Arnold-Chiari Anomaly: Symptoms and Treatment

The anomaly of Arnold-Chiari is a violation of the structure and location of the cerebellum, the brain stem relative to the skull and the spinal canal. This condition refers to congenital malformations, although it does not always manifest itself from the first days of life. Sometimes the first symptoms appear after 40 years. The anomaly of Arnold-Chiari can manifest itself with various symptoms of brain damage, spinal cord, impaired circulation of cerebrospinal fluid. The point in diagnosis is usually magnetic resonance imaging. Treatment is carried out conservatively and surgically. From this article you can learn more about the symptoms, diagnosis and treatment methods for the Arnold-Chiari anomaly.

Normally, the boundary between the brain and spinal cord is at the level between the bones of the skull and the cervical spine. There is a large occipital opening, which, in fact, serves as a conditional line. Conditional, because the brain tissue passes into the spinal cord without interruption, without a clear boundary. All the anatomical structures located above the large occipital foramina, in particular the medulla oblongata, the bridge and the cerebellum, belong to the structures of the posterior cranial fossa. If these formations (one or all of them) descend below the plane of the large occipital orifice, then the Arnold-Chiari anomaly arises. Such an incorrect arrangement of the cerebellum, medulla oblongata leads to compression of the spinal cord in the region of the cervical spine, prevents normal circulation of the cerebrospinal fluid. Sometimes the anomaly of Arnold-Chiari is combined with other malformations of the craniovertebral transition, that is, the place of transition of the skull to the spine. In such combined cases, the symptomatology is usually more pronounced and makes itself felt quite early.

The anomaly of Arnold-Chiari bears the name of two scientists: the Austrian pathologist Hans Chiari and the German pathologist Julius Arnold. The first in 1891 described a number of anomalies in the development of the cerebellum and brainstem, the second in 1894 gave an anatomical description of the lowering of the lower hemispheres of the cerebellum into the large occipital foramen.

Varieties of Arnold-Chiari anomaly

According to statistics, the anomaly of Arnold-Chiari occurs with a frequency of, up to, cases per 100 000 population. Such a wide range is partly due to the heterogeneity of this developmental malformation. What is it about? The fact is that the Arnold-Chiari anomaly is divided into four subtypes (described by Chiari), depending on from what structures are lowered into the large occipital orifice and how much they are wrong in structure:

• anomaly of Arnold-Chiari I - when the amygdala of the cerebellum descends from the cranium into the vertebral canal (the lower part of the cerebellar hemispheres);
• anomaly of Arnold-Chiari II - when a large part of the cerebellum (including the worm) descends into the vertebral canal, the medulla oblongata, IV ventricle;
• anomaly of Arnold-Chiari III - when below the large occipital foramen are located almost all the structures of the posterior cranial fossa (cerebellum, medulla oblongata, IV ventricle, bridge). Quite often they are located in the cerebral hernia of the cervico-occipital region (the situation when there is a defect in the spinal canal in the form of the vertebral arches, and the contents of the dural sac, that is, the spinal cord with all the membranes, protrude into this defect). The diameter of the large occipital opening in the case of this type of anomaly is increased;
• anomaly of Arnold-Chiari IV - underdevelopment (hypoplasia) of the cerebellum, but the cerebellum itself (or rather, what was formed in its place) is correctly located.

I and II types of vice are more common. This is due to the fact that III and IV types are usually not compatible with life, death occurs in the first days of life.

Up to 80% of all cases of Arnold-Chiari anomaly is combined with the presence of syringomyelia (a disease characterized by the presence of cavities in the spinal cord replacing the brain tissue).

In the development of anomalies, the leading role belongs to the disturbances in the formation of brain and spinal structures in the intrauterine period. However, the following factor should also be taken into account: head trauma received during childbirth, repeated craniocerebral injuries in childhood can damage bone seams in the base of the skull. As a result, the normal formation of the posterior cranial fossa is disrupted. It becomes too small, with a flattened ramp, because of which all the structures of the posterior cranial fossa simply can not fit in it. They "look for a way out" and rush into the large occipital orifice, and then into the vertebral canal. This situation is to some extent considered an acquired Arnold-Chiari anomaly. Also, symptoms similar to the Arnold-Chiari anomaly can occur with the development of a head tumor The brain, which causes the hemispheres of the cerebellum to move into the large occipital foramen and vertebral channel.

