-Introduction:
Among the malformations of the cranio-cervical junction due to its frequency of presentation and the severity of the symptoms,
the Chiari syndrome type I Fig. 1 and syringomyelia Fig. 3 stand out.
The Chiari type I malformation (CM-I) is a malformation of the development of the occipital mesodermal somites.
The most extreme form is the herniation of structures of the lower portion of the cerebellum,
cerebellar tonsils and brainstem through the foramen magnum,
reaching even the spinal canal.
In addition,
(CM-I) is often associated with scoliosis.
Fig. 7 The rate of scoliosis in pediatric patients with CM-I has been described up to 80% without necessarily being associated with syringomyelia.
Some authors have speculated that the etiology of scoliosis is related to the expansive effect of the syringe of the spinal cord,
thus affecting the function of the medial motor neurons,
producing an imbalance of the paraspinal musculature and predisposing the individual to spinal deformity.
Other authors have suggested tonsillar compression as an alternative etiology of scoliosis in patients with CM-I.
Despite the uncertainty of the etiology,
scoliosis in the context of syringomyelia and CM-I is often treated with surgical decompression to stabilize the spinal deformity.
Various studies have shown the importance of early neurosurgical intervention in patients with scoliosis to prevent or slow the progression of the curve because orthopedic treatments are often insufficient in these cases Fig. 8 .
Although this approach is widely practiced,
there are no guidelines to identify patients at risk of concurrent spinal deformity.
The hypothesis has been raised in a study that a syringe size greater than 6 mm presents a greater risk of spinal deformity.
(CM-I) affects both sexes,
with a slight predominance in women.
The beginning symptoms can appear at any age,
although they usually appear between 25 and 30 years and are very rare among those over 60 years.
-Definition:
-The Chiari malformation is a generally congenital disease,
which consists of an anatomical alteration of the base of the skull,
in which there is herniation of the cerebellum and brainstem through the foramen magnum to the cervical canal.
Fig. 2
-The cerebellar tonsils varies with age.
In neonates,
the tonsils are located just below the foramen magnum and descend further during childhood,
reaching their lowest point somewhere between 5 and 15 years of age.
As the individual ages further the tonsils usually ascend coming to rest at the level of the foramen magnum.
As such although 5mm descent in an adult should be viewed with suspicion,
in a child it is most likely normal.
-The term syringomyelia derives from the Latin syrinx,
which means "tube".
It is a chronic disorder of the spinal cord in which a tubular cavity (central) extends through several segments usually occurs in the cervical region,
although it can extend cranially to the trunk of the brain or caudal to the thoracic or lumbar segments.
It is admitted that 40-75% of Chiari type I malformations are associated with syringomyelia.
Conversely,
almost 90% of syringomyelias are associated with Chiari malformation.
The incidence of syringomyelia is around 8.4 cases / year / 100,000 people.
Fig. 3 Fig. 4 Fig. 5 Fig. 6
- The presence of a Cobb angle greater than or equal to 10º is diagnostic criteria for scoliosis.
The scoliosis that is associated with syringomyelia according to the series almost always has the curvature to the left,
unlike the idiopathic scoliosis that is usually dextrous scoliosis.
Fig. 7
-The classification of the Chiari malformation comprises four subtypes:
-Chiari malformation type I: There is a descent of the cerebellar tonsils,
and sometimes of the vermis,
through the foramen magnum,
below C1-C2. Descent of the tonsils through the foramen magnum (> 5/6mm),
there is no hydrocephalus and the IV ventricle is in its normal location.
Fig. 2
-Chiari malformation type II: Herniation of the cerebellar tonsils,
vermis,
fourth ventricle and brainstem occurs through the foramen magnum.
Almost all patients have a cord anchored with a lumbo-sacral myelocele or a myelomeningocele.
Within the findings we can find tonsils and spinal bulb located inferiorly to the foramen magnum and next to it.
(CM-II) can be associated to other types of intracranial alterations (tentorial hypoplasia,
craniolacunia and anomalies in Silvio.
-Chiari malformation type III: Occipital or cervical encephalocele.
It is accompanied by heterotopias,
dysgenesis of the corpus callosum,
heterotopias,
syringohiromyelia,
bony defects at the level of the occiput and in the posterior elements of the upper cervical spine.
The diagnosis is currently made in the prenatal phase.
-Chiari malformation type IV: Severe cerebellar hypoplasia without observing a displacement of the contents of the posterior fossa through the foramen magnum.
A hypoplasia of the brainstem is also observed.
-There are four types of syringomyelia:
- Type I: Syringomyelia with obstruction of the foramen magnum and dilation of the central duct,
it is associated with Chiari type I and with other obstructive lesions of the foramen magnum.
Fig. 6
- Type II: Syringomyelia without obstruction of the foramen magnum or idiopathic.
- Type III: Syringomyelia associated with other diseases of the spinal cord such as spinal cord tumors (intramedullary),
traumatic myelopathy,
arachnoiditis and spinal pachymeningitis,
myelomalacia secondary to compression of the spinal cord (tumor,
spondylosis).
-Type IV: pure hydromyelia,
usually associated with hydrocephalus
-Scoliosis:
It is considered that a curvature greater than 10º in the coronal plane corresponds to scoliosis.
Values lower than 10º are considered "attitude" or "position" scoliosis.
Fig. 7
According to its magnitude,
the scoliotic curves can be cataloged in:
-Mild: Curves less than 20 °
-Moderate: Curves from 20 ° to 40 °
-Severe: Curves greater than 50 °