The Medial Transorbital Approach in Cranioendoscopic Skull Base Tumor Resections for Locally Advanced Tumors

Abstract

Background:

Orbital structure preservation and avoidance of facial incisions without compromising oncological outcome are key to maintaining function and quality of life in locally advanced sinonasal tumor surgery. A transorbital approach at our institution has proven invaluable during cranioendoscopic skull base tumor resections and there are few descriptions of this in the literature.

Methods:

An IRB-approved retrospective chart review was conducted at a tertiary cancer center for patients between 2020 and 2022 undergoing cranioendoscopic tumor resections utilizing a transorbital approach. Data collected included histopathology, sinus origin, disease extent, stage, operative details, length of stay, neo-adjuvant treatment and adjuvant treatment. Recurrence, survival, and complication rates were assessed.

Results:

Four patients were identified for inclusion, including a SMARCB1-deficient carcinoma, esthesioneuroblastoma, squamous cell carcinoma and meningioma. All patients had resection of gross and microscopic disease with preservation of orbital contents. Post-operatively, one patient had mild diplopia on inferior gaze, all other patients had normal vision. Median follow-up was 9.5 months. One patient had recurrence of disease intracranially.

Conclusions:

The cranioendoscopic approach with a medial transorbital incision has multiple benefits. It avoids the need for a Weber-Ferguson incision with associated facial scar, allows for early intra-operative assessment for orbital invasion using tactile feedback and safe dissection of disease while protecting the globe and rectus muscles. This leads to preservation of eye function while ensuring an oncological resection. Other advantages include ligation of the anterior ethmoid artery and access for reconstruction of the medial orbital wall.

Introduction

The approach to orbital invasion in locally advanced sinonasal tumors remains a surgical challenge during cranioendoscopic skull base tumor resection. The increasing use of endoscopic rather than open surgery to avoid facial incisions means additional approaches might be necessary to confirm or rule out orbital involvement. A transorbital or transcaruncular approach to the medial orbital wall has been described for non-malignant pathology, such as thyroid-related orbitopathy, drainage of orbital abscesses, mucocele marsupialization, medial rectus entrapment, and schwannoma.^1–3 Small case series have also described its use in sinonasal carcinoma invading extraconal orbital fat.^3,4 At our institution, we have utilized the medial transorbital approach in more advanced tumors involving the skull base that require a cranioendoscopic approach. The objectives of this study were to: (A) Describe the medial transorbital approach in cranioendoscopic surgery for locally advanced tumors; (B) Discuss the advantages and limitations of the approach; (C) Provide a limited description of outcomes in a small series.

Methods

After receiving Institutional Review Board approval, we conducted a retrospective chart review at a tertiary cancer center for patients undergoing cranioendoscopic tumor resections using a transorbital approach between 2020 and 2022. All patients underwent a cranioendoscopic approach including bifrontal craniotomy, transnasal endoscopic resection, and transorbital incision, performed by neurosurgical, head and neck, and ophthalmology teams. Data collected included histopathology, stage, anatomical extent of disease, neo-adjuvant treatment, surgical approach, length of surgery, length of stay, complications, adjuvant treatment, recurrence, and follow-up.

Surgical Technique

Generally, transnasal endoscopic tumor dissection and craniotomy are performed first to address sinonasal and intracranial aspects of the tumor, until the medial and inferior orbital walls are isolated. A lateral canthotomy and inferior cantholysis can then be made to aid exposure during the medial orbital dissection. An inferior margin traction suture is placed using 6-0 silk and the medial canthus is then identified. Curved Westcott tenotomy scissors are used to make the transcaruncular incision between the caruncle and plica semilunaris, approximately 20mm in length (Figure 1A and 2A). This incision can subsequently be lengthened through the conjunctiva to the superior and inferior fornix for adequate exposure. The dissection to the medial orbital wall is performed with the aid of a rake to retract the caruncle and a malleable retractor to protect the globe. The periosteum can then be inspected to identify any tumor invasion into the orbit. A bridle suture of the medial rectus is routinely used to retract and protect vital structures lateral to the medial rectus. For this, a 6-0 silk suture is used to capture the anterior aspect of the medial rectus approximately 10mm posterior to its insertion. This maneuver is particularly important if the tumor is invading through the periosteum. After periosteal incision, dissection can be continued in a subperiosteal plane, utilizing fine suction and a malleable retractor (Figure 1B and 2B). Neurosurgical patties are employed under the malleable retractor to help retract fat. The anterior and posterior ethmoids are routinely cauterized to maintain intranasal hemostasis. Frozen specimens can be sent along with dissection of any orbital tumor, which takes place in conjunction with the endoscopic surgeon medially and neurosurgeon superiorly. After the resection, acellular dermal matrix (e.g., AlloDerm^™: LifeCell Corp, Branchburg, NJ) may be used for reconstruction of the medial orbital wall. The conjunctival incision can be left to heal with secondary intention or closed with interrupted sutures. Finally, the lateral canthal tendon can be reapproximated with Vicryl (Ethicon Inc, Somerville, NJ) suture and the dermis can be closed.

