Step 7. Expose the parapharyngeal space and the tensor veli palatini muscle (Fig. 3.14)
Step 8. Expose the clivus and posterior fossa dura (Fig. 3.24)
Step 9. Remove the ramus of the mandible (Fig. 3.33)
Step 10. Expose the high cervical and paraclival regions (Fig. 3.34)
Illustrated Steps with Commentary
Fig. 3.1 (Step 1) Incise the skin and elevate the flap.A preauricular skin incision is made extending a standard frontal skin incision inferiorly along the mandible. A second incision extends from the inferior orbital rim back along the top of the zygoma. Thus, the skin incision includes a hemicoronal incision, a preauricular incision, a high cervical incision, a temporal incision, a conjunctival incision, and a paranasal incision.Fig. 3.2 Reflection of the skin flap.A reflection of the skin flap exposes the frontal bone, the temporalis and masseteric muscles, the zygoma, and the maxilla. As part of the temporal incision, the frontal branch of the facial nerve is transected and tagged. The nerve is reanastamosed at the time of the closure. The preauricular dissection must be deep to the superficial layer of the parotid gland and lateral to the main trunk of the facial nerve to avoid facial nerve injury. The facial nerve and its branches in the parotid gland are elevated with the facial flap. The main trunk of the facial nerve should be preserved when possible; however, if a high cervical incision is required, the facial nerve can be transected, tagged, and repaired during wound closure. In this specimen, the facial nerve is transected. The parotid gland, including the facial nerve, is raised with the facial flap. (DTF, deep temporal fascia; F, frontal bone; MM, masseteric muscle; Mx, maxilla; Or, orbit; Zy, zygomatic arch)Fig. 3.3 Reflection of the masseteric muscle.Inferior reflection of the masseteric muscle exposes the ramus of the mandible. (DTF, deep temporal fascia; F, frontal bone; Mx, maxilla; Or, orbit; RM, ramus of the mandibule; Zy, zygomatic arch)Fig. 3.4 (Step 2) Perform orbito-zygomaticmaxillary osteotomies.The zygomatic arch and the anterior wall of the maxilla are removed in one piece. (DTF, deep temporal fascia; F, frontal bone; Mx, maxilla; Or, orbit; RM, ramus of the mandibule; Zy, zygomatic arch)Fig. 3.5 Exposure after the osteotomy.An osteotomy of the zygoma and the maxilla exposes the coronoid process of the mandibule, the fat tissue in the pterygopala-tine fossa, and the maxillary sinus. The lateral wall of the orbit has also been removed. (DTF, deep temporal fascia; F, frontal bone; Fat, fat tissue; MxS, maxillary sinus; Or, orbit; RM, ramus of the mandibule)Fig. 3.6 Removal of adipose tissue exposing the contents of the pterygopalatine fossa.The removal of the adipose tissue behind the posterior wall of the maxillary sinus exposes the pterygopalatine fossa. The deep temporal fascia is removed to show the relationship between the insertion of the temporalis muscle and the coronoid process. (F, frontal bone; MxS, maxillary sinus; Or, orbit; RM, ramus of the mandibule; TM, temporalis muscle)Fig. 3.7 (Step 3) Reflect the temporalis muscle.An inferior reflection of the temporalis muscle exposes the base of the middle fossa. The temporalis muscle with the coronoid process is detached with a drill and reflected. (F, frontal bone; MxS, maxillary sinus; Or, orbit; T, temporal bone; TM, temporalis muscle)Fig. 3.8 Reflection of the temporalis muscle with the coronoid process to preserve the posterior deep temporal artery.The coronoid process is fractured obliquely and left attached to the temporalis muscle to preserve the blood supply to the muscle through the posterior deep temporal artery. (DTA, deep temporal artery; F, frontal bone; MA, maxillary artery; MxS, maxillary sinus; Or, orbit; T, temporal bone; TM, temporalis muscle)Fig. 3.9 Exposure of the lateral pterygoid muscle.Removal of a main trunk of the internal maxillary artery and the pterygoid venous plexus exposes the superior and inferior heads of the lateral pterygoid muscle. (DTA, deep temporal artery; F, frontal bone; iLPM, inferior head of the lateral pterygoid muscle; MxS, maxillary sinus; Or, orbit; sLPM, superior head of the lateral pterygoid muscle; T, temporal bone; TM, temporalis muscle)Fig. 3.10 (Step 4) Remove the lateral pterygoid muscle.Removal of the superior and inferior heads of the lateral pterygoid muscle exposes the infratemporal and pterygopalatine fossae. The branches of the mandibular nerve are