The total petrosectomy is the ultimate procedure for viewing the front of the brainstem. Unlike anterior approaches through the face, this exposure affords the surgeon a view of the structures lateral to the midline. By necessity, the patient will loose hearing on the side of the exposure. Although the procedure is most often used to treat large petroclival meningiomas, it also can be employed to treat chordomas.
Key Steps
Position: Lateral
Step 1.“C” shaped skin incision from above the temporal line to below the mastoid tip (Fig. 17.1)
Step 2. Elevation of large vascularized graft (Fig. 17.4)
Fig. 17.1 (Step 1) Skin incision.A large “C” shaped skin incision is made from just above the temporal line to just below the mandibular angle. (MA, mandibular angle)Fig. 17.2 Identifying the greater auricular nerve.The greater auricular nerve should be identified and preserved. This nerve can serve as a graft if needed. (GAN, greater auricular nerve)Fig. 17.3 Raising the skin flap.The scalp is raised through the loose tissue plane. As much loose tissue as possible is left on the pericranium and fascia so that the vascularized flap will be as thick as possible. (GA, galea aponeurotica; GAN, greater auricular nerve; OM, occipitalis muscle; TPM, temporoparietal muscle)Fig. 17.4 (Step 2) Outlining a vascularized flap.A large vascularized flap is harvested before the craniotomy is performed. This flap is based anteriorly and incorporates the pericranium and the superficial layer of the temporal fascia. The edges of the skin flap are raised to make the vascularized flap as large as possible. (GA, galea aponeurotica; OM, occipitalis muscle; SCM, sternocleidomastoid muscle; TPM, temporoparietal muscle)Fig. 17.5 Raising the vascularized flap.(GAN, greater auricular nerve; SCM, sternocleidomastoid muscle; SNL, superior nuchal line; TM, temporalis muscle)Fig. 17.6 Dividing the external auditory canal.The external auditory canal is incised. The lateral end of the canal will be closed in three layers. (EAC, external auditory canal; GAN, greater auricular nerve; SCM, sternocleidomastoid muscle; SNL, superior nuchal line; TM, temporalis muscle)Fig. 17.7 Raising the temporalis muscle.The temporalis muscle is elevated from the bone and retracted anteriorly. (GAN, greater auricular nerve; RZy, root of the zygoma; SCM, sternocleidomastoid muscle)Fig. 17.8 Cutting the greater auricular nerve.The greater auricular nerve is cut in a part of the high cervical approach. The nerve is cut in such a way as to preserve a length of nerve for a possible graft. (RZy, root of the zygoma; SCM, sterno-cleidomastoid muscle)Fig. 17.9 (Step 3) Closure of the external auditory canal.The external auditory canal is divided and closed using a triple closure technique as outlined in Figs. 17.10 to 17.14. (EAC, external auditory canal; SCM, sternocleidomastoid muscle)Fig. 17.10 Undermining the external auditory canal.The skin is dissected from the external canal as deep into the canal as is possible. This will provide a cuff of tissue that will facilitate a watertight closure. If all the squamous epithelium from the ear canal and eardrum is not removed, the patient may develop an epidermoid tumor.Fig. 17.11 Inverting the skin of the external auditory canal.The skin edges are inverted so that all squamous epithelium is pushed out into the external ear.Fig. 17.12 Stitching the external auditory canal.The inverted skin of the external auditory canal is stitched closed from within the ear.Fig. 17.13 Double closure of the external auditory canal.The fascia is pulled together over the external auditory canal with a second layer of sutures.Fig. 17.14 Triple closure of the external auditory canal using a vascularized flap.A flap of temporoparietal fascia is rotated back over this suture line as a third layer of closure.Fig. 17.15 (Step 4) Posterior reflection of the sternocleidomastoid muscle.All posterior neck muscles should be elevated from the occipital bone and retracted posteriorly to afford the surgeon an anterolateral view. For this demonstration each muscle layer will be retracted separately. (SpCM, splenius capitis muscle)Fig. 17.16 (Step 4) Posterior reflection of the splenius capitis muscle.(LCM, longissimus capitis muscle; OA, occipital artery)Fig. 17.17 (Step 4) Posterior reflection of the longissimus capitis muscle exposing the styloid diaphragm.