الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Anatomical variations of PNS are numerous and confusing. Careful examination is required to identify these variations to avoid intraoperative complications. The development of maxillary sinus is completed at the age of puberty, before which we can’t comment on the sinus size. In our thesis we studied types of small maxillary sinus; silent sinus syndrome and hypoplastic maxillary sinus. Both are rare but MSH is more common representing 83.33%. Both are mostly discovered incidentally and not necessarily associated with sinusitis especially SSS. The SSS representing 16.67% of cases with the patients commonly present with facial asymmetry and spontaneous painless enophthalmos without history of trauma or surgery or even sinusitis. The pathogenesis is collapse of the sinus walls due to chronic outflow obstruction with resultant increased orbit size and middle meatus.
Radiologically, it is diagnosed by small sinus with fully developed alveolar recess having laterally bent uncinate process against the infero-medial wall of the orbit which increases the risk of orbit injury during FESS. Other signs include: total/partial sinus opacification, obliterated OMC, increased orbital volume and thinned out all or some sinus walls. SSS was bilateral in 40%, right in 40% and left in 20%.
MDCT helps detect these signs to reduce intraoperative complications and reduce morbidity.
Cases with MSH are asymptomatic and commonly discovered incidentally. MSH has many theories for its causes; congenital and acquired.
Radiologically MSH was defined as small sinus didn’t develop its alveolar recess with thick sinus walls. The position of UP and the orbit size were not significantly changed. It can be classified as mild and severe by comparing transverse and vertical dimensions of sinus to their corresponding of the orbit. Mild cases represented 48% and severe cases represented 52%.
The retro-antral fat pad was thought by some authors to be a specific sign of SSS but in our study we found that it was prominent in only 40% of cases of SSS, prominent in 64% of cases of MSH and even prominent bilaterally in some unilateral cases with small sinus. Again it is not sensitive or specific for diagnosing SSS or MSH.
SSS and MSH could be associated with maxillary or other sinuses variations as found in 12 cases such as maxillary sinus septations, anomalies of UP, accessory ostium, Haller’s cell and concha bullosa. These can lead to either obstructed osteomeatal complex, sinus opacification and in late stages may lead to SSS or even intraoperative complications so they should be carefully reported