The following is a summary of “Mapping lower-limbs muscle vulnerability in patients with ALS: The role of upper and lower motor neurons,” published in the June 2024 issue of Neurology by Milella, et al.
Despite prior research suggesting a specific pattern of weakness in patients with amyotrophic lateral sclerosis (ALS) lower limbs (LL), the limited sample sizes and conflicting results necessitate further investigation.
Researchers conducted a retrospective study to assess lower limb muscle weakness patterns at the knee, ankle, and toes in a large group of patients with ALS and the influence of upper (UMN) and lower (LMN) motor neuron damage on the patterns.
They assessed the strength of flexor and extensor muscles in 1250 legs of newly diagnosed patients with ALS at the knee, ankle, and toe joints. The UMN and LMN burden were quantified using validated scores. Statistical analyses included within-subjects ANOVA for muscle type (flexor/extensor) and anatomical sites (knee/ankle/toes) and mixed-factorial ANOVA to investigate the influence of UMN and LMN impairments on muscle weakness patterns.
The results showed a significant proximal-to-distal decline in muscle strength. The knee’s flexor and extensor muscles surpassed those at the ankle and toes. Extensor muscles were generally weaker than flexors at each site, except at the knee. More significant UMN impairment accentuated the difference between flexors and extensors, particularly affecting extensor strength at the ankle and toes. Higher LMN impairment was associated with more pronounced weakness in ankle and toe flexors compared to knee flexors.
Investigators concluded that ALS caused weaker flexor muscles in the foot and toes compared to the knee extensor, with UMN damage worsening this pattern and lower motor neuron damage showing greater weakness distally.
Source: jns-journal.com/article/S0022-510X(24)00233-8/abstract#%20
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