(DM, digastric muscle)Fig. 17.18 (Step 4) Removal of the styloid diaphragm exposing the obliquus capitis superior muscle.(DM, digastric muscle; OCSM, obliquus capitis superior muscle)Fig. 17.19 (Step 4) Identification of the horizontal portion of the vertebral artery in the suboccipital triangle.The vertebral artery can be tethered to the lamina of the atlas by a bony or fibrous band. This specimen has an incomplete (fibrous) canal tethering the vertebral artery to the groove of the atlas. (C1, C1 [atlas]; DM, digastric muscle; EAC, external auditory canal; ICA, internal carotid artery; IJV, internal jugular vein; LSM, levator scapulae muscle; MT, mastoid tip; OCIM, obliquus capitis inferior muscle; OCSM, obliquus capitis superior muscle; RCMjM, rectus capitis major muscle; VA, vertebral artery; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.20 Enlarged view of the suboccipital triangle.In this specimen, a fibrous band is seen passing over the V3 segment of the vertebral artery tethering the artery to the “J-groove” of the atlas. A high cervical dissection is only occasionally combined with a total petrosectomy. We include a high cervical dissection in the demonstration for completeness. (JG, J-groove for the vertebral artery; OCIM, obliquus capitis inferior muscle; OCSM, obliquus capitis superior muscle; PA, posterior arch of the C1 [atlas]; RCMjM, rectus capitis major muscle; VA, vertebral artery)Fig. 17.21 Anatomical relationships in the high cervical region.The obliquus capitis superior, obliquus capitis inferior, rectus capitis lateralis, splenius cervicalis, and levator scapulae muscles attach to the transverse process of the atlas. The rectus capitis major, obliquus inferior, and obliquus superior outline the superior suboccipital triangle. The obliquus inferior, splenius cervicalis, and semispinalis cervicis muscles outline the inferior suboccipital triangle. (DM, digastric muscle; ICA, internal carotid artery; IJV, internal jugular vein; IX, glossopharyngeal nerve; LSM, levator scapulae muscle; OCIM, obliquus capitis inferior muscle; TC1, transverse process of the C1; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.22 Posterior reflection of the obliquus capitis superior muscle.The obliquus capitis superior is detached from the occipital bone. Care should be taken not to disrupt the vertebral artery or the venous plexus that lies inferior to this muscle. (C1, C1 [atlas]; DM, digastric muscle; EAC, external auditory canal; ICA, internal carotid artery; IJV, internal jugular vein; LSM, levator scapulae muscle; MT, mastoid tip; OCIM, obliquus capitis inferior muscle; RCMjM, rectus capitis major muscle; VA, vertebral artery; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.23 Exposing the occipital condyle and C1 facet.This specimen has a fibrous canal band that completes the canal over the J-groove of the atlas for the vertebral artery, which must be cut before the artery can be mobilized. The C1 occipital joint lies anterior to the V3 segment of the vertebral artery. (C1, C1 [atlas]; LSM, levator scapulae muscle; MT, mastoid tip; OCIM, obliquus capitis inferior muscle; RCMjM, rectus capitis major muscle; VA, vertebral artery; XI, accessory nerve)Fig. 17.24 (Step 5) Mastoidectomy with labyrinthectomy exposing the vestibule.The technique for performing a mastoidectomy and labyrinthectomy is outlined in chapter 14. (SS, sigmoid sinus)Fig. 17.25 Labyrinthectomy exposing the internal auditory canal.The internal auditory canal is found communicating with the posterior fossa dura. The fundus of the canal is entered by drilling through the superior wall of the vestibule. The facial nerve is on the superior side of Bill’s bar. (G, genu [second turn or external genu] of the facial nerve; IAC, internal auditory canal; T-VII, tympanic segment of the facial nerve; V-VII, vertical segment of the facial nerve)Fig. 17.26 (Step 6) Outlining the temporal and suboccipital craniotomies.A groove is drilled posterior to the digastric groove connecting to the mastoidectomy. A second groove is drilled above the root of the zygoma connecting to the mastoidectomy posteriorly and extending along the anterior border of the middle fossa to the sphenoid ridge anteriorly. At least two bur holes are placed along the circumference of the proposed flap. If the dura is tenaciously attached to the bone, additional bur holes