Brain herniation is a deadly side effect of very high pressure inside the skull that occurs when part of the brain is squeezed throughout the structure inside the skull. The brain can shift past structures such as the falx cerebri, cerebelli tentorium, and even through the foramen magnum (the hole at the base of the skull connecting the spinal cord with the brain). Herniation can be caused by a number of factors that cause mass effect and increase intracranial pressure (ICP): this includes traumatic brain injury, intracranial hemorrhage, or brain tumor.
Herniation can also occur in the absence of high ICP when mass lesions such as hematoma occur in the boundary of the brain compartment. In such cases the local pressure increases in the place where the herniation occurs, but this pressure is not transmitted throughout the brain, and therefore is not listed as an increase in ICP.
Because the herniation places extreme pressure on the part of the brain and thereby cuts the blood supply to different parts of the brain, it is often fatal. Therefore, extreme measures are taken at the hospital to prevent the condition by reducing intracranial pressure, or decompressing (drying) a hematoma that puts local pressure on the part of the brain.
Video Brain herniation
Classification
The tentorium is an extension of the dura mater that separates the cerebellum from the cerebrum. There are two main classes of herniation: supratentorial and infratentorial. Supratentorial refers to structural herniation usually found on tentorial nicks, and infratentorial refers to structures normally found underneath.
- Supratentorial herniation
- Uncal (transtentorial)
- Center
- Cingulate (subfalcine/transfalcine)
- Transkalvarial
- Tectal (posterior)
- Infratentorial herniation
- Up (trebtar up or up transtentorial)
- Tonsillar (bottom cerebellum)
Uncal herniation
In subtle herniation, the general subtype of transtentorial herniation, the innermost part of the temporal lobes, cysts, can be suppressed in such a way that it moves toward the tentorium and exerts pressure on the brain stem, especially the midbrain. The tentorium is a structure inside the skull formed by the dura mater of the meninges. Tissues can be stripped from the cerebral cortex in a process called decortication.
The cyst may suppress the oculomotor nerve (aka CN III), which may affect the parasympathetic input to the eye on the affected nerve side, causing the affected pupil to dilate and fail to narrow in response to light as it should. The dilation of the pupil often precedes the CN III compression somatic motor effect called oculomotor nerve palsy or third nerve palsy. This palsy presents as a deviation of the eye to the "down and out" position due to loss of innervation to all muscular ocular motions except for the lateral rectus (innervated by the nerve abducens (aka CN VI) and superior tilt (innervated by the trolear nerve aka CN IV). in this sequence because the parasympathetic fibers surround the CN III motor fibers and are therefore compressed first.
Posterior ipsilateral posterior cerebral artery compression will result in ischemia of the major ipsilateral visual cortex and contralateral visual deficit in both eyes (contralateral homonymous hemianopsia).
Another important finding is the false localization , called the Kundohan notch, which results from the compression of the contralateral cerebral crest containing descending corticospinalis and some corticobulbar tract fibers. This causes the Ipsilateral hemiparesis to refer to herniation and contralateral hemiparesis with reference to the cerebral crus.
With the increased pressure and development of the hernia there will be brain stem distortion leading to Duret hemorrhage (tearing of the small vessels in the parenchyma) in the median and paramedian zone of the mesencephalon and the pons. The outbreak of this blood vessel causes the bleeding to be linear or ignited. Impaired brain stem can cause decomposed posture, respiratory depression, and death. Other possibilities resulting from brain stem distortion include lethargy, slow heartbeat, and pupil dilatation.
The uncal herniation can develop into a central herniation. The sliding uncus syndrome represents a herniation without change in the level of consciousness and other sequelae mentioned above.
Herniation center
In the central herniation, diencephalon and temporal lobe portions of both hemispheres are squeezed through a notch in cerebelli tentorium. Transtentorial herniation can occur when the brain moves up or down across the tentorium, called herniation increases and decreases herniation respectively; However descendent herniation is much more common. Downstream herniation can stretch the branches of the basilar artery (the pontine artery), causing them to tear and bleed, known as Duret hemorrhage. The result is usually fatal. Other symptoms of this type of herniation include small pupils of eyes, dilated, and fixed with paralyzed eye movements that give a distinctive "sunset" appearance. Also found in these patients, often as terminal complications is the development of diabetes insipidus due to compression of the pituitary stalk. Radiographically, the downward herniation is characterized by the obliteration of the suprasellar cistern from the temporal lobe herniation to the tentorial hiatus with associated compression of the cerebral cerebral. Upward herniation, on the other hand, can be radiographically characterized by obliteration of the quadrigeminal cistern. Intracranial hypotension syndrome has been known to mimic transtentorial herniation downward.
cingulate herniation
In Transcalvarial herniation
In transcalvarial herniation , the brain squeezes through a fracture or surgical site in the skull. Also called "external herniation", this type of herniation may occur during craniectomy, surgery where a skull crease is removed, a protruding area of ​​the brain preventing the skull piece being replaced during surgery.
