Visualization of Motor Cortex Involvement by 18F-THK5351 PET Potentially Strengthens Diagnosis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) involves both upper motor neurons (UMNs) and lower motor neurons. The detection of UMN involvement, a core component of ALS criteria, is primarily dependent on neurological examination because of a lack of definitive biomarkers. We present the 18F-THK5351 PET images of a 76-year-old man diagnosed with ALS comorbid with Alzheimer disease, demonstrating marked accumulation of 18F-THK5351 in the bilateral precentral gyri. Because 18F-THK5351 binds to monoamine oxidase B highly expressed in astrocytes, where the neurodegenerative process is ongoing, our case highlights that 18F-THK5351 tracer should be a useful marker for detecting UMN neurodegeneration in ALS.