Infratemporal fossa approach (ITFA) type A
General
Differences between Fisch’s Infratemporal Fossa Approach (ITFA) types A, B, and C:
Aspect | Type A | Type B | Type C |
Target region | Jugular foramen, infralabyrinthine temporal bone, mandibular fossa, posterior infratemporal fossa | Petrous apex, clivus, horizontal segment of internal carotid artery (ICA) | External auditory canal, middle ear, and mastoid area |
Surgical exposure | Radical mastoidectomy, extensive exposure around mandibular area and temporal bone | Subtotal petrosectomy, removal of anterior external auditory canal wall and zygomatic arch | Focus on middle ear and mastoid with lateral skull base exposure |
Facial nerve management | Usually involves facial nerve transposition | Facial nerve usually preserved, less manipulation compared to Type A | Facial nerve preserved with minimal manipulation |
Mandibular involvement | Access involves manipulation around mandibular fossa | May involve articular disc and condylar process resection; often requires mandible traction | No mandibular manipulation |
Indications | Tumors or lesions at jugular foramen, posterior infratemporal fossa | Lesions at petrous apex, clivus, lateral skull base with vascular involvement | Lesions in external auditory canal, middle ear, mastoid region |
Commonly addressed lesions | Glomus jugulare tumors, schwannomas around jugular bulb | Cholesteatoma, petrous apex lesions, certain skull base tumors | Chronic otitis media, mastoiditis, some lateral skull base tumors |
Complexity and invasiveness | More extensive dissection, higher complexity due to facial nerve and vascular structures | Moderately extensive, balanced exposure preserving key neurovascular elements | Least extensive among the three, more lateral and extracranial |
- Is the workhorse of tympanojugular paragangliomas surgery
- Essential facts to be considered while obtaining adequate surgical exposure are
- Whether the FN needs to be mobilised
- Whether the middle ear can be preserved
- Degree of ICA involvement
- Extent of intracranial extension
- Allows access to the
- Jugular foramen
- Infralabyrinthine areas
- Apical compartments of the petrous bone
- Vertical segment of the internal carotid artery
- Key feature in this approach is the anterior transposition of the FN, which opens up the above-mentioned areas for dissection
- Structures that prevent lateral access to these areas include
- Tympanic bone
- Digastric muscle
- Styloid process
- Removed to obtain unhindered access.
- Morbidity with ITFA-A includes
- Conductive hearing loss
- Temporary or permanent dysfunction of the FN
- Temporary masticatory problems
Surgical steps
- A postauricular skin incision is performed.
- A small, anteriorly based musculoperiosteal flap is elevated to help in closure afterward.
- The external auditory canal is transected as before.
- FN is identified at its exit from the temporal bone.
- The main trunk is found at the perpendicular bisection of a line joining the cartilaginous pointer to the mastoid tip.
- The main trunk is traced in the parotid until the proximal parts of the temporal and zygomatic branches are identified.
- The posterior belly of the digastric muscle and the sternocleidomastoid muscle are divided close to their origin.
- The internal jugular vein and the external and internal carotid arteries are identified in the neck.
- The vessels are marked with umbilical tape.
- The skin of the external auditory canal, the tympanic membrane, the malleus, and the incus are removed.
- A canal wall-down mastoidectomy is performed, with removal of the bone anterior and posterior to the sigmoid sinus.
- The FN is skeletonized from the stylomastoid foramen to the geniculate ganglion.
- The last shell of bone is removed using a double-curved raspatory.
- The suprastructure of the stapes is preferably removed after cutting its crura with microscissors.
- The inferior tympanic bone is widely removed, and the mastoid tip is amputated using a rongeur. A new fallopian canal (arrow) is drilled in the root of the zygoma superior to the Eustachian tube.
- The FN is freed at the level of the stylomastoid foramen using strong scissors.
- The soft tissues at this level are not separated from the nerve.
- The mastoid segment is next elevated using a Beaver knife to cut the fibrous attachments between the nerve and the fallopian canal.
- The tympanic segment of the nerve is carefully elevated, using a curved raspatory, until the level of the geniculate ganglion is reached.
- A non-toothed forceps is used to hold the soft tissue surrounding the nerve at the stylomastoid foramen, and anterior rerouting is carried out.
- A tunnel is created in the parotid gland to lodge the transposed nerve.
- The tunnel is closed around the nerve using two sutures.
- A closer view shows the FN in its new bony canal, just superior to the Eustachian tube.
- The nerve is fixed to the new bony canal using fibrin glue. Drilling of the infralabyrinthine cells is completed, and the vertical portion of the internal carotid artery is identified.
- The mandibular condyle is separated from the anterior wall of the external auditory canal using a large septal raspatory.
- The Fisch infratemporal fossa retractor is applied, and the mandibular condyle is anteriorly displaced, with care being taken not to injure the FN.
- The anterior wall of the external auditory canal is further drilled, thus completing the exposure of the vertical portion of the internal carotid artery.
- A small incision is made in the posterior fossa dura just behind the sigmoid sinus, through which an aneurysm needle is passed.
- Another incision is made just anterior to the sinus to allow for the exit of the needle.
- The sinus is closed by double ligation with a Vicryl suture.
- Suture closure of the sinus, however, may lead to gaps in the dural incision, with a higher risk of cerebrospinal fluid leakage postoperatively.
- Alternatively, the sigmoid sinus can be closed with Surgicel extraluminal packing.
- The structures attached to the styloid process are severed.
- The styloid is fractured using a rongeur and is then cut with strong scissors.
- The remaining tough fibrous tissue surrounding the internal carotid artery at its ingress into the skull base is carefully removed using scissors. The internal jugular vein in the neck is double ligated and cut or closed with vascular clips (easier and faster method).
- The vein is elevated superiorly, with care being taken not to injure the related LCNs.
- In cases in which the 11th nerve passes laterally, the vein has to be pulled under the nerve carefully to prevent it from being damaged.
- If necessary (as in the case of TJPs), the lateral wall of the sigmoid sinus can be removed.
- Removal continues down to the level of the JB.
- The lateral wall of the JB is opened.
- Bleeding usually occurs from the apertures of the inferior petrosal sinus and the condylar emissary vein.
- This is controlled by Surgicel packing.
- If there is limited intradural extension, the dura is opened without injury to the endolymphatic sac.
- At the end of the procedure, the Eustachian tube is closed by a piece of muscle.
- The dural opening is closed by a muscle plug or with only abdominal fat.
- We never use a rotated temporalis muscle (as suggested by Fisch) in order to avoid esthetic problems but the sternocleidomastoid muscle and the digastric muscle are sutured together and the temporalis muscle is left in its place.
Abbreviations
- C1, atlas; C2, axis; Ch, cochlea; CO, cochlea; DM, posterior belly of the digastric muscle; ev, emissary vein; Involvement of the facial nerve (FN); ICA, internal carotid artery; IJV, internal jugular vein; IX, glossopharyngeal nerve; JB, jugular bulb; LSM, levator scapulae muscle; Lv, vein of Labbe; OC, occipital condyle; P, parotid gland; pc, clinoid process; pp, pterygoid plate; M, mandible; SCM, sternocleidomastoid muscle; SP, styloid process; SPCM, splenius capitis muscle; sph, sphenoid sinus; za, zygomatic arch; sps, superior petrosal sinus; TA, transverse process of atlas; TP, transverse process of the atlas; TS, transverse sinus; V2, maxillary branch of trigeminal nerve; V3, mandibular branch of trigeminal nerve; VA, vertebral artery; VII, facial nerve; XI, spinal accessory nerve; XII, hypoglossal nerve.
Extensions of the infratemporal fossa type A approach (ITFA-A)
- Based on the ITFA-A approach, various extensions can be added depending on the extent of the pathology.
- General
- For C2–C4 tumors
- This allows additional posteroinferior and medial access to the jugular fossa, widening the exposure, thus facilitating venous and neural control.
- The widened angle also affords better access to the petrous apex, medial to the carotid artery.
- Very rarely, a far lateral is employed with full exposure of the vertebral artery.
- Permits only superior and anterior exposure of the Jugular bulb (JB).
- For larger tumors, such as classes C2–C4 tumors involving the LCNs, a transcondylar-transtubercular extension is required in addition to the classic ITFA-A.
- This extension facilitates inferomedial access to the JB above the lateral mass of the atlas and occipital condyle.
- STEPS OF ITFA-A WITH TRANSTUBERCULAR-TRANSCONDYLAR EXTENSION
- After the ITFA-A is performed.
- Identification of the splenius capitis muscles.
