Endoscopic endonasal transpterygoid nasopharyngectomy: Anatomical considerations and technical note.

BACKGROUND: The study was designed to identify new landmarks in the parapharyngeal segment of the internal carotid artery (ICA) for nasopharyngectomy and describe a surgical procedure of endoscopic endonasal transpterygoid nasopharyngectomy (EETPN). METHODS: Four cadaveric specimens were injected with colored silicone and subjected to CT scanning before dissection. The nasopharyngeal skull base was exposed using the endoscopic endonasal transpterygoid approach. The clinical data of four patients with nasopharyngeal malignances who underwent EETPN were reviewed. RESULTS: The lateral edge of the longus capitis muscle medially; the foramen lacerum, petrous apex spine and the stump of the levator veli palatini muscle superior laterally; and the upper parapharyngeal ICA laterally constitute the ICA-longus capitis muscle-petrous apex spine triangle which was a novel landmark for the upper parapharyngeal segment of the ICA. CONCLUSION: The ICA-longus capitis muscle-petrous apex spine triangle are important landmarks of the upper parapharyngeal segment of the ICA.

Intrapetrous Internal Carotid Artery: Evaluation of Exposure, Mobilization and Surgical Maneuvers Feasibility from a Retrosigmoid Approach in a Cadaveric Model.

OBJECTIVES: To provide a quantification of the exposure of the vertical and horizontal segments of the intrapetrous carotid artery (IPCA) and to evaluate the possibilities of its mobilization and of performing surgical maneuvers on it using the retrosigmoid approach. METHODS: Twelve surgical dissections were performed bilaterally on 6 fresh cadavers. Predissection computed tomography (CT) scans with bone fiducials for intraoperative navigation were acquired. A retrosigmoid craniectomy was performed. The inframeatal space was drilled, the horizontal (HoIPCA) and vertical (VeIPCA) segments of the IPCA were exposed, and their measurements were recorded. The carotid canal was enlarged, the artery was carefully detached from the bone, and a vessel loop was inserted in order to mobilize its horizontal segment. Afterwards we performed different surgical maneuvers: We inflated a 5-French Fogarty balloon to compress the IPCA and repaired a 7-mm arteriotomy with a running suture. Specimens underwent a new CT scan to evaluate the amount of bone removal and the integrity of the inner ear structures. RESULTS: The HoIPCA and VeIPCA were exposed and anatomically preserved in all specimens without injuring the surrounding neurovascular structures. The HoIPCA presented an average length of 24.89 mm (range: 19.41-31.47 mm), and the VeIPCA presented an average length of 10.07 mm (range: 8.92-11.58 mm). The possibility of IPCA mobilization and the feasibility of performing surgical maneuvers were demonstrated. Postdissection CT scan showed the preservation of inner ear structures. CONCLUSION: Exposure and mobilization of the IPCA using a retrosigmoid approach are feasible and could represent a viable option for the possibility of reaching a total resection of selected skull base tumors, even when involvement of the carotid canal is present.

Anatomic Assessment of Petrous Internal Carotid Artery, Facial Nerve, and Cochlea Through the Anterior Transpetrosal Approach.

The aim of this study was to measure the related parameters of the cochlea, so as to allow preoperative assessment of the anatomic relationship of the petrous internal carotid artery (ICA), the facial nerve (FN), and the cochlea during skull base surgery. Seven parameters of these 3 structures were examined in the computed tomographic scan of 120 patients. The shortest distance from the cupula cochleae to the petrous ICA and the FN is as follows: 19.39 (1.01) mm to the stylomastoid foramen (D2), 10.27 (0.80) mm to the midpoint of the genu of FN canal (D3), 13.66 (0.88) mm to the exocranial opening of the carotid canal (D4), and 5.64 (1.03) mm to the midpoint of carotid knee (D5). The shortest distance between the mastoid segment of FN canal and the vertical segment of the petrous ICA (D6) was 13.33 (1.25) mm. The angle between D2 and D3 was measured at 45.66 (3.31)°, and the angle between D4 and D5 was measured at 41.08 (2.64)°. Clinically, it is relatively safe to work within the distances and angles measured in this research, and these results may give surgeons a practical and specific view of these 3 structures in the skull base approaches such as anterior transpetrosal approach to achieve the best possible surgical outcome and maximize safety.