exposed. (DTA, deep temporal artery; MxS, maxillary sinus; Or, orbit; T, temporal bone; TM, temporalis muscle; V3, mandibular nerve )Fig. 3.11 Removal of the posterior wall of the maxillary sinus.The infratemporal and pterygopalatine fossae and the maxillary sinus that become a corridor to the anterior and anterolateral skull base are well exposed. (DTA, deep temporal artery; F, frontal bone; LL, lateral lamina of the pterygoid process; MxS, maxillary sinus; Or, orbit; T, temporal bone; TM, temporalis muscle; V3, mandibular nerve )Fig. 3.12 (Step 5) Perform a frontotemporal craniotomy.A frontotemporal craniotomy is elevated. (DTA, deep temporal artery; FD, frontal dura; LL, lateral lamina of the pterygoid process; MxS, maxillary sinus; Or, orbit; TD, temporal dura; TM, temporalis muscle; V3, mandibular nerve )Fig. 3.13 (Step 6) Flattening the floor of the middle fossa and removal of the medial wall of the maxillary sinus to expose the nasal cavity.Flattening the floor of the middle fossa with a diamond drill exposes the mandibular (V3), maxillary (V2), and vidian nerves, and the sphenoid sinus. A medial wall of the maxillary sinus is also removed. (FD, frontal dura; Or, orbit; SS, sphenoid sinus; TD, temporal dura; TM, temporalis muscle; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.14 (Step 7) Expose the parapharyngeal space and the tensor veli palatini muscle.The tensor velli palatini muscle arises from the scaphoid fossa at the top of the pterygoid process and posteriorly from the medial aspect of the spine of the sphenoid bone. This thin and triangular shaped muscle is attached to the anterolateral membranous wall of the eustachian tube lateral to the levator veli palatine muscle. The tendon passes around the pterygoid hamulus. (Or, orbit; SS, sphenoid sinus; TD, temporal dura; TM, temporalis muscle; TVPM, tensor veli palatini muscle; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.15 Exposure of the eustachian tube (auditory or pterygotympanic tube).Removal of the tensor velli palatini muscle exposes the eustachian tube. (ET, eustachian tube; Or, orbit; SS, sphenoid sinus; TD, temporal dura; TM, temporalis muscle; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.16 Enlargement of Fig. 3.15.The superior constrictor muscle of the pharynx is well seen. The fibrous layer that supports the pharyngeal mucosa is thickened above the superior constrictor to form the pharyngobasilar fascia. The fascia is attached to the basilar part of the occipital bone and the petrous part of the temporal bone medial to the eustachian tube, and to the posterior border of the medial pterygoid plate and pterygomandibular raphe. (DTA, deep temporal artery; ET, eustachian tube; LVPM, levator velli palatini muscle; Or, orbit; PhxBF, pharyngobasilar fascia; SCPhx, superior constrictor muscle of the pharynx; SS, sphenoid sinus; TD, temporal dura; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.17 Overview of the exposure.(ET, eustachian tube; FD, frontal dura; Or, orbit; SS, sphenoid sinus; TD, temporal dura; TM, temporalis muscle; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.18 Identification of the longus capitis and rectus capitis anterior muscles.The longus capitis and rectus capitis anterior muscles are seen through the retropharyngeal space. The rectus capitis is a short muscle originating from the anterior mass and transverse processes of the atlas. The longus capitis originates from the anterior tubercle of C3-6. Both insert into the occipital bone anterior to the foramen magnum. (DTA, deep temporal artery; ET, eustachian tube; ICA, internal carotid artery; LCpM, longus capitis muscle; Or, orbit; RCAM, rectus capitis anterior muscle; RM, ramus of the mandibule; SCPhx, superior constrictor muscle of the pharynx; SPhM, stylopharyngeal muscle; V3, mandibular nerve )Fig. 3.19 Identification of the glossopharyngeal nerve.The glossopharyngeal nerve is observed passing over the stylopharyngeal muscle. The nerve passes lateral to the internal carotid artery. (ET, eustachian tube; ICA, internal carotid artery; IX, glossopharyngeal nerve; LCpM, longus capitis muscle; Or, orbit; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; SPhM, stylopharyngeal muscle)Fig. 3.20 Review of anatomical relationships in the retropharyngeal space.The rectus capitis anterior muscle lies posterior and medial to the longus capitis muscle and under the internal carotid artery, the glossopharyngeal nerve, and