Persistent Primitive Hypoglossal Artery (PPHA) - A Rare Anomaly with Literature Review.

Persistent primitive hypoglossal artery (PPHA) is a rare embryonic carotid vertebrobasilar artery anastomosis. Hypoglossal artery arises from the internal carotid artery (ICA) between the C1 and C2 vertebral levels and traverses through the hypoglossal canal to join the vertebro-basilar system. We present a rare case of an anomalous right sided PPHA as a sole supply to posterior circulation of brain with absent/hypoplastic bilateral vertebral arteries in a two year child who had presented with acute left sided haemiplegia. Three dimensional time of flight magnetic resonance angiography identified an anomalous vessel arising from the right internal carotid artery at the level of axis vertebra and joining the vertebra-basilar arterial system after coursing through the right hypoglossal canal. This anomaly when present may predispose the person to aneurysm formation, ischaemia in the posterior circulation and atherosclerotic disease of the intracranial vessels.