Eustachian tube and internal carotid artery in skull base surgery: an anatomical study.

OBJECTIVES/HYPOTHESIS: The eustachian tube (ET) is an important landmark in skull base surgery, which has a close relationship with the petrous segment of the internal carotid artery (ICA). The goal of the current study was to establish the detailed anatomic relationship of the ET and petrous segment of the ICA. STUDY DESIGN: Anatomical study. METHODS: Six silicon-injected adult cadaveric heads (12 sides) were dissected using a lateral infratemporal fossa approach (type C) and endoscopic endonasal approach. The ET and ICA were exposed; their detailed relationships were demonstrated. High-quality pictures were obtained. RESULTS: In the anterior genu/foramen lacerum segment of the ICA, the vidian nerve was an important landmark. The cartilaginous ET was divided into four segments, from anterior to posterior: nasopharyngeal, pterygoid, lacerum, and petrosal segment. The anterior and inferior wall of the carotid canal was consistently between the horizontal ICA and petrous segment of the cartilaginous ET. In the posterior genu of the ICA, the bony part of the ET, and the tendon of the tensor tympani muscle were paramount landmarks. The posterior genu of the ICA was imbedded in the carotid canal. The landmarks of the junction of the cartilaginous ET and bony ET were the sphenoid spine and foramen spinosum. CONCLUSIONS: The anatomical segmentation of the ET provides the basis for safe and effective transection of the ET in skull base surgery. An understanding of the complex relationships of the ET and petrous segment of the ICA is paramount for surgically dealing with disease located within the region of the ET and petrous segment of the ICA. LEVEL OF EVIDENCE: NA

Anatomic study of the distance between the articular eminence and foramen spinosum and foramen spinosum and petrotympanic fissure.

PURPOSE: The middle meningeal artery is in close proximity to the medial aspect of the temporomandibular joint (TMJ). A major potential complication of surgery in the area of the TMJ is possible severance of the middle meningeal artery. An understanding of the relationship of the middle meningeal artery to easily identifiable landmarks lateral to the TMJ can help prevent the complications associated with TMJ surgery. The aim of the present study was to define the location of the middle meningeal artery by relating the distance between the easily identifiable bony landmarks of the articular eminence, petrotympanic fissure, and foramen spinosum. MATERIALS AND METHODS: Using a cross-sectional study design, we selected dried skulls from the Hamman-Todd skeleton collection at the Cleveland Museum of Natural History that were older than 20 years of age at death. The primary study variables were the distances between the articular eminence and foramen spinosum and the foramen spinosum and petrotympanic fissure. To appropriately analyze the variables, stratifications of age, gender, race, and anatomic location were applied. To measure the relationship between the stratifications and distances, a multivariate analysis of variance test was performed. The statistical results were deemed significant at P < .05. RESULTS: The sample consisted of 354 skulls or a total of 708 complexes. In analyzing the data, we noted that the only stratifications that bore any statistical significance were gender, with P < .0001, and the race-distance correlation, with a P value of .0007. CONCLUSIONS: The results of the present study suggest a definite difference in regard to gender on the distance between both sets of anatomic landmarks. Future studies could be tailored to further explore the effect of age on the distance, as a slight correlation was noted in our study.

Endoscopic approach to the trigeminal nerve: an anatomic study.

OBJECTIVE: To describe an endoscopic perspective of the surgical anatomy of the trigeminal nerve. METHODS: Nine adult cadaveric heads were dissected endoscopically. RESULTS: Opening the pterygopalatine fossa is important because many key anatomical structures (V2, pterygopalatine ganglion, vidian nerve) can be identified and traced to other areas of the trigeminal nerve. From the pterygopalatine ganglion, the maxillary nerve and vidian nerve can be identified, and they can be traced to the gasserian ganglion and internal carotid artery. An anteromedial maxillectomy increases the angle of approach from the contralateral nares due to an increase in diameter of the piriform aperture, and provides excellent access to the mandibular nerve, the petrous carotid, and the cochlea. CONCLUSIONS: Identification of key anatomical structures in the pterygopalatine fossa can be used to identify other areas of the trigeminal nerve, and an anteromedial maxillectomy is necessary to expose the ipsilateral mandibular nerve and contralateral cranial level of the trigeminal nerve.

