Measurement of anatomical relationships of facial nerve canal related to middle ear and mastoid surgery on multi-slice computed tomography-multiplanar reformation images

Abstract

To investigate the anatomical relationships of facial nerve canal related to middle ear and mastoid surgery by multi-slice computed tomography (MSCT) and its multiplanar reconstruction ( MPR) technology. High-resolution CT scanning with multislice spiral CT of temporal bones without bone abnormality of 373 ears in 187 adult patients were examined. All original images were processed by MPR. The distances between facial nerve canal (FNC) and jugular foramen (JF), lateral surface of mastoid bone (M), external acoustic canal (EAC), posterior fossa dural plate (PFD), sigmoid sinus (SS), promontory (P), cochlear window (CW), pyramidal eminence (PE), posterior semicircular canal (PSC), oval window (OW), head of malleus (MH), incus lenticular process (ILP) and lateral semicircular canal (LSC) were measured on different MPR images. These measurements were also analyzed with respects to side, gender, pneumatization and jugular foramen position differences. On average, FNC-JF was 5.43 mm, FNC-M 15.99 mm, FNC-EAC 4.42 mm, FNC-PFD 9.01 mm, FNC-SS 9.44 mm, FNC-P 6.02 mm, FNC-CW 6.51 mm, FNC-PE 2.64 mm, FNC-PSC 3.12 mm, FNC-OW 1.19 mm, FNC-MH 2.27 mm, FNC-ILP 3.09 mm and FNC-LSC 0.90 mm. FNC-M was longer in males than that of females (P < 0.05). FNC-JF and FNC-SS were longer on left side than those of the right (P < 0.05). FNC-PFD was shorter on left side (P < 0.05). FNC-PFD, FNC-EAC, FNC-SS and FNC-M were longer in well pneumatized mastoids than those of poorly pneumatized mastoids (P < 0.05). FNC-PE was longer in poorly pneumatized mastoids than that of well pneumatized mastoids (P < 0.05). FNC-PFD, FNC-P, FNC-CW and FNC-PSC were longer in bones with jugular foramen variation than those of bones without jugular foramen variation (P < 0.05). FNC-JF, FNC-SS and FNC-M were longer in bones without jugular foramen variation than those of bones with jugular foramen variation (P < 0.05). Anatomical relationships of facial nerve canal related to middle ear and mastoid surgery can be accurately measured on MSCT-MPR images. It is helpful to avoid injuring facial nerve in middle ear and mastoid surgery.