Symptoms

One of the manifestations of the anomaly of Arnold-Chiari may be hydrocephalus.

The main clinical manifestations of the Arnold-Chiari anomaly are associated with compression of the brain structures. At the same time, blood vessels that feed the brain, the paths of the liquorice, the roots of the cranial nerves passing through this region are squeezed.

It is accepted to distinguish 6 neurological syndromes, which can be accompanied by an anomaly of Arnold-Chiari:

• hypertensive-hydrocephalus;
• cerebellar;
• bulbar-pyramidal;
• radicular;
• vertebrobasillar insufficiency;
• syringomyelitic.

Naturally, not all six syndromes are always present. Their severity varies to some extent, depending on what structures and how much are squeezed.

Hypertensive-hydrocephalicthe syndrome develops as a result of disturbed circulation of the cerebrospinal fluid (CSF). Normally, the cerebrospinal fluid flows freely from the subarachnoid space of the brain to the subarachnoid space of the spinal cord. The lowered lower part of the tonsils of the cerebellum blocks this process, like a bottle stopper. The formation of cerebrospinal fluid in the vascular plexuses of the brain continues, and by and large, there is nowhere to drain it (not counting the natural suction mechanisms, which in this case is not enough). Likvor accumulates in the brain, causing an increase in intracranial pressure (intracranial hypertension) and an expansion of liquor-containing spaces (hydrocephalus). This manifests itself as a headache of a bursting nature, which is amplified by coughing, sneezing, laughing, straining. Pain is felt in the back of the neck, neck area, possibly neck muscles tension. There may be episodes of sudden vomiting, in no way related to eating.

Cerebellarthe syndrome manifests itself as a violation of the consistency of movements, "drunken" gait, and a loss in the performance of purposeful movements. Patients are worried about dizziness. There may be a tremor in the limbs. Speech may be broken (it becomes divided into separate syllables, chanting). Quite a specific symptom is "nystagmus, beating down". This involuntary twitching of the eyeballs, directed, in this case, down. Patients may complain of double vision in the eyes due to nystagmus.

Bulbar-pyramidalthe syndrome is named after the names of the structures that are subjected to compression. Bulbus is the name of the medulla oblongata because of its bulbous shape, therefore bulbar syndrome signifies the defeat of the medulla oblongata. And the pyramids are the anatomical formations of the medulla oblongata, which are bundles of nerve fibers that carry impulses from the cortex of the cerebral hemispheres to the nerve cells of the anterior horns of the spinal cord. Pyramids are responsible for arbitrary movements in the limbs and trunk. In accordance with the above, the bulbar-pyramidal syndrome clinically manifests itself as a muscle weakness in limbs, numbness and loss of pain and temperature sensitivity (the fibers pass through the elongated brain). The compression of the nuclei of the cranial nerves located in the brain stem causes the development of disorders vision and hearing, speech (due to movement disorders in the tongue), nasal voices, pinches at eating, embarrassment respiration. Possible short-term loss of consciousness or loss of muscle tone with a conserved consciousness.

Radicularthe syndrome in the case of the Arnold-Chiari anomaly is the appearance of signs of impaired function of the cranial nerves. This can be a violation of the mobility of the tongue, a nasal or hoarse voice, a violation of food ingestion, hearing defects (including tinnitus), impaired sensation on the face.

Vertebrobasilar insufficiency syndromeis associated with a violation of blood supply in the corresponding blood pool. Because of this, there are attacks of dizziness, loss of consciousness or muscle tone, problems with vision. As you can see, it becomes clear that most of the symptoms of the Arnold-Chiari anomaly do not arise from one immediate cause, but from the combined effects of various factors. Thus, fits of loss of consciousness are caused both by compression of specific centers of the medulla oblongata, and by violation of blood supply in the vertebrobasilar basin. A similar situation occurs with visual, hearing, dizziness and so on.

