A 40-year-old male presents with bilateral upper limb weakness, muscle atrophy, and fasciculations for 1 year. No sensory deficit or urinary incontinence. Examination: Shoulder muscle strength V, elbow joint muscle strength V, wrist joint muscle strength IV, opponens pollicis muscle and interosseous muscles strength II-III, slightly increased muscle tone in upper limbs, bilateral biceps and triceps reflexes (+++), right Hoffmann's sign positive, left Babinski sign positive, atrophy of thenar and hypothenar eminences and interosseous muscles bilaterally. The most likely diagnosis is: