記住我
OPERATIVE NUANCES: STEP BY STEP (VIDEO SECTION)
Year : 2023 | Volume
: 71
| Issue : 5 | Page : 888-892
Endonasal Endoscopic Trans-pterygoid Approach for Modified Jeffersons Type D V3 Schwannoma
Ravi Sankar Manogaran1, Kanika Arora1, Manjul Muraleedharan1, Prince Kumar2, M Aleesha2, Ramandeep Singh Virk2
1 Neuro Otology Unit, Department of Neurosurgery, C-Block, SGPGIMS, Raebareli Road, Lucknow, Uttar Pradesh, India
2 Department of Otolaryngology, Head and Neck Surgery, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
Correspondence Address:
Ramandeep Singh Virk
Department of Otolaryngology, Head and Neck Surgery PGIMER, Chandigarh - 160 012
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0028-3886.388053
How to cite this article:Key Message: Combining trans-maxillary modified Denker's approach with the trans-pterygoid approach provides safe and reliable access to the skull base as lateral as foramen ovale and infra-temporal fossa.
Trigeminal schwannomas (TSs) are the most common non-vestibular schwannomas with a peak incidence in the 4–5th decade. They are benign and moderately vascular lesions, and their presentation and extension into the likes of superior orbital fissure, foramen ovale, rotundum, petrous apex, and middle or posterior cranial fossa depend on the nerve root/s involved.[1]
The excision of these tumors presents a unique challenge as they involve one of the most complex areas of human body – the cranium and the cranial base. With a tightly packed neurovascular network, any surgical manipulation here needs an extensive knowledge of the anatomy and finesse in dissection.
The world of surgery now expands around the key concept of being “minimally invasive”. Lesions of the skull base which required craniotomies are at present being successfully removed without them, thanks to the advent of neuro-navigation and higher end endoscopes. We hereby discuss a totally endonasal endoscopic approach to an excision of modified Jefferson's Type D V3 schwannoma. The exposure was achieved by an extended endonasal route by taking a trans-pterygoid approach. A discussion on case selection and achieving safe and complete resection is also attempted.
Objectives
To demonstrate the feasibility and safety of a minimally invasive extended endonasal endoscopic trans-maxillary approach, specifically the trans-pterygoid approach, to Meckel's cave and infratemporal fossa, by achieving complete excision of a modified Jefferson's Type D V3 schwannoma.
ProcedureCase details
A 46-year-old female with no known co-morbidities or addictions presented with complaints of a perceived decrease in sensation over the right lower half of the face for around 6 months. She also had occasional tingling-associated jaw movements. The patient had complaints of weakness or difficulty in chewing. The examination showed a decrease in sensation to both fine and coarse touch as tested on the skin over the right half of the mandible. There was no history of trauma, with dental, oral, or nasal procedures. The rest of the cranial nerve examination was normal. The patient was evaluated with contrast-enhanced magnetic resonance imaging (MRI). T2W MRI coronal sections showed a dumbbell-shaped hetero-intense lesion occupying the supero-medial part of right infratemporal fossa with widening of foramen ovale and an intracranial extradural component involving the Meckel's cave area. The lesion was heterogeneously enhancing in T1W contrast images. In view of the radiological features, location, and clinical features, a working diagnosis of schwannoma was made, and after adequate counseling and obtaining consent, the patient was planned for the procedure.
Surgical technique
The video shows a V3 schwannoma (Modified Jefferson's type D), excised endoscopically using the endo-nasal trans-pterygoid approach with the assistance of plasma ablation. It helps us understand endoscopic relationships and landmarks in the skull base to obtain wide exposure of the infratemporal fossa and Meckel's cave area without injury to major neurovascular structures.
