Could PLS represent a UMN-predominant ALS syndrome?
P Corcia1, P Couratier2, C Ingre3
1Coordination Centre for Rare Disease Reference Centres (CRMR) ALS and other motor neurone diseases (FILSLAN), CHRU Bretonneau, 2, boulevard Tonnellé, 37000 Tours, France; UMR 1253 iBrain, Tours University, Inserm, 10, boulevard Tonnellé, 37000 Tours, France.
Revue Neurologique
|May 23, 2024
Summary
Primary lateral sclerosis (PLS) is a motor neuron disease primarily affecting upper motor neurons. New evidence suggests lower motor neuron involvement, blurring the lines between PLS and amyotrophic lateral sclerosis (ALS).
Area of Science:
- Neurology
- Neurodegenerative Diseases
- Motor Neuron Disorders
Background:
- Primary lateral sclerosis (PLS) is characterized by pure upper motor neuron (UMN) degeneration, accounting for approximately 3% of motor neuron diseases.
- PLS typically has a less severe prognosis than amyotrophic lateral sclerosis (ALS), making early differentiation crucial.
- The classical distinction relies on the lower motor neuron (LMN) system being spared in PLS, unlike in ALS.
Purpose of the Study:
- To investigate the potential involvement of the lower motor neuron (LMN) system in patients diagnosed with Primary Lateral Sclerosis (PLS).
- To re-evaluate the diagnostic criteria for PLS in light of emerging evidence suggesting LMN impairment.
Main Methods:
- Review of clinical and complementary examination data in PLS patients.
- Analysis of existing literature and evidence regarding LMN system function in PLS.
- Comparative study of clinical phenotypes between PLS and ALS.
Main Results:
- While classically UMN-dominant, a significant body of evidence indicates that the LMN system can be impaired in PLS.
- This finding challenges the strict separation between PLS and ALS based solely on LMN involvement.
Conclusions:
- Primary Lateral Sclerosis may not always present as a pure UMN condition.
- PLS could be considered a phenotype of amyotrophic lateral sclerosis (ALS) with predominantly UMN involvement.
- Further research is needed to refine diagnostic criteria and understand the spectrum of motor neuron diseases.
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