To the Editor: We read with great interest the recent article "Refining the Anatomy of Percutaneous Trigeminal Rhizotomy: A Cadaveric, Radiological, and Surgical Study" by Yuanzhi et al1 recently published in Operative Neurosurgery. In this anatomic manuscript, they divided the percutaneous trigeminal corridor into the buccal, inferior temporal, and Meckle cave segments. In addition, they stressed the importance of the precondylar reference line that coincides with the foramen ovale in 75% and the carotid canal in 70% of the computed tomography scans. Furthermore, they introduced the concept of the ovale-carotid-pterygoid triangle. We published a similar study in 2010 in Acta Neurochirugica.2 In that publication, we introduced the concept of the "inverted pyramid"2,3 focused on the extracranial trajectory of this corridor (Figure 1). Three segments were defined: the inferior segment from the cutaneous penetration to the parotid duct (Figure 2), the middle third from the parotid duct to the lateral pterygoid muscle (LPM) (Figure 3), and the superior third from the LPM to the plexus triangularis (Figure 4). A particular emphasis on the location of the maxillary artery (MA) in this route was placed. In half of the cases, the MA traveled through the middle of the pyramid and the other half through the upper third. In an additional paper titled "The maxillary artery and its variants: an anatomical study with neurosurgical applications,4" we studied the course of this artery through anatomic microdissections dividing the MA into 3 segments: mandibular, pterygoid, and pterygopalatine. Then, we correlated our findings with 3-dimensional (3D) head and neck computed tomography angiography reconstructions. One of the main conclusions of this manuscript was that the pterygoid segment of the MA may run either laterally to the LPM in 66% (lateral variant) or medially in 33% (medial variant) of the cases.FIGURE 1.: Illustration depicting the pyramid concept. The base of this pyramid has 3 corners, the main one regarding the "plexus triangularis" also known as trigeminal ganglion (target) and 2 additional ones: the mid pupillary line and a point 3 centimeters in front of the tragus. The tip of this pyramid corresponds to the entrance at the probe at the skin level, which is 3 cm off the lateral aspect of the mouth's corner. A.t.n., auriculotemporal nerve; Buccal n., buccal nerve; Bucinator m, buccinator muscle; Chorda t., chorda tympany; Eustahian t., Eustachian tube; Facial a., facial artery; Facial v, facial vein; I.C.A., internal carortid artery; I.J.V., internal jugular vein; Inf. alv.n., inferior alveolar nerve; Lingual n., lingual nerve; M.m.a., middle meningeal artery; Masseter n., masseter nerve; Maxillary a., maxillary artery; Med. pteryg. M., medial pterygoid muscle; Parotid d., parotid duct; V1, ophthalmic branch of the trigeminal nerve; V2, maxillary branch of the trigeminal nerve, V3, mandibular branch of the trigeminal nerve. Adapted with permission from Alvernia JE, Sindou MP, Dang ND, et al. Percutaneous approach to the foramen ovale: an anatomical study of the extracranial trajectory with the incorrect trajectories to be avoided. Acta Neurochir (Wien). 2010;152(6):1043–1053. ©2010 Springer Nature.FIGURE 2.: To better understand the anatomy of this pyramid's concept, we have proposed to divide it into 3-thirds. The inferior third which comprises the structures contained from the skin puncture site (pyramid's tip) to the parotid duct (parotid d.). For illustration purposes, the masseter muscle has been detached from its zygomatic insertion. To expose the right Gasserian ganglion and the plexus traingularis (Plexus T.), a right frontotemporal craniotomy has been performed. Additional structures shown in this dissection include the following: Buccal n., buccal nerve; Buccinator m., buccinator muscle; Coronoid p., coronoid process; Facial v., facial vein; foramen spinosum; Hiatus for GSPN, Hiatus for the great superior petrosal nerve; Masseter m., Masseter muscle; Masseter n., Masseter nerve; Plexus T., plexus triangularis; Parotid d., parotid duct; Temp. M, temporalis muscle; V3, mandibular branch of the trigeminal nerve; Zyg. Arch, zygomatic arch. Adapted with permission from Alvernia JE, Sindou MP, Dang ND, et al. Percutaneous approach to the foramen ovale: an anatomical study of the extracranial trajectory with the incorrect trajectories to be avoided. Acta Neurochir (Wien). 2010;152(6):1043–1053. ©2010 Springer Nature.FIGURE 3.: The middle third of this pyramid goes from the parotid duct (Parotid d.) up the lateral pterygoid muscle (Lat. Pteryg. m.). For illustration purposes, the right zygomatic arch and the right ascending branch of the mandible have been removed and the lateral aspect of the middle fossa floor has been drilled off. Additional structures depicted in this dissection are Buccal n., buccal nerve; Buccinator m., buccinator muscle; Facial v., facial vein; Hiatus for GSPN, Hiatus for great superior petrosal nerve; Inf. alv. n., inferior alveolar nerve; Lat. Pteryg. m., lateral pterygoid muscle; Lingual n., lingual nerve; Masseter m., masseter muscle; Tentorium; Plexus T., plexus triangularis; Parotid d., par otid duct; V3, mandibular branch of the trigeminal nerve. Adapted with permission from Alvernia JE, Sindou MP, Dang ND, et al. Percutaneous approach to the foramen ovale: an anatomical study of the extracranial trajectory with the incorrect trajectories to be avoided. Acta Neurochir (Wien). 2010;152(6):1043–1053. ©2010 Springer Nature.FIGURE 4.: The superior third of this pyramid is the "base of this imaginary structure" and goes from the lateral pterygoid muscle (Lat. pteryg. m.) (Figure 3) up to the plexus triangularis. Because the base of the pyramid is most of the floor of the middle cranial fossa, a partial drilling of the anterior aspect of the right petrous bone and the right greater wing of the spenoidal bone has been performed to further the dissection and show the petrous portion of the internal carotid artery as well as the auditory tube (Auditory t.). Additional structures shown in this dissection include the following: A.t.n., auriculo-temporalnerve; Chorda t., chorda tympani; Buccal n., buccal nerve; buccinator m, buccinator muscle; Facial v., facial vein; IJV, internal jugular vein; M.m.a., middle meningeal artery; Inf. alv. n., inferior alveolar nerve; Lat. pteryg. p., lateral pterygoid process; Lingual n., lingual nerve; masseter m., masseter muscle; Maxillary a., maxillary artery; Med. Pteryg m, medial pterygoid muscle; Parotid d., parotid duct; V3, mandibular branch of the trigeminal nerve; V2, maxillary branch of the trigeminal nerve; V1, ophthalmic branch of the trigeminal nerve. Adapted with permission from Alvernia JE, Sindou MP, Dang ND, et al. Percutaneous approach to the foramen ovale: an anatomical study of the extracranial trajectory with the incorrect trajectories to be avoided. Acta Neurochir (Wien). 2010;152(6):1043–1053. ©2010 Springer Nature.We found the computed tomography angiography 3D reconstruction to be beneficial in identifying the course of the MA in its pterygoid segment for whatever the trigeminal lesioning technique through the Foramen Ovale5,6 allowing us to predict these 2 variants with 100% accuracy. In the lateral variant, the MA is always away from the percutaneous foramen ovale trajectory. By contrast, in the medial variant, the artery is near the foramen ovale, and in up to 16%, the MA is directly in the probe's trajectory. We agree with Dr Yuanzhi et al that coupling anatomy and imaging,7 including 3D computed tomography reconstruction and even neuronavigation for the percutaneous transforaminal ovale approach, increases the procedure's accuracy and decreases the risk of complications.8