Herniate up
The increased pressure on the posterior fossa may cause the cerebellum to rise through tentorial opening in up , or cerebellar herniation . The brain is being pushed through the tentorial deck. It also pushes the middle brain down. This is also known as transtentorial herniation because it occurs in tentorium cerebelli.
Herniation of tonsillers
In tonsil herniation , also called herniation under the brain , transforaminal herniation, or â € Å"coningâ €, the cerebellar tonsils move downward through the foramen magnum which may cause compression of the lower and upper brainstem. cervical spinal cord as they pass through the foramen magnum. Increased pressure on the brain stem can lead to dysfunction of centers in the brain responsible for the control of respiratory and cardiac functions. The most common signs are headache that is hard to break, head slope, and neck stiffness due to tonsillic impaction. The level of consciousness may decrease and also cause flaccid paralysis. Blood pressure instability is also seen in these patients.
Herniation of the cerebellar tonsillers is also known as Chiari malformation (CM), or previously an Arnold-Chiari malformation (ACM). There are four types of Chiari malformations, and they represent a very different disease process with different symptoms and prognosis. This condition can be found in asymptomatic patients as incidental findings, or may be severe to life-threatening. This condition is now diagnosed more frequently by radiologists, as more patients undergo an MRI scan of their head, especially an upright MRI, which is more than twice as sensitive to detect this condition. Serebellar tonsillar ectopia (CTE) is a term used by radiologists to describe "low-lying" cerebellar tonsils but does not meet the radiographic criteria for definition as Chiari malformation. The currently accepted radiographic definition for Chiari malformation is that the cerebellar tonsils are located at least 5mm below the foramen magnum level. Some doctors have reported that some patients appear to experience symptoms consistent with Chiari malformation without evidence of tonsil herniation radiography. Sometimes this patient is described as having 'Chiari [type] 0'.
There are many possible causes of tonsil herniation including: a descending posterior fossa or malformation (the lower part, the back of the skull) does not provide enough space for the cerebellum; hydrocephalus or abnormal CSF volume pushes the exhaled tonsils; or dural tension draws the brain to the caudal. Connective tissue disorders, such as Ehlers Danlos Syndrome, can be attributed.
For further evaluation of tonsil herniation, a CINE flow study was used. This type of MRI examines CSF flow in cranio-cervical joints. For people with symptoms but with no clear MRI evidence, especially if the symptoms are better in the supine and worse position when standing/standing straight, a straight MRI may be useful.
Maps Brain herniation
Signs and symptoms
Brain herniation often presents with abnormal posture of a characteristic position of the extremities that indicate severe brain damage. These patients have a low level of consciousness, with Glasgow Coma Scores three to five. One or both pupils may widen and fail to narrow in response to light. Vomiting can also occur due to compression of the vomiting center in the medulla oblongata.
Treatment and prognosis
Treatment involves removal of a mass of etiology and decompression craniectomy. Brain herniation can cause severe disability or death. In fact, when herniation is seen in CT scans, the prognosis for meaningful recovery of neurologic function is poor. The patient may become paralyzed on the same side as the lesion causing the pressure, or damage to the part of the brain caused by the herniation can cause paralysis on the opposite side of the lesion. Damage to the midbrain, which contains a reticular activating tissue that regulates consciousness, will result in a coma. Damage to the cardiac respiratory center in the medulla oblongata will cause respiratory problems and (second) cardiac arrest. Ongoing investigations concerning the use of neuroprotective agents during prolonged post-traumatic periods of brain hypersensitivity associated with the syndrome.
Cause
The causes of brain herniation include:
- Edema brain
- Hematoma
- Stroke
- Tumor
- Infection
See also
- Decompression craniectomy
- second impact syndrome
References
External links
- Brain Herniation Diagram
- Brain Herniation Tutorial - downloadable leaflets.
Source of the article : Wikipedia
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