have a sudden coma or pupils with varying pupil size should be considered as a hernia. Patients with increased intracranial pressure who suddenly stop breathing or have a crisis after lumbar puncture should consider the foramen magnum hernia.

The diagnosis of pupil changes in the cerebellar notch hernia should pay attention to the following conditions:

(1) Whether the patient has used a dilated pupil or a miotic agent, and whether there is a disease such as cataract.

(2) In patients with cerebral hernia, if the pupils on both sides are dilated, not only the pupils, but also the tension of the levator muscle of the two eyes can be checked. Side, often the lesion side.

(3) Patients with cerebral hernia have dilated pupils on both sides. After treatment with dehydrating agents and improvement of cerebral hypoxia, the pupil changes to one side shrinks and one side remains dilated. Can suggest the lesion side.

(4) In patients with cerebral hernia, if the pupils are not large, if the larger pupil is sensitive to light, there is no paralysis of the extraocular muscles, and the tension of the levator muscle is low on the smaller pupil side. Ill side. This is due to the stimulation of the parasympathetic nerve fibers of the oculomotor nerve on the affected side.

(5) Lumbar puncture is generally forbidden for patients with cerebral hernia. Even if the pressure in the spinal canal measured by lumbar puncture is not high, it does not represent intracranial pressure. The cerebellar tonsil hernia can block the intracranial and spinal fluid circulation in the spinal canal.

(6) CT cerebellar notch hernias show deformation or disappearance of the basal cistern (upper saddle pool), ring cistern, and quadrilateral cistern. The inferior hernia shows obvious asymmetry and displacement of the midline.

(7) MRI: Observe the deformation and disappearance of cerebellum during cerebral hernia, and directly observe brain structures such as hook gyrus, para hippocampal gyrus, interbrain, brainstem and cerebellar tonsil.

Cerebral hernia treatment

Treatment of cerebral hernia is caused by a sharp increase in intracranial pressure. When making a diagnosis of cerebral hernia, a rapid intravenous infusion of hypertonic drugs to reduce intracranial pressure should be performed according to the principle of treatment of increased intracranial pressure to relieve the condition and gain time. When the diagnosis is made, quickly complete the preparation for craniotomy according to the condition, and remove the cause as soon as possible, such as removing intracranial hematomas or removing brain tumors. If the diagnosis is difficult to diagnose or the cause cannot be removed, the following palliative surgery can be used to reduce intracranial hypertension and rescue brain hernia.

Cerebral hernia extraventricular drainage

It can effectively reduce intracranial pressure in the short term and temporarily relieve the condition. The effect is particularly significant in cases with hydrocephalus.

Cerebral hernia decompression

Cerebellar notch hernia can be used for subtemporal decompression, and occipital foramen can be used for suboccipital decompression. This kind of decompression often causes a large amount of bulging of brain tissue, which causes great damage to the function of the brain. Therefore, it is inevitable to use it.

Cerebral hernia cerebrospinal fluid shunt

Applicable to cases with hydrocephalus, which can be selected according to specific conditions and conditions:

ventricle shunt

ventriculoperitoneal shunt;

ventricular atrial shunt.

Cerebral hernia decompression

When a large amount of brain tissue bulges during craniotomy, and the brain cavity cannot be closed, a partial lobe resection must be performed to reduce the pressure. But this can only be considered as a last resort. ^[2]

Prevention and health care of cerebral hernia disease

Cerebral hernia is the most dangerous sign of cerebrovascular disease. About half of patients die from a hernia. Therefore, in the acute phase, close attention should be paid to changes in patients' breathing, pulse, temperature, blood pressure and pupils, early detection of cerebral hernia, and active dehydration treatment to control intracranial hypertension and reduce mortality.