Chiari Anomaly

Chiari Anomaly
Chiari anomaly is a congenital disorder of the development of the rhomboid brain, which is characterized by a discrepancy in the size of the brain structures and the posterior cranial fossa. This pathological process leads to the lowering of the brain stem and tonsils of the cerebellum, as well as their infringement. Normally, the tonsils of the cerebellum should be located slightly above the large occipital foramen. But in patients with Chiari anomaly, these tonsils descend to the first or second cervical vertebrae, which leads to blocking the flow of cerebrospinal fluid.

The content of the article:
Causes of Chiari anomaly
Classification of Chiari anomaly
Symptoms of Chiari anomaly
Diagnosis of Chiari anomaly
Treatment of Chiari anomaly
Forecast of the Chiari anomaly
Chiari Anomaly
The disease is very rare, as there are about 3-8 cases per one hundred thousand people. A mild form of pathology can occur without pronounced symptoms and does not require treatment. More severe forms of Chiari anomaly are accompanied by constant headache, dizziness, fainting, decreased hearing and visual acuity, respiratory disorders, muscle hypotrophy. For the treatment of Chiari anomaly, which is accompanied by such symptoms, a neurosurgical operation is prescribed.

Causes of Chiari anomaly
The causes of pathology currently remain the subject of research by scientists. One of the hypotheses connects the occurrence of Chiari anomaly with a decrease in the posterior cranial fossa, which leads to its gradual exit beyond the occipital foramen. Another hypothesis proves the occurrence of pathology due to an increase in the brain, which provokes the ejection of the contents of the posterior cranial fossa through the occipital opening.

Scientists agree that there are three main pathological factors that cause the disease. These include congenital osteoneuropathy, hydrodynamic trauma of the cerebrospinal fluid in the wall of the central canal of the spinal cord, as well as pathologies that have arisen due to birth trauma. The exacerbation of the disease can be triggered by hydrocephalus, which causes an increase in brain volume. Traumatic brain injuries also negatively affect the patient’s health.

In neurology, it is also customary to identify risk factors that can provoke the development of Chiari abnormality in the fetus. These factors include the mother’s bad habits: smoking or frequent drinking of alcoholic beverages during the child’s gestation. The cause of the disease may also be taking medications that the doctor did not prescribe, as well as transferred viral diseases.

Classification of Chiari anomaly
In neurology , it is customary to distinguish four main types of Chiari anomaly:

The first type. For this type of Chiari anomaly, the omission of the tonsils of the cerebellum is characteristic slightly below the occipital foramen. Often, this pathology is accompanied by hydromyelia — the presence of a large accumulation of cerebrospinal fluid in the central canal of the spinal cord. Adolescents and adults are at risk of getting this type of pathology.
The second type. This type of anomaly is often diagnosed in the first days of a newborn baby’s life. This pathology is characterized by the passage through the occipital foramen not only of the tonsils of the cerebellum, but also of its worm, the fourth ventricle and the medulla oblongata. This type of anomaly can also be combined with hydromyelia. The second type of Chiari anomaly is characterized by myelomeningocele (spinal hernia).
The third type. Chiari anomaly of the third type is extremely rare. It is usually accompanied by abnormalities such as posterior brain displacement and high encephalomeningocele. In most cases, these developmental disorders lead to death. The third and second types of Chiari anomaly can be combined with such disorders of the nervous system as polymicrogyria, heterotopia of the cerebral cortex, an inflection of the sylvian aqueduct, an anomaly of the corpus callosum, cysts of the Mozhandi orifice.
The fourth type. This pathology is characterized by underdevelopment of the cerebellum, in which its downward displacement is not observed. This type of disease is usually attributed to the pathologies of the Dandy Walker.
Symptoms of Chiari anomaly
The most common type of Chiari anomaly is the first. Its most characteristic manifestations are considered to be a severe violation of the cranial nerves, bulbar (defeat of the lingual, vagus and sublingual nerves), syringomyelic and cerebrospinal hypertension syndromes. The first signs of the disease usually appear in adolescence. Until this time, the disease can proceed without noticeable symptoms.

Cerebrospinal hypertension syndrome in the first degree of Chiari anomaly is accompanied by severe headache, which increases during coughing, sneezing, neck muscle tension. Often patients complain of vomiting attacks that are not provoked by the nature and intake of food. During a neurological examination, doctors diagnose patients with increased neck muscle tone. Cerebellar disorders such as cerebellar ataxia, speech disorders and nystagmus are also observed in patients.

As a result of damage to the brain stem, as well as nerves located in it, patients experience symptoms of Chiari anomaly such as swallowing disorders, hearing and vision loss, regular dizziness, sleep apnea syndromes, tinnitus, orthostatic collapse. Usually, with sharp turns of the head, severe dizziness and tinnitus only increase. In addition, head turns sometimes lead to sudden fainting.

