Rotational changes in the morphology of the vertebral artery at a common site of artery dissection.
Bibliographic record
Abstract
OBJECTIVE: Given that vertebral artery dissection and transient vertebrobasilar insufficiency occurs commonly at the C1-C2 junction, the objective was to study, in vivo, the normal rotational anatomy at C1-C2 using magnetic resonance angiography (MRA) with 3-dimensional (3D) reconstructions and to correlate these reconstructions with our experience of dissection location. METHODS: 3D phase-contrast MRAs were obtained from the foramen magnum to C3 in 4 normal volunteers in neutral and rotated (45 degrees) positions. The magnitude images were used as source images for 3D reconstruction. The images from only 1 of the volunteers were completely motion free, and these were subjected to arterial length calculations using image analysis wire frame outline of the vessel. All angiograms of vertebral artery dissection obtained at our institution from 1993 to 1997 were also reviewed. RESULTS: 3D reconstructions document elongation (approximately 7% in quantitatively analyzed case) and slight narrowing of the artery contralateral to the direction of head rotation from C2 to the dural entry point. The artery turns most sharply and is subject to the anterior force of the rotating C1 vertebra as it exits the C1 foramen. Of 14 cases of vertebral artery dissection, 50% occurred between the transverse foramen and the posterior lamina of C1. CONCLUSIONS: With head rotation, the contralateral vertebral artery undergoes the greatest anatomical distortion as it exits the C1 transverse foramen. This increased stress may account for the higher frequency of dissections at this location.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".