What Causes Numbness In My Left Arm?

My husband was taken to hospital last night after suffering with numbness & inability to move left arm. He had a splitting headache that he had all week, His mouth was drooped down although his speech was fine, he also felt dizzy & his throat felt tight. After investigations (CT scan, chest x-ray, MRI scan which all came back clear as did all his blood tests) he was sent home pending a further review by a clinic but no diagnosis was given? Can you give me any idea what these symptoms could be please