Very rare, sometimes called cervicogenic vertigo. Symptomatic vertebral basilar insufficiency (loss of consciousness, stroke) caused by mechanical occlusion of the vertebral artery at the atlantoaxial level during head rotation.

The usual location of the occlusion is the C1-C2 junction where the vertebral artery is immobilized between the transverse foramen of C1 and C2, along the sulcus arteriosus. But other causes have been described: bony outgrowth of a cervical vertebra, fibrous band in C6 at the entrance of the foramen of C6.

The compression is normally not very important and the severe forms remain asymptomatic if the circle of Willis is functional. In some cases, the vertebral artery contralateral to the direction of rotation is stretched. The problem is more frequent on the left because the left vertebral artery is dominant (wider) in the majority of the population.

Contributing factors: congenital anomalies or instability of the cervical vertebrae

Lateral view of the atlas-axis joint in neutral position (A), with 10° rotation (B) and with 20° rotation (C). The caliber of the vertebral artery decreases with increasing rotation.

Anesthetic implications:

avoid prolonged head rotation in case of congenital cervical spine abnormalities, monitoring of cerebral NIRS

References : 

• Tenthlei L, Raju K, Joseph J.
  Challenges of anaesthetising a child with Bow Hunter’s syndrome and dilated cardiomyopathy for occipitocervical fusion.
  BMJ Case reports 2023 ; doi.org/10.1136/bcr-2022-253834
• Jadeja N, Nalleballe K.Pearls & Oy-sters:
  Bow Hunter syndrome: a rare cause of posterior circulation stroke.
  Neurology 2018 ; 91: 329-31.

Updated: May 2023