Figure 1.

A: Artistic depiction of transcaruncular incision marked between the caruncle and plica semilunaris.

B: Artistic depiction of medial orbital wall exposure and assessment for tumor invasion. The caruncle is retracted with a rake and orbital contents protected with a malleable retractor.

Figure 2.

A: Preoperative marking of transcaruncular incision between the caruncle and plica semilunaris.

B: Intraoperative image of caruncle retraction with a rake and orbital contents protected with a malleable retractor.

Results

We identified 4 patients for inclusion, with a median age of 37 years (range 21-65 years). Table 1 shows disease characteristics and treatment. The median transorbital approach was used in a range of tumors including SMARCB1-deficient carcinoma, esthesioneuroblastoma, squamous cell carcinoma, and meningioma. Disease origin was ethmoid or frontal sinus and all patients had locally advanced disease. Median total surgical time was 9 hours and 38 minutes (range 7 hours 50 minutes to 10 hours 53 minutes) and median length of stay was 8.5 days (range 7-22). Median follow-up was 9.5 months (range 7-25 months).

Table 1:

Patient, tumor, and treatment characteristics

Patient	Diagnosis	Sinus origin	Disease extent	Stage	Neoadjuvant treatment	Adjuvant treatment
1	SMARCB1-deficient carcinoma	Ethmoid	Eroding lamina; Intracranial	T4bN0M0	Docetaxel/cisplatin/5FU	Etoposide/cisplatin; proton radiotherapy
2	Esthesioneuroblastoma	Ethmoid	Intracranial	T4bN1M0	Etoposide/cisplatin	Cisplatin; proton radiotherapy
3	Squamous cell carcinoma	Ethmoid	Eroding lamina; Intracranial	T3N0M0	Cisplatin/docetaxel	Radiotherapy
4	Meningioma	Frontal	Extraconal periorbital fat; cribriform plate	-	-	-

Case 1: SMARCB1-Deficient Carcinoma

A 33-year-old male presented with 2 months of right nasal obstruction. Flexible nasendoscopy revealed a polypoid intranasal lesion. Imaging and biopsy confirmed a T4bN0M0 right ethmoid SMARCB1 deficient sinonasal carcinoma eroding the septum and cribriform plate into the frontal lobes bilaterally. The tumor appeared to erode the lamina papyracea on imaging (Figure 3A). The patient underwent 2 cycles of induction docetaxel/cisplatin/5FU (TPF), resulting in some regression of the intranasal tumor component with growth of the intracranial component. Subsequent cranioendoscopic surgery included bifrontal craniotomy, frontal lobe resection, cranialization of the frontal sinus, endoscopic transnasal resection, and medial orbitotomy. The medial orbitotomy incision between the caruncle and plica semilunaris, extended superiorly and inferiorly, allowed broad exposure of the medial orbital wall periosteum. A plane was noted between the tumor and periorbita, allowing for the tumor to be dissected free from the orbital contents. The skull base defect was reconstructed with a pericranial flap, AlloDerm, and fibrin sealant. The patient was discharged on postoperative day 22 at his neurological baseline. He received adjuvant treatment of etoposide, cisplatin, and proton radiotherapy. He was free from disease 3 months posttreatment with no ophthalmic complications.

Figure 3.

A: T2 axial MRI of right ethmoid SMARCB1 deficient sinonasal carcinoma eroding the septum, lamina and encroaching on the orbit.

