Effects of Head and Neck Positions on Blood Flow in the Vertebral, Internal Carotid, and Intracranial Arteries: A Systematic Review.

Background: Manual therapy interventions targeting the neck include various positions and movements of the craniocervical region. The hemodynamic changes in various spinal positions potentially have clinical relevance.

Objectives: To investigate the effects of craniocervical positions and movements on hemodynamic parameters (blood flow velocity and/or volume) of cervical and craniocervical arteries.

Methods: A search of 4 databases (PubMed, Embase, CINAHL, and Index to Chiropractic Literature) and, subsequently, a hand search of reference lists were conducted. Full-text experimental and quasi-experimental studies on the influence of cervical positions on blood flow of the vertebral, internal carotid, and basilar arteries were eligible for this review. Two independent reviewers selected and extracted the data using the double-screening method.

Results: Of the 1453 identified studies, 31 were included and comprised 2254 participants. Most studies mentioned no significant hemodynamic changes during maximal rotation (n = 16). A significant decrease in hemodynamics was identified for the vertebral artery, with a hemodynamic decrease in the position of maximum rotation (n = 8) and combined movement of maximum extension and maximum rotation (n = 4). A similar pattern of decreased hemodynamics was also identified for the internal carotid and intracranial arteries. Three studies focused on high-velocity thrust positioning and movement. None of the studies reported hemodynamic changes. The synthesized data suggest that in the majority of people, most positions and movements of the craniocervical region do not affect blood flow.

Conclusion: The findings of this systematic review suggest that craniocervical positioning may not alter blood flow as much as previously expected.

Level Of Evidence: Therapy, level 2a. .