Endoscopic endonasal dissection of the infratemporal fossa: Anatomic relationships and importance of eustachian tube in the endoscopic skull base surgery

Introduction:Numerical classification systems for the internal carotid artery (ICA) are available, but modifications have added confusion to the numerical systems. Furthermore, previous classifications may not be applicable uniformly to microsurgical and endoscopic procedures. The purpose of this study was to develop a clinically useful classification system.Materials and Methods:We performed cadaver dissections of the ICA in 5 heads (10 sides) and evaluated 648 internal carotid arteries with computed tomography angiography. We identified specific anatomic landmarks to define the beginning and end of each ICA segment.Results:The ICA was classified into eight segments based on the cadaver and imaging findings: (1) Cervical segment; (2) cochlear segment (ascending segment of the ICA in the temporal bone) (relation of the start of this segment to the base of the styloid process: Above, 425 sides [80%]; below, 2 sides [0.4%]; at same level, 107 sides [20%]; P < 0.0001) (relation of cochlea to ICA: Posterior, 501 sides [85%]; posteromedial, 84 sides [14%]; P < 0.0001); (3) petrous segment (horizontal segment of ICA in the temporal bone) starting at the crossing of the eustachian tube superolateral to the ICA turn in all 10 samples; (4) Gasserian-Clival segment (ascending segment of ICA in the cavernous sinus) starting at the petrolingual ligament (PLL) (relation to vidian canal on imaging: At same level, 360 sides [63%]; below, 154 sides [27%]; above, 53 sides [9%]; P < 0.0001); in this segment, the ICA projected medially toward the clivus in 275 sides (52%) or parallel to the clivus with no deviation in 256 sides (48%; P < 0.0001); (5) sellar segment (medial loop of ICA in the cavernous sinus) starting at the takeoff of the meningeal hypophyseal trunk (ICA was medial into the sella in 271 cases [46%], lateral without touching the sella in 127 cases [23%], and abutting the sella in 182 cases [31%]; P < 0.0001); (6) sphenoid segment (lateral loop of ICA within the cavernous sinus) starting at the crossing of the fourth cranial nerve on the lateral aspect of the cavernous ICA and located directly lateral to the sphenoid sinus; (7) ring segment (ICA between the 2 dural rings) starting at the crossing of the third cranial nerve on the lateral aspect of the ICA; (8) cisternal segment starting at the distal dural ring.Conclusions:The classification may be applied uniformly to all skull base surgical approaches including lateral microsurgical and ventral endoscopic approaches, obviating the need for 2 separate classification systems. The classification allows extrapolation of relevant clinical information because each named segment may indicate potential surgical risk to specific structures.

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“…Classification of this segment has been provided in detail previously[22632353738394041424344] [Table 3]. …”

Section: Discussionmentioning

confidence: 99%

Proposed clinical internal carotid artery classification system

Abdulrauf

Ashour

Marvin

et al. 2016

J Craniovert Jun Spine

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“…The TC approach allowed exposure of the inferior two-thirds of the tumor. The EEA provided direct exposure of the pterygopalatine and infratemporal fossae and skull base [ 9 ] with an excellent view of the infraorbital nerve, cranial nerve V3, sphenoid sinus, Eustachian tube, internal maxillary artery, and foramen lacerum at the skull base (Figure 3C ). This allowed tumor dissection at the foramen ovale under direct view.…”

Section: Discussionmentioning

confidence: 99%

“…The internal maxillary artery was identified laterally and ligated with endoscopic clips. The transpterygoid approach was carried out to dissect the tumor from the Eustachian tube [ 9 ], expose the foramen ovale, and delineate the tumor involvement at the skull base (Figure 2B ). At this point, the foramen ovale and rotundum were dissected preserving V2 and V3.…”

Section: Case Presentationmentioning

confidence: 99%

Combined Endonasal-Transcervical Approach to a Metastatic Parapharyngeal Space Papillary Thyroid Carcinoma

Benet¹,

J²,

El‐Sayed³

2015

Cureus

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Purpose: Although papillary thyroid carcinoma metastases to the parapharyngeal space are rare, the high amount of fat tissue allows tumors to grow clinically undetectable until they invade most of the parapharyngeal space. We describe for the first time a combined endonasal and transcervical approach for a parapharyngeal metastasis from a papillary thyroid carcinoma.Materials and Methods: A 51-year-old male with a previous history of papillary thyroid carcinoma presented with left ear fullness and left-sided facial numbness. Imaging revealed a 4x3 cm pre-styloid parapharyngeal space mass invading the foramen ovale and extending below the palate. Needle biopsy confirmed metastatic papillary thyroid carcinoma.Results: The lesion was resected with a combined endoscopic endonasal and transcervical approach. Postoperative MRI revealed gross total resection, and the patient recovered from his symptoms.Conclusion: This novel approach provides access to pre-styloid parapharyngeal tumors with superior extension to the skull base, avoiding more extensive traditional open approaches.

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“…Postero-medial of the nerve, there is the foramen lacerum, postero-lateral there is the mandibular nerve, infero-medial there is the Eustachian tube, and anterior the pterygopalatine fossa [ 251 ]. As rule (“clock concept”) it is generally accepted to first remove bony structures inferior-medial and then inferior-lateral of the Vidian nerve, if needed (on the left side: procedure in counterclockwise direction from 9:00 to 6:00, and then to 3:00) – the nerve directs the surgeon in dorsal direction to the horizontal part of the internal carotid artery in the petrous bone [ 250 ], [ 252 ], [ 253 ], [ 254 ], [ 255 ]. The recommendations slightly vary in their detailed formulation [ 249 ], [ 250 ].…”

Section: Basic Principles Of Rhino-neurosurgerymentioning

confidence: 99%

“…In reference to a styloid “diaphragm” consisting of muscular parts (posterior digastric muscle, stylohyoid muscle, stylopharyngeal muscle) and a stylopharyngeal aponeurosis, a pre- and poststyloid compartment can be differentiated. The latter contains the carotid artery, the internal jugular vein as well as the inferior cranial nerves IX–XII [ 146 ], [ 152 ], [ 243 ], [ 252 ], [ 264 ], [ 273 ]. The most important landmark for the preparation of the poststyloid compartment is the Eustachian tube.…”

Section: Basic Principles Of Rhino-neurosurgerymentioning

confidence: 99%