The paratemporal segment of the maxillary sinus: a new sign for assessment of size.

The area of the maxillary antrum in Waters' view has been measured in 68 patients using a mechanical planimeter. The mean area was 6.04 +/- 0.25 cm2. The part of the antrum lateral to the innominate line (defined as the paratemporal segment) has a mean area of 0.72 +/- 0.07 cm2. The latter diminishes in small antra and approaches zero when the total antral area falls below 3.48 cm2. It is proposed that the innominate line (Stenvers), or its extension, descends lateral to the field of the small maxillary sinus and may be used as an additional sign of such abnormality.