OBJECTIVE: To determine the effects of cervical contralateral rotation and cervical contralateral lateral flexion on vertebral artery blood flow velocity.

DESIGN AND SETTING: A prospective study was performed at a private chiropractic clinic.

PATIENTS: One hundred forty-eight patients had their vertebral arteries insonated as part of the premanipulative screening procedure.

INTERVENTION: The vertebral arteries were insonated using a Doppler ultrasound velocimeter in the neutral position, during cervical contralateral rotation to the end range and during contralateral lateral flexion to the end range.

MAIN OUTCOME MEASURES: Persistence or loss of Doppler signals from the vertebral arteries during neck movement was recorded.

RESULTS: Of 280 vertebral arteries able to be insonated, 5% (0 < 5% < 9% at p = .99 confidence interval) had Doppler signals that stopped during contralateral rotation. Doppler signals from all 187 vertebral arteries tested during lateral flexion persisted, whereas 6 (3.2%) of this group of arteries had signals that ceased during contralateral rotation.

CONCLUSION: Vertebral artery Doppler signals from patients can be greatly reduced or extinguished during contralateral cervical rotation. However, this is an unusual finding. The same phenomenon was not observed during contralateral cervical lateral flexion, which suggests that there may be less mechanical stress placed on the vertebral artery during lateral flexion.

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