Instrumented assessment of lower and upper motor neuron signs in amyotrophic lateral sclerosis using robotic manipulation: an explorative study.
D J L Stikvoort García, B T H M Sleutjes, W Mugge and 5 others
PMID 39472924WHAT IT FOUND
A robotic wrist test detected signs of upper motor neuron loss in ALS patients.
The machine measured increased reflexive force feedback, which correlated with clinical severity scores. This offers a potential objective tool to distinguish upper from lower motor neuron damage, though the sample was small and exploratory.
Key findings
01Reflexive force feedback gain was significantly elevated in ALS patients with upper motor neuron signs in the tested arm compared to healthy controls.
02The magnitude of the reflexive torque response was associated with the severity of upper motor neuron signs as graded by a clinical score.
03Muscle strength, a marker of lower motor neuron loss, did not correlate with the reflexive force feedback measure, suggesting the two types of damage can be distinguished.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study was exploratory with a very small sample size (15 patients and 15 controls). Patients with severe weakness were excluded, so the results do not apply to advanced ALS stages. The control group was significantly younger than the patient group, which could affect neuromuscular properties, although the authors state age differences were unlikely to have influenced the specific reflex findings. The model assumed linear behavior, which may not accurately reflect complex motor control, especially during compliance tasks where model fits were poor. The study did not include disease controls with isolated upper motor neuron loss (like Primary Lateral Sclerosis), making it difficult to confirm that the findings are specific to ALS UMN signs rather than other conditions.
Declared interests
The study was funded by Stichting ALS Nederland (ALS Foundation Netherlands).
The easy way to misread this
Do not interpret these results as evidence that robotic assessment is a ready-to-use clinical tool for ALS diagnosis. The study was a small proof-of-concept that failed to validate the method in severe weakness or distinguish ALS from other UMN disorders. The statistical significance rests on a tiny sample of 15 patients, and the exclusion of those with severe weakness limits generalizability.