Cerebellar tonsillar herniation

Brief introduction of cerebellar tonsil malformation The cerebellar tonsil malformation is also known as the Arnold-Chiari malformation. The Arnold-Chiari syndrome is a congenital dysplasia of the hindbrain. It is a congenital hindbrain malformation that causes abnormal embryonic development to cause the lower medulla and the lower part of the fourth ventricle to penetrate the spinal canal. The cerebellar tonsil is extended into a wedge shape and enters the occipital foramen or cervical spinal canal. In severe cases, part of the lower iliac crest is also inserted into the spinal canal. The lingual pharyngeal, vagus, accessory, sublingual and other posterior cranial nerves and the upper cervical nerve root are pulled down. The occipital foramen and the upper cervical canal are filled, and the cerebrospinal fluid circulation is blocked to cause hydrocephalus. This disease is often accompanied by other craniocerebral deformities such as spinal meningocele, cervical spondylolysis and cerebellar hypoplasia. basic knowledge The proportion of illness: 0.002% Susceptible people: infants and young children Mode of infection: non-infectious Complications: syringomyelia hydrocephalus

The cause of cerebellar tonsillar malformation

(1) Causes of the disease

The exact cause of the disease is unclear and may occur in the third month of the fetus, and may also be associated with excessive tissue growth or brain stem dysplasia and cerebrospinal fluid dynamics between the ventricular system and the subarachnoid space.

(two) pathogenesis

There are different opinions on the pathogenesis of scholars, among which the traction theory is the most popular opinion in the past. Patients with spina bifida and spinal meningocele are fixed in the spina bifida, during the growth and development, the spine and spinal cord. The growth rate is different, the spinal cord can not move up according to normal conditions, causing the spinal cord and cerebellum tissue to be moved downward, and the cerebellar tonsil sac is produced.

It is also believed that the influence of spinal cord traction is mainly limited to the lumbosacral region, and the chest segment is rarely affected. At the same time, patients with tethered cord syndrome do not have cerebellar tonsillar mandibular deformity. Therefore, spinal meningocele and cerebellar tonsil are considered. The squat is not related, but the primary deformity of the medulla, cerebellum, spinal cord, occipital bone and brain. During the development process, the volume of the posterior fossa is small, and the brain tissue is overgrowth, so that some brain tissue is excised from the occipital foramen, cerebellar tonsil At the same time, the medulla also has different degrees of downward movement. In severe cases, the medulla can be completely displaced outside the occipital foramen, which causes the medullary dorsal flexion, the cranial nerves, the cervical nerves to be pulled, and the spinal cord to be compressed and flattened. The brain tissue adheres to the spinal cord and surrounding structures, the occipital bone is occluded, the midbrain tube or the fourth ventricle is blocked by the mesenteric occlusion, forming obstructive hydrocephalus, which can aggravate the cerebellar tonsil sac, and the median hole can be accompanied by syringomyelia. Or other large occipital deformities.

In addition, some people have proposed the hydrocephalus theory that the cerebellar tonsil is caused by the downward pressure of the baby's hydrocephalus.

The cerebellar tonsil is prolonged, and the extracranial sacral sac is the basic pathological change. In severe cases, it is inserted into the upper cervical spinal canal, accompanied by the medulla and fourth ventricle extending downward at the same time. The medulla becomes long and breaks into the spinal canal. Inside, the lower part of the fourth ventricle also penetrates into the spinal canal, which is also an important feature of this deformity. The cerebellar tonsil is often filled with the cisterna magna, accompanied by tissue adhesion, subarachnoid occlusion, and sometimes cyst formation due to cerebellum The medullary occlusion, the fourth ventricle mesenteric adhesion, or the midbrain tube adhesion occlusion can cause obstructive hydrocephalus, the medulla and upper cervical spinal cord are deformed and deformed, the cervical spinal cord is displaced downward, and the cerebellum is pulled down to make the brain nerve The tension is long, and the upper cervical nerve enters the intervertebral foramen in the upward direction; there may be a midbrain shift, and the bridge pool, the outer pool, and the annular pool may be merged.

Cerebellar tonsil malformation prevention

Mainly pay attention to women during pregnancy, perinatal health and disease prevention and can not use drugs at random to prevent the birth of congenital malformations.

