Peer-Review Reports

Endonasal Endoscopic Approaches to the Paramedian Skull Base Danielle de Lara1, Leo F. S. Ditzel Filho1, Daniel M. Prevedello1, Ricardo L. Carrau2, Pornthep Kasemsiri2, Bradley A. Otto2, Amin B. Kassam3

Key words Endoscopy - Endonasal approach - Infratemporal fossa - Middle cranial fossa - Posterior fossa - Pterygopalatine fossa - Skull base

- OBJECTIVE:

Abbreviations and Acronyms CN: Cranial nerve CSF: Cerebrospinal fluid EEA: Endoscopic endonasal approach ET: Eustachian tube ICA: Internal carotid artery V2: Second branch of the trigeminal nerve V3: Third branch of the trigeminal nerve

- RESULTS:

-

From the Departments of 1 Neurosurgery and 2 OtolaryngologyeHead & Neck Surgery, The Ohio State University Medical Center, Columbus, Ohio, USA; and 3 Division of Neurological Surgery, University of Ottawa, Ottawa, Ontario, Canada To whom correspondence should be addressed: Ricardo L. Carrau, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 6S:S121-S129. http://dx.doi.org/10.1016/j.wneu.2014.07.036 Journal homepage: www.WORLDNEUROSURGERY.org

To describe the technical and anatomic nuances related to endoscopic endonasal approaches (EEAs) to the paramedian skull base.

- METHODS:

Surgical indications, limitations, and technical aspects pertaining to EEAs designed to access areas oriented in the coronal plane are systematically reviewed with special attention to caveats, pitfalls, and common complications and how to avoid them. Case examples are presented. The paramedian skull base may be divided into anterior (corresponding to the orbit and its contents), middle (corresponding to the middle cranial, pterygopalatine, and infratemporal fossae), and posterior (includes the craniovertebral junction lateral to the occipital condyles and the jugular foramen) segments. EEAs to the anterior segment offer access to the intraconal orbital space and the optic canal. A transpterygoid corridor typically precedes EEAs to the middle and posterior paramedian approaches. EEAs to the middle segment provide wide exposure of the petrous apex, middle cranial fossa (including cavernous sinus and Meckel cave), and infratemporal and pterygopalatine fossae. Finally, EEAs to the posterior segment access the hypoglossal canal, occipital condyle, and jugular foramen.

- CONCLUSIONS:

Approaches to the paramedian skull base are the most challenging and complex of all endoscopic endonasal techniques. Because of their technical complexity, it is recommended that surgeons master endoscopic endonasal anatomic approaches oriented to median structures (sagittal plane) before approaching paramedian (coronal plane) pathologies.

Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.

INTRODUCTION Endoscopic endonasal approaches (EEAs) have become a feasible option for the management of benign and malignant cranial base pathologies, bringing a new perspective to the treatment of skull base disorders (1, 10). Expanded endoscopic approaches can be classified according to the orientation of the surgical field (target area) under 2 main categories: 1) approaches to the median skull base (access to structures in the sagittal plane) and 2) approaches to the paramedian skull base (access to more lateral structures, located in the coronal plane) (5, 9, 12). Traditionally, middle and posterior cranial fossa pathologies have been treated through lateral routes, such as transpterional, transpetrosal (anterior and

posterior), and retrosigmoid/far lateral approaches. These approaches are well established, and they are effective in wellselected patients, especially in patients whose lesions extend to the lateral aspect of the middle and posterior fossae. However, when lateral approaches are used for lateral lesions that extend medially to the ventral brainstem, they may require undesirable manipulation and retraction of neural tissue (16). Under these circumstances, paramedian EEAs can be a great alternative to avoid neural tissue and vascular retraction (10, 20). Modular EEAs are defined based on the anatomy of the corridor and their target areas and their relationship with critical structures. In the coronal plane, the most critical and defining structure is the internal carotid artery (ICA). The ICA can be divided into segments that have their own

