Vertebral Artery Invagination in Neural Foramen
For vertebral artery loop formation causing cervical radiculopathy, obtain MRI and CT angiography for diagnosis, attempt conservative management first, and if symptoms persist after 3-4 months, proceed with full-endoscopic posterior foraminotomy or microsurgical decompression with interpositional graft placement.
Diagnostic Approach
When vertebral artery invagination into the cervical neural foramen is suspected, imaging is critical to avoid catastrophic complications during surgery or interventional procedures 1. The diagnostic sequence should be:
- MRI with MR angiography as first-line imaging to identify the vertebral artery loop and its relationship to the neural foramen 1
- CT angiography to confirm the diagnosis and provide detailed anatomical information for surgical planning 2, 3
- Look for enlargement of the intervertebral foramen on plain radiographs, which should raise suspicion for this rare entity 1
This anatomical variant occurs in approximately 11.4% of patients, with the C5 level being most common, followed by C4, C7, and C3 4. The vertebral artery on the anomalous side is typically smaller in diameter 4.
Clinical Presentation
Patients present with:
- Unilateral cervical radiculopathy at the affected level (most commonly C5 or C6)
- Neck pain with arm radiation
- Positive Spurling sign
- Potential motor weakness in the corresponding myotome 2, 3
- In rare cases, occipital neuralgia when C2-C3 is involved 5
Treatment Algorithm
Initial Management: Conservative Treatment (3-4 months)
Begin with non-operative management including physical therapy, NSAIDs, and activity modification 2. The 2011 ASA/ACCF/AHA guidelines emphasize medical management for vertebral artery disease, though these primarily address atherosclerotic disease rather than anatomical variants 6, 7.
Surgical Intervention for Failed Conservative Treatment
When conservative treatment fails after 3-4 months, surgical decompression is indicated 2, 3. Two primary surgical approaches have demonstrated success:
Option 1: Full-Endoscopic Posterior Foraminotomy
- Minimally invasive uniportal approach 2
- Enlarges the neural foramen without directly manipulating the vertebral artery
- Demonstrated complete symptom resolution at 3 months in recent case reports 2
- Lower risk profile compared to open procedures
Option 2: Microsurgical Decompression with Interpositional Graft
- Posterior approach with meticulous dissection of adhesions between the vertebral artery and nerve root 3, 5
- Placement of Teflon patch or interpositional spacer between the artery and nerve root 3, 5
- Consider intraoperative angiography to confirm arterial patency 5
- Perform in hybrid operating room when available 5
Arterial transposition should be avoided when the vertebral artery is dominant or has limited mobility, as this increases risk of vascular injury 5. Instead, focus on adequate osseous decompression with lateral mass resection if needed 8.
Critical Surgical Considerations
Anatomical Pitfalls to Avoid
- The vertebral artery can extend up to 3.8 mm medially beyond the medial wall of the transverse foramen 4
- During anterior cervical approaches, do not dissect more than 3.8 mm medial to the vertical line of the medial transverse foramen wall 4
- The pedicle width is typically broader on the anomalous side at levels adjacent to the unusual entrance, making pedicle fixation safer at these levels if needed 4
- Failure to identify this variant preoperatively can result in vertebral artery injury during routine cervical surgery, transforaminal epidural injections, or vertebrobasilar angiography 1
Surgical Technique Specifics
For foraminotomy procedures:
- Perform C5 and C6 lateral mass resection to adequately enlarge the foraminal space when the loop is at C5-6 8
- Keep the vertebral artery in place rather than attempting mobilization 8
- If multiple levels are involved (e.g., concurrent degenerative stenosis), address all symptomatic levels during the same procedure 3
Expected Outcomes
Patients typically experience:
- Complete resolution of radiculopathy within 3 months following appropriate surgical decompression 2, 3, 5
- Resolution of motor deficits when present 3
- Slow but consistent pain improvement, with complete relief by 3 months 8
The key to successful management is recognizing this rare entity preoperatively through appropriate vascular imaging, as overlooking it can lead to serious complications including vertebral artery injury and stroke 1.