Arnold-Chiari malformation is a congenital hypoplasia of the embryonic hindbrain, characterized by herniation of the inferior cerebellar tonsil into the spinal canal, causing a range of symptoms.
How is submicrocephalic tonsillar herniation malformation typed?
Type I: The cerebellar tonsils are elongated and penetrate into the spinal canal in a tongue-like manner through the foramen magnum, but the fourth ventricle remains on the foramen magnum; Type II: The fourth ventricle and its choroid and medulla oblongata herniate below the foramen magnum together with the cerebellar tonsils, and the V~XII pairs of cerebral nerves are stretched and displaced to varying degrees, and can descend to the middle cervical segment in severe cases; Type III: Chiari II with cervical spina bifida and Type III: Chiari II with cervical spina bifida and spondylolisthesis; Type IV: Chiari malformation with cerebellar hypoplasia.
What are the clinical manifestations?
The clinical manifestations of Chiari I malformation are related to the degree of displacement of the lower herniated tissue, the presence or absence of bone deformities or other congenital malformations, and the presence or absence of spinal hydrocele.
1.Chiari I malformation
Headache is a common symptom, mainly located in the suboccipital area, which is aggravated by movement and coughing, and can affect life and work in the later stage. There are less cerebral nerve symptoms, mainly facial numbness, diplopia, tinnitus, hearing impairment, pronunciation and swallowing disorder. When the medulla oblongata and superior cervical medulla are affected, motor and sensory impairment will occur to varying degrees. When the cerebellum is affected, nystagmus and ataxia appear. In severe cases, increased intracranial pressure may appear, such as headache, nausea and vomiting.
2.Chiari II malformation
Many infants with Chiari II malformation are born with spinal cord spondylolisthesis, and most of the patients with spinal cord spondylolisthesis can be seen with Chiari malformation on MRI. Newborns often present with severe respiratory stridor, apnea, absence of the vomiting reflex, and tetraplegia. Older children are less likely to have an acute onset of symptoms, which are mainly nystagmus, limb weakness or spasticity, ataxia, neck pain, and dysphagia. Most children with Chiari I malformation also have scoliosis and other congenital malformations of the head.
Why is magnetic resonance imaging (MRI) the adjunctive test of choice for this disease?
MRI is currently the best imaging test for diagnosing Chiari malformation and spinal cord cavitation because it shows soft tissue deformities very clearly and without damage to the body. In contrast to dynamic MRI, T2-weighting can be used to study the flow pattern of the cerebrospinal fluid, which is useful for understanding the fluid dynamics of the fluid in the fluid-filled cavity. It is generally believed that surgery is effective in patients with abnormal cerebrospinal fluid fluid dynamics; conversely, surgery is not effective. sagittal plane of TSE sequence can adequately display Chiari malformation, and can clearly show where the cerebellum, brainstem and cervical medulla are located from different angles, as well as the influence of the bone and cartilage in the occipitocervical region on the surrounding neural tissue, and can also well show its complication of the spinal fluid cavity, as well as flattened skull base, atlanto-occipital The degree and extent of bony deformities such as flat skull base and atlanto-occipital fusion can also be well visualized.
What treatment should be taken?
Usual care should be taken to avoid trauma and hyperextension of the head and neck to avoid exacerbation of symptoms or respiratory arrest with medulla oblongata compression.
1.Treatment principles for Chiari I type
(1) Patients with no symptoms may not consider surgery for the time being, but close follow-up is required.
(2) Patients with clinical symptoms but without spinal cord hydrocele should undergo decompression of the posterior cranial fossa and cervical 1~2 segments.
(3) Patients with spinal cord cavitation should undergo decompression of the posterior cranial fossa and cervical 1~2 segments alone, or perform spinal cord cavitation shunt at the same time, as appropriate.
(4) Patients with other deformities of the occipital cervical region that require surgical solution can be treated together.
2.Chiari II type
It is generally believed that Chiari II malformation is an irreversible congenital malformation and decompression is not effective, but early surgery is still recommended because it helps to relieve the disease, and if there are other malformations, the corresponding treatment should be done, such as repair of spinal cord spinal membrane expansion and ventriculo-abdominal shunt if there is hydrocephalus.
What is the prognosis?
The prognosis is good for most patients, but the earlier the onset of symptoms (e.g., in infancy), the worse the prognosis. The previous surgical results show that the greatest number of patients have improved painful symptoms after surgery, and most of the muscle tonicity is also relieved, while hyperalgesia is the least progressed. Complications after posterior decompression surgery include death, neurological dysfunction, and irregular respiratory heartbeat. Sensory dissociation or bilateral upper extremity muscle atrophy may occur.