Annals of Anatomy · 2026

CTA-Based Vertebral-Level Origin, Transverse-Foramen Entry, and V1 Loop Morphology of the Vertebral Artery

A structured CTA companion that reads the proximal vertebral artery as a three-part pattern: vertebral-level origin, transverse-foramen entry, and V1 shape. The paper emphasises side-specific and bilateral description rather than a single “normal” template.

Calotă RN · Rusu MC · Jianu AM · Ann Anat. 2027 Jan;269:153374 · Epub 2026 Sep 8 · PMID 42710688 · doi: 10.1016/j.aanat.2026.153374

This microsite condenses the paper into interactive reading paths. Use the buttons below to switch between anatomical logic, key findings, and practical implications.

Pattern logic

Why combine origin, entry level, and V1 morphology?

Each descriptor answers a different anatomical question: where the artery begins, where it enters the cervical osseous tunnel, and how it behaves in the uncovered V1 segment. The paper argues that proximal extracranial VA anatomy is best described by combining all three.

Origin height

Origin may follow the expected subclavian pattern or depart from it, especially on the left, shifting the take-off level and endovascular approach.

Transverse-foramen entry

C6 entry remains the common baseline, whereas non-C6 entry reflects a reconfigured cervical course with different exposure risks.

V1 morphology

A straight, gently curving, or looped V1 segment adds the dynamic surface shape that origin and entry level alone cannot predict.

Take-home point: The paper’s main contribution is a combined descriptor for proximal VA anatomy rather than isolated reporting of single features.

Three-layer reading scheme

1. Origin levelArch-side take-off or subclavian take-off defines the proximal starting geometry.

2. Entry levelC4/C5/C6/C7 entry levels determine how long the uncovered V1 segment remains exposed.

3. V1 shapeStraight, curved, or looped V1 morphology explains tortuosity and local redundancy.

The same artery can have a usual origin but unusual entry level.
Looping should not be inferred from entry level alone.
Bilateral reporting matters because right and left patterns are frequently non-mirror images.

CTA report

A CTA-oriented reporting sequence

For practical reporting, the paper can be read as a checklist: document origin, entry level, then V1 shape, and finally assess whether the opposite side matches or differs.

Step 1

State the side and the vessel origin clearly, especially if the left VA arises directly from the aortic arch.

Step 2

Record transverse-foramen entry level, because higher or lower entry changes the unprotected cervical segment.

Step 3

Characterise V1 morphology, noting loops or marked redundancy that may complicate procedures.

Take-home point: A reproducible report sequence turns anatomical variability into clinically legible information.

Suggested report flow

Side firstDescribe the right and left arteries separately.

Origin nextRecord the parent vessel and relative origin height.

Entry nextSpecify the cervical level of foraminal entry.

Finish with V1 morphologyAdd whether the V1 segment is straight, curved, or looped.

A bilateral summary should conclude whether the pattern is symmetric or asymmetric.
The method is useful for both anatomical research and clinical CTA reporting.
Explicit pattern language reduces ambiguity in multidisciplinary communication.

Implications

Why the proximal VA triad matters clinically

Origin, entry, and V1 shape together influence exposure length, surface vulnerability, access difficulty, and the risk of misreading a looped or ectatic segment.

Surgery

Variant entry levels and loops matter during anterior cervical, lower neck, and craniocervical procedures.

Intervention

Endovascular access depends on take-off geometry and proximal angulation.

Interpretation

A combined pattern reduces the temptation to treat non-standard arteries as isolated anomalies.

Take-home point: The study turns proximal VA variability into a compact, clinically useful anatomical language.

Clinical translation

Exposure riskLong uncovered V1 segments remain more surgically visible.

Access geometryOrigin angle shapes guidewire and catheter behaviour.

Imaging accuracyLooped V1 segments can mimic exaggerated tortuosity unless mapped systematically.

Variant anatomy should be communicated before procedures rather than discovered during them.
Side-specific description is especially relevant because left-sided variants are common in vertebral-artery anatomy.
The microsite intentionally mirrors the article’s pattern-based reading strategy.