Basilar imagination : a rare cause of "top of basilar artery" syndrome.

"Top of Basilar Artery" Syndrome as the presentation of CVJ anomalies is extremely rare. The association between skeletal CVJ anomalies and vertebro-basilar insufficiency (VBI) is recognised and angiographic abnormalities of the vertebro-basilar arteries and their branches have been reported. Atlanto-axial dislocation (AAD) is the commonest skeletal cranio-vertebral junction (CVJ) anomaly in India, followed by occipitalisation of atlas and basilar invagination. They usually present with a progressive neurological deficit (70 - 94% cases) implicating the high cervical cord, lower brainstem, and cranial nerves. We report one such case with the even more rare presentation of "Top of Basilar Artery" Syndrome as the initial presentation of basilar invagination.