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Published on: October 10, 2025
A pilot study for evaluation of hypotonia in children with neurofibromatosis type 1
Elizabeth A Soucy1, Lauren E Wessel1, Feng Gao2
1Department of Neurology, Washington University School of Medicine, St Louis, MO, USA.
Insights
This study identified objective criteria for pediatric hypotonia in children with neurofibromatosis type 1. Head lag and increased hip range of motion accurately predict hypotonia.
Area of Science:
- Pediatric Neurology
- Developmental Pediatrics
- Clinical Assessment
Background:
- Hypotonia lacks objective diagnostic criteria in pediatrics.
- Neurofibromatosis type 1 (NF1) can present with hypotonia, requiring better assessment tools.
Purpose of the Study:
- To establish objective diagnostic criteria for hypotonia in children with NF1.
- To identify specific physical examination findings predictive of hypotonia in this population.
Main Methods:
- Evaluated 55 children (1-7 years) with NF1.
- Assessed objective tone metrics: ankle dorsiflexion, knee extension, hip abduction, triceps fat percentage, grip strength, and head lag during pull-to-sit test.
- Utilized multivariate logistic regression to identify predictors of hypotonia.
Main Results:
- Head lag during the pull-to-sit test combined with increased hip range of motion significantly predicted hypotonia.
- These specific objective measures demonstrated accuracy in identifying hypotonia in the study cohort.
Conclusions:
- Head lag and increased hip range of motion serve as accurate, objective predictors of hypotonia in children with NF1.
- These findings suggest potential for broader application in assessing pediatric hypotonia across different populations.
Abstract:
There are currently no objective criteria to evaluate pediatric hypotonia. The purpose of this pilot study was to identify diagnostic criteria for assessing hypotonia in children with neurofibromatosis type 1. Fifty-five subjects between the ages of 1 and 7 years with a diagnosis of neurofibromatosis type 1 were evaluated. A physical therapist recorded a subjective tone assessment and objective tone metrics, including ankle dorsiflexion, knee extension, hip abduction, triceps fat percentage, grip strength, and head lag during a pull-to-sit test. Multivariate logistic regression analysis showed the presence of head lag paired with increased hip range of motion was a significant predictor of hypotonia. The presence of head lag on a pull-to-sit test paired with increased hip range of motion is an accurate predictor of hypotonia in children with neurofibromatosis type 1. These objective measures should be prospectively evaluated in other pediatric populations for their ability to predict hypotonia.