are made and a groove is drilled across the transverse sinus.Fig. 17.27 Elevating the craniotomy.Fig. 17.28 Identifying the middle meningeal artery passing through the middle fossa cranial base.The middle meningeal artery can be followed to the foramen spinosum. (AE, arcuate eminence; GSPN, greater superficial petrosal nerve; MMA, middle meningeal artery)Fig. 17.29 Identifying the lateral loop formed by the mandibular and maxillary divisions of the trigeminal nerve.The foramen ovale and rotundum are identified. The exit canals of the mandibular and maxillary branches of the trigeminal nerves are opened. Care is taken to cool the drill with irrigation so as not to burn the nerves. Heating the nerves can lead to postoperative paresthesias. The dura propria is separated from the trigeminal nerve. (GG, gasserian ganglion; GSPN, greater superficial petrosal nerve; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve )Fig. 17.30 Identifying the greater superficial petrosal nerve and translocating the mandibular division of the trigeminal nerve anteriorly.The greater superficial petrosal nerve runs into the vidian canal behind the gasserian ganglion and the mandibular division of the trigeminal nerve. The vidian canal leaves the middle fossa through the anterior wall of foramen lacerum. (GG, gasserian ganglion; GSPN, greater superficial petrosal nerve; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve )Fig. 17.31 (Steps 7 and 8) Anterior petrosectomy exposing the horizontal portion of the internal carotid artery.The bone medial to the greater superficial petrosal nerve has been removed to expose the carotid artery. The cochlea, which lies medial to the C6-7 genu, has been drilled away. Because the labyrinth has been opened, removal of the cochlea causes no further neurological deficit. (C6, C6 portion of the internal carotid artery; GG, gasserian ganglion; GSPN, greater superficial petrosal nerve; IAC, internal auditory canal; T-VII, tympanic segment of the facial nerve; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve )Fig. 17.32 Dividing the greater superficial petrosal nerve from the geniculate ganglion.The facial nerve is freed by dividing the greater superficial petrosal nerve as it branches from the geniculate ganglia. Transposition of the facial nerve almost always results in facial weakness, so the surgeon must determine that exposure afforded by the transposition is necessary. (C6, C6 portion of the internal carotid artery; GnG, geniculate ganglion; GSPN, greater superficial petrosal nerve; IAC, internal auditory canal; T-VII, tympanic segment of the facial nerve; V3, mandibular nerve )Fig. 17.33 Posterior translocation of the facial nerveThe facial nerve, released from the greater superficial petrosal nerve, is translocated posteriorly to expose the entire anterior petrous bone. (C6, C6 portion of the internal carotid artery; GSPN, greater superficial petrosal nerve; IAC, internal auditory canal; T-VII, tympanic segment of the facial nerve; V3, mandibular nerve )Fig. 17.34 (Step 9) Posterior translocation of the facial nerve.(C6, C6 portion of the internal carotid artery; GSPN, greater superficial petrosal nerve; V3, mandibular nerve ; VII, facial nerve)Fig. 17.35 Further petrosectomy exposing the vertical and horizontal portion of the internal carotid artery.With the facial nerve transposed, the surgeon is able to resect the bone from the vertical segment of the carotid artery (V7) to the condyle. (C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; GG, gasserian ganglion; V3, mandibular nerve ; VII, facial nerve)Fig. 17.36 Overview of the resection at this stage as viewed from the middle fossa.(C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; GG, gasserian ganglion; JT, jugular tubercle; LS, lateral sinus; SS, sigmoid sinus; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; VII, facial nerve)Fig. 17.37 Overview of the resection at this stage as viewed from the posterior fossa.