What is the likely diagnosis for a 50-year-old male with limb weakness, clumsiness, slurred speech, and difficulty swallowing, and how would you confirm it?

The likely diagnosis for a 50-year-old male presenting with limb weakness, clumsiness, slurred speech, and difficulty swallowing is amyotrophic lateral sclerosis (ALS), with diagnostic confirmation typically involving clinical evaluation and electromyography. Differential diagnoses include functional neurological disorder and stroke, which require distinct diagnostic approaches.