Presentation
Recurrent headache, numbness and weakness of both hands.
Patient Data
MR spine revealed cystic syringohydromyelia involving all the cervical and dorsal cord from the medulla oblongata superiorly to the conus medullaris inferiorly.
Small posterior fossa with downward herniation of the cerebellar tonsils are noted. No hydrocephalic changes.
Horizontal orientation of the clivus associated with posterior tilt and superior migration of the odontoid process.
The tonsillar herniation is estimated to be 7 mm below the foramen magnum
The dense projects 9 mm above the chamberlain line and 11 mm above the McGregor line.
Case Discussion
Chiari I malformation consists of downward tonsillar herniation and syringomyelia. As an association with this syndrome there is also basilar invagination as shown by flat basioccipt (platybasia) and upward odontoid projection. Normally the dens should project up to 3 mm above Chamberlain line and 5 mm above Mc Gregor line.
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