MRI morphometry of the neocortex in patients with periventricular nodular heterotopia
Bibliographic record
Abstract
Background. Human corticogenesis is broadly divided into three phases: proliferation, migration and cortical organization. Accordingly, a defect in any of these phases results in a malformation of cortical development (MCD). By allowing the in vivo visualization of MCDs, magnetic resonance imaging (MRI) has been instrumental in their classification. One such MCD is gray matter heterotopia (GMH), defined as out-of-place masses of gray matter (GM) – termed "nodules" – containing neurons that have failed to migrate to their intended destination. Such nodules have variable presentation in terms of location, lateralization, size and spread in the brain. Three distinct subtypes of GMH have been recognized: periventricular nodular heterotopia (PVNH), subcortical heterotopia, and band heterotopia. The focus of my Master's project is specifically the PVNH subtype of GMH. As all types of GMH, PVNH is highly epileptogenic, and the epilepsy is often drug-resistant. Purpose. To quantify whole-brain changes in cortical thickness and curvature in PVNH, and to assess the spatial relationship between nodules and regions of change.Methods. We obtained T1-weighted (1 x 1 x 1 mm3) images in 41 patients with PVNH and 41 controls on 1.5T- and 3T-scanners. Patients were further divided into unilateral (UL) vs. bilateral (BL) PVNH. Images were registered into stereotaxic space to adjust for differences in brain volume and orientation. We manually mapped the location of nodules, and algorithmically extracted whole-brain neocortical thickness and curvature. We used whole-brain linear modeling to perform group-wise statistics.Results. Nodules were evenly distributed along the ventricles in BL-PVNH, but tended to cluster around the trigone in UL-PVNH. Compared to controls, both UL-PVNH and BL-PVNH patients had increased cortical thickness and curvature in several regions of the brain. Increases in cortical thickness and curvature were found in the same hemisphere as the nodules in UL-PVNH, while in BL-PVNH cortical thickness increases were found bilaterally in the prefrontal cortex, and curvature increases were found bilaterally in the temporal lobe. In both cohorts, morphometric anomalies did not colocalize spatially with the nodules, as assessed by a visual inspection. Significance. The quantitative approach we used here provides precise measurements of cortical thickness and curvature in PVNH, as opposed to qualitative and subjective visual descriptions. The hemispheric colocalization finding makes it more likely that both the heterotopic nodules and the cortical thickening are the results of the same disrupted developmental mechanism. Conversely, the absence of a spatial relationship between heterotopic nodules and morphometric anomalies suggests differential cellular signaling and migration pathways.
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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 | 0.001 | 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".