Neuropathologic Features of Pontocerebellar Hypoplasia Type 6
Bibliographic record
Abstract
Pontocerebellar hypoplasia is a group of severe developmental disorders with prenatal onset affecting the growth and function of the brainstem and cerebellum. The rarity and genetic heterogeneity of this group of disorders can make molecular diagnosis challenging. We report 3 siblings who were born to nonconsanguineous parents, were hypotonic at birth, developed seizures, had repeated apneic spells, and died within 2 months of life. Neuroimaging showed that all had profound cerebellar hypoplasia and simplified cortical gyration. Genetic analysis by whole-exome sequencing demonstrated compound heterozygous mutations in the mitochondrial arginyl transfer RNA synthetase gene RARS2, indicating that the children had pontocerebellar hypoplasia type 6. Autopsies on the younger twin siblings revealed small and immature cerebella at an approximate developmental age of less than 18 weeks. The basis pontis showed regressive changes, and the medulla had marked inferior olivary hypoplasia. The brains of both twins were microencephalic and had simplified gyri; cortices were immature, and deep white matter had extensive astrocytosis. The findings suggest a near-normal embryologic period followed by midgestation developmental slowing or cessation and later regression in select anatomic regions. This is the first detailed description of neuropathologic findings associated with pontocerebellar hypoplasia type 6 and demonstrates the profound effects of RARS2 disruption during early neurodevelopment.
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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) | 0.001 | 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) | 0.001 | 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".