Generally, when a part of the cerebellum, which is known as cerebellar tonsils
, is located under the foramen magnum, it is known as a Chiari malformation.Chiari malformation is categorised into four types: Type I Chiari malformation is asymptomatic.
The term Chiari malformation (CM), also known as the Arnold-Chiari malformation, refers to caudal displacement of the cerebellar tonsils
through the foramen magnum.
Chiari I malformation is defined radiographically as a simple displacement of the cerebellar tonsils
5 mm or greater below the foramen magnum and is distinguished from Chiari II and Chiari III malformations occurring with myelodysplasia and cervical encephalocele, respectively (9).
The base of the brain has cerebellar tonsils
, which in large part are responsible for our balance and coordination.
Among the possible malformations of the craniocervical junction, Chiari malformation Type I is notable for its frequency and it is defined as a set of congenital anomalies of the metencephalon that result in abnormal relations between various structures: The cerebellum, the cerebellar tonsils
, the medulla oblongata, the cervical medulla and the base of the skull.
investigated the position of the cerebellar tonsils
relative to the foramen magnum and the position of the iter relative to the incsiural line in 7 patients with IH, comparing them to normative data from Reich et al.
Two hours later, the Spa[O.sub.2] and the ETC[O.sub.2] slightly decreased and anisocoria was observed; and an urgent CT scan of the head demonstrated a diffuse cerebral edema and the herniation of the cerebellar tonsils
(Figures 1(a) and 1(b), respectively).
To investigate for an occipital headache, at 3.7 years old, she underwent an MRI that disclosed a CM1 with herniation of the cerebellar tonsils
beneath the foramen magnum of 17 mm (Figure 1).
"Position of cerebellar tonsils
in the normal population and in patients with Chiari malformation.
In CM-1, variable caudal displacement of cerebellar tonsils
occurs into the upper cervical canal.
Cranial magnetic resonance imaging (MRI) revealed that his cerebellar tonsils
extended approximately 10 mm inferiorly through the foremen magnum, which represented a type I Arnold-Chiari malformation.
Computed Tomography Scan of the head showed multiple hypodense areas in the cerebellum, inferior herniation of cerebellar tonsils
with obstructive hydrocephalus.