(C6, C6 portion of the internal carotid artery; GG, gasserian ganglion; JT, jugular tubercle; LS, lateral sinus; SS, sigmoid sinus; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; VII, facial nerve)Fig. 17.38 Removing the mastoid tip.The mastoid tip lateral to the stylomastoid foramen is removed. The stylomastoid foramen lies at the anterior end of the digastric groove. (GG, gasserian ganglion; JB, jugular bulb; LS, lateral sinus; OC, occipital condyle; SS, sigmoid sinus; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; VII, facial nerve)Fig. 17.39 Exposing the jugular foramen.The bone anterior to the occipital condyle is removed to expose the jugular foramen. (C7, C7 portion of the internal carotid artery; GG, gasserian ganglion; ICA, internal carotid artery; IJV, internal jugular vein; JB, jugular bulb; LS, lateral sinus; OC, occipital condyle; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve)Fig. 17.40 Identifying the occipital and C1 condyles.The occipital condyle is located behind the jugular foramen. The vertebral artery overlies the joint between the condyle and the lateral mass of C1. (C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; JB, jugular bulb; JT, jugular tubercle; OC, occipital condyle; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve; XI, accessory nerve)Fig. 17.41 (Step 10) Condylectomy.The occipital posterior condyle is removed up to the hypoglossal canal. (C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; JB, jugular bulb; JT, jugular tubercle; OC, occipital condyle; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.42 Identifying the hypoglossal canal.(C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; JB, jugular bulb; SS, sigmoid sinus; VA, vertebral artery; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.43 Anatomical relationships seen after condylectomy.(C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; IX, glossopharyngeal nerve; JB, jugular bulb; OC, occipital condyle; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.44 Neural structures in the jugular foramen behind the jugular bulb.The lower cranial nerves exit the neural foramen medial to the jugular vein. (C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; IX, glossopharyngeal nerve; JB, jugular bulb; SS, sigmoid sinus; X, vagus nerve; XI, accessory nerve)Fig. 17.45 Posterior translocation of the jugular bulb (pars venosa translocation) with anterior translocation of the internal carotid artery.The inferior petrosal sinus must be detached from the jugular vein before the jugular vein and bulb are transposed posteriorly. Transposing the jugular vein reveals the vagal, glossopharyngeal, and spinal accessory nerves. (C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; IPS, inferior petrosal sinus; IX, glossopharyngeal nerve; JB, jugular bulb; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve; X, vagus nerve; XI, accessory nerve; XII, hypoglossal nerve)Fig. 17.46 Posterior translocation of the jugular bulb and lower cranial nerves (pars nervosa and venosa translocation).The pars nervosa is transposed to demonstrate the underlying anatomy. During surgery, such manipulation of the lower cranial nerves would almost certainly result in postoperative swallowing difficulty, and this is rarely done. (C7, C7 portion of the internal carotid artery; IJV, internal jugular vein; IPS, inferior petrosal sinus; IX, glossopharyngeal nerve; JB, jugular bulb; SS, sigmoid sinus; VA, vertebral artery; VII, facial nerve; X, vagus nerve; XI, accessory nerve)Fig. 17.47 Exposing the jugular tubercle.Transposing the lower cranial nerves exposes the jugular tubercle, which lies under the lower cranial nerves. (PT, petrosal tip)Fig. 17.48 Partial clivectomy.The lower clivus can be partially resected once the jugular tubercle is removed. (CL, clivus)Fig. 17.49 Drilling the posterior wall of the lateral mass of the atlas to expose the extracranial vertebral artery.The posterior wall of the transverse process, the posterior costal lamella, is opened with a diamond drill. Care is taken not to injure the veins that surround the vertebral artery. Venous bleeding is meticulously controlled with bipolar cautery to preserve the surgeon’s view through a bloodless field.Fig. 17.50 Posterior translocation of the extracranial vertebral artery.Care is taken to assess the quality of the vertebral artery before attempting the transposition. Transposing a calcified atherosclerotic artery can crack the artery or release emboli into the bloodstream.Fig. 17.51 Anatomical relationship in a high cervical portion after partial removal of the lateral mass of the atlas.Partial removal of the lateral mass of the atlas and the inferior occipital condyle provides the surgeon a flatter trajectory toward the