Question category: Neurology
A 37 year old joiner is referred to the clinic as he has a 6 month history of lower back pain. It had come on suddenly 6 months ago. He now has shooting pain down the back of both legs worse on left than right. He also has numbness in his left foot. On examination the pain is reproduced at 20 degrees straight leg lift on left. He has reduced sensation over the sole of his foot of his foot and his ankle reflex is diminished and plantars are down going. Which of the following is the likely diagnosis?