The cerebellar tonsils
were also prominent, without definite herniation.
3 mm increase of basion-atlas interval), anterior flexion of the occipitoatlantal joint (8 degree decrease of clivus-axis angle), increased basilar impression, and cerebellar ptosis with downward displacement of cerebellar tonsils
to C-1 (white arrow).
In this case the cerebellar tonsils
were herniating through the foramen magnum when the imaging study was done.
Chiari I malformation is characterized by low-lying cerebellar tonsils
In addition, although decompression surgery of the cerebellar tonsils
is indicated as an effective treatment of the syringomyelia-Chiari I complex, resulting in the regression of symptoms during the immediate postoperative period or clinical improvement in 78% of cases , in the present study surgery did not result in clinical improvement and aggravation of the symptoms was observed.
This is due in some part to the relief that a surgical correction of the protruding cerebellar tonsils
can provide, allowing more normal function of the nervous system.
Spontaneous CSF leaks also can cause generalized sagging of the brain with downward displacement of the cerebellar tonsils
that is clearly visible on MRI with gadolinium.
There may also be descent of the cerebellar tonsils
, obliteration of prepontine, perichiasmatic cisterns, flattening of the optic chiasm, crowding of the posterior fossa, as well as decreased ventricular size, according to Dr.
Both Chiari type I (Chiari 1) and type II malformations include a narrow foramen magnum and cerebellar herniation; the type I malformation is characterized by the cerebellar tonsils
extending at least 3 mm below the foramen magnum, and typically, an elongated medulla is present (Semple & McClure, 1996).
Chiari I malformation consists of herniation of the cerebellar tonsils
into the foramen magnum, thus crowding the craniocervical junction.
The lower part of the cerebellum, called the cerebellar tonsils
, hangs down through the opening at the bottom of the skull and causes blockage of spinal fluid to the spinal canal.
1) cerebellar tonsils
are situated above the foramen magnum, although occasionally it may pass through the foramen magnum.
Computed Tomography Scan of the head showed multiple hypodense areas in the cerebellum, inferior herniation of cerebellar tonsils
with obstructive hydrocephalus.
Subsequent magnetic resonance imaging detected a herniation of the cerebellar tonsils
to the level of C2 and the presence of a cervical syrinx--findings consistent with a Chiari I malformation.