Basilar Invagination is cranio vertebral junction anomaly of
the osseous structure seen as prolapse of odontoid processing of
oramen Magnum with flattening of clivus. It is mostly congenital
whereas basilar impression is upward displacement of Dens due to
softening of the bones of the skul base and is mostly acquired. The
diagnosis primarily depends upon the radiology.
We present acase ofa 8year old patient presenting with at
axiavertigo and pain in The neck MRIT2W images shows upward
prolapse of odontoid into for a men Magnum within dentation
of medulaoblongata. McRaeline, Chamberlaineline and Mc
Gregorlineare showing odontoid process 3mm, >5mm and >4.5mm
respectively, Hence diagnosis of basilar invagination was made [1-
Basilar Invagination is craniovertebral junction anomalyseen as
prolapse of Odontoid process into for a men Magnum with flattening
of clivus. It is mostly Congenital where as basilar impression is
upward displacement of Dens due to Softening of the bones of the
skul base and is mostly acquired. Patient presents Depending upon
crowding and mass effect caused with headache, neckpain, vertigo,
Cranial Nerve deficit, lower limb at axia and other neurological
signs caused by Syring ohydromylia (Figure 1).
Figure 1:A 8year old patient presenting with at axiavertigo and pain in the neck MRIT2W images shows upward prolapse of
odontoidintoforamenmagnum with indentation of medulaoblongata. McRaeline (d) Chamberlaineline (e) and Mc Gregorline
(f) are showingodontoid process 3mm,>5mm and>4.5mm respectively, hencediagnosis of basilar invagination was made.
Key Imaging diagnostic clue
1) Tip of odontoid process prolapsing into for a men
Magnum, may cause crowding and indentation of brainstem.
2) Tip of odontoid processis >5mm above McRaeline, 3mm>
Chamberlaine and >4.5mm Mc Gregorline.
Developmental CV Janomaly-Atlanto-dental-axial instability
or CVJ stenosis. Inflammatory of Infective–Increased AtlantodentalInterface
Acquired basilar Impression-displacement of
occipital condyles into for amen magnum secondary to bone