- The posterior fossa dura is uncovered toward the occipital skull base in order to start drilling of the jugular process and occipital condyle.
- The drilling of the jugular process is commenced followed by the identification and drilling of the occipital condyle superior to the atlanto-occipital joint posteromedial to the JB.
- The hypoglossal canal is then identified between the jugular tubercle and the occipital condyle above the vertebral artery, if indicated.
- Tumor removal is commenced at this point.
- The IJV is closed with vascular clips.
- The IJV is mobilized up to the jugular fossa by mobilizing it away from the spinal accessory nerve.
- The tumor is peeled away from the dura of the posterior cranial fossa.
- The infiltrated bone of the fallopian canal and tympanic bone is then drilled out.
- The tumor is debulked from the JB area.
- The infiltrated infralabyrinthine cells are drilled out. T
- he sigmoid sinus is opened to expose the tumor within. The IJV is opened to expose the distal end of the tumor. The inferior petrosal sinus is packed with Surgicel® packing.
- The tumor is then separated from the LCNs.
- The ICA is identified after extensive drilling of the bone of the vertical portion of the carotid canal and the tumor around is coagulated with bipolar coagulation.
- The tumor is gently separated from the wall of the ICA. Further drilling of all the suspect bone of the infralabyrinthine and apical cells is carried out until complete removal is accomplished.
- If required, the internal carotid artery is partially mobilized and the infiltrated clivus is drilled out.
- The posterior fossa dura is not opened and the intradural portion of the tumor is left behind, to be removed in a second stage.
- Closure of the Eustachian tube, cavity obliteration, and watertight closure of the subcutaneous and cutaneous tissues are carried out as with conventional ITFA-A.
- Occasionally required for otic capsule involvement.
- A modified transcochlear approach is uncommonly required to access petrous apex, clival involvement, and infratemporal fossa involvement.
Transcondylar-transtubercular extension
Translabyrinthine extension
Lateral to medial dissection the jugular foramen
Abbreviation:
- A., artery; Asc., ascending; Aur., auricular; Br., branch; Cap., capitis; Car., carotid; Chor. Tymp., chorda tympani; CN, cranial nerve; Cond., condylar; Dors., dorsal; Eust., eustachian; Ext., external; Fiss., fissure; Gl., gland; Gr., greater; Inf., inferior; Int., internal; Jug., jugular; Laryn., laryngeal; Lat., lateral, lateralis; Lev., levator; Long., longus; M., muscle; Mast., mastoid; Men., meningeal; N., nerve; Obl., oblique; Occip., occipital; Pal., palatini; Pet., petrosal, petrous; Pharyn., pharyngeal; Post., posterior; Proc., process; Pteryg., pterygoid; Rec., rectus; Retromandib., retromandibular; Scap., scapulae; Seg., segment; Semicirc., semicircular; Sig., sigmoid; Squamotymp., squamotympanic; Sternocleidomast., sternocleidomastoid; Stylogloss., styloglossus; Stylomast., stylomastoid; Stylophar., stylopharyngeus; Submandib., submandibular; Sup., superior; Temp., temporal; Tens., tensor; TM., temporomandibular; Trans., transverse; Tymp., tympanic, tympany; V., vein; Vel., veli; Vent., ventral; Vert., vertebral.
- The skin and scalp around the ear have been reflected to expose the area lateral to the jugular foramen. The sternocleidomastoid is exposed behind and the parotid gland in front of the ear.
- The greater occipital nerve and occipital artery reach the subcutaneous tissues by passing between the attachment of the trapezius and sternocleidomastoid muscles to the superior nuchal line.
- The external acoustic meatus is located a little forward of the deep site of the jugular bulb.
- Removal of the superficial muscles and parotid gland exposes the facial nerve, temporalis and masseter muscles, posterior belly of the digastric, and the internal jugular vein.
- The sternocleidomastoid muscle has been reflected backward to expose the accessory nerve entering its deep surface.
- The mandibular ramus and condyle, medial and lateral pterygoid muscles, and posterior belly of the digastric have been removed to expose the styloid process, which is located lateral to the jugular foramen.
- The internal carotid artery ascends to enter the carotid canal in front of the jugular foramen.
- Both the jugular foramen and carotid canal are situated behind the tympanic part of the temporal bone, which forms the posterior wall of the condylar fossa.
