Thanks for writing in. Low lying cerebellar tonsils are described as cerebellar ectopia and it can lead to
tonsillar herniation.In Tonsillar herniation or Downward cerebellar herniation the cerebellar tonsils move
downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical
spinal cord as they pass through the foramen magnum.
Increased pressure on the brainstem can result in dysfunction of the centers in the brain responsible for
controlling respiratory and cardiac function.Tonsillar herniation of the cerebellum is also known commonly as
a Chiari Malformation (CM) which previously was called an Arnold Chiari Malformation (ACM). The currently
accepted radiographic definition for a Chiari malformation are cerebellar tonsils that lay at least 5mm below
the level of the foramen magnum.
There are many suspected causes of tonsillar herniation including Spinal cord tethering or occult tight filum
terminale ; decreased or malformed posterior fossa not providing enough room for the cerebellum; hydrocephalus
or abnormal CSF volume pushing the tonsils out; connective tissue disorders, such as Ehlers Danlos Syndrome,
can be associated as well.
The symptoms that you mentioned are of brainstem compression, which might be occuring due tonsillar
Treatment includes measures to reduce intracranial tension, there by preventing tonsillar herniation.