WORLD NEUROSURGERY 82 [6S]: S121-S129, DECEMBER 2014

distinct landmarks (Table 1) (10, 12). Additional important anatomic landmarks include the pterygoid plates, the vidian canal, and foramina rotundum and ovale (with the second and third branches of the trigeminal nerve [V2 and V3], respectively) (15, 22). PARAMEDIAN EEAS Paramedian EEAs must be considered in 3 different depths as the working corridor advances from an anterior to posterior. In general, the anterior coronal plane relates to the anterior cranial fossa and orbits, the middle coronal plane relates to the middle cranial fossa and temporal lobe, and the posterior coronal plane relates to the posterior cranial fossa (1, 10). Based on their relationship to different segments of the ICA, the middle and posterior

www.WORLDNEUROSURGERY.org

S121

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

Table 1. Endoscopic Landmarks to Segments of the ICA Segment

Anatomic Landmark

Parasellar

mOCR

Vertical ICA

Medial pterygoid

Horizontal ICA

Vidian nerve

Carotid canal

ET (bony)

Ascending ICA

ET (cartilaginous)

ICA, internal carotid artery; mOCR, medial opticocarotid recess; ET, eustachian tube.

paramedian approaches may be classified as follows: zone 1 or medial petrous apex approach (posterior to the paraclival ICA), zone 2 or infrapetrous approach (inferior to the petrous ICA), zone 3 or suprapetrous approach (superior to the petrous ICA and lateral to the paraclival ICA), zone 4 or lateral cavernous sinus approach (superior to Meckel cave approach, i.e., Meckel cave), zone 5 or middle fossa/ infratemporal fossa approach (lateral to the petrous ICA and anterior to the parapharyngeal ICA), zone 6 or occipital transcondylar approach (posterior to the eustachian tube [ET] and medial to the parapharyngeal ICA), and zone 7 or jugular foramen approach (posterior and lateral to the parapharyngeal ICA) (9, 10, 12). A transpterygoid corridor is the initial step to gain endonasal access to most of the zones in the middle and posterior coronal plane (9). Anatomic Considerations As with any other surgical technique, a flawless EEA is based on a profound understanding of the ventral skull base anatomy. A complex group of bones, fissures, foramina, and neurovascular structures must be taken into consideration. The sphenoid bone is located in the center of the cranial base in intimate contact with many important arterial, venous, and neural structures, such as the internal carotid and basilar arteries, the cavernous sinuses, and associated cranial nerves (CNs). Pneumatization of the sphenoid bone and sphenoid sinus creates a natural corridor, allowing the surgeon to approach various neurovascular structures with minimal drilling or manipulation of intracranial structures (1, 16).

S122

www.SCIENCEDIRECT.com

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

The body of the sphenoid bone forms part of the medial wall of the orbital apex and superior orbital fissure. The medial wall of the orbit is also formed by the ascending process of the palatine bone, the lamina papyraceae of the ethmoid bone, the lacrimal bone, and the frontal process of the maxilla (from posterior to anterior). The orbital medial wall is extremely thin at the level of the lamina papyraceae, which separates the ethmoid sinus cells and the orbit. At the junction of the roof and the medial wall of the orbit is the frontoethmoidal suture. This suture represents an important landmark as the anterior and posterior ethmoidal foramina, in which the respective anterior and posterior ethmoidal arteries and nerves traverse (7, 14). The greater wing of the sphenoid bone forms a large part of the lateral wall of the orbit, the floor of the middle fossa, and the roof of the infratemporal fossa. The infratemporal fossa is an anatomic space located under the floor of the middle cranial fossa and posterior to the maxilla that contains the parapharyngeal and masticator spaces. It communicates medially with the pterygopalatine fossa through the pterygomaxillary fissure, which is continuous with the inferior orbital fissure (3, 5). These fissures form a half-mooneshaped pathway and can be used as a surgical landmark because they delimit surgical boundaries between the pterygopalatine (medially) and the infratemporal fossae (laterally) (3, 6). The pterygopalatine fossa is bound by the pterygoid process posteriorly, the palatine bone anteromedially, and the maxilla anterolaterally (Figure 1) (3, 15, 18). It contains a superficial (i.e., anterior) vascular compartment that contains the maxillary artery (also known as internal maxillary artery) and its terminal branches. A posterior neural compartment includes the pterygopalatine ganglion, which receives parasympathetic and sympathetic fibers through the vidian nerve, and sensory fibers from the descending palatine nerve and the maxillary nerve (V2). The vidian nerve, formed by the union of the greater superficial petrosal nerve and the deep petrosal nerve, is one of the most important surgical landmarks when navigating on the coronal plane. It consistently marks the level of the horizontal ICA in the petrous bone.

Figure 1. Endoscopic view of a cadaveric dissection of the pterygopalatine fossa. ET, eustachian tube; IMAx, internal maxillary artery; LPP, lateral pterygoid plate; MPP, medial pterygoid plate; VC, vidian canal (sectioned).

