Question category: Neurology
A 52 year old male presents with weakness in his arms. He has noticed he has been dropping things and his hands appeared thinned. He has also had some difficulty walking. On examination there is evidence of wasting in his hands and biceps with evidence of fasciculation. His biceps and supinator reflexes are brisk. Sensation is normal. In the lower limbs there is evidence of a spastic gait and his plantars are upgoing. Which of the following is the most likely diagnosis?