Complications of cerebellar tonsillar malformation Complications syringomyelia hydrocephalus

Arnold-Chiari malformations often associated with other large occipital foramen deformities and spinal meningocele defects, including syringomyelia, skull spinal fusion malformations, basal depression, arachnoid adhesions, dural straps, cervical spinal kinks, hydrocephalus Etc; other malformations include multiple cerebellar malformations, gray matter ectopic, hydrocephalus, gliosis or bifurcation of the midbrain tube, tetrapocy beak-like malformation, internal calvarial depression, meningocele, spinal cord longitudinal fissure , the fourth ventricle cyst and so on.

Cerebellar tonsil malformation symptoms common symptoms ataxia nausea intracranial pressure increased radiation pain tinnitus drunken gait double vision persistent pain sensory disorder neuron migration abnormalities

According to the severity of the lesion, it is divided into 3 types:

Type I is the lightest type, which shows that the cerebellar tonsils penetrate into the spinal canal through the occipital foramen. The medulla is slightly displaced forward and downward. The fourth ventricle is normal, often with cervical syringomyelia and cranial neck. Bone deformity.

Type II is the most common type, manifested as cerebellar tonsils with or without the ankle into the spinal canal, the fourth ventricle becomes longer and lower, and some structures such as the skull, dura, midbrain, cerebellum, etc. Incomplete, 90% have hydrocephalus, often combined with syringomyelia, abnormal neuronal migration, spinal meningocele and so on.

Type III is the most severe type, rare, manifested as medulla, cerebellar vermis, fourth ventricle and part of the cerebellar hemisphere into the upper part of the spinal canal, combined with occipital meningeal bulging, and obvious head and neck deformity, cerebellar malformation, etc. .

Chiari reclassified it into 4 types. He added type IV to the first 3 types: cerebellar hypoplasia, but did not break into the spinal canal. This type is not accepted.

There are more women with cerebellar tonsillar malformation than men, type I is more common in children and adults, type II is more common in infants, type III is often seen in the neonatal period, type IV is often present in infancy, and it is reported that from symptom onset to admission time 6 weeks to 30 years, an average of 4.5 years.

The most common symptoms of cerebellar tonsil malformation are pain, usually pain in the occipital, neck and arms, burning-like radiation pain, a few local pain, usually persistent pain, and often painful in the neck. Other symptoms include dizziness, tinnitus, double vision, unstable walking and muscle weakness.

Common signs include lower extremity reflexes and upper limb muscle atrophy. About 50% of patients have sensory disturbances, upper limbs often have pain, and temperature is reduced, while lower extremities are degenerative sensation, nystagmus is common, the incidence rate is 43%, and soft palate is weak. Patients with cough accounted for 26.7%, optic disc edema was rare, and those with optic disc edema were accompanied by cerebellar or pons brain tumors. Saez (1976) was divided into 6 types according to their main signs, and each type showed:

1. The occipital macropore area is 38.3%, which is the cranial vertebral junction lesion involving the cerebellum, the lower brain stem and the cervical spinal cord. It is characterized by headache, ataxia, nystagmus, dysphagia and exercise weakness, and corticospinal tract. The symptoms of the spinal thalamus bundle and the dorsal column, various symptoms appear comprehensively, it is difficult to determine which structure is the main affected person.

2. The onset of intracranial pressure increases 21.7%. The prominent symptoms are headache when exerting force, nausea, vomiting, blurred vision and dizziness when the headache occurs or after headache. The nervous system examination is normal or only slight and not too Clear positioning signs.

3. The central part of the spinal cord is damaged by 20%. The symptoms and signs are mainly attributed to the internal or central lesions of the cervical spinal cord. It is characterized by pain-sensing sensory disturbance of the scapular region, segmental weakness or long-short symptoms, similar to syringomyelia or Clinical manifestations of intramedullary tumors.

4. Cerebellar type accounts for 10%, mainly manifested as gait, trunk, or limb ataxia, nystagmus, sputum and corticospinal tract disease.

5. The tonic type accounted for 6.7%, showing a state of tonicity, paroxysmal urinary incontinence, moderate to severe paralysis of the limbs, and lower limbs than the upper limbs.