- The tensor and levator vela palatini muscles are attached to the eustachian tube in the area below the horizontal segment of the petrous carotid.
- The infratemporal fossa is located below the greater wing of the sphenoid.
- The mandibular nerve passes through the foramen ovale to enter the upper part of the infratemporal fossa.
- Branches of the ascending pharyngeal artery pass through the jugular foramen to supply the surrounding dura.
- The hypoglossal nerve passes forward across the external and internal carotid artery.
- The styloid process has been removed to expose the glossopharyngeal, vagus, accessory, and hypoglossal nerves descending between the internal carotid artery and the internal jugular vein in the area immediately below the jugular foramen.
- CN 9 descends along the lateral side of the internal carotid artery.
- CN 11 passes backward across the lateral surface of the internal jugular vein.
- CN 12 passes through the hypoglossal canal, which is located below and medial to the jugular foramen, and descends with the nerves exiting the jugular foramen.
- The occipital artery gives rise to a meningeal branch, which passes through the jugular foramen to supply the surrounding dura, and to the stylomastoid artery, which passes through the stylomastoid foramen with the facial nerve.
- The superior and inferior oblique have been exposed by reflecting the more superficial muscles.
- The C1 transverse process and rectus capitis lateralis rest against the posterior surface of the internal jugular vein.
- The rectus capitis lateralis attaches to the jugular process of the occipital bone at the posterior margin of the jugular foramen.
- Retracting the levator scapulae exposes the segment of the vertebral artery ascending through the C2 transverse foramen in front of the ventral ramus of the C2 nerve root.
- The vertebral artery, as it passes medially along the upper surface of the posterior arch of the atlas, is situated in the floor of the suboccipital triangle located between the superior and inferior oblique and rectus capitis posterior major.
- The internal carotid artery has been displaced posteriorly to expose the branches of the ascending pharyngeal, which pass through the foramen lacerum, jugular foramen, and hypoglossal canal to supply the surrounding dura.
- Chorda tympani exits the skull in the medial part of the condylar fossa by first passing through the petrotympanic and then along the squamotympanic sutures.
- The tympanic bone forming the lower and anterior margin of the external meatus has been removed, but the tympanic sulcus to which the tympanic membrane attaches has been preserved.
- The surface of the temporal and occipital bones surrounding the jugular foramen and carotid canal have an irregular surface that serves as the attachment of the upper end of the carotid sheath.
- The mastoid segment of the facial nerve and the stylomastoid foramen are situated lateral to the jugular bulb.
- The chorda tympani
- Arises from the mastoid segment of the facial nerve
- Course
- Along the deep side of the tympanic membrane crossing the neck of the malleus.
- It exits the skull by passing through the petrotympanic and squamotympanic sutures
- Joins the lingual branch of the mandibular nerve distally.
- The carotid ridge separates the
- Carotid canal
- Jugular foramen.
- Meningeal branches of the ascending pharyngeal and occipital arteries enter the jugular foramen.
- The glossopharyngeal, vagus, and accessory nerves pass through the jugular foramen on the medial side of the jugular bulb
- The tympanic ring and bone lateral to the tympanic cavity have been removed. The internal carotid artery has been displaced forward out of the carotid canal to expose the carotid sympathetic nerves that ascend with the artery.
- The glossopharyngeal, vagus, accessory, and hypoglossal nerves exit the skull on the medial side of the internal carotid artery and jugular vein.
- The glossopharyngeal and hypoglossal nerves pass forward along the lateral surface of the internal carotid artery, and the accessory nerve descends posteriorly across the lateral surface of the internal jugular vein.
- The vagus nerve descends in the carotid sheath.
- The tympanic segment of the facial nerve passes below the lateral semicircular canal and turns downward as the mastoid segment to exit the stylomastoid foramen.
- The stylomastoid foramen and the mastoid segment are located lateral to the jugular bulb.
- The semicircular canals are located above the jugular bulb.
- A probe has been placed in the eustachian tube, which passes downward, forward, and medially from the tympanic cavity and across the front of the petrous carotid.
- The third trigeminal division passes through the foramen ovale on the lateral side of the eustachian tube
- The tensor tympany muscle passes backward above the eustachian tube and gives rise to a tendon that turns sharply lateral around the trochleiform process to attach to the malleus.
- The chorda tympani crosses the inner surface of the tympanic membrane and neck of the malleus.
- The round window opens into the vestibule.
