Persistent Steal Physiology during a Ramp Cerebrovascular Reactivity Assessment Correlates with Severe Cortical Thinning in Steno-Occlusive Disease
Bibliographic record
Abstract
ABSTRACT BACKGROUND AND PURPOSE: Steal physiology, a marker of severe cerebrovascular impairment, is associated with cortical thinning, a morphological phenomenon seen in patients with chronic supply artery steno-occlusive disease. This link has been previously established only with a sudden “step” hypercapnic stimulus. The significance of steal patterns derived from a gradual “ramp” stimulus, and their association with structural brain injury, is unclear. We investigated how steal patterns derived from both step and ramp stimuli compare and relate to the severity of cortical thinning in patients with steno-occlusive disease. MATERIALS AND METHODS: Thirty-two patients with unilateral cortical steal, characterized by an asymmetric paradoxical reduction in blood flow during vasodilatory stimuli due to impaired vascular reserve in one hemisphere, were retrospectively identified from a prospectively maintained database. Cerebrovascular reactivity (CVR) was mapped using BOLD MRI during sequential step and ramp CO2 stimuli from a sequential gas delivery system. The spatial extent of cortical steal (volume with negative CVR) was quantified and correlated with inter-hemispheric cortical thickness differences for each stimulus type. RESULTS: The spatial extent of cortical steal physiology derived from the ramp stimulus was consistently smaller, averaging 81% of that seen with the step stimulus (p=0.004). Both stimulus approaches demonstrated significant correlations with cortical thinning (step: r=0.56, p<0.001; ramp: r=0.49, p=0.004). Patients exhibiting steal during both stimulus types showed more pronounced cortical thinning compared to those demonstrating steal only during step stimuli, suggesting that persistent steal across both protocols indicates more severe cerebrovascular impairment. CONCLUSIONS: The persistence of steal physiology seen during a gradual ramp stimulus reveals a more serious hemodynamic impairment than steal observed only during a sudden step challenge in patients with steno-occlusive disease. While the step stimulus is highly sensitive, its greater spatial extent of steal includes all hemodynamically vulnerable tissues, even those with slower but potentially effective collateral responses. The ramp stimulus gives these tissues more time for vascular response to evolve fully, thereby isolating persistent steal that represents complete failure of collateral circulation. This failed adaptation is associated with more severe structural brain injury. Therefore, multi-stimulus CVR protocols may offer a more nuanced approach to risk stratification. ABBREVIATIONS: BOLD＝blood-oxygen-level-dependent; CVR＝cerebrovascular reactivity.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".