Intraoperatively, the nerve can be followed posteriorly up to the level of the foramen lacerum allowing the surgeon to identify the ICA safely (12, 16, 17, 22). Pneumatization of the sphenoid sinus extending into the greater sphenoid wing bears a lateral sphenoid recess (i.e., pterygoid recess), which projects under the middle fossa. The anteromedial portion corresponds to Meckel cave, containing the trigeminal (gasserian) ganglion (4, 7, 16). Removal of the lateral wall of the sphenoid sinus exposes the periosteum of the middle fossa. CN VI is the most vulnerable structure intradurally. Understanding its anatomy is paramount to avoid an accidental injury. CN VI exits the brainstem at the level of the vertebrobasilar junction (level of the sphenoid sinus floor), pierces the clival dura mater posterior to the paraclival ICA, and advances between the dural layers superolaterally toward Dorello’s canal; it angulates anteriorly under Gruber ligament to enter the cavernous sinus immediately lateral to the parasellar ICA. CN VI goes into the superior orbital fissure running parallel to the horizontal segment of the cavernous ICA and first branch of the trigeminal nerve. CN VI must be monitored, carefully identified, or avoided to prevent postoperative palsy (8, 10). Anterior Coronal Plane Transorbital Approach. Transorbital EEAs are designed to reach both extraconal and intraconal lesions. The most common

WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.036

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

indications for extraconal approaches are sinonasal lesions that displace, erode, or invade the medial wall of the orbit and for decompression of the orbit or optic nerves in the presence of Graves disease, trauma, or unresectable intraconal pathology (19). Intraconal approaches are designed to address intraorbital benign space-occupying lesions, such as schwannomas, hemangiomas, and meningiomas. A transorbital EEA begins with complete anterior and posterior ethmoidectomies to expose the medial wall of the orbit. Removal of the lamina papyraceae and decompression of the medial aspect of the optic canal follow. If needed, the approach can be extended into the intraconal compartment opening the periorbita and exposing the medial and inferior rectus muscles. The gap between these 2 extraocular muscles represents the window for intraconal access (10, 19). Important anatomic landmarks include the optic nerves, the anterior and posterior ethmoidal arteries, and the ophthalmic artery with its branches. Because the ophthalmic arteries and the optic nerves cannot be mobilized, they constitute the lateral limits of the approach (Figure 2). Middle Coronal Plane As previously addressed, the approaches to the middle coronal plane can be divided into 5 different zones, according to their relationship with specific segments of the ICA. With the exception of zone 1, the approach to all zones starts with a transpterygoid approach using the maxillary sinus as the working corridor (9). When studying the middle coronal plane, it is also useful to divide its 5 modular approaches further into 2 general categories based on whether they are below the horizontal segment of the petrous ICA (infrapetrous approaches) or above it (suprapetrous approaches) (9, 10). EEAs may be combined whenever necessary to resect lesions involving more than 1 of the zones described. Basic Transpterygoid Approach. A transpterygoid approach starts with an uncinectomy, anterior ethmoidectomy, and enlargement of the maxillary ostium to obtain a wide middle meatus antrostomy. The sphenopalatine and posterior nasal arteries are identified at the

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

sphenopalatine foramen, and their branches are coagulated. The infraorbital canal is visualized superiorly, and the posterior wall of the maxillary sinus is removed (i.e., anterior wall of the sphenopalatine foramen), exposing the soft tissue contents of the pterygopalatine fossa. Sacrifice of the pharyngeal artery and nerve that run medially through the palatovaginal canal on the superomedial aspect of choana allows the lateral retraction of the soft tissues of the pterygopalatine (7). The vidian foramen and foramen rotundum are identified posteriorly in the sphenoid bone. Whenever possible, the vidian nerve and artery are transposed from the vidian canal and preserved (17). After the vidian nerve is transposed or sectioned, the soft contents of the pterygopalatine fossa are lateralized, and the base of the pterygoid plate is drilled. The lateral sphenoid recess is opened, and the base of the pterygoid plates is drilled. This exposure allows direct access to the medial infratemporal fossa (1, 3, 9). Infrapetrous Approaches. A zone 1 or petrous apex approach is indicated for lesions affecting or expanding the medial petrous apex, such as chondrosarcomas and cholesterol granulomas. As an approach, it essentially requires a lateral extension of the middle third transclival approach (Figure 3). The approach is initiated with wide bilateral sphenoidotomies, removal of the sphenoid sinus floor, and removal of the basopharyngeal fascia from the undersurface of the sphenoid sinus floor. Complete drilling of the sphenoid sinus floor is carried back until the floor is flush with the clival recess and the area of the foramen lacerum is defined (9). It is important to define the position of the ICA, and the paraclival ICA canal occasionally is removed to allow the lateralization of the vessel to access a lesion extending laterally behind the ICA. In these situations, the vidian nerve is followed posteriorly leading directly to the lacerum segment of the ICA. It is important to remove the bone medial and lateral to the ICA to enhance lateralization; this provides direct access to the petrous apex (9). It is important to remember that CN VI is adjacent to this area as it passes through Dorello canal, immediately

