Startle Reflex in Primary Lateral Sclerosis ( <scp>PLS</scp> ): A Comparison With Amyotrophic Lateral Sclerosis ( <scp>ALS</scp> )

SR is significantly more common in PLS than in ALS. Notably, UMN-predominant ALS, although limited in number, showed a higher prevalence of SR (6 out of 6, 100%), indicating that predominant UMN involvement may be a key determinant of SR across both conditions. These hypothesis-generating findings suggest that SR may serve as a novel clinical marker in PLS and UMN-predominant ALS, warranting further validation through prospective studies.