Definition

  • Bow-Hunter syndrome (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

Etiopathogenesis

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Clinical presentation

  • clinical symptoms are provoked by unilateral rotation of the head (combined with retroflection), which disappear after returning the head to the neutral position
    • transient vertigo, visual disturbances
    • drop attack or syncope
    • TIA/stroke in the posterior circulation
  • usually present in concomitant contralateral vertebral artery pathology (hypoplasia, stenosis/occlusion), which means that the dominant vertebral artery is compressed

Diagnostic evaluation

Dynamic Doppler ultrasonography

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Standard and dynamic cervical spine X-ray

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

Dynamic DSA

  • DSA is performed during symptomatic movement
  • enables to detect the side and level of the compression (can be anywhere from C6 input to C1/2 stage)
  • DSA can’t tell the exact cause of the compression

Dynamic CTA

  • able to detect the exact site and cause of the compression
  • higher radiation burden compared to DSA

Dynamic MRA

  • MR angiography can be a reliable and less invasive diagnostic tool and can be used instead of DSA
  • it is suitable for confirming sufficient postoperative decompression and for recurrence monitoring  (Anaizi, 2013)
Bow-hunter syndrom - hypertrophic transverse process with compression of vertebral artery (CTA)
Bow-Hunter syndrom - dynamic DSA demonstrates VA occlusion during head rotation
Bow-Hunter syndrom - dynamic MRA demonstrates VA occlusion during head rotation (Anaizi, 2014)

Management

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