WORLD NEUROSURGERY 82 [6S]: S121-S129, DECEMBER 2014

behind and above the petrous apex. The main anatomic structures at risk during performance of this approach are the ICA and CN VI (8, 16). A zone 2 or petroclival approach is most commonly indicated for the treatment of chondrosarcomas and chordomas. The approach is initiated as described previously for a zone 1 petrous apex approach, with an extension of the working corridor to the medial maxilla (anterior) and the fossa of Rosenmüller (posterior) (9). The relationship between the vidian nerve, vidian artery, and ICA serves as the most important anatomic landmark for this approach (Figure 4) (17, 22); the pterygopalatine fossa is exposed removing the posterior wall of the maxilla, and the vidian nerve and canal are identified (22). The vidian nerve is followed posteriorly (removing its surrounding bone) to the point where it encounters the lacerum segment of the ICA (vidian artery is not always present). After the foramen lacerum is exposed, the corridor is expanded into the infrapetrous area. The ICA does not need to be exposed; however, its full dissection is usually necessary in cases of malignancies, such as chondrosarcomas. To expose the inferior aspect of the petrous bone, the foramen lacerum is disconnected from the superior aspect of the ET cartilage. Horizontal cuts are performed at that level, and the dense fibrocartilaginous tissue is retracted inferiorly allowing for direct visualization of the petrous apex below the ICA. If necessary, the ET is completely removed to allow full exposure of the petroclival synchondrosis (Figure 5). Suprapetrous Approaches. A zone 3 approach is indicated to access lesions located in Meckel cave through the quadrangular space. The most common pathologies in this location are invasive adenoid cystic carcinomas, meningiomas, schwannomas, and invasive pituitary adenomas. The quadrangular space is limited by the horizontal petrous ICA inferiorly, ascending vertical cavernous/paraclival ICA medially, CN VI superiorly (in the cavernous sinus), and maxillary division of the trigeminal nerve (V2) laterally (1, 9). Exposure is initiated with a transpterygoid approach isolating the maxillary nerve and following it superiorly until the foramen rotundum is identified and following the

www.WORLDNEUROSURGERY.org

S123

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

Figure 2. Transorbital approach. A previously healthy, 35-year-old man presented with complaints of progressive visual loss in the right eye. Preoperative magnetic resonance imaging was performed, and an intraconal meningioma was diagnosed. The patient underwent an endoscopic endonasal transorbital approach, and the tumor was completely resected. Preoperative T1-weighted and T2-weighted coronal (A), sagittal (B), and axial (C and D) images of an intraconal meningioma. (E) Surgical specimen.

vidian canal to identify the anterior genu of the ICA. To expose the ICA and the anterior face of Meckel cave better, the bone separating V2 and the vidian canal is drilled away exposing the petrous, lacerum, and paraclival segments of the ICA (3). The bone of the middle fossa is drilled, and the periosteal dura mater is exposed and opened into the quadrangular space.

S124

www.SCIENCEDIRECT.com

A dural opening into the quadrangular space is performed from a medial-tolateral direction—from the genu of the ICA toward V2. It is important to stay below the level of CN VI and lateral to the ICA to avoid the superior portion of the cavernous sinus and consequently damage to the CNs within the cavernous sinus. The key anatomic landmarks in this approach are V2, CN VI, and the ICA (10).