- The stapes sit in the oval window.
- The promontory is located lateral to the basal turn of the cochlea.
- The greater petrosal nerve courses along the floor of the middle fossa on the upper surface of the petrous carotid.
- The deep petrosal nerve arises from the sympathetic bundles on the internal carotid artery.
- The deep and greater petrosal nerves join to form the vidian nerve, which passes forward through the vidian canal to join the maxillary nerve and pterygopalatine ganglion in the pterygopalatine fossa.
- The pharyngobasilar fascia and upper part of the longus capitis have been reflected downward to expose the lower margin of the clivus.
- The vertical segment of the petrous carotid has been removed.
- The cochlea, which has been opened, is located above the lateral genu of the petrous carotid.
- The tympanic segment of the facial nerve passes posteriorly below the lateral semicircular canal.
- The retrosigmoid and presigmoid dura have been opened.
- The lateral wall of the vestibule and cochlea have been removed.
- The vestibule, semicircular canals, and cochlea are exposed above the jugular bulb and lateral genu of the petrous carotid.
Medial to lateral dissection the jugular foramen
A., artery; Atl., atlanto-; Aur., auricular; Br., branch; Bridg., bridging; Car., carotid; CN, cranial nerve; Coch., cochlear; Cond., condyle; Endolymph., endolymphatic; Gang., ganglion; Glossophar., glossopharyngeal; Hypogl., hypoglossal; Inf., inferior; Int., internal; Intrajug., intrajugular; Jug., jugular; Labyr., labyrinthine; Lat., lateral; Occip., occipital; Pet., petrosal; Proc., process; Sig., sigmoid; Subarc., subarcuate; Sup., superior; Temp., temporal; Vert., vertebral.
- The CN9, CN10, CN11 pierce the dural roof of the jugular foramen.
- CN9 is separated from the CN10 by a narrow dural septum.
- The jugular dural fold projects downward and medially from the lateral and upper margin of the jugular foramen over the site at which the nerves enter the dura roof of the foramen.
- CN7, CN8 and labyrinthine artery enter the internal acoustic meatus.
- The subarcuate branch of the AICA enters the subarcuate fossa.
- The endolymphatic sac is located between the dural layers lateral to the jugular foramen.
- A bridging vein from the medulla joins the inferior petrosal sinus on the medial side of the jugular bulb.
- The dura has been removed from the posterior surface of the temporal bone.
- The intrajugular processes of the temporal and occipital bones, which are connected by a fibrous bridge, the intrajugular septum, separates the sigmoid and petrosal parts of the foramen.
- The CN9, 10, 11 enter the intrajugular part of the foramen by penetrating the dura on the medial side of the intrajugular process of the temporal bone.
- The CN9 enters the jugular foramen below the cochlear aqueduct.
- The CN10 enters the jugular foramen behind the glossopharyngeal nerve. The auricular branch of the vagus nerve (Arnold's nerve) arises at the level of the superior ganglion and passes around the anterior wall of the jugular bulb.
- CN11
- Is formed by multiple rootlets, which arise from the medulla and spinal cord.
- The accessory rootlets collect together to form a bundle that blends into the lower margin of the vagus nerve at the level of the jugular foramen.
- The lower vagal and accessory roots pass across the surface of the jugular tubercle.
- CN9 expands at the site of the superior and inferior ganglia.
- The superior ganglion of the CN10 is located at the level of or just below the dural roof of the foramen, the inferior ganglion of the CN 10 is located below the foramen at the level of the atlanto-occipital joint.
Retrosigmoid approach to jugular foramen
A., artery; A.I.C.A., anteroinferior cerebellar artery; Chor., choroid; CN, cranial nerve; Glossophar., glossopharyngeal; Jug., jugular; Plex., plexus; Vert., vertebral.
- The cerebellum has been elevated to expose the nerves in the right cerebellopontine angle. The CN9 and CN10 are separated by the dural septum at the level of the dural roof of the jugular foramen.
- The CN9 enters the glossopharyngeal meatus
- The CN10 enters the vagal meatus with the branches of the CN11
- Both meatus are very shallow compared with the internal acoustic meatus.
- The superior and lateral margins of both meatus project downward and medially over the nerves entering the meatus.
- The vertebral artery displaces the hypoglossal rootlets posteriorly so that they intermingle with the rootlets of the accessory nerve.