The patient was kept in supine position with the head flexed at 30 degrees and slightly tilted toward the left. Adequate decongestion of bilateral nasal cavities was done with adrenaline-soaked dehydrated hydroxylated polyvinyl acetate (MerocelTM). Sphenoid ostium was identified on the left side. A Naso-septal flap (Hadad's flap) taking supply from the left naso-septal branch of the left sphenopalatine artery was harvested and kept in the nasopharynx. The posterior part of the septal cartilage and the perpendicular plate of the ethmoid along with the rostrum of sphenoid were removed (posterior septectomy). A septal flap was raised on the right side – incisions were given posteriorly at the level of sphenoid ostium superiorly and then inferiorly (the septal mucosal incisions). This anteriorly based septal flap from the right side was then rotated over the edge of posterior septectomy and then brought anteriorly in the left nasal cavity and was then sutured to the septal mucosa left after the Hadad's flap was raised. This reverse Hadad's flap thus covers the cartilage bared at areas of posterior septectomy and the donor site of Hadad's creating a post of cavity having a completely mucosa-covered remnant septum.
A complete anterior and posterior ethmoidectomy was then done on the right side. Right sphenoid ostium was identified. Inferior turbinate on the right side was removed. An endoscopic medial maxillectomy via modified Denker's approach was done. This was done by identifying the pyriform aperture initially and then raising a subperiosteal flap over the anterior maxillary wall up to the infra-orbital foramen. Using a cutting burr, the anterior, anterolateral, and medial walls of maxilla were removed. Inferiorly, the bony edges were flushed with the floor of maxilla. The nasolacrimal duct which comes into view while the medial wall was removed was given sharp cut as superior as possible and removed. A wide sphenoidotomy was done bilaterally.
The ascending portion of the palatine bone and the posterior wall of maxilla were removed using drill and Kerrison's punch, exposing the contents of pterygopalatine fossa (PPF) and the medial part of the infra-temporal fossa (ITF). The right sphenopalatine artery was identified in the pterygopalatine fossa and was ligated. The contents of the PPF were then lateralized using plasma ablation. The course of infra-orbital nerve was then identified along with its exit point from the foramen rotundum, which served as a landmark for the middle cranial fossa (MCF).
Using a diamond and a cutting burr, the pterygoid wedge and pterygoid body were drilled out. The Vidian Nerve and V2 were identified in their respective foramina exiting the skull base. The bony segment between these two were drilled out, exposing the dura of middle cranial fossa. Going laterally over the skull base, a widened foramen ovale with tumor coming out of it was identified. The bone around the foramen ovale was carefully drilled out, and complete exposure of foramen ovale was achieved. This was then flushed with the previously exposed part of the MCF dura.
The contents of the ITF were then carefully dissected off the greater wing of sphenoid, and the tumor was delineated. The tumor in the ITF was then partially decompressed to ease the extra-capsular dissection and delivery. Using a ring curette, tumor from the foramen ovale was dissected out. The intracranial extradural portion occupying the Meckel's cave region was debulked using ring curette and curved suction. Surgicel was kept in the intra-cranial cavity, and hemostasis was achieved. The skull base was closed using fat and Surgicel and then covered with the already raised naso-septal flap. Nasal cavity was packed using MerocelTM packs.
Outcomes
The nasal packs were removed after 48 hours. The patient had an extremely smooth post- operative course. There were no complaints of post-op bleeding, headache, fever, CSF leak, or any orbital symptoms. The post-operative CT showed near total removal of the tumor.
Paraesthesia persisted over the right lower jaw area, but the tingling on jaw movements disappeared. The nasal cavity healed well with good epithelialization and minimal to no crusting at 6 months post-op follow-up [Figure 1].
Video link
QR Code:
Video timeline with audio transcript
0.00s to 0.14s: Title, Declaration, and Short History
0.15s to 0.24s: T2W MRI Coronal sections showing dumbbell-shaped hetero-intense lesion occupying the supero-medial part of right infratemporal fossa with widening of foramen ovale and the intracranial extradural component involving the Meckel's cave area. The lesion was heterogeneously enhancing in T1W contrast images.
0.25s to 0.38s: Left nasal cavity decongestion using adrenaline-soaked dehydrated hydroxylated polyvinyl acetate (MeroceleTM) sponges. Sphenoid ostium was identified.
0.39s to 0.58s: Left-side naso-septal flap based on the naso-septal branch of the left sphenopalatine artery harvested and kept in the nasopharynx.
0.59s to 1.09s: Deviated part of septal cartilage and part of the perpendicular plate of ethmoid along with rostrum of sphenoid were removed.
