The first slide talks about the cases where of Lhermitte sign can be seen and the second one about the clinical findings. Overall, the sign is positive when there is a demylination of nerves in the cervical region that leads to the shock like feel down the spine when one bends his/her neck. It's interestingly also called the "barber chair phenomenon" as the position in which the sign appears to be positive is just similar to how when a person has a haircut.. Nothing to do with a barber's chair in real 😉💁♀️