The anatomical relationship between the eustachian tube and petrous internal carotid artery.

OBJECTIVES/HYPOTHESIS: The aim of the present study was to investigate the relationship between the eustachian tube (ET) and petrous internal carotid artery (ICA) in whole-mount human temporal bone specimens. STUDY DESIGN: Descriptive study. METHODS: Histologically prepared serial sections of 10 adult temporal bones were included in the study. Five specific landmarks were selected to evaluate relationships between the petrous segment of the ICA and the ET. The selected distances were measured using computer software (Metamorph 7.5.2.0; Molecular Devices, LLC, Sunnyvale, CA). RESULTS: The ET and the ICA get close posteriorly, and the bony part of the ET and the ICA generally share the same wall. CONCLUSIONS: The junctional part of the ET may be a safe landmark to identify and protect the ICA during endoscopic endonasal surgery of the cranial base. Knowledge of the anatomical relationships of the ET and petrous part of the ICA, as well as their relationship with other surgical and radiological landmarks, would be useful to surgeons.

A new transvenous approach to the carotid-cavernous sinus via the inferior petrooccipital vein.

OBJECT: The transvenous approach via the inferior petrosal sinus (IPS) is commonly used as the most appropriate for carotid-cavernous fistula (CCF) or cavernous sinus sampling. However, sometimes the IPS is not accessible because of anatomical problems and/or complications, therefore an alternative route is needed. In this paper, the authors present and discuss the utility of a transvenous approach to the cavernous sinus via the inferior petrooccipital vein. METHODS: Four patients, 3 with dural CCFs and the other with Cushing disease, in whom endovascular surgical attempts failed using a conventional venous approach via the IPS, underwent a transvenous approach to the cavernous sinus via the inferior petrooccipital vein (IPOV). One dural CCF case had only cortical venous drainage, the second CCF also mainly drained into the cortical vein with slight inflow into the superior ophthalmic vein and inferior ophthalmic vein, and the third demonstrated drainage into the superior and inferior ophthalmic veins and IPOV. RESULTS: In all cases, the cavernous sinus could be accessed successfully via this route and without complications. CONCLUSIONS: The transvenous approach to the cavernous sinus via the IPOV should be considered as an alternative in cases when use of the IPS is precluded by an anatomical problem and there are no other suitable venous approach routes.

Arteriovenous fistula involving the inferior petroclival vein--case report.

A 68-year-old man presented with an extremely rare extracranial arteriovenous fistula (AVF) involving the inferior petroclival vein (IPCV) with retrograde venous drainage into an ophthalmic vein through the anterior condylar confluence and inferior petrosal sinus manifesting as ocular symptoms. The AVF was successfully treated by selective transvenous embolization with platinum coils. AVF involving the IPCV should be recognized as a possible extracranial lesion manifesting as clinical symptoms similar to cavernous sinus dural AVF.

Aneurysm of the petrous portion of the internal carotid artery at the foramen lacerum: anatomic, imaging, and otologic findings.

Aneurysms of the petrous portion of the internal carotid artery (ICA) are rare. Their etiology is usually congenital, traumatic, or mycotic. Depending on the size and location of the aneurysm, the direction of its growth, and the specific adjacent structures involved, patients may or may not present with signs and symptoms. When signs and symptoms do manifest, they may include headaches, epistaxis, a vascular retrotympanic mass with hemotympanum and/or otorrhagia, pulsatile tinnitus, hearing loss, vertigo, and Horner syndrome or Raeder paratrigeminal neuralgia. We describe the imaging aspects of the case of a 27-year-old man who presented with a 5-day history of unilateral symptoms secondary to a lesion located in the area of the right foramen lacerum. The lesion proved to be an aneurysm of the petrous portion of the ICA. We discuss the anatomic, imaging, and otologic aspects of ICA aneurysms in this location.

Treatment of dural arteriovenous fistulas presenting as pulsatile tinnitus.

