Use the clinical features of MERRF syndrome, it mean that ALS is a spectrum disease, and ALS and FTD biologically and clinically linked to frame the working diagnosis and next step; anchor the next clinical decision to it rather than restating it. Make it mean that ALS is a spectrum disease the checkpoint that determines whether you escalate testing, narrow the differential, or change treatment.

ALS is best understood as a spectrum that can extend from motor-only disease to motor and cognitive-behavioral overlap; Shared genetics and proteinopathies link ALS and frontotemporal dementia; Adult anterior horn cell disease includes ALS, SMA, PMA, and post-polio syndromes; Genetic susceptibility and lifelong environmental exposure both contribute to ALS risk; Spinal-onset disease starts in the limbs, while bulbar-onset disease starts with speech and swallowing