6. The ball paralysis type accounts for 3.5%, and there is a manifestation of brain damage in the posterior group.

The cerebellar tonsil mandibular deformity type I mainly manifests as the occipital macropore area compression syndrome, that is, the posterior group cranial nerve symptoms, cerebellar signs, cervical nerve and cervical cord disease, increased intracranial pressure and syringomyelia, type II is After birth, there may be feeding difficulties, wheezing, asphyxia, combined with mental retardation, progressive hydrocephalus, high intracranial pressure and posterior group neurological symptoms.

Examination of cerebellar tonsil malformation

Cerebrospinal fluid examination: low pressure of lumbar puncture CSF, positive neck test, increased protein content of cerebrospinal fluid, but rarely more than 1g / L, waist wear should be cautious, with intracranial hypertension is prohibited.

1. Cranial plain film

The skull and cranial vertebrae can show their combined bone deformities, such as basal depression, occipital fusion, spina bifida, and Klippel-Feil syndrome.

2. CT scan

CT scans show various pathological changes mainly through spinal canal and cerebral angiography combined with coronary scanning and sagittal reconstruction techniques.

Type I: CT manifestations: 1 The cerebellar tonsils are displaced downwards, and the degree of incision into the spinal canal is different. The axial position is like the anterior spinal canal of the spinal canal, and the two oval-shaped soft tissue blocks, which extend upward with the cerebellum, and the cerebral pool The angiography and coronal position are clearer, but it should be noted that the cerebellar tonsil is still within the normal range of less than 3 mm of the occipital foramen, with a boundary abnormality of 3 to 5 mm, a pathological state of 5 mm or more, and 2 medullary and fourth ventricle positions. Normal, but the fourth ventricle can be prolonged, 3 can be associated with hydrocephalus (0% to 40%), 4 often combined with syringomyelia, and about 1/3 to 1/2 of patients have skull fusion disorder.

Type II: CT performance in addition to the performance of type I, there are changes in the skull, dura mater, brain, ventricles and pools.

Cranial and dura mater changes: cranial cap bone fracture at birth, disappeared 2 to 4 weeks or months after birth, cerebellum grows in the narrow cranial fossa, and even oppresses the erosion slope and the tibial rock, after the light rock The edge is flat or sag, and the inner ear canal becomes shorter. In severe cases, the sacral curvature changes in the two rock sections and the slope, the occipital foramen enlarges, the cerebral palsy is poorly developed or perforated, and the previous 2/3 is most susceptible to axial position and Crest-enhanced scanning can not see the complete linear enhancement of cerebral palsy or linear reinforcement interruption, the cerebellum curtain is attached to the vicinity of the occipital foramen, making the posterior cranial fossa narrower, the cerebellar meridian enlarged, and losing the normal "V" shape. Form a "U" shape.

Changes in the midbrain and cerebellum: the quadrilateral dorsal process fuses, forming a bird's beak with most of the midbrain, and hangs down to the cerebellar hemisphere. The cerebellum protrudes from the cerebral phenotype and changes in a pagoda shape, and the temporal lobe and occipital lobe correspond. Displacement, cerebellum around the brain stem growth can protrude into the cerebral cerebral horn pool, like a two-way growth of the mass, the cerebellum in the cerebellopontine angle pool and the ventral side of the pons form a "three-peak" change.

Due to dysplasia of the cerebral palsy, the cerebral gyrus of the midline of the brain appears interlaced, and the ventricles and cerebral cisterns are abnormal: the fourth ventricle is small, elongated and moved downward, and the normal fourth ventricle should reach the upper part of the rock in the axial position. /3, the disease is lower than this level, the third ventricle is slightly enlarged, the middle block is enlarged, the third ventricle is partially disproportionately narrow, the asymmetry of the lateral ventricle is enlarged, the occipital angle is larger than the forehead, and the caudate nucleus is pressed against the forehead It is concave, the tip is sharpened, the coronal position is clear, the transparent compartment is often absent, the cranial fossa is smaller or occluded, the quadrilateral pool is enlarged, 90% has hydrocephalus, often accompanied by narrowing of the middle cerebral water tube or Reflexes, often combined with other malformations, such as abnormal neuronal migration, skull base depression, longitudinal spinal cord and so on.

Type III: CT manifested as medulla, pons, cerebellar vermis and cerebellar hemisphere. The lower cerebral palsy enters the upper cervical spinal canal. The fourth ventricle is often compressed, accompanied by hydrocephalus, with obvious skull base depression and large occipital bone. The enlargement of the pores and the brain swelling of the occipital cerebral ventricle often lead to secondary malnutrition and microcephaly.

