Abstract WP127: Diagnostic Value of the Ivy Sign Compared to MR With Cerebrovascular Reactivity in Decompensated Moyamoya Arteriopathy
Bibliographic record
Abstract
Introduction: MR cerebrovascular reactivity (CVR) mapping during rapid manipulation of end-tidal pCO2 is used to assess hemodynamic compromise in patients with Moyamoya arteriopathy (MMA). Leptomeningeal ivy sign on MRI FLAIR sequence may indicate regions of decreased perfusion, which would be an inexpensive and easy way to screen for hemodynamic compromise. The purpose of this study was to examine the diagnostic value of the ivy sign compared to MR CVR. Methods: For this retrospective cross-sectional study, we included consecutive patients with uncompensated MMA who were eligible for extracranial-intracranial bypass surgery and completed a preoperative MRI FLAIR with CVR study. Patients with incomplete or artefact degraded imaging were excluded. Two neuroradiologists who were blinded for the CVR result independently assessed the degree of ivy sign on axial 2D FLAIR imaging as grade 0, 1 or 2 in 8 predefined brain regions. Two different readers, blinded for ivy sign, independently assessed the presence or absence of steal in the same regions on MR CVR. Consensus was reached for discordant findings. We assessed interrater agreement using weighted kappa followed by diagnostic accuracy measures for the ivy sign using MR CVR as a reference. Results: We enrolled 73 patients (41/73 (56.1%) female; mean age 43). 47/73 (64%) patients had bilateral MMA with on average 3 brain regions with abnormal CVR. Interrater agreement was good for ivy sign (weighted kappa 0.63 (95%CI 0.54-0.71)) and excellent for CVR (kappa 0.95 (95% CI 0.87-1.00)). For a total of 156/584 (26.7%) brain regions, there was agreement between a positive ivy sign and the presence of steal on CVR and 240/584 (41%) brain regions had no ivy sign and normal CVR. The sensitivity of the ivy sign was 64.5%, specificity 70.2%, positive predictive value 60.5% and negative predictive value 73.6% with an AUC of 0.68 (95% CI 0.64-0.72) Conclusions: In this preselected cohort with high pretest probability for hemodynamic compromise, the diagnostic accuracy of the ivy sign compared to MR CVR was limited and needs to be used with caution to determine haemodynamic status in MMA.
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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 | 0.002 | 0.008 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".