Dessication means the disc is drying up at L1, L4-5 and L5-S1. At the L4-5 level there is a bulging disc putting pressure on the spinal canal, and that same disc bulge is putting pressure on the openings where the nerves come into the area.
I am assuming this is what you want since you didn't ask any questions. If there is more you need, please post with more information and keep in mind that this is just a general impression and not exact.
Carol