Low Lying Cerebellar Tonsils - MRI

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Permalink Reply by balachandran on December 11, 2009 at 7:34am

You are right.
cerebellar tonsils in cervical spinal canal is an ectopic .
low lying cerebellar tonsil,peg shaped,> 5 mm below foramen magnum is certainly Chiari type 1.

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Permalink Reply by Jayesh SR on December 11, 2009 at 7:45am

Congenital tonsillar ectopia is Type 1 Chiari malformation.Vermis, 4th ventricle and medulla will be normal.
Cerebellar tonsils ascend with increasing age

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Permalink Reply by SJ Rodgers on December 12, 2009 at 4:19am

Tonsils do not have to be peg-shaped for CM dx. Low-lying cerebellar tonsils (LLCT) measure less than the generally accepted 5mm required for CM dx, but can be just as troublesome, they can obstruct retrocerebellar CSF flow and disrupt brain function. Tonsillar ectopia is a synonym for LLCT.
I highly recommend reading the series of CM studies done by TH Milhorat et al, starting with the 1999 "Chiari Malformation Redefined," up through this year's report of their discovery of the association between LLCT, hereditary disorders of connective tissue (HDCT) and tethered spinal cord. In a large cohort, 63% of patients with LLCT were found to have symptomatic tethered spinal cords, and sectioning the filum terminale improved the patients' symptoms.

I'd be happy to discuss this subject in detail at your convenience.

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