A zone 4 approach accesses the superior cavernous sinus. This approach is rarely indicated, and its use is limited to patients with an existing CN deficit (CNs III, IV, VI), such as patients with a cavernous sinus syndrome secondary to an apoplectic pituitary adenoma. This approach is a continuation of a zone 3 approach, extending the dural opening above the quadrangular space. Minimal venous

WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.036

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

Figure 4. Endoscopic view of a cadaveric dissection of the infratemporal fossa. The infratemporal fossa and the dura mater of Meckel cave are exposed. The vidian nerve is followed posteriorly to the anterior genu of the internal carotid artery. ICA, internal carotid artery; IMAx, internal maxillary artery; LOCR, lateral opticocarotid recess; VN, vidian nerve; VI, abducens nerve; V1, first branch of trigeminal nerve; V2, second branch of trigeminal nerve; V3, third branch of trigeminal nerve.

Figure 3. Preoperative axial computed tomography scan (A) and axial (B), coronal (C), and sagittal (D) T1-weighted magnetic resonance imaging scans of a lesion at the petrous apex. The sharply marginated expansive lesion with increased signal intensity on T1-weighted images is strongly suggestive of a cholesterol granuloma. The patient underwent an expanded endoscopic endonasal petrous apex approach for tumor removal. Postoperative axial computed tomography scans (E and F) show the tumor resection and working corridor.

WORLD NEUROSURGERY 82 [6S]: S121-S129, DECEMBER 2014

bleeding on opening the space is the norm because the tumor typically thromboses the sinus. Copious venous bleeding is encountered when the tumor is removed (10). The incision is performed on the periosteum of the superior orbital fissure and the cavernous ICA at the level of the siphon, and the dissection is performed immediately lateral to the ICA. The inferolateral trunk of the ICA is a good landmark for the caudal extent of the exposure. Structures at risk during this approach are CNs III, IV, V, and VI and the ICA with its sympathetic fibers (2). The zone 5 approach is designed to reach the middle cranial and infratemporal fossae. Common pathologies in this region include invasive carcinomas extending from the sinonasal tract or nasopharynx, cerebrospinal fluid (CSF) leaks, encephaloceles, schwannomas, and meningiomas (3, 5, 6). During a zone 5 approach, full exposure of the pterygopalatine fossa is necessary. The posterior wall of the maxilla is removed, and the periosteum of the pterygopalatine fossa can be incised to dissect its soft tissue contents. In the event that a full exposure of the infratemporal fossa is needed, the maxillary artery and its branches should be controlled early in the dissection.

www.WORLDNEUROSURGERY.org

S125

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

Figure 5. A 57-year-old woman with a history of double vision and a sixth cranial nerve palsy in the left eye presented to the Neurological Surgery Department. Magnetic resonance imaging scan obtained on admission revealed a petroclival lesion, compatible with a chondrosarcoma. Complete tumor removal was achieved via an expanded endonasal approach

As previously mentioned, the nerves are located in a posterior compartment of the pterygopalatine fossa, and a decision to lateralize or medialize the soft tissues of the pterygopalatine fossa is made to approach the disease. Intensive bleeding from the pterygopalatine venous plexus is expected and can be controlled with bipolar electrocautery or hemostatic paste. The pterygoid process (base and pterygoid plates) can be drilled and reduced as needed for the approach. The dissection continues lateral to the lateral pterygoid plate to reach the infratemporal fossa. The posterosuperior aspect of the lateral pterygoid plate is an important landmark for

S126

www.SCIENCEDIRECT.com

petroclival approach. Preoperative axial (A), coronal (B), and sagittal (C) T1-weighted contrast-enhanced magnetic resonance imaging scans show the lesion arising from the petroclival region. Postoperative axial (D), coronal (E), and sagittal (F) T1-weighted contrast-enhanced magnetic resonance imaging scans show complete tumor resection.

the identification of the mandibular nerve (V3), which is immediately posterior. When the middle cranial fossa needs to be approached, the pterygoid base is drilled posteriorly preserving V2 and the vidian nerve in the direction of the middle cranial fossa. The lateral wall of the lateral recess of the sphenoid is drilled, and the periosteal dura mater is exposed and incised between the first branch of the trigeminal nerve and V2 (anteromedial triangle of the middle cranial fossa) or in between V2 and V3 (anterolateral triangle of the middle cranial fossa) (Figure 6) (5). Relevant structures in this approach include the soft tissue contents of the pterygomaxillary

fissure, such as the internal maxillary artery with its branches, the vidian nerve, and the trigeminal nerve (V2 and V3) branches. Posterior Coronal Plane. A zone 6 approach is an inferior extension of a zone 2 approach and comprises the region immediately posterior to the ET and medial to the parapharyngeal ICA. Common pathologies in this location are paragangliomas, schwannomas, nasopharyngeal malignancies, chordomas, and meningiomas. The working corridor for this approach is the inferior aspect of the medial maxilla and nasopharynx. The ET helps as an important

WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.036

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

Figure 6. Preoperative contrast-enhanced T1-weighted axial (A and B) and coronal (C) magnetic resonance imaging scans. An extensive nasopharyngeal and skull base tumor involving the left pterygopalatine fossa and middle fossa is shown, consistent with the diagnosis of adenocarcinoma. (D) Intraoperative navigation image shows the working corridor to the infratemporal and temporal fossae.

landmark to identify safely the ICA parapharyngeal segment (cartilaginous ET) and the carotid canal in the petrous bone (bony ET) (5, 18).

The medial aspect of the occipital condyle is just lateral to the foramen magnum, and the hypoglossal canal is positioned superolateral inside the

WORLD NEUROSURGERY 82 [6S]: S121-S129, DECEMBER 2014

condyle (lateral limit of this approach). Stability is maintained if the occipital-C1 joint is not transgressed (10, 19). The supracondylar area can also be drilled, and it yields access to the jugular tubercle of the occipital bone immediately medial to the inferior petrosal sinus and jugular foramen. The superior limit of this approach is the petroclival synchondrosis. Above this area is considered part of the infrapetrous area (zone 2). The lateral limits of the approach are the hypoglossal canal (inside the condyle) and the parapharyngeal ICA. The most important structures in this approach are the parapharyngeal and petrous segments of the ICA and the hypoglossal nerve (CN XII) exiting the hypoglossal canal inferiorly and laterally. The zone 7 approach is a lateral extension of a zone 6 approach to access the parapharyngeal ICA and the jugular foramen. Indications for this approach are invasive carcinomas, paragangliomas, schwannomas, and certain skull base meningiomas. The ET is an important landmark because it allows direct identification of the ICA. The ET runs parallel and anterior to the petrous ICA, and it enters the petrous bone just medial to the ascending parapharyngeal ICA before it enters into the petrous canal (5). With rare exceptions, the ET is removed to allow exposure of the parapharyngeal ICA and petroclival synchondrosis, which lead to the jugular foramen. An endonasal Doppler acoustic ultrasound probe is valuable when dissecting the soft tissue lateral to the ET to avoid an ICA injury. After localizing the ICA, the jugular foramen may be found just lateral and posterior. To facilitate the tumor resection, an endoscopic Denker approach (i.e., Sturman-Canfield approach) and anterior maxillotomy is frequently performed (10). The parapharyngeal ICA, jugular foramen, jugular vein, and lower CNs (CNs IX, X, XI) are the most important anatomic structures in this approach (Figure 7). COMPLICATIONS EEAs involve multiple technical challenges to the surgeon regarding tumor removal and complication avoidance. Neurophysiologic monitoring (somatosensory evoked potentials) and CN electromyography are used routinely because they are helpful in

www.WORLDNEUROSURGERY.org

S127

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

Figure 7. A 40-year-old woman presented with a sixth cranial nerve palsy in the right eye. Preoperative magnetic resonance imaging scans (AeC) revealed an extensive mass lesion, involving the middle, posterior, and

preventing vascular and neural injuries. Computer-assisted navigation, using preoperative computed tomography angiography fused with magnetic resonance imaging, confirms the surgeon’s anatomic assessment of the field. During endoscopic endonasal surgery, 2 tasks are crucial to avoid complications, hemostasis and water-sealed skull base reconstruction. Postoperative CSF leaks are the most common complication. Skull base reconstruction after a paramedian endoscopic approach is performed as previously described. The main objective is to restore the natural isolation of the intracranial structures from the sinonasal cavity, avoiding a CSF leak and secondary complications, such as infection or meningitis. In cases in which there is no

S128

www.SCIENCEDIRECT.com

infratemporal fossae. The patient underwent endoscopic endonasal removal of the tumor, which was confirmed to be a chordoma. (DeF) Postoperative images are shown. The patient’s recovery was uneventful.

