Introduction: The potential linkage between upper (UMN) and lower motor neuron (LMN) involvement in amyotrophic lateral sclerosis (ALS) has not yet been fully elucidated. There is ongoing discussion as to whether ALS is primarily a disease of UMNs or LMNs.
Methods: We performed a retrospective analysis of 189 ALS patients from our ALS outpatient database to investigate the different spreading patterns of UMN and LMN affection in disease progression in relation to the onset region.
Results: The body region with the highest UMN involvement at onset in general also had the highest frequency of LMN signs and vice versa. This is in line with the hypothesis of a focal onset of disease, which then spreads to adjacent areas. However, there was a great variation between ALS phenotypes.
Discussion: These observations support the hypothesis of focal damage of a localized group of motor neurons, which then spreads to adjacent motor neurons.
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