Giant serpentine vertebrobasilar aneurysm with vertebral artery hypoplasia and fenestration- a case report.

Intracranial aneurysm in paediatric age group is rare and association of the aneurysm with congenital vertebral artery anomaly is further rarer. We describe such a case in an 11-year-old male patient who consulted a paediatrician about headache and vertigo, and a noncontrast CT (NCCT) head revealed peripherally calcified hyperdense mass in prepontine and basal cisterns. Magnetic resonance imaging (MRI) including contrast enhanced magnetic resonance angiography (MRA) revealed partially thrombosed giant serpentine aneurysm of right vertebrobasilar artery and contralateral hypoplastic vertebral artery with fenestration. The nondominant left vertebral artery gave off the posterior inferior cerebellar artery, then became hypoplastic and joined with its counterpart to form the basilar artery. This pattern is called as type 9. The patient was kept on conservative management. The role of MRI in this congenital anomaly and its association with vertigo and aneurysm of vertebro-basilar artery is discussed.