intraoperative CSF leak but there is vascular exposure, we still favor a vascularized reconstruction (often the nasoseptal flap) to cover and protect the ICA. The introduction and refinement of the vascularized nasoseptal mucosal flap for the reconstruction of the ventral skull base are important advancements that dramatically reduced the incidence of CSF leaks (10, 11). The selected corridor correlates with the type and incidence of complications. In general, paramedian approaches are associated with higher rates of vascular complications (3.8%) (10), probably associated with the intimate relationship to the various segments of the ICA. Internal tumor debulking and extracapsular tumor dissection are strongly advocated because this facilitates the

visualization and dissection of the surrounding vessels and nerves. Hemostasis is paramount to adequate endoscopic visualization. Low-flow venous or capillary bleeding is controlled by irrigation with warm saline (40 Ce42 C). Drilling with a diamond burr and judicious use of bone wax are useful to control bleeding from bone surfaces. Venous bleeding from the cavernous sinus, basilar plexus, or pterygoid plexus can be copious and is best controlled with hemostatic material gently applied with cottonoids or pastelike hemostatic agents (13). Applying direct compression, compressive packing, suture repair, and endovascular reconstruction can control arterial high-flow bleeding, similar to that from the ICA. More recent studies have

WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.036

PEER-REVIEW REPORTS DANIELLE DE LARA ET AL.

elucidated effective maneuvers to control catastrophic ICA bleeding intraoperatively, including use of large-bore suctions, placement of the scope through the side of less bleeding, use of a lens cleansing device, and use of a muscle patch or packing. It is also important to maintain cerebral perfusion with adequate resuscitation, maintaining blood pressure and providing anticoagulation to avoid embolic phenomena. The patient can be taken to interventional radiology to complete the permanent sacrifice of the vessel or to insert a stent in the area of injury. Some rare situations require permanent occlusion of the vessel (10, 21). For these reason, we strongly recommend that the team performing endoscopic skull base surgery, particularly in the coronal plane, is also proficient in cerebrovascular techniques. CONCLUSIONS EEAs have become an important option for the treatment of ventral skull base lesions because they offer the possibility of tumor resection with minimal manipulation of brain and CNs. Approaches in the coronal plane represent the most challenging and complex of all endoscopic endonasal skull base surgery techniques. Detailed understanding of the ventral skull base anatomy, extensive training in endonasal endoscopic surgery, and proper microsurgical technique are the key elements to achieve a successful paramedian endoscopic approach. REFERENCES

ENDONASAL ENDOSCOPIC APPROACHES TO PARAMEDIAN SKULL BASE

study and clinical considerations. Neurosurg Focus 19:E5, 2005. 4. Dallan I, Lenzi R, Bignami M, Battaglia P, SellariFranceschini S, Muscatello L, Seccia V, Castelnuovo P, Tschabitscher M: Endoscopic transnasal anatomy of the infratemporal fossa and upper parapharyngeal regions: correlations with traditional perspectives and surgical implications. Minim Invasive Neurosurg 53:261-269, 2010. 5. Falcon RT, Rivera-Serrano CM, Miranda JF, Prevedello DM, Snyderman CH, Kassam AB, Carrau RL: Endoscopic endonasal dissection of the infratemporal fossa: anatomic relationships and importance of eustachian tube in the endoscopic skull base surgery. Laryngoscope 121:31-41, 2011. 6. Hartnick CJ, Myseros JS, Myer CM 3rd: Endoscopic access to the infratemporal fossa and skull base: a cadaveric study. Arch Otolaryngol Head Neck Surg 127:1325-1327, 2001. 7. Hofstetter CP, Singh A, Anand VK, Kacker A, Schwartz TH: The endoscopic, endonasal, transmaxillary transpterygoid approach to the pterygopalatine fossa, infratemporal fossa, petrous apex, and the Meckel cave. J Neurosurg 113: 967-974, 2010. 8. Iaconetta G, Fusco M, Cavallo LM, Cappabianca P, Samii M, Tschabitscher M: The abducens nerve: microanatomic and endoscopic study. Neurosurgery 61 (3 Suppl):7-14 [discussion 14], 2007. 9. Kassam AB, Gardner P, Snyderman C, Mintz A, Carrau R: Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the clivus, petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus 19:E6, 2005. 10. Kassam AB, Prevedello DM, Carrau RL, Snyderman CH, Thomas A, Gardner P, Zanation A, Duz B, Stefko ST, Byers K, Horowitz MB: Endoscopic endonasal skull base surgery: analysis of complications in the authors’ initial 800 patients. J Neurosurg 114:1544-1568, 2011.

1. Bhatki AM, Carrau RL, Snyderman CH, Prevedello DM, Gardner PA, Kassam AB: Endonasal surgery of the ventral skull base—endoscopic transcranial surgery. Oral Maxillofac Surg Clin North Am 22:157-168, 2010.

