"Abductor Sparing": A New Selective Involvement in ALS

Area of Science:

• Neurology
• Neurodegenerative Diseases

Background:

• Selective muscle involvement is documented in amyotrophic lateral sclerosis (ALS), but lower limb studies are limited.
• A preliminary observation suggested hip abductor (Ab) preservation in ALS, termed "abductor sparing".

Purpose of the Study:

• To investigate and verify the phenomenon of "abductor sparing" in the lower limbs of patients with ALS.
• To compare lower limb muscle weakness patterns between ALS patients and those with other pyramidal weakness.

Main Methods:

• Retrospective identification of patients with confirmed ALS and those with other pyramidal weakness.
• Evaluation of Medical Research Council (MRC) scores for 10 lower limb muscle groups.
• Comparison of muscle weakness proportions (MRC score ≤4) between groups.

Main Results:

• 61 ALS patients and 27 pyramidal group patients were analyzed.
• Big toe extensors and hip flexors were most frequently weak in both groups.
• Hip abductors (Ab) were significantly less weak in ALS patients (30%) compared to the pyramidal group (70%), confirming abductor sparing.

Conclusions:

• Amyotrophic lateral sclerosis patients exhibit a distinct lower limb muscle weakness pattern characterized by abductor sparing, differentiating them from other pyramidal syndromes.
• Abductor sparing in ALS may serve as a potential early diagnostic biomarker.
• Further large-scale, blinded studies are necessary to validate these findings.