Late-Onset Friedreich Ataxia
Bibliographic record
Abstract
BACKGROUND: Friedreich ataxia (FA), the most common hereditary ataxia, is caused by pathological expansion of GAA repeats in the first intron of the X25 gene on chromosome 9. Since the discovery of the gene, atypical features are increasingly recognized in individuals with FA, and up to 25% of patients with recessive or sporadic ataxia do not fulfill the Harding or Quebec Cooperative Study on Friedreich's Ataxia criteria for FA. Late-onset FA (LOFA) is defined as onset after age 25 years. OBJECTIVES: To describe and further delineate the clinical and magnetic resonance imaging findings in patients with LOFA and to review the literature. DESIGN: Clinical evaluation and comparison of clinical data and investigations. SETTING: Ataxia clinics at UCLA and Cedars-Sinai Medical Center. PATIENTS: Thirteen patients with LOFA with 13 sex-matched and Inherited Ataxia Progression Scale-matched patients with typical FA. RESULTS: Gait and limb ataxias were seen in all the participants. Dysarthria, loss of vibration sense, and abnormal eye movements were also common in both groups. Patients with LOFA more often had lower limb spasticity (40% vs 0%; chi2 = 4.0; P = .04) and retained reflexes (46.1% vs 7.7%; chi2 = 3.46; P = .05). They had no complaint of sphincter disturbances, and there was no evidence of cardiomyopathy on echocardiograms (chi2 = 4.0; P = .04). Five of 9 patients with LOFA had cerebellar atrophy on neuroimaging. CONCLUSIONS: Patients with gait and limb ataxias, dysarthria, loss of vibration sense, and fixational instability after age 25 years should be considered for molecular testing for GAA expansion in the FA gene. In contrast to previous studies, cerebellar vermian atrophy is not an uncommon finding.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 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) | 0.004 | 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".