vertebral artery competency test performed with the client seated

Special Orthopedic Assessment Tests – Vertebral Artery Competency Test

Note: This is the twelfth blog post article in a series of 14 articles on Assessment/Diagnosis of musculoskeletal conditions of the neck (cervical spine). See below for the other articles in this series.

The Vertebral Artery Competency Test (VACT) is designed to assess the competency of blood flow through the vertebral arteries in the upper neck.

Figure 17. Vertebral artery competency test (VACT). The VACT assesses for competency of blood flow to the back of the brain through the vertebral arteries. The therapist asks the client to rotate the neck to one side, and then extend and laterally flex it to the other side. (Courtesy of Joseph E. Muscolino. Photography by Yanik Chauvin.)



  • Vertebral artery competency test is critically important if stretching of the neck into extension and/or rotation will be performed during treatment.
  • Vertebral artery competency test is also critically important if joint mobilization of the neck (Grade IV or Grade V), especially the upper neck, will be be performed during treatment.
  • The test is performed by having the seated client rotate the neck and head to one side and then drop the head and neck back on the opposite shoulder (rotation to one side, lateral flexion to the opposite side, and extension); the client should then be asked to pick a point and visually focus on it.
  • The client then holds this position for approximately 30 seconds (Fig. 17).
  • Once completed, vertebral artery competency test should be repeated to the other side.
  • This orthopedic assessment test can also be performed with the client supine and their head off the table.
  • Some versions of this test do not involve the lateral flexion component. Instead, extension is simply coupled with rotation.


  • The posture required for the vertebral artery competency test can be uncomfortable for clients with most every musculoskeletal condition of the neck; however, local neck pain and referral of sensory symptoms into the upper extremity do not constitute a positive sign. For the test result to be considered positive, the client must experience neurologic symptoms such as dizziness, light-headedness, ringing in the ears, nausea, or nystagmus (the eyes darting back and forth). If any of these symptoms begin to appear, discontinue the test immediately, even if the client has not maintained the position for the full 30 seconds.
  • The reasoning is that the position required for this test naturally closes off blood flow in one vertebral artery (the one opposite the side of rotation). In a healthy person, the other vertebral artery continues to supply blood to the back of the brain, so no symptoms occur. However, if this other vertebral artery is occluded (closed off) as a result of atherosclerotic/arteriosclerotic plaque (known as vertebrobasilar ischemia or vertebrobasilar insufficiency/VBI), the brain will be deprived of blood, causing the symptoms.
  • This test is also sometimes known as vertebral-basilar artery competency test.


  • If vertebral artery competency test produces positive results to either side, it is critically important to not reproduce this position when treating the client, especially positions that combine extension with rotation to that side. Elderly clients and clients at risk for arterial disease and stroke are especially vulnerable to this problem.
  • Further, if the test is positive, the client should be referred to a physician.
  • There is considerable controversy as to the validity of the vertebral artery competency test. However, there is no alternative assessment procedure. And, given the possible catastrophic result if vertebral artery occlusion is missed, it is still recommended by many sources to perform this test on all clients who present for neck treatment, especially if stretching and joint mobilization of the upper neck will be performed.

 Click here for more on precautions and contraindications for manual therapy when treating the neck. 

This blog post article is the twelfth in a series of 14 blog post articles on Assessment/Diagnosis of musculoskeletal (neuro-myo-fascio-skeletal) conditions of the neck (cervical spine).

 The articles in this series are:

  1. Introduction to Assessment/Diagnosis of the Neck
  2. Verbal and Written Health History
  3. Overview of Physical Examination Assessment
  4. Postural Assessment
  5. Neck General Orthopedic Assessment: Range of Motion and Manual Resistance
  6. Palpation Assessment
  7. Motion Palpation (Joint Play) Assessment
  8. Special Orthopedic Assessment Tests for the Neck – Space Occupying Conditions
  9. Special Orthopedic Assessment Tests – Space Occupying Conditions – Slump Test
  10. Orthopedic Assessment of Thoracic Outlet Syndrome – Adson’s, Eden’s, Wright’s
  11. Orthopedic Assessment of Thoracic Outlet Syndrome – Brachial Plexus Tension Test
  12. Special Orthopedic Assessment Tests – Vertebral Artery Competency Test
  13. Treatment Strategy and Treatment Techniques
  14. Assessment and Treatment of Specific Musculoskeletal Conditions