clivus and anterior skull base.Fig. 17.52 Anterior translocation of the internal carotid artery and posterior translocation of the lower cranial nerves, jugular bulb, and internal jugular vein.A very broad working space is obtained by transposing the arteries, veins, and nerves. The lower cranial nerves should not be manipulated unless they lie in the planned surgical trajectory or are not functioning before the surgery.Fig. 17.53 (Step 11) Dural opening.The posterior fossa dura is opened anterior to the sigmoid sinus. The superior petrosal sinus is ligated and cut. Care is taken not to injure the veins draining from the supratentorial compartment toward the sigmoid sinus. (Po, pons; V, trigeminal nerve; VII, facial nerve)Fig. 17.54 Exposing the pons and adjacent structures as seen from an anterolateral direction.A very flat view of the clivus anterior to the pons is obtained. Both vertebral arteries forming the basilar artery are easily reached. (AntCh, anterior choroidal artery; C5, C5 portion of the internal carotid artery; ICA, internal carotid artery; III, oculomotor nerve; P2, P2 segment of the posterior cerebral artery; Pcom, posterior communicating artery; SCA, superior cerebral artery; V, trigeminal nerve; VI, abducens nerve)Fig. 17.55 The hypoglossal nerve.The ipsilateral hypoglossal nerve runs under the vertebral artery. (C7, C7 portion of the internal carotid artery; Po, pons; V, trigeminal nerve; VA, vertebral artery; VII, facial nerve; IX, glossopharyngeal nerve; X, vagus nerve; XII, hypoglossal nerve)Fig. 17.56 The vertebrobasilar junction.(AICA, anterior inferior cerebellar artery; C7, C7 portion of the internal carotid artery; IX, glossopharyngeal nerve; Po, pons; V, trigeminal nerve; VA, vertebral artery; VI, abducens nerve; VII, facial nerve; X, vagus nerve)Fig. 17.57 The lower basilar artery.(AICA, anterior inferior cerebellar artery; BA, basilar artery; IX, glossopharyngeal nerve; Po, pons; V, trigeminal nerve; VA, vertebral artery; VII, facial nerve; X, vagus nerve)Fig. 17.58 The mid-basilar artery.(AICA, anterior inferior cerebellar artery; BA, basilar artery; IX, glossopharyngeal nerve; V, trigeminal nerve; VA, vertebral artery; VI, abducens nerve; VII, facial nerve; X, vagus nerve)Fig. 17.59 The third through the twelfth cranial nerves.The surgeon has an excellent view of the lateral and anterior pons and the anterior medulla. (AICA, anterior inferior cerebellar artery; BA, basilar artery; V, trigeminal nerve; VA, vertebral artery; VII, facial nerve)Fig. 17.60 The oculomotor nerve, supracerebellar, posterior cerebral, posterior communicating, and anterior choroidal arteries.The oculomotor nerve and trochlear nerves enter the tentorial edge. The posterior tentorium is left intact to protect the inferior temporal lobe. The internal carotid artery gives rise to the posterior communicating artery and the anterior choroidal artery. (AICA, anterior inferior cerebellar artery; III, oculomotor nerve; IV, trochlear nerve; IX, glossopharyngeal nerve; Po, pons; SCA, superior cerebral artery; V, trigeminal nerve; VA, vertebral artery; VI, abducens nerve; VII, facial nerve; X, vagus nerve)Fig. 17.61 The internal carotid, posterior communicating, and anterior choroidal arteries.(AntCh, anterior choroidal artery; C5, C5 portion of the internal carotid artery; ICA, internal carotid artery; III, oculomotor nerve; P2, P2 segment of the posterior cerebral artery; Pcom, posterior communicating artery; SCA, superior cerebral artery; V, trigeminal nerve; VI, abducens nerve)Fig. 17.62 The optic nerve over the internal carotid artery.(AntCh, anterior choroidal artery; C5, C5 portion of the internal carotid artery; ICA, internal carotid artery; II, optic nerve; III, oculomotor nerve; P2, P2 segment of the posterior cerebral artery; Pcom, posterior communicating artery; SCA, superior cerebral artery; V, trigeminal nerve; VI, abducens nerve)Fig. 17.63 The upper basilar artery.(BA, basilar artery; C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; II, optic nerve; III, oculomotor nerve; IV, trochlear nerve; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve)Fig. 17.64 The basilar tip.