Transient absence of F-waves in acute myelopathy: a potential source of diagnostic error.
Bibliographic record
Abstract
BACKGROUND: The frequent absence of F-waves in lesions of the nerve roots and proximal nerve is well known, with absence of F-waves occasionally the only electrophysiologic manifestation of early Guillain-Barré Syndrome. It is less well known that acute central nervous system lesions can cause disappearance of F-waves. CASE DESCRIPTION: A 25 year old woman presented with quadriparesis and sensory loss progressive over several days. Hyporeflexia and hypotonia were present. Imaging studies were initially negative. Electrophysiologic testing was normal apart from the diffuse absence of F-waves. This led to strong consideration of the diagnosis of Guillain-Barré Syndrome, and treatment for this diagnosis. However, imaging studies ultimately revealed the diagnosis to be transverse myelitis. F responses normalized 6 weeks after the initial study. CONCLUSIONS: F responses are significantly modulated by central nervous system factors. The relevant experimental and clinical literature is reviewed. The relevance of this to the diagnosis of Guillain-Barré Syndrome has not been previously emphasized, but our experience confirms that the absence of F-waves in a patient with acute weakness accompanied by hyporeflexia and hypotonia does not distinguish between peripheral nerve and central nervous system lesions.
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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 | 0.010 | 0.091 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.001 | 0.003 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.005 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".