Compression Syndromes of the Vertebral Artery at the Craniocervical Junction.

Compression syndromes of the vertebral artery that occur at the craniocervical junction are extremely rare causes of haemodynamic insufficiency of the posterior cerebral circulation. The aetiology of the compression syndrome may be a malformation, trauma, tumour, infection or degenerative pathology. This may lead to dynamic vertebral artery occlusion where the vessel courses around the atlas and the axis-the so-called V3 segment. This in turn may result in insufficient collateral flow to the posterior fossa. The clinical picture is a vertebrobasilar insufficiency syndrome of variable expression ranging from vertigo to posterior fossa stroke. The typical clinical presentation is syncope occurring during rotation of the head, also known as 'bow hunter's syndrome'. The workup is based on dynamic angiography and computed tomography angiography. The treatment of choice is surgical vascular decompression, resulting in a good clinical outcome. However, in some instances, atlantoaxial fusion may be indicated. Alternatively, conservative and endovascular options have to be considered in inoperable patients.