Cognitive dysfunction, gait, and motor impairment in neurofibromatosis type 1

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Abstract

This commentary is on the original article by Champion et al. on pages 468–474 of this issue.

This study replicates the results of previous research documenting delays in motor proficiency,[1] cognition,[2] memory, and attention[3] in children with neurofibromatosis type 1 (NF1). It is unique in that the authors evaluated the temporospatial parameters of gait and examined the relationship of balance, running speed, and agility to memory and reasoning. However, there are several issues regarding the treatment of data in this article that are of concern and may limit the plausibility of the findings.

Champion et al.[4] hypothesize that both cognitive and motor impairments arise from a shared neurodevelopmental process and may be attributed to decreased striatal dopamine levels or a cerebellar mechanism, based on the relationships they identified. Readers should be cautious in interpreting the relationship between motor abilities and cognitive/behavioral impairments because of the small sample size (n=39) and the large number of variables (12) used in the analysis.

This research provides initial information about the types of changes observed in the gait temporospatial parameters of children with NF1. The base of support variable derived from the GaitRite system has low accuracy and reliability in children,[5, 6] and the temporospatial data were not normalized by leg length or step count presenting a risk of bias from short stature.[7] The mean z-score for velocity, cadence, stride length, and base of support was within 1SD of control values. Although statistically significant, these differences may not be clinically important. The percent of the gait cycle spent in single limb support (−1.38SD) was decreased and may be reflective of poor balance in children with NF1.

The strength of this study is in identifying balance as an important parameter, both in explaining motor skill delay and gait impairments. Researchers should be mindful of using the standard protocol of the measures. The Bruininks-Oseretsky Test of Motor Proficiency, Second Edition (BOT-2) standard score, not the scale score used in this study, is the appropriate score for evaluating changes between a participant and the normative population.[8] The BOT-2 scale score can be used to compare one subtest to another. The balance subtest normalized mean scale scores were lower than running speed and agility, and upper limb coordination subtests. Additionally, 72% of the participants demonstrated impaired balance. Continued exploration of balance as an important factor in gait and motor abilities of children with NF1 and the relationship between balance ability and cognition/behavior appears warranted.

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