OBJECTIVE: To describe the clinical picture and treatment of dural arteriovenous fistulas (DAVFs) presenting as pulsatile subjective tinnitus. STUDY DESIGN: Review of prospectively collected data. SETTING: Academic referral center. PATIENTS: Fourteen patients with clinically and radiographically diagnosed DAVFs. INTERVENTIONS: Treated by endovascular route. MAIN OUTCOME MEASURES: Treatments, clinical course, complications, and evolution were evaluated. RESULTS: All patients presented with sleep-disruptive pulsatile tinnitus. Other symptoms included severe headaches, papilledema, proptosis, blepharoptosis, visual disturbances, and hemiparesis. Cortical venous drainage was present in 4 cases. Endovascular treatment was performed at least once by the arterial route in 14 patients and the venous route in 4 patients. The origin of tinnitus was always a vessel in or above the petrous bone. When these arteries or veins could not be visualized in the final control, the tinnitus disappeared. In the patients whose tinnitus returned, a vessel in the petrous bone could always be seen. There was no mortality. CONCLUSION: Endovascular treatment is an effective and safe treatment of DAVFs presenting as tinnitus.

An aberrant vascular channel in the petrous bone: persistent lateral capital vein?

An aberrant channel was identified on CT in the petrous bone in four patients presenting with unrelated otological symptoms. These channels occurred unilaterally in each case. In two patients, the channel was seen to run between the sigmoid sinus sulcus and the superior petrosal sinus sulcus; in one of these patients, a vascular structure was identified within this channel on MRI, connecting the sigmoid sinus and the superior petrosal sinus. In the two other patients, an aberrant channel was seen between the superior petrosal sinus sulcus and the posterior genu of the facial nerve canal. There were no symptoms that could be attributed to the presence of these channels.We postulate that these aberrant vascular channels correspond to a persistent embryological vein, the lateral capital vein.

Endoscopic anatomy of the petrous segment of the internal carotid artery.

BACKGROUND: Exposure of the petrous (C2) segment of the internal carotid artery (ICA; petrous carotid) is necessary to treat lesions that have spread from the intracranial space or adjacent sinonasal region. Recent advancements in endonasal-endoscopic approaches to the anterior skull base raise the possibility of extending these approaches beyond the sinonasal cavity. In this cadaveric study, we evaluate the feasibility and extent of exposure of the petrous carotid artery via a combined endoscopic endonasal approach. METHODS: Endoscopic dissection was performed in four formalin-fixed cadaver heads (eight sides). An endoscopic, endonasal, transmaxillary approach was used to identify the cervical and petrous carotid artery. RESULTS: With the endoscopic endonasal, Caldwell-Luc approach, we could visualize the ventral petrous bone after dissecting the contents of the pterygopalatine fossa and infratemporal fossa. Careful dissection allowed exposure of the petrous carotid artery from the upper cervical carotid to the foramen lacerum. CONCLUSION: In this cadaveric study using an endoscopic endonasal approach for exposure of the petrous carotid artery, combination with the transmaxillary-transpterygopalatine-transinfratemporal approaches permitted exposure of the ventral portion of the artery. The anatomy presented will assist experienced endoscopic skull base surgeons in the removal of lesions involving the ventral skull base.

Microsurgical anatomy and surgical exposure of the petrous segment of the internal carotid artery.

OBJECTIVE: The petrous segment of the internal carotid artery has been exposed in the transpetrosal, subtemporal, infratemporal, transnasal, transmaxillary, transfacial, and a variety of transcranial approaches. The objective of the current study was to examine anatomic features of the petrous carotid and its branches as related to the variety of approaches currently being used for its exposure. METHODS: Twenty middle fossae from adult cadaveric specimens were examined using magnification of x3 to x 40 after injection of the arteries and veins with colored silicone. RESULTS: The petrous carotid extends from the entrance into the carotid canal of the petrous part of the temporal bone to its termination at the level of the petrolingual ligament laterally and the lateral wall of the sphenoid sinus medially. The petrous carotid from caudal to rostral was divided into 5 segments: posterior vertical, posterior genu, horizontal, anterior genu, and anterior vertical. Fourteen (70%) of the 20 petrous carotids had branches. The branch that arose from the petrous carotid was either a vidian or periosteal artery or a common trunk that gave rise to both a vidian and 1 or more periosteal arteries. The most frequent branch was a periosteal artery. CONCLUSION: An understanding of the complex relationships of the petrous carotid provides the basis for surgically accessing any 1 or more of its 5 segments.

