Bow Hunter’s syndrome

David Goldemund M.D.
Updated on 12/12/2023, published on 09/12/2021


  • Bow Hunter’s syndrome (also known as Rotational vertebral artery occlusion syndrome) is a symptomatic vertebrobasilar insufficiency caused by mechanical compression of the vertebral artery (VA) at the level of the atlanto-axial joint during head rotation within the normal physiologic range


  • rotation and head tilt lead to vertebral artery compression, disrupting flow in the posterior circulation
  • location of compression:
    • at the level C1/2 (atlantoaxial type) – during contralateral head rotation  [Sorensen, 1978]
    • at the level C2-6 (subaxial type) – associated with ipsilateral head rotation  [Miele, 2008]
    • combined disability
  • etiology
    • congenital skeletal abnormalities
    • atlantoaxial hypermobility
    • bone abnormalities, including large osteophytes
    • vascular malformation
    • vertebral instability
    • fibrous streaks (often observed during surgery)
    • aberrant course of the vertebral artery
Bow-hunter syndrome

Clinical presentation

  • clinical symptoms are provoked by unilateral head rotation (combined with retroflexion) and disappear when the head is returned to the neutral position
  • symptoms usually occur with concomitant contralateral vertebral artery pathology (hypoplasia, stenosis/occlusion), indicating that the dominant vertebral artery is compressed

Diagnostic evaluation

Dynamic Doppler ultrasonography

  • ultrasound may detect flow in the vertebral artery during head rotation combined with tilt (according to the patient’s reported provocation position)
  • reliable, easy to perform method that can be used for both screening and follow-up
  • it is useful to add TCCD examination, especially for type 2 (subaxial) diagnosis, where head rotation to the examined side makes extracranial examination difficult
    • evaluation of the V4 segment helps to determine the hemodynamic significance of dynamic compression
Bow Hunter syndrome type I - flow in the left VA at rest (left) and after rotation of the head to the right. Rotation induces a significant reduction in flow (occlusive pattern with systolic peaks)
Bow-Hunter type I (atlanto-axial) - flow in the vertebral artery extra- and transcranially at rest (left) and after head rotation contralaterally (right). Reduced extracranial flow and flow reversal in the V4 segment are demonstrated).

Standard and dynamic cervical spine X-ray

  • detects morphologic abnormalities in the spine
  • dynamic images assess spinal instability
  • functional views should not be performed on trauma patients without strict instructions from a clinician

Dynamic DSA

  • DSA is performed at rest and then during the movement, provoking typical symptoms
  • it identifies the side and level of the compression (which can range from the C6 entrance to the C1/2 level)
  • DSA, however, cannot determine the exact cause of the compression

Dynamic CTA

  • able to identify both the exact location and cause of the compression
  • involves  higher radiation exposure compared to other methods

Dynamic MRA

  • MR angiography can serve as a reliable and less invasive diagnostic tool, potentially replacing DSA
  • it is suitable for confirming adequate postoperative decompression and monitoring recurrence  (Anaizi, 2013)


Bow-hunter syndrome - CTA shows a hypertrophic transverse process compressing the vertebral artery (CTA)
Bow-Hunter syndrom - dynamic DSA demonstrates the VA occlusion during head rotation
Bow-Hunter syndrome - dynamic MRA demonstrates occlusion of the VA during rotation of the head (Anaizi, 2014)


Treating this condition requires careful consideration, as the long-term prognosis of untreated forms remains unknown

  • the conservative approach is recommended in most cases
  • for severe posterior fossa symptoms, surgical solutions are available
    • vertebral body fusion (for atlanto-axial instability)
    • deliberation of the vertebral artery course (anterior/posterior vertebral artery decompression)
  • if the flow in the contralateral AV is restricted, e.g., by severe proximal stenosis, then primary stenting of this stenosis should be considered

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Bow Hunter´s syndrome