(AntCh, anterior choroidal artery; BA, basilar artery; ICA, internal carotid artery; III, oculomotor nerve; IV, trochlear nerve; P1, P1 segment of the posterior cerebral artery; P2, P2 segment of the posterior cerebral artery; Pcom, posterior communicating artery; SCA, superior cerebral artery; V, trigeminal nerve; VI, abducens nerve)Fig. 17.65 The abducens nerve in the cavernous sinus.Opening the cavernous sinus between the trochlear and trigeminal nerves (Parkinson’s triangle) reveals the intracavernous abducens nerve. The carotid artery lies medial to the nerve. Unless the cavernous sinus is packed with tumor, this opening will result in significant venous bleeding. (GG, gasserian ganglion; III, oculomotor nerve; IV, trochlear nerve; V, trigeminal nerve; V1, ophthalmic nerve [first division of the trigeminal nerve]; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; VI, abducens nerve)Fig. 17.66 The petroclinoidal fold.The forceps hold the petroclinoidal fold in the dura, which bridges the petrous bone and the posterior clinoid. (GL (PSL), Gruber’s ligament [petrosphenoid ligament]; PCL, petroclinoid ligament; VI, abducens nerve)Fig. 17.67 The abducens nerve and the petrosphenoidal (Gruber’s) ligament.The abducens nerve bends sharply to pass under the petrosphenoid ligament. (C5, C5 portion of the internal carotid artery; GL (PSL), Gruber’s ligament [petrosphenoid ligament]; IPS, inferior petrosal sinus; PCL, petroclinoid ligament; VI, abducens nerve)Fig. 17.68 Opening Dorello’s canal.The tip of a dissector points the petrosphenoid (Gruber’s) ligament. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; GL (PSL), Gruber’s ligament [petrosphenoid ligament]; III, oculomotor nerve; IV, trochlear nerve; V, trigeminal nerve; VI, abducens nerve)Fig. 17.69 Opening the inferior petrosal sinus to expose the abducens nerve.The abducens nerve passes through a fibrous canal between its entrance into the clival dura and its emergence under the petrosphenoid ligament into the cavernous sinus. (VI, abducens nerve)Fig. 17.70 The abducens nerve.(IPS, inferior petrosal sinus; VI, abducens nerve)Fig. 17.71 The abducens nerve and the sympathetic nerve, which travels with the internal carotid artery.(C5, C5 portion of the internal carotid artery; SpP, sympathetic plexus; VI, abducens nerve)Fig. 17.72 Fusing the abducens and the sympathetic nerve.(C5, C5 portion of the internal carotid artery; GG, gasserian ganglion; SpP, sympathetic plexus; V, trigeminal nerve; V1, ophthalmic nerve [first division of the trigeminal nerve]; V2, maxillary nerve [second division of the trigeminal nerve]; V3, mandibular nerve ; VI, abducens nerve)Fig. 17.73 The oculomotor nerve into the lateral wall of the cavernous sinus.The oculomotor nerve travels in a canal through the tentorium before reaching the lateral wall of the cavernous sinus. This canal can be opened to increase the surgeon’s working space in front of the midbrain. The trochlear nerve crosses the oculomotor nerve approximately 7 mm anterior to the oculomotor nerve entering the canal, limiting the length of the oculomotor canal that can be safely opened. (III, oculomotor nerve; IV, trochlear nerve; V, trigeminal nerve)Fig. 17.74 Further removal of the clivus.(C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; CL, clivus; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve)Fig. 17.75 Skeletonizing the sphenoid sinus.The sphenoid sinus extends a variable distance into the clivus. Opening that sinus creates a problem of closing off the air spaces from the subarachnoid space at the end of the case. The sphenoid sinus should not be opened except to remove a tumor. (C5, C5 portion of the internal carotid artery; C6, C6 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; CL, clivus; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve)Fig. 17.76 The mucosa of the sphenoid sinus.(CL, clivus; SpS, sphenoid sinus; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve)Fig. 17.77 Opening the sphenoid sinus.(C5, C5 portion of the internal carotid artery; C7, C7 portion of the internal carotid artery; CL, clivus; SpS, sphenoid sinus; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve)Fig. 17.78 Final view of the surgical exposure.
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15 Combined Petrosal Approach
14 Transmastoid Approach: Retrolabyrinthine, Translabyrinthine, and Transcochlear Approaches
13 Anatomy for Posterolateral Skull Base Surgery
3 Transfacial Transmaxillary Approach
18 Anatomy for Posterior Skull Base Surgery
12 Middle Fossa Rhomboid Approach (Anterior Petrosectomy)
