Greenberg et al reported the Chiari Severity Index for evaluating a patient with a Type I Chiari malformation. The authors are from Washington University in Saint Louis.
Patient selection: Chiari malformation type 1
Parameters:
(1) clinical grade based on headache and myelopathic symptoms
(2) neuroimaging grade, based on syrinx size in mm
Headache
Myelopathic Symptoms
Clinical Grade
classic Chiari headache
none
1
poorly localized headache
none
1
frontotemporal headache
none
2
no headache
none
2
NA
present
3
Syrinx Size
Neuroimaging Grade
no syrinx
A
syrinx < 6 mm
A
syrinx >= 6 mm
B
where:
• Myelopathic symptoms include numbness, weakness, hyperreflexia and unsteady gait.
• A syrinx is a contiguous spinal cord cavitation measuring at least 3 mm in maximum diameter on T2-weighted MRI.
Grades
Chiari Severity Index
Improvement
1A and 1B
1
83%
2A and 3A
2
69%
2B and 4B
3
45%
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