A 36-year-old man was seen in the emergency room following s…

A 36-year-old man was seen in the emergency room following sudden onset of numbness involving his right arm and hand.  He denied any sensory changes involving his face or lower limbs.  On clinical examination you note intact perception of light touch and pinprick of the right upper extremity, but he is unable to distinguish among different coins when asked to retrieve a particular one from a small container with his right hand.  He is able to perform this task easily and without error when using his left hand. These clinical findings are suggestive of which  type of lesion?