Definition: At the end of the 19th century, in the 1860s, the German pathologist Chiari described four types of congenital anomalies in which the cerebellum and brain tissues droop, which he named after himself.
Type 1: Arnold-Chiari (AC Type 1) anomaly is the extension of the tonsils of the cerebellum into the cervical spinal canal.
Type 2: Arnold- Chiari (AC Type 2) anomaly, on the other hand, involves the extension of the cerebellum structures into the cervical spinal canal besides the tonsils of the cerebellum. In this type of anomaly, there is a myelomeningocele sac in the lumbar region.
Type 3: Arnold-Chiari (AC Type 3) anomaly is the presence of myelomeningocele sac in the neck region and midbrain structures in the sac.
Type 4: In Arnold-Chiari (AC Type 4) anomaly, the cerebellum tissues are not developed, as well as the midbrain tissues are sagging.
Type-1 Cerebellum prolapse:
The main feature of this type of anomaly is that the tonsils of the cerebellum protrude into the cervical spinal canal under the foramen magnum. In this disease, the circulation of the Cerebrospinal Fluid (CSF) in both the brain and the spinal cord canal It causes pressure changes in the brain and an increase in intracranial pressure after its deterioration.
There are 3 theories put forward in the formation of this disease;
1: Hydrodynamic theory; pressure difference between intracranial pressure and spinal canal
2: Mechanical theory; CSF circulation is impaired due to adhesions in the cerebellum
3: Wrong development; cerebellum tissues are elongated as a local extension of pervasive developmental disorder.
Type-1 Cerebellum prolapse is more common in youth. The most common age is 20-30 years. It is seen more frequently in women than in men. It is seen in childhood.
Type-1 Cerebellum prolapse: Clinical complaints and findings:
The most common complaints of cerebellum prolapse are pain in the head, neck, neck and shoulders, especially after intermittent increased intracranial pressure. . Headache, especially at night, wakes you up from sleep. Headache is usually accompanied by nausea and sometimes vomiting. The headache is followed by pain and stiffness in the nape, sometimes radiating to the shoulders. The pain happens from time to time, sometimes not at all because of the intermittent course of the CSF circulation. In addition, shoulder, lower back or leg pains are seen, these pains are not reflected. Pain and pressure or pressure sensation in the neck, shoulders and arms are the most common complaints. These pains are followed by dizziness and imbalance complaints. As a reflection of the increased intracranial pressure, there are complaints of blurred vision in the eyes, double vision, pain and pressure behind the eyes and the inability to look at the light and the sun. After that, 30-40% of gait disturbances (ataxias) are seen. Less frequently, 15-25% of the time, dysphagia, speech disorder, nystagmus, and cerebellum cranial nerve palsies are seen. Since the cerebellum is a balance center, the cerebellum is under pressure. especially fine movements or coordinated movements and sometimes tremors in the hands are seen. Balance disorder under the title of ataxia is dominant.
Type 1 cerebellum prolapse is seen together in 30% of childhood and adolescent progressive scoliosis
Diagnosis
Magnetic Resonance Imaging (MRI) is the best examination method today in the examination of this malformation. In cervical MRI examination, one or both cerebellum tonsils lie under the foramen magnum. However, this sagging is not significant numerically. Because the causes of cerebellar entrapment are different, for example, even a 3 mm droop may make cerebellum prolapse complaining, or an 8 mm droop may never cause any complaints. Such anomalies may be accompanied by anomalies such as small posterior fossa, platybase, atlanto-occipital assimilation or basilar invagination. Therefore, the presence of these anomalies should be carefully investigated with 3D Computed Tomography tests of the neck region. Bone anatomical details of the cerebellum and foramen magnum in the brain tomography test. is examined. This examination is very important in surgical strategy. Also, the dynamics of brain CSF should be reviewed for CSF circulation in the brain. Hydro-syringomyelia cavities are seen together in 50-60% of Arnold-Chiari malformations.
DIFFERENTIAL DIAGNOSIS
These patients are usually examined and treated in many different branches in hospitals.
1: They are examined and treated in neurology outpatient clinics due to headache,
2:: They are investigated primarily as vertigo under the heading of dizziness,
3:: Neurosurgery due to neck hernia They are investigated in orthopedic physical therapy and pain outpatient clinics,
4: They are treated by psychiatry clinics under the heading of depression
5: They are triggered by chest diseases under the heading of sleep apnea and respiratory problems
6 : Sometimes they are examined by cardiology clinics due to chest pain and shortness of breath
7: They are examined by gastro-entrology clinics with the complaint of nausea.
8: Demyelinating (multiple sclerosis) diseases of the cerebellum
Treatment
The treatment of this anomaly is surgery. Unfortunately, there is no medical treatment for this anomaly. The main question in treatment is whether this anomaly gives complaints or not. The answer to this question is very important. The aim of surgical treatment is to relieve the deteriorated neural structures in the cranio-cervical region and to restore the posterior cavity bone structures to restore CSF circulation. Surgical techniques applied in the surgical treatment of cerebellum prolapse type 1′; suboccipital craniectomy, removal of arachnoid adhesions, tonsillar resection and duraplasty.
Causes of anterior compression before performing suboccipital decompression; platybase, C-1 assimilation should be defined. In such cases, other anomalies accompanied by cerebellum prolapse should be defined correctly. In this case, surgical intervention on the neck should be considered after removing the anterior pressure by mouth.
Alternative surgical techniques such as sirengo-subarachnoid, sireno-pleural shunt are applied in cases with spinal cavitation such as hydro/syringomyelia in Arnold-Chiari malformation.
The first problem in pediatric A-Chiari malformation cases is the indication for surgery. A-Chiari type 1 diagnosis in this age group is mostly an accidental finding. There is no definite consensus on surgical treatment in this age group. In the surgical treatment results of adult group Arnold-Chiari malformations; In particular, 100% of the patients who underwent suboccipital craniectomy, C-1 laminectomy, and duraplasty showed improvement in complaints, and 80% of syringomyelia patients had a reduction in cavitation with syringomyelia.
In conclusion: Type-1 cerebellum prolapse is a congenital anomaly and its formation results in compression of nerve elements and inhibition of CSF circulation after a mechanical block. Generally, there are different subjective or objective complaints at the young adult age. Headache, neck pain and shoulder pain are the most common complaints among these complaints: 60% of the patients have syringomyelic cavitation in the spinal cord. Cervical MRI is the gold standard in diagnosis, and the tonsils of the cerebellum have migrated into the cervical spinal canal. A- The treatment of Chiari type 1 is surgery. Suboccipital decompression and duraplasty are the most common surgical treatments. The results of the surgical treatment are excellent if the surgeon removes the pressure, if any, in the neck area, bone, or the reason that prevents the circulation of CSF in the cerebellum. If the cause of the cerebellum prolapse is not eliminated, unfortunately, improvement in complaints should not be expected. Diseases found in the differential diagnosis of such unsuccessful conditions or other cerebellar diseases should be reviewed.