11. Kassam AB, Thomas A, Carrau RL, Snyderman CH, Vescan A, Prevedello D, Mintz A, Gardner P: Endoscopic reconstruction of the cranial base using a pedicled nasoseptal flap. Neurosurgery 63 (1 Suppl 1):ONS44-ONS52 [discussion ONS52-53], 2008.

2. Cavallo LM, Cappabianca P, Galzio R, Iaconetta G, de Divitiis E, Tschabitscher M: Endoscopic transnasal approach to the cavernous sinus versus transcranial route: anatomic study. Neurosurgery 56 (2 Suppl):379-389 [discussion 379-389], 2005.

12. Kassam AB, Vescan AD, Carrau RL, Prevedello DM, Gardner P, Mintz AH, Snyderman CH, Rhoton AL: Expanded endonasal approach: vidian canal as a landmark to the petrous internal carotid artery. J Neurosurg 108: 177-183, 2008.

3. Cavallo LM, Messina A, Gardner P, Esposito F, Kassam AB, Cappabianca P, de Divitiis E, Tschabitscher M: Extended endoscopic endonasal approach to the pterygopalatine fossa: anatomical

13. Kassam A, Snyderman CH, Carrau RL, Gardner P, Mintz A: Endoneurosurgical hemostasis techniques: lessons learned from 400 cases. Neurosurg Focus 19:E7, 2005.

14. Kassam A, Snyderman CH, Mintz A, Gardner P, Carrau RL: Expanded endonasal approach: the rostrocaudal axis. Part I. Crista galli to the sella turcica. Neurosurg Focus 19:E3, 2005. 15. Mousa Sadr Hosseini S, Razfar A, Carrau RL, Prevedello DM, Fernandez-Miranda J, Zanation A, Kassam AB: Endonasal transpterygoid approach to the infratemporal fossa: correlation of endoscopic and multiplanar CT anatomy. Head Neck 34: 313-320, 2012. 16. Prevedello DM, Ditzel Filho LF, Solari D, Carrau RL, Kassam AB: Expanded endonasal approaches to middle cranial fossa and posterior fossa tumors. Neurosurg Clin N Am 21:621-635, 2010. 17. Prevedello DM, Pinheiro-Neto CD, FernandezMiranda JC, Carrau RL, Snyderman CH, Gardner PA, Kassam AB: Vidian nerve transposition for endoscopic endonasal middle fossa approaches. Neurosurgery 67 (2 Suppl Operative): 478-484, 2010. 18. Rivera-Serrano CM, Terre-Falcon R, FernandezMiranda J, Prevedello D, Snyderman CH, Gardner P, Kassam A, Carrau RL: Endoscopic endonasal dissection of the pterygopalatine fossa, infratemporal fossa, and post-styloid compartment. Anatomical relationships and importance of eustachian tube in the endoscopic skull base surgery. Laryngoscope 120 (Suppl 4):S244, 2010. 19. Snyderman CH, Pant H, Carrau RL, Prevedello D, Gardner P, Kassam AB: What are the limits of endoscopic sinus surgery? The expanded endonasal approach to the skull base. Keio J Med 58: 152-160, 2009. 20. Theodosopoulos PV, Guthikonda B, Brescia A, Keller JT, Zimmer LA: Endoscopic approach to the infratemporal fossa: anatomic study. Neurosurgery 66:196-202 [discussion 202-203], 2010. 21. Valentine R, Wormald PJ: Controlling the surgical field during a large endoscopic vascular injury. Laryngoscope 121:562-566, 2011. 22. Vescan AD, Snyderman CH, Carrau RL, Mintz A, Gardner P, Branstetter BT, Kassam AB: Vidian canal: analysis and relationship to the internal carotid artery. Laryngoscope 117:1338-1342, 2007.

Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 19 September 2013; accepted 25 July 2014 Citation: World Neurosurg. (2014) 82, 6S:S121-S129. http://dx.doi.org/10.1016/j.wneu.2014.07.036 Journal homepage: www.WORLDNEUROSURGERY.org

WORLD NEUROSURGERY 82 [6S]: S121-S129, DECEMBER 2014

Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.

www.WORLDNEUROSURGERY.org

S129

Endonasal endoscopic approaches to the paramedian skull base.

To describe the technical and anatomic nuances related to endoscopic endonasal approaches (EEAs) to the paramedian skull base...
2MB Sizes 0 Downloads 7 Views