Need help understanding what is the difference between chronic illness with exacerbation progression and chronic illness with severe exacerbation progression. I was using the examples in the AANS Managing Coding book and one office visit with cervical stenosis of spinal canal was coded with chronic illness with exacerbation (moderate). Then the other office visit with spondylosis and stenosis at L4-5, L5-S1 was coded with chronic illness with severe exacerbation progression (high). What makes one more severe than the other one?? Is it because the second one has 2 chronic illnesses?? I'm trying to find something in writing to back it all up. Thanks in advance.