Marked Platybasia and Basilar Invagination
nPlatybasia
nBasal angle: Nasion to tuberculum, dorsal clival lines >143 degrees (this pt has approx 220 degrees)
nBasilar Invagination
nDens 5 mm or half its height above foramen magnum
nMcGregor’s and Chamberlain’s line
nVery similar- McG post hard palate to undersurface of occiput, Ch from h.p. to opisthion (mid portion of foramen magnum)
nKllippel Feil, cleidocranial dysplasia, achondroplasia, Paget’s, rickets, OI, others
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