1.10s to 1.27s: Right-side septal flap was identified and incisions were given at the level of sphenoid ostium posteriorly along with inferior and superior septal mucosal incisions over the posterior part of septum, and this was used to cover the exposed cartilage of the donor site on the left side (reverse Hadad's flap).
1.28s to 1.31s: Visualization of sphenoid keel after posterior septectomy.
1.32s to 1.49s: Right-side middle turbinate was partially resected.
1.50s to 2.09s: Using plasma ablation and a micro-debrider, right-side anterior ethmoidectomy and complete posterior ethmoidectomy were done. Right sphenoid ostium was identified.
2.10s to 2.15s: Inferior turbinate on the right side was removed.
2.16s to 2.33s: Endoscopic endonasal medial maxillectomy (modified Denker's) was started with identification of pyriform aperture and elevation of subperiosteal flap over the anterior wall of maxillary sinus till the infraorbital foramen.
2.34s to 2.53s: Using a cutting burr, the anterior part of the medial wall of the maxilla, the anterior, and the part of antero-lateral wall of maxilla were drilled out. Inferiorly, the bony edges were flushed with the floor of the maxilla.
2.54s to 3.00s: Nasolacrimal duct was identified, and a sharp cut was made.
3.01s to 3.09s: Bilateral wide sphenoidotomy done.
3.10s to 3.33s: The ascending portion of the palatine bone and the postero-medial wall of the maxillary sinus was removed using drill and Kerrison's punch. The contents of pterygopalatine fossa and the medial part of the infratemporal fossa were exposed.
3.34s to 3.44s: Hemostasis was achieved using the plasma ablation technique.
3.45s to 3.55s: Ligation of the sphenopalatine artery was done.
3.56s to 4.09s: Pterygopalatine fossa contents were lateralized using plasma ablation.
4.09s to 4.18s: The course of infraorbital nerve and its exit point from the foramen rotundum were clearly demarcated, and this was used as the landmark for the middle cranial fossa.
4.18s to 4.42s: Using diamond and cutting burr, the pterygoid wedge and pterygoid body were drilled out.
4.42s to 4.45s: Transected Vidian nerve was demarcated.
4.45s to 5.06s: The bony segment between the V2 and the Vidian was drilled out, and the middle fossa dura was identified by drilling the part of the greater wing of sphenoid.
5.06s to 6.04s: Widened foramen ovale with tumor coming out was identified. The bone around the foramen ovale was carefully drilled out, and complete exposure of the foramen ovale was done. This was flushed with the part of the middle cranial fossa dura.
6.04s to 6.38s: Infratemporal fossa contents were dissected off from the greater wing of sphenoid to delineate the tumor.
6.38s to 7.06s: The tumor in the infratemporal fossa was partially decompressed to ease the extra-capsular dissection and the tumor delivery.
7.06s to 7.25s: Using ring curette, tumor from the foramen ovale was dissected out.
7.25s to 8.06s: The intracranial extradural portion occupying the Meckel's cave region was debulked using ring curette and curved suction.
8.06s to 8.28s: Surgicel was kept in the intracranial cavity, and hemostasis was achieved.
8.28s to 8.38s: Fat and Surgicel were kept in the infratemporal fossa area and were covered with the naso-septal flap.
8.38s to 8.46s: Post-op CT showing near total removal of the tumor.
8.46s to 8.50s: Slide showing alternative approaches used in V3 schwannoma management.
8.48s to 8.54s: Slide showing pros and cons of the endoscopic endonasal approach.
8.54s to 8.59s: References.
Pearls and pitfalls
A combination of modified Denker's with the trans-pterygoid approach gives good exposure of the Meckel's cave and infratemporal fossa.
The endoscopic approach to Type D schwannomas provides the advantage of avoiding a craniotomy and also obliviates the need to retract the temporal lobe. Compared to an open approach, the chances of problematic CSF rhinorrhea and ICA injury are more in endoscopic approaches. To avoid this, the dissection should be meticulous and the landmarks, especially the internal carotid artery, Vidian nerve, and dura, should be positively identified.
The use of reverse Hadad's flap helps in faster healing with minimal post-operative nasal crusting in trans-nasal approaches to the anterior skull base.
