How is cerebellar tonsillar ectopia measured?
How is cerebellar tonsillar ectopia measured?
The position of the cerebellar tonsils is measured on sagittal T1- or T2-weighted images of the cervical spine or brain by drawing a line at the foramen magnum from the inner margin of the ophisthion to the basion, and then measuring the distance from that line to the inferior most margin of the cerebellar tonsils.
What mm is considered Chiari malformation?
A diagnosis of a Chiari malformation usually signifies that the cerebellar tonsils protrude below the foramen magnum (often cited as at least 5 millimeters, though this is controversial).
What is a mild cerebellar tonsillar ectopia?
Ectopia indicates an inferior position of the cerebellar tonsils. Cerebellar Tonsillar Ectopia denotes all cases including congenital and acquired in which the cerebellar tonsils are below the base of the skull. Cerebellar Tonsillar Ectopia includes asymptomatic and symptomatic cases of all degrees of severity.
What is a borderline cerebellar tonsillar ectopia?
Some medical conditions are associated with a higher frequency of headaches. Borderline cerebellar tonsillar ectopia which may be defined as the downward extension of cerebellar tonsils of <5 mm below the foramen magnum is among these conditions.
Is Chiari a 5mm malformation?
The classic definition of Chiari I is herniation greater than 5mm below the foramen magnum. However, the size of herniation seen on MRI does not closely correlate with symptoms. Someone without herniation may have severe symptoms while another with 20-mm herniation may have no symptoms.
What is borderline low lying cerebellar tonsils?
Normally, the cerebellar tonsils should lie no more than 3 mm below the foramen magnum. Extension below the foramen between of 3 and 5 mm is considered borderline. Chiari malformations larger than 5 mm but smaller than 10 mm are symptomatic in approximately 70% of patients.
Is cerebellar tonsillar ectopia normal?
Tonsillar ectopia, encompassing slight descent of the cerebellar tonsils and Chiari I malformations, are disorders observed routinely in older children and adults and are believed to be an acquired form of the Chiari malformations.
How far should cerebellar tonsils extend?
What is mildly low lying cerebellar tonsils?
Low-lying tonsils, sometimes also called benign tonsillar ectopia, is a subtype of cerebellar tonsillar ectopia denoting asymptomatic and only slight downward descent of the cerebellar tonsils through the foramen magnum and is distinct from Chiari I malformations.
Is Chiari malformation the same as cerebellar tonsillar ectopia?
If there is only a slight tonsillar protrusion thru the foramen magnum and the patient does not exhibit typical symptoms of Chiari, the patient may be diagnosed as having cerebellar tonsil ectopia – sometimes considered a milder form of Chiari malformation.