3. MRI examination

MRI examination is a non-invasive examination, which can clearly show the structure of the posterior cranial fossa and can directly observe the syringomyelia. Therefore, it is especially suitable for the diagnosis of Arnold-Chiari malformation. Combined with CT, other bone deformities can be found.

MRI diagnosis of this disease type I, mainly based on cerebellar tonsil into the spinal canal, when the cerebellar tonsil is more than 5cm above the occipital foramen is morbid, with a median sagittal T1-weighted image is most suitable for observing the position and size of the cerebellar tonsil. The MRI manifestations are: 1 skull base cervical deformity, basilar artery compression, cervical vertebrae and occipital fusion, neck 2, neck 3 partial fusion, Klippel-Feil syndrome, cervical recessive spina bifida, 2 cerebellar tonsils through the occipital foramen Prolonged, prolonged to neck 1 accounted for 62%, extended to neck 2 accounted for 25%, extended to neck 3 accounted for 3%, 3 occipital large pool shrink, often with dura mater, arachnoid and spinal cord adhesion, 4 combined with syringomyelia, 5 combined hydrocephalus.

The MRI manifestations of Arnold-Chiari malformation type II are as follows: 1 the spinal cord is displaced downward, the upper cervical nerve root rises to its export level, 2 the brain stem is significantly prolonged, the medulla protrudes into the cervical medullary canal, 3 cerebellum dysplasia, and the tail end Prolonged, through the occipital hole to the upper edge of the cervical 1 vertebral arch, 4 narrow cerebellum tongue-like protrusion, through the neck 1 vertebral ring, from the dorsal medullary side down to the neck 2 ~ 4 level, even to the upper end of the thoracic vertebra, 5 in the neck The fourth ventricle portion has different degrees of expansion, sometimes forming a punctiform diverticulum, protruding into the medulla at the dorsal aspect of the upper cervical spinal cord.

The abnormalities of type II combined with other nervous systems are as follows: 1 skull and dura mater abnormalities: inner sulcus of the cranial parietal bone, scallop-like changes in the slope and rock, enlargement of the occipital foramen and enlargement of the posterior cranial fossa, partial loss or perforation of the cerebral palsy, cerebellum Curtain dysplasia, 2 midbrain and cerebellar abnormalities: the cap is beaker-shaped, the cerebellum is tower-shaped, the brainstem overlaps with the surrounding cerebellum, the cerebellar margin is placed, 3 ventricles and cerebral ventricles are abnormal: the fourth ventricle is prolonged and moved down, Flattened, the middle block is enlarged, the transparent partition is absent, the asymmetry of the lateral ventricle is enlarged, the cerebral pool of the posterior cranial fossa is compressed, 4 other abnormalities: meningocele, syringomyelia, longitudinal fissure, gray matter ectopic, Cerebellum back, cerebral aqueduct stenosis, corpus callosum and fourth ventricle cysts.

Diagnosis and diagnosis of cerebellar tonsil malformation

diagnosis

According to the age of onset, clinical manifestations and auxiliary examination, the diagnosis of cerebellar tonsillar mandibular malformation is generally not difficult, especially the clinical application of CT and MRI makes its diagnosis simple, accurate and rapid.

Differential diagnosis

The disease should be differentiated from the cerebellar tonsil occipital foramen magnum. The former tonsils are mostly tongue-shaped, often with other malformations, while the latter tonsils are mostly conical, and can also show intracranial space-occupying lesions. The signs are not difficult to identify.

Large occipital condyle: When there is a space-occupying lesion in a certain cavity in the skull, the pressure of the sub-chamber is higher than the pressure of the adjacent sub-chamber, so the brain tissue in the high-pressure part is squeezed and displaced to the low-pressure part, that is, It is a brain palsy. Occipital macroporous sputum, also known as cerebellar tonsil sputum, mostly occurs in the posterior fossa hematoma or space-occupying lesions, which directly causes the cranial cavity pressure to increase severely, causing the cerebellar tonsils to be squeezed and smashed downwards; In the middle and late stages, the pressure on the screen increases to the lower part of the cerebellum, and eventually the occipital foramen will be complicated. There are two types of occipital foramen: acute sputum and chronic sputum.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.