Possible symptoms of the disease include laryngeal paresis, which provokes difficulty breathing and hoarseness of the voice, as well as atrophic lesions of half of the tongue. Patients may also be diagnosed with tetraparesis, accompanied by a decrease in muscle strength in the arms.

In rare cases, Chiari anomaly can be combined with syringomyelia — a chronic pathology of the nervous system, which is characterized by the formation of a cavity in the spinal cord. In this situation, the patient is diagnosed with syringomyelic syndrome during diagnosis. This syndrome is manifested by the following symptoms: numbness, sensitivity disorders, muscular hypotrophy, neuroarthropathy, violation of abdominal reflexes, pelvic disorders.

The second and third types of Kyaria abnormalities have a similar clinical picture. In addition, signs of these diseases can be noticed already in the first minutes of the baby’s life. For the second type of pathology, such signs as periods of respiratory arrest, noisy breathing, bilateral laryngeal paresis, problems with swallowing, during which liquid food is thrown into the nose, are considered characteristic. Newborns may also be diagnosed with cyanosis of the skin and nystagmus. The third type of Chiari anomaly is accompanied by more serious and life-threatening complications for the newborn, therefore provokes a fatal outcome.

Diagnosis of Chiari anomaly
Most standard neurological diagnostic procedures do not allow detecting pathology and making a correct diagnosis. Nevertheless, the results of neurological examination and examinations such as electroencephalography, echo-encephalography and rheoencephalography allow the doctor to suspect the presence of pathology in the patient. With the help of these techniques, it is possible to identify signs of increased intracranial pressure. It is possible to detect bone pathologies that are characteristic of Chiari anomaly with the help of skull radiography.

More information about Chiari anomaly can be obtained through computed tomography (CT) and spiral computed tomography of the brain (CT). However, even thanks to the clear visualization of the bone structures of the craniovertebral junction, both of these methods do not always help to make an accurate diagnosis. Therefore, magnetic resonance imaging (MRI) is considered the only effective and reliable method of diagnosing the disease.

Since the success of its implementation depends on the immobility of the patient, young children undergo the procedure in a state of sleep caused by taking medications. To obtain a more extensive and accurate picture of the disease, as well as the detection of meningocele (craniocerebral or spinal hernia), the doctor may additionally prescribe an MRI of the spine. Diagnosis of Chiari anomaly must necessarily be used not only to confirm the diagnosis, but also to search for other diseases that often accompany this congenital pathology.

Treatment of Chiari anomaly
Treatment of Chiari anomaly can be conservative and surgical. In some cases, when the pathology is not accompanied by pronounced symptoms, treatment may not be required at all. If patients who have been diagnosed with pathology complain of pain in the neck and occipital region, as well as other unpleasant symptoms, in this case, they are prescribed medication. Chiari anomaly therapy involves taking muscle relaxants, analgesics and anti-inflammatory drugs.

However, conservative treatment is not always effective. Usually, if a patient has such neurological disorders as impaired muscle tone and sensitivity, disorders of cranial nerves, paresis, doctors are forced to resort to surgical treatment of the disease. One of the most common operations used to treat pathology is craniovertebral decompression.

Craniovertebral decompression
During the operation, the occipital opening is expanded by removing a small part of the occipital bone. Then the surgeon resects the posterior halves of the two cervical vertebrae and the tonsils of the cerebellum in order to eliminate compression of the brain stem. At the next stage of Chiari anomaly surgery, the patch is sewn into the dura mater, which normalizes the circulation of cerebrospinal fluid.

Bypass surgery
For the treatment of Chiari anomaly, the doctor may also prescribe a bypass operation. It involves the drainage of cerebrospinal fluid from the central canal of the spinal cord. With the help of a lumboperitoneal shunt, this substance can be removed to the abdominal or thoracic cavities.

The effectiveness of surgical intervention is about 50-85%. However, doctors emphasize that the operation should be performed before the appearance of serious neurological disorders, because otherwise, after surgery, the patient’s recovery may be partial or not at all. The main task of the doctor in such cases is considered to be the stabilization of the patient and the prevention of further development of the disease.

Forecast of the Chiari anomaly
The prognosis for a patient with Chiari anomaly depends on what type of pathology he was found to have. For example, patients with Chiari anomaly of the first type may not need special treatment all their lives. However, if patients who have been diagnosed with the first or second type of disease have pronounced symptoms, they need to urgently undergo an examination by a neurologist. Timely surgery will help to avoid serious complications. Chiari anomaly of the third type is practically untreatable and very often leads to the death of the patient.

The disease can be accompanied by a number of serious complications. In particular, the patient may be diagnosed with an increase in intracranial hypertension, as well as the accumulation of fluid in the cranial cavity (hypertension-hydrocephalus syndrome). Since some patients with Chiari anomaly cannot move independently, they are likely to develop congestive pneumonia. In the case of a complex course of the disease, respiratory disorders and even its stopping may occur.

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