A new approach to the classification of maxillary sinus hypoplasia with relevant clinical implications

The purpose of this study was to discover the prevalence of maxillary sinus hypoplasia (MSH) and associated malformations. A total of 490 consecutive axial and coronal computerized tomographic (CT) scans of the paranasal sinu ses were obtained from patients with chronic sinusitis. CT scans were asses sed for the presence of MSH and associated anatomic variations. A new class ification of MSH was made, and the diagnostic criteria listed. The frequenc y of anatomic variations coexisting with MSH was also estimated. MSH was en countered in 21 (4.2%) of the 490 patients. Unilateral types I, II and III MSH were seen in 7 (1.4%), 6 (1.2%) and 8 (1.6%) respectively. MSH was bila teral only in 3 (0.6%) patients, one of which was a bilateral type II. In t he remaining two bilateral MSH cases, there was a type II MSH on one side a nd type III MSH on the other in each patient. Middle conchal pneumatization was the most common coexisting anatomic anomaly in MSH, followed by agger nasi cell, secondary middle concha, paradoxical middle concha and superior conchal pneumatization. A patient with MSH should be carefully evaluated pr ior to any sinus surgery in order to avoid surgical complications. With pre cise CT assessments, an MSH can be diagnosed and distinguished from other m axillary sinus anomalies. With the additional criterion of orbital enlargem ent, and the help of reproducible measurement techniques explained in this study, an objective diagnosis and classification can be made in further inv estigations of MSH.