Lesions and pseudolesions of the cavernous sinus and petrous apex.

Endoscopic surgery using an expanded endonasal approach now allows surgical access to an increasing range of parasellar, suprasellar, clivus, and petrous apex lesions. Accurate preoperative planning requires proper interpretation of CT and MRI results. It is essential to identify important anatomic landmarks and to recognize the appearance of common lesions and pseudolesions. Postoperative imaging must evaluate for residual tumors and identify iatrogenic conditions.

Petrous carotid artery's in situ bypass: anatomic study.

The purpose of our study was to reveal the possibility of cervical-to-petrous carotid artery in situ bypass with maximum preservation of cranial nerves. Four human cadavers prepared in formalin were investigated. Eight surgical approaches were used (bilateral exposure on each cadaver). The skin incision started from the level of the temporomandibular joint. The VII, IX, X, and XII cranial nerves, starting from the stylomastoid angle, were maximally preserved. Resection of the styloid process, subluxation of the mandibular joint, and milling of tympanic bone revealed the petrous carotid artery. Exposure of the carotid bifurcation was performed with a mini-skin incision. After dividing the petrous internal carotid artery (ICA) and the cervical ICA, the cervical ICA was dilated using a Fogarty catheter to simulate aneurysmal dilatation. The patient's saphenous vein after stripping was utilized for the bypass. The vein was passed into the lumen of the dilated cervical ICA, and a cervical-to-petrous carotid bypass was performed. In each case, the described technique made it possible to expose the intrapetrous carotid artery adequately. In two cases it was impossible to make a luxation, and therefore the mandibular branch was resected. The vertical segment's mean length was 12 mm (range 10-15 mm). In all cases, the VII, IX, X, and XII cranial nerves were preserved maximally. The main points of the approach are luxation of the mandibular articulation and milling of the tympanic bone. Our study in cadavers suggests the possibility of petrous carotid artery bypass without exposing the cervical ICA.

Endoscopic anatomy of the pterygopalatine fossa and the transpterygoid approach: development of a surgical instruction model.

INTRODUCTION: The pterygopalatine fossa (PPF) is a narrow space located between the posterior wall of the antrum and the pterygoid plates. Surgical access to the PPF is difficult because of its protected position and its complex neurovascular anatomy. Endonasal approaches using rod lens endoscopes, however, provide better visualization of this area and are associated with less morbidity than external approaches. Our aim was to develop a simple anatomical model using cadaveric specimens injected with intravascular colored silicone to demonstrate the endoscopic anatomy of the PPF. This model could be used for surgical instruction of the transpterygoid approach. METHODS: We dissected six PPF in three cadaveric specimens prepared with intravascular injection of colored material using two different injection techniques. An endoscopic endonasal approach, including a wide nasoantral window and removal of the posterior antrum wall, provided access to the PPF. RESULTS: We produced our best anatomical model injecting colored silicone via the common carotid artery. We found that, using an endoscopic approach, a retrograde dissection of the sphenopalatine artery helped to identify the internal maxillary artery (IMA) and its branches. Neural structures were identified deeper to the vascular elements. Notable anatomical landmarks for the endoscopic surgeon are the vidian nerve and its canal that leads to the petrous portion of the internal carotid artery (ICA), and the foramen rotundum, and V2 that leads to Meckel's cave in the middle cranial fossa. These two nerves, vidian and V2, are separated by a pyramidal shaped bone and its apex marks the ICA. CONCLUSION: Our anatomical model provides the means to learn the endoscopic anatomy of the PPF and may be used for the simulation of surgical techniques. An endoscopic endonasal approach provides adequate exposure to all anatomical structures within the PPF. These structures may be used as landmarks to identify and control deeper neurovascular structures. The significance is that an anatomical model facilitates learning the surgical anatomy and the acquisition of surgical skills. A dissection superficial to the vascular structures preserves the neural elements. These nerves and their bony foramina, such as the vidian nerve and V2, are critical anatomical landmarks to identify and control the ICA at the skull base.