Syringomyelitisthe syndrome does not always arise, but only in cases of a combination of the Arnold-Chiari anomaly with cystic changes in the spinal cord. These situations are manifested by a dissociated sensitivity disorder (when temperature, pain, and tactile sensitivity are severely disrupted, and deep (limb position in space) remains intact), numbness and muscle weakness in some limbs, impaired pelvic function (urinary incontinence and feces). You can read about what syringomyelia manifests in a separate article.

Each variety of the Arnold-Chiari anomaly has its own clinical features. Anomaly Arnold-Chiari type I may not manifest itself to 30-40 years (as long as the body is young, the compression of structures is compensated). Sometimes this type of vice is an accidental finding when conducting a magnetic resonance imaging for another disease.

Type II is often combined with other vices: meningomyelocele of the lumbar region and stenosis of the aqueduct of the brain. Clinical manifestations arise from the first minutes of life. In addition to the main symptoms, the child has a loud breathing with periods of his stop, violation of ingestion of milk, ingestion of food in the nose (the child suffers, chokes, and can not sucking the breast).

Type III is also often combined with other malformations of the brain and cervico-occipital region. In the cerebral hernia in the cervico-occipital region, not only the cerebellum, but also the medulla oblongata, occipital lobes can be located. This vice is practically incompatible with life.

IV type by some scientists, recently, is not considered a symptomatic complex of Chiari in the modern presentation, because it is not accompanied by the omission of the underdeveloped cerebellum in the large occipital hole. However, the classification of the Austrian Chiari, who first described this pathology, also contains the IV type.

Diagnostics

The combination of a number of the symptoms described above, allows the doctor to suspect the anomaly of Arnold-Chiari. But to accurately confirm the diagnosis it is necessary to carry out computer or magnetic resonance imaging (the latter method is more informative). The image obtained with the help of magnetic resonance imaging demonstrates the omission of structures of the posterior cranial fossa below the large occipital foramen and confirms the diagnosis.

Treatment

The choice of treatment method for the Arnold-Chiari anomaly depends on the presence of symptoms of the disease.

If the vice was detected accidentally (that is, it has no clinical manifestations and does not disturb the patient) when conducting a magnetic resonance imaging for another disease, the treatment is not performed at all. The patient is followed by dynamic observation so as not to miss the moment of appearance of the first clinical symptoms of compression of the brain.

If the anomaly manifests itself as an insignificantly expressed hypertensive-hydrocephalic syndrome, then attempts are made to conservative treatment. For this purpose use:

• dehydration drugs (diuretics). They reduce the amount of CSF, contribute to the reduction of the pain syndrome;
• non-steroidal anti-inflammatory drugs in order to reduce pain syndrome;
• muscle relaxants in the presence of muscle tension in the cervical region.

If the use of drugs is sufficient, then for a period this stops. If there is no effect, or the patient shows signs of other neurologic syndromes (muscle weakness, loss of sensitivity, signs of impaired function of the cranial nerves, periodic attacks of loss of consciousness, and so on), then they resort to a surgical treatment.

Operative treatment consists in trepanation of the posterior cranial fossa, removal of part of the occipital bone, resection of the lowered in the large occipital foramen of the cerebellum, dissection of adhesions of the subarachnoid space, interfering circulation cerebrospinal fluid. Sometimes a shunt operation may be necessary, the purpose of which is to withdraw excess cerebrospinal fluid. "Extra fluid" through a special tube (shunt) is discharged into the thoracic or abdominal cavity. Determining the moment when there is a need for surgical treatment is a very important and important task. Long-term changes in sensitivity, loss of muscle strength, defects of the cranial nerves may not recover completely after surgery. Therefore, it is important not to miss the moment when it is really possible to do without surgery. In type II, surgical treatment is indicated in almost 100% of cases without prior conservative treatment.

Thus, the Arnold-Chiari anomaly is one of the evils of human development. It can be asymptomatic, and can manifest itself from the first days of life. Clinical manifestations of the disease are very diverse, diagnosis is carried out using magnetic resonance imaging. Treatment approaches are different: from the absence of any intervention to operational methods. The volume of treatment is determined individually.