*2.4.6 Triangles on the anterior and posterior surfaces of the petrous portion*

Kawase's triangle: Borghei-Razavi et al. evaluated the safety of this posteromedial middle fossa triangle for removal of the tumors locating or spreading into the cerebellopontine angle and petroclival area. Kawase's triangle was identified

#### **Figure 5.**

*The surgical triangles on the anterior surface: Kawase's triangle: Post-med (posteromedial triangle) and Glasscock's triangle: post-lat (posterolateral triangle). FS, foramen spinosum; GG, geniculate ganglion; TI, trigeminal impression.*

**19**

**Figure 6.**

*fossa anteriorly and the sigmoid sinus posteriorly.*

*Surgical Anatomy of the Temporal Bone DOI: http://dx.doi.org/10.5772/intechopen.93223*

GSPN describing the base [3, 5, 16].

are located [5, 9].

be removed [1, 5, 6].

between the GSPN laterally, the geniculate ganglion at the AE posteriorly, and ganglion gasserian at the trigeminal impression anteriorly. During anterior petrosectomy for accessing the posterior cranial fossa via middle fossa, the GSPN forms

Glasscock's triangle, or the posterolateral middle fossa triangle, is identified between the TN (V3), the geniculate ganglion at the AE and FS (**Figure 5**). The margins of this triangle are formed by a line between where the GSPN crosses under V3 and the FS medially, a line between the FS and geniculate ganglion laterally, and

Rhomboid area (Kawase triangle+postmeatal area) is situated between the GPN, petrous ridge, AE, and the posterior border of the V3. A large tumor located in the midline skull base or spreading into the infratemporal and petroclival region even the cavernous sinus can be removed by extended EEA through V2-V3 corridor to avoid complications including ICA injury, IPS bleeding, TN injury and CSF leak [31]. Trautmann's triangle is bounded by the SPS superiorly, SS posteriorly, and solid angle which is formed by three SCs anteriorly (**Figure 6**). In this triangle, the retrolabyrinthine tract from the MA, the endolymphatic sac, and the vestibular aqueduct

Donaldson's line is a surgical line that is parallel to the LSC whereas it is vertical to the posterior SSC and divide it into superior and inferior portions. Below this line medial to the labyrinth the endolymphatic sac is situated. Citelli's angle (sinodural angle); is bounded by the middle fossa dura plate (SPS) superiorly, posterior fossa dura plate (bony plate covering the MA) anteriorly and the SS posteriorly (**Figure 6**). During mastoidectomy the air cells in this triangle should

*The surgical triangles on the posterior surface: Trautmann's triangle margins are formed between the superior petrosal sinus superiorly, the sigmoid sinus posteriorly, and the semicircular canals antero-inferiorly. Star: Citelli's angle (sinodural angle) is formed between the dural plates of the middle fossa superiorly, the posterior* 

the lateral border of the surgical approach (**Figure 5**) [30].

#### *Surgical Anatomy of the Temporal Bone DOI: http://dx.doi.org/10.5772/intechopen.93223*

*Oral and Maxillofacial Surgery*

used to treat the FC pathologies [27].

herpes virus, is responsible for 50% of peripheral FN palsies. The FC dehiscence can be congenital or secondary to the surgical intervention or pathology of adjacent structures and results in cerebrospinal fluid (CSF) otorrhea. Several surgical approaches, including the translabyrinthine, transcochlear and retrosigmoid, are

Ossification of the petrous portion begins from the 14 centers that fuse to form

otic capsule and is completed at birth. The petrous portion develops from the cartilaginous differentiation of the mesenchyme by endochondral ossification at the 16th week of gestation. The cementum layer in teeth roots and petrous portion of the temporal bone contain the optimal endogenous DNA substrate which can provide information to specify the geographic location for genomic analyses [28]. Damgaard et al. reported that the prevalence of the endogenous DNA contents in nonpetrous bones and teeth is ranged from 0.3 to 20.7%, while the levels for petrous bones ranges between 37.4 and 85.4% [29]. Due to the high density and resistance to harsher climatic conditions of the petrous bone, the otic capsule of the petrous bone preserves DNA substrate extremely well and has much higher endogenous DNA level than the teeth by 5.2-fold on average. So, it is currently acknowledged as the

optimal substrates for ancient genomic research [28, 29].

*2.4.6 Triangles on the anterior and posterior surfaces of the petrous portion*

Kawase's triangle: Borghei-Razavi et al. evaluated the safety of this posteromedial middle fossa triangle for removal of the tumors locating or spreading into the cerebellopontine angle and petroclival area. Kawase's triangle was identified

*The surgical triangles on the anterior surface: Kawase's triangle: Post-med (posteromedial triangle) and Glasscock's triangle: post-lat (posterolateral triangle). FS, foramen spinosum; GG, geniculate ganglion; TI,* 

**18**

**Figure 5.**

*trigeminal impression.*

between the GSPN laterally, the geniculate ganglion at the AE posteriorly, and ganglion gasserian at the trigeminal impression anteriorly. During anterior petrosectomy for accessing the posterior cranial fossa via middle fossa, the GSPN forms the lateral border of the surgical approach (**Figure 5**) [30].

Glasscock's triangle, or the posterolateral middle fossa triangle, is identified between the TN (V3), the geniculate ganglion at the AE and FS (**Figure 5**). The margins of this triangle are formed by a line between where the GSPN crosses under V3 and the FS medially, a line between the FS and geniculate ganglion laterally, and GSPN describing the base [3, 5, 16].

Rhomboid area (Kawase triangle+postmeatal area) is situated between the GPN, petrous ridge, AE, and the posterior border of the V3. A large tumor located in the midline skull base or spreading into the infratemporal and petroclival region even the cavernous sinus can be removed by extended EEA through V2-V3 corridor to avoid complications including ICA injury, IPS bleeding, TN injury and CSF leak [31].

Trautmann's triangle is bounded by the SPS superiorly, SS posteriorly, and solid angle which is formed by three SCs anteriorly (**Figure 6**). In this triangle, the retrolabyrinthine tract from the MA, the endolymphatic sac, and the vestibular aqueduct are located [5, 9].

Donaldson's line is a surgical line that is parallel to the LSC whereas it is vertical to the posterior SSC and divide it into superior and inferior portions. Below this line medial to the labyrinth the endolymphatic sac is situated. Citelli's angle (sinodural angle); is bounded by the middle fossa dura plate (SPS) superiorly, posterior fossa dura plate (bony plate covering the MA) anteriorly and the SS posteriorly (**Figure 6**). During mastoidectomy the air cells in this triangle should be removed [1, 5, 6].

#### **Figure 6.**

*The surgical triangles on the posterior surface: Trautmann's triangle margins are formed between the superior petrosal sinus superiorly, the sigmoid sinus posteriorly, and the semicircular canals antero-inferiorly. Star: Citelli's angle (sinodural angle) is formed between the dural plates of the middle fossa superiorly, the posterior fossa anteriorly and the sigmoid sinus posteriorly.*
