Otosteon for localization of the horizontal segment of facial nerve on multislice CT multiplanar reconstruction images.

The objective of this study was to find out the relationship between the horizontal segment of facial nerve (HFN) and otosteon to facilitate prediction of the location of HFN during facial nerve decompression. The plane perpendicular to the line between the superior border of meatus acusticus externus and supraorbital margin was named the base plane. Parameters of 150 patients (300 observations) with healthy middle ears were measured on high-resolution spiral multislice computed tomographic multiplanar reconstruction (MPR) images that were parallel to the base plane. Geniculate ganglion was considered as the beginning of HFN. The shortest distances between HFN and head of malleus (HM), neck of malleus (NM), short limb of incus (SI), long limb of incus (LI), and stapes (S) were measured respectively on different MPR images. The data gained were analyzed by statistical method and were also analyzed with respect to side and gender. On average, HFN-HM was 0.6546 cm, HFN-NM was 0.3680 cm, HFN-SI was 0.2731 cm, HFN-LI was 0.2275 cm, and HFN-S was 0.2162 cm. HFN-NM and HFN-SI were longer on the right side than those of the left (P < 0.05). HFN-SI and HFN-LI were longer in males than those of females on the right side (P < 0.05). Otosteon is considered an excellent bone landmark which easily showed on computed tomographic images and can easily be found in facial nerve decompression. Otosteon could be used to find the location of HFN during surgery. Furthermore, facial nerve localization is the key to facial nerve decompression. Our results may provide more detailed information to predict the location of HFN during facial nerve decompression.