the stylopharyngeal muscle in the retropharyngeal space. (ET, eustachian tube; ICA, internal carotid artery; IX, glossopharyngeal nerve; LCpM, longus capitis muscle; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; SPhM, stylopharyngeal muscle)Fig. 3.21 The course of the eustachian tube.A metal bar is inserted into the eustachian tube that connects the middle ear to the nasopharynx. (ET, eustachian tube; LCpM, longus capitis muscle; PhxBF, pharyngobasilar fascia; SCPhx, superior constrictor muscle of the pharynx; SS, sphenoid sinus; TD, temporal dura; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.22 After removal of the eustachian tube.The longus capitis muscle originates from the anterior tubercles of the third, fourth, fifth, and sixth cervical vertebrae and becomes broad and thick above, where it is inserted into the inferior surface of the basilar part of the occipital bone. The rectus capitis anterior is a short, flat muscle situated behind the upper part of longus capitis. It arises from the anterior surface of the lateral mass of the atlas and the root of its transverse process, and ascends almost vertically to the inferior surface of the basilar part of the occipital bone immediately anterior to the occipital condyle. (DTA, deep temporal artery; LCpM, longus capitis muscle; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; V3, mandibular nerve )Fig. 3.23 Division of the mandibular nerve.A spine of the sphenoid bone is well seen after the mandibular nerve is divided. The spine is the inferior lateral corner of the greater wing of the sphenoid bone. The spine fits into the groove between the petrous and squamosal portions of the temporal bone and lies just behind the foramen spinosum. (DTA, deep temporal artery; IX, glossopharyngeal nerve; LCpM, longus capitis muscle; Or, orbit; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; SSph, spine of the sphenoid bone; TD, temporal dura)Fig. 3.24 (Step 8) Exposure of the basilar part of the occipital bone (clivus) through the retropharyngeal space.An upper part of the basilar part of the occipital bone is exposed compressing the pharyngobasilar fascia and the superior constrictor muscle anteriorly. (CL, clivus; DTA, deep temporal artery; LCpM, longus capitis muscle; Or, orbit; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; SS, sphenoid sinus; TD, temporal dura; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.25 Removal of the longus capitis muscle.The rectus capitis anterior muscle is well exposed after the longus capitis muscle is removed. (CL, clivus; DTA, deep temporal artery; Or, orbit; RCAM, rectus capitis anterior muscle; SCPhx, superior constrictor muscle of the pharynx; SS, sphenoid sinus; TD, temporal dura; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.26 Removal of the rectus capitis anterior muscle.Removal of the rectus capitis anterior muscle exposes the basilar part of the occipital bone. (CL, clivus; DTA, deep temporal artery; OcC, occipital condyle; Or, orbit; SCPhx, superior constrictor muscle of the pharynx; SS, sphenoid sinus; TD, temporal dura; V3, mandibular nerve ; Vi, vidian nerve; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; Vi, vidian nerve)Fig. 3.27 Exposure of the occipital and C1 condyles.The occipital, C1 condyle, and facet lie behind the rectus capitis anterior muscle. The anatomical relationship between the internal carotid artery that enters into the carotid canal, the spine of the sphenoid bone, the facet, and the anterior arch of the atlas is well seen from an anterolateral direction. (aC1, anterior arch of the C1 [atlas]; C1C, C1 condyle; CL, clivus; DTA, deep temporal artery; ICA, internal carotid artery; IX, glossopharyngeal nerve; OcC, occipital condyle; Or, orbit; SCPhx, superior constrictor muscle of the pharynx; SPhM, stylopharyngeal muscle; TD, temporal dura)Fig. 3.28 Elevation of the temporal base with the dura mater.Elevation of the basal temporal dura exposes the C5 portion of the internal carotid artery as it exits the carotid canal in the middle fossa. (C1C, C1 condyle; C5, C5 portion of the internal carotid artery; CL, clivus; ICA, internal carotid artery; OcC, occipital condyle; Or, orbit; SSph, spine of the sphenoid bone; TD, temporal dura)Fig. 3.29 Exposure of the intracranial extradural portion of the internal carotid artery.The C5 and C6 segments of the internal carotid artery can be exposed by opening the intrapetrous carotid canal. The canal can be opened from a lateral direction by drilling through the bony eustachian canal and the canal that houses the tensor tympani muscle. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; DTA, deep temporal artery; OcC, occipital condyle; Or, orbit; SCPhx, superior constrictor muscle of the pharynx; TD, temporal dura)Fig. 3.30 Drilling of the basilar part of the occipital bone (clivectomy).The basilar part of the occipital bone is drilled under the internal carotid artery. The posterior fossa dura is exposed. (aC1, anterior arch of the C1 [atlas]; C1C, C1 condyle; C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; DTA, deep temporal artery; OcC, occipital condyle; Or, orbit; PD, posterior fossa dura; SCPhx, superior constrictor muscle of the pharynx; TD, temporal dura)Fig. 3.31 Partial clivectomy.The bony edge of the dorsum sellae is seen by lifting the internal carotid artery. (aC1, anterior arch of the C1 [atlas]; C1C, C1 condyle; CL, clivus; DS, dorsum sellae; DTA, deep temporal artery; OcC, occipital condyle; Or, orbit; PD, posterior fossa dura; SCPhx, superior constrictor muscle of the pharynx; TD, temporal dura)Fig. 3.32 Exposure of the posterior fossa dura.Removal of the basilar portion of the occipital bone with a diamond drill exposes the posterior fossa dura. (aC1, anterior arch of the C1 [atlas]; C1C, C1 condyle; CL, clivus; DTA, deep temporal artery; OcC, occipital condyle; Or, orbit; PD, posterior fossa dura; SCPhx, superior constrictor muscle of the pharynx; TD, temporal dura)Fig. 3.33 (Step 9) Remove the ramus of the mandible.After the ramus of the mandible is removed, the stylopharyngeal, styloglossus, and the styloid muscles are well exposed. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; ICA, internal carotid artery; IX, glossopharyngeal nerve; SCM, sternocleidomastoid muscle; SGM, styloglossus muscle; SHL, stylohyoid ligament; SHM, stylohyoid muscle; SPhM, stylopharyngeal muscle; StyP, styloid process)Fig. 3.34 (Step 10) Expose the three muscles that attach to the styloid process (magnification of Fig. 3.33).The stylopharyngeal, styloglossus, and stylohyoid muscles are well seen. The stylohyoid ligament runs parallel to the stylohyoid muscle. The glossopharyngeal nerve and the high cervical portion of the internal carotid artery are seen between the sty-loglossus and the stylopharyngeal muscles. (aC1, anterior arch of the C1 [atlas]; C1C, C1 condyle; ICA, internal carotid artery; OcC, occipital condyle; IX, glossopharyngeal nerve; SCM, sterno-cleidomastoid muscle; SGM, styloglossus muscle; SHL, stylohyoid ligament; SHM, stylohyoid muscle; SPhM, stylopharyngeal muscle; StyP, styloid process)Fig. 3.35 Removal of the lateral wall of the nasal cavity.The nasal septum is seen after the lateral wall of the nasal cavity is removed. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; ICA, internal carotid artery; NS, nasal septum; Or, orbit; PD, posterior fossa dura; SCM, sternocleidomastoid muscle; SMs, muscles that attached to the styloid process; StyP, styloid process; TD, temporal dura; Vo, vomer)Fig. 3.36 Removal of the orbit.The orbit is removed and the ethmoid sinus is skeletonized through the medial wall of the orbital cavity. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; Et, ethmoid sinus; FD, frontal dura; ICA, internal carotid artery; NS, nasal septum; PD, posterior fossa dura; SCM, sternocleidomastoid muscle; SMs, muscles that attach to the styloid process; StyP, styloid process; TD, temporal dura; Vo, vomer)Fig. 3.37 Ethmoidectomy.After ethmoidectomy the anterior skull base is exposed. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; Et, ethmoid sinus; FD, frontal dura; ICA, internal carotid artery; NS, nasal septum; PD, posterior fossa dura; SCM, sternocleidomastoid muscle; SMs, muscles that attach to the styloid process; SS, sphenoid sinus; StyP, styloid process; TD, temporal dura; Vo, vomer)Fig. 3.38 Removal of the nasal septum.After the nasal septum is removed the superior, middle, and inferior turbinates on opposite sides are exposed. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; CL, clivus; Et, ethmoid sinus; FD, frontal dura; ICA, internal carotid artery; IT, inferior turbinate; MT, middle turbinate; PD, posterior fossa dura; SCM, sternocleidomastoid muscle; SMs, muscles that attach to the styloid process; ST, superior turbinate; StyP, styloid process; TD, temporal dura)
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