Submicrocephalic herniation malformation, or Arnold-Chiari malformation, is a manifestation of congenital hypoplasia of the embryonic hindbrain, characterized by herniation of the submicrocephalic tonsils into the spinal canal, resulting in 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 herniated below the foramen magnum together with the cerebellar tonsils, and the V~XII pairs of cerebral nerves were stretched and displaced to different degrees, and in severe cases, they could descend to the middle cervical segment;
Type III: Chiari type II with cervical spina bifida and spondylotic bulge;
4.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 the pain is severe in the later stage, which can affect life and work. 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.
Many infants with Chiari II malformation are born with spinal cord spondylolisthesis, and most of the patients with spinal cord spondylolisthesis can be seen 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 II 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) Combined with other occipital and cervical deformities requiring surgical solution, they can be treated together.
Chiari type II is generally considered to be an irreversible congenital malformation, and decompression is not effective. However, early surgery is still recommended because it helps to relieve the disease, and if other malformations are present, the corresponding treatment should be done, such as spinal cord bulge repair and ventriculo-abdominal shunt for 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 the least progress is made in sensory loss. Complications after posterior decompression surgery include death, neurological dysfunction, and irregular respiratory heartbeat.