DiscussionTSs are the most common non-vestibular schwannomas of the body with the ophthalmic division being the most common site of origin. The intracranial extent of the tumor is decided by its point of origin. The ones arising from trigeminal root, ganglia, and divisions are intradural, interdural, and extradural, respectively.[1]
The classifications, mainly Jefferson's,[2] Day and Fukushima's modified version of the Jefferson classification system,[3] and Yoshida and Kawase,[4] are based on the position and extent of the tumor. As modified Jefferson's considers the tumors of ITF with minimal intracranial extension separately, we have found it useful in the skull base surgery practice. Constant facial pain is commonly seen in tumors of the middle fossa due to the relatively fixed position of the Gasserian ganglion in the petrous bone. But the facial pain is intermittent in posterior fossa schwannomas as they cause compression of trigeminal roots which are mobile.[5]
The 'one plan fits all' approach is now being replaced by 'to each tumor its own' treatment plans. As for most of other benign lesions, the patient's quality of life dictates a treatment plan to minimize morbidity and maximize safety.
Management of these benign lesions includes wait and watch with regular follow-up in asymptomatic small tumors, biopsy/subtotal excision in cases with atypical features, rapid progression, or if the diagnosis of TG is questionable. This can be done with a simple percutaneous biopsy of Meckel cave with minimally invasive routes under fluoroscopic guidance.[6] One of the techniques described for this percutaneous biopsy involves “entering 2.5 cm lateral to the labial commissure using a needle which is then advanced through the cheek, medial to the ramus of the mandible, all the way to the inferior skull base where the foramen ovale is penetrated”. This is utilized mainly for lesions involving the cave or V3 (mandibular division of trigeminal nerve). Alternatively, a biopsy can also be done via an endoscopic endonasal approach, which is more tedious but gives wider exposure to all divisions of the nerve and can be changed intra-procedure from a simple biopsy to a tumor resection if necessary.
The attempts at surgical excision which warrant the same due to size, location, or symptoms can be either open or endoscopic. The open approaches are based on where the tumor is located.[7],[8] While “retrosigmoid craniotomy” and “Kawase's approach” are used for tumors predominantly in the posterior cranial fossa (PCF), in predominantly middle cranial fossa tumors, a purely anterior approach becomes a viable option via either a “pterional or FTOZ (frontotemporal-orbitozygomatic) craniotomy”.
Radiation therapy in the form of stereotactic radiosurgery (SRS) or fractionated radiotherapy is also utilized as a non-surgical option. While SRS is used for small-to- moderate-sized tumors with intact cranial nerve function, for larger tumors, it can be used as an adjunct after initial resection. Fractionated radiotherapy on the other hand can be utilized for large tumors that are at higher risk for microsurgical resection and are not candidates for SRS.[8]
The paramedian and parasellar location makes the Meckel's cave accessible via a trans-nasal endoscopic approach.[8] The tumor can displace the carotid artery in any direction. This along with an increased incidence of CSF leak in the post-operative period makes a thorough study of the pre-operative radiology essential before attempting a trans-nasal excision of schwannoma. The absence of retraction of the brain surface along with a heads-on view of the infratemporal fossa makes this approach perfect for tumors predominantly occupying the ITF with minimal intracranial extension.
ConclusionFor modified Jefferson's Type D schwannomas, an extended trans-nasal endoscopic approach in the form of a trans-pterygoid approach can provide satisfactory exposure of the vital structures, helping in near complete excision of the lesions in infratemporal fossa, foramen ovale, and Meckel's cave area. The approach is minimally invasive with minimal post-operative sequelae and problematic complications. A good grasp over the endoscopic anatomy of the anterior skull is a pre-requisite.
Acknowledgment
We are extremely thankful to the patient who trusted her selves in our care and kindly consented for the publication of the same in the greater cause of kindling a scientific discussion. Her willingness to share her medical journey and provide informed consent for publication has been instrumental in advancing medical knowledge and improving patient care. This video was presented in the North American Skull Base Society 32nd Annual Meeting 2023 at Florida, USA. The treating team is extremely grateful for the same.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
留言 (0)