I would think they would. Our ds had his first sinus ct scan after 4 wks of ceftin for what was obviously a sinus infection, followed by two months of non-stop illness, including fevers, ear infections, etc. & 2 more antibiotics. At the time of the ct scan, we THOUGHT his sinuses were clear because he didn't have ANY nasal symptoms. That ct was pretty much the same as what you said your child's was like. When another 6 wks of a stronger antibiotic didn't clear it, we were referred to an ENT for sinus surgery to clean them out. Now, we know not to judge by nasal symptoms but more by other symptoms. HTH.