- Another specimen showing the relationship of the rhomboid lip and choroid plexus protruding from the foramen of Luschka to the glossopharyngeal and vagus nerves.
- The choroid plexus protrudes laterally behind the glossopharyngeal nerves.
- The rhomboid lip is a thin layer of neural tissue that forms the ventral margin of the foramen of Luschka at the outer end of the lateral recess.
- CN9, CN 10 are consistently separated by a dural septum at the level of the roof over the jugular foramen. The jugular dural fold projects downward and medially over the lateral edge of the glossopharyngeal and vagal meatus and over the site at which the nerves penetrate the dura.
- Intracranial view of the right jugular foramen with the cerebellar hemisphere retracted medially.
- CNs IX, X, and XI enter the jugular foramen.
- A dural septum separates CN IX from CN X as it enters the glossopharyngeal meatus.
- The multiple rootlets of CN X and CN XI coalesce and enter through the vagal meatus.
Postauricular exposure of the jugular foramen
A., artery; Aur., auricular; Cap., capitis; Car., carotid; Chor. Tymp., chorda tympani; CN, cranial nerve; Coch., cochlear; Gl., gland; Gr., greater; Inf., inferior; Int., internal; Intrajug., intrajugular; Jug., jugular; Laryn., laryngeal; Lat., lateral, lateralis; M., muscle; Med., medial; Mid., middle; N., nerve; Obl., oblique; Occip., occipital; Pet., petrosal, petrous; Post., posterior; Proc., process; Rec., rectus; Semicirc., semicircular; Sig., sigmoid; Sternocleidomast., sternocleidomastoid; Stylomast., stylomastoid; Sup., superior; Symp., sympathetic; Tr., trunk; Trans., transverse; V., vein.
- The C-shaped retroauricular incision provides access for the mastoidectomy, neck dissection, and parotid gland displacement.
- The scalp flap has been reflected forward to expose the sternocleidomastoid and the posterior part of the parotid gland.
- The more superficial muscles and the posterior belly of the digastric have been reflected to expose the internal jugular vein and the attachment of the superior and inferior oblique to the transverse process of C1.
- A mastoidectomy has been completed to expose the facial nerve, sigmoid sinus, and capsule of the semicircular canals.
- The jugular bulb is exposed below the semicircular canals.
- The chorda tympani arises from the mastoid segment of the facial nerve and passes upward and forward.
- The tympanic segment of the facial nerve courses below the lateral canal.
- Enlarged view of the caudal part of the exposure shown in C.
- The facial nerve and styloid process cover the extracranial orifice of the jugular foramen.
- The facial nerve crosses the lateral surface of the styloid process.
- The stylomastoid artery arises from the postauricular artery.
- The rectus capitis lateralis attaches to the jugular process of the occipital bone behind the jugular foramen.
- The external auditory canal has been transected and the middle ear structures have been removed, except the stapes, which has been left in the oval window.
- The lateral edge of the jugular foramen has been exposed by completing the mastoidectomy, transposing the facial nerve anteriorly, and fracturing the styloid process across its base and reflecting it caudally.
- The rectus capitis lateralis has been detached from the jugular process of the occipital bone.
- The petrous carotid is surrounded in the carotid canal by a venous plexus.
- The lateral wall of the jugular bulb has been removed while preserving the medial wall and exposing the opening of the inferior petrosal sinus into the jugular bulb.
- Removing the venous wall exposes the glossopharyngeal, vagus, accessory, and hypoglossal nerves, which are hidden deep to the vein.
- The main inflow from the petrosal confluens is directed between the glossopharyngeal and vagus nerves.
- The intrajugular ridge extends forward from the intrajugular process, which divides the jugular foramen between the sigmoid and petrosal parts.
- The glossopharyngeal, vagus, and accessory nerves enter the dura on the medial side of the intrajugular process, but only the glossopharyngeal nerve courses through the foramen entirely on the medial side of the intrajugular ridge.
- The vagus nerve also enters the dura on the medial side of the intrajugular process, but does not course along the medial side of the intrajugular ridge.
- The intrajugular process and ridge have been removed to expose the passage of the glossopharyngeal, vagus, and accessory nerves through the jugular foramen.
- The tip of a right-angle probe identifies the junction of the cochlear aqueduct with the pyramidal fossa, just above where the glossopharyngeal nerve penetrates the dura.
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