A 69-year-old male presents with bilateral upper extremity weakness and atrophy for 3 years. This started with left hand weakness, stiffness, and the need to focus considerably to perform simple tasks. There is no numbness, tingling, pain, or history of trauma . The weakness then progressed to involve the entire left arm, with significant atrophy and loss of function. Six months ago, he started developing similar but milder symptoms in the right hand. He also noticed twitching in both upper extremities, left more than the right. Lower extremities, bowel, and bladder functions are normal. He used to smoke cigarettes but quit 25 years ago and takes five alcoholic drinks per week.

On examination, cranial nerves are intact; there are tongue fasciculations with protrusion. There is significant atrophy and fasciculations of both upper extremities. Motor strength: deltoid 4 on the right, 4− on the left; biceps 4 on the right, 3+ on the left; triceps 4+ on the right, 3+ on the left; wrist extension 4 on the right, 3+ on the left, wrist flexion 4 on the right, 2 on the left; hand grip 4 on the right, 1 on the left; hand intrinsics 3 on the right, 1 on the left; lower extremities 5 bilaterally except left iliopsoas and EHL 4+. Sensation is normal to pinprick and light touch. Deep tendon reflexes are 2+ and symmetric, except biceps reflex 3+ bilaterally. There is a right Hoffman sign and bilateral Babinski sign. Gait is normal; Romberg sign is negative.