B: Coronal computerized tomography (CT) scan with contrast showing a Kadish D right ethmoid esthesioneuroblastoma eroding the right orbital wall into the medial extraconal orbit

C: Axial CT of the left ethmoid SCC eroding lamina papyracea

D: Axial CT of bifrontal meningioma eroding the cribiform plate into the sinonasal cavity and right orbit

Case 2: Esthesioneuroblastoma

A 41-year-old male presented with progressive right nasal obstruction, epiphora, and cervical lymphadenopathy. Subsequent cross-sectional imaging and biopsy confirmed T4bN1M0 esthesioneuroblastoma (Kadish stage D) of ethmoid origin. He was treated with 2 cycles of neoadjuvant etoposide/cisplatin with no response, before proceeding to staged surgery: right parotidectomy and levels II-V neck dissection, followed by cranioendoscopic resection and right medial orbitotomy. Preoperative computerized tomography (CT) (Figure 3B) showed esthesioneuroblastoma invading through the right lamina papyracea into the medial extraconal orbit. After transnasal endoscopic excision of the sinonasal component, a Caldwell-Luc incision was required to clear remaining tumor from the floor of the maxillary sinus. The tumor had eroded the right lamina papyracea so a medial transorbital approach was used to ensure complete excision and preserve the periorbita. Lateral canthotomy and inferior cantholysis aided in the mobilization of the globe and access medially. An incision between the caruncle and plica semilunaris was carried to the superior and inferior fornix, extending along the medial aspect of the lower lid to adequately expose the periosteum of the medial orbital wall. A medial rectus traction suture was placed to assist dissection. The tumor was mobilized from the orbital fat and periorbita partially excised as a margin. The intracranial portion of the tumor was removed via craniotomy and reconstructed with a pericranial flap. The patient was discharged on postoperative day 9 with no ophthalmic complications. Figure 4A and 4B demonstrates postoperative CT with preserved orbital contents and no residual disease. The patient underwent adjuvant cisplatin and proton radiotherapy, with no evidence of recurrence 9 months postoperatively.

Figure 4:

Axial computerized tomography scan with contrast (A) and coronal T1 MRI (B), 7 months post-resection of Kadish D esthesioneuroblastoma. Orbital contents are preserved with no evidence of disease recurrence.

Case 3: Squamous Cell Carcinoma

A 65-year-old male was referred with left ethmoid sinus squamous cell carcinoma that had transformed from inverted papilloma, previously operated on endoscopically at an outside institution. He had undergone 3 cycles of induction cisplatin/docetaxel. Imaging and endoscopic examination demonstrated erosion of the lamina papyracea (Figure 3C) and cribriform plate, with extension into the frontal sinus. The patient underwent cranioendoscopic resection (Figure 5A) and medial transorbital approach. An incision was made between the caruncle and plica semilunaris, followed by lateral canthotomy, inferior cantholysis, and medial rectus bridle suture to aid mobilization. The conjunctival incisions were extended superiorly and inferiorly to access the medial orbital wall. Dissection continued in the subperiosteal plane, and the bone was noted to be hyperostotic and bowed laterally. A small osteotomy was made to aid with complete resection of the intranasal tumor. AlloDerm was used to reconstruct the medial orbital wall defect (Figure 5B). A pericranial flap and vascularized nasoseptal flap were used for the skull base. The patient was discharged on day 7 and underwent adjuvant radiotherapy. He had no evidence of recurrence 6 months postoperatively, with only mild diplopia on inferior gaze that continued to improve.

Figure 5.

A: Intraoperative view of SCC dissection via bifrontal craniotomy

B: Intraoperative transnasal endoscopic view of AlloDerm placement to reconstruct the medial orbital wall

C: Intraoperative image of calvarial graft placement for skull base reconstruction after meningioma resection

Case 4: Atypical Meningioma

A 21-year-old female presented with a 2-year history of headache and subsequent emesis. Her past medical history included retinoblastoma treated with left eye enucleation and adjuvant chemoradiotherapy. On pre-operative imaging the tumor was centered on the right side of the anterior cranial fossa, crossing the midline and eroding through the cribiform plate into the sinonasal cavity and right orbit (Figure 3D). It measured 8.3 x 6.7 cm in greatest coronal and 8.0 x 5.3 in greatest axial dimension, causing midline shift and mass effect. The sinonasal portion extended into the ethmoid sinuses bilaterally, eroded the septum and medial wall of the right maxillary sinus. The lesion extended through the lamina papyracea into the right orbit. The patient underwent a bifrontal craniotomy, transnasal endoscopic approach, medial and lateral orbitotomy. A macroscopic margin was maintained between the frontal lobe and the tumor, which was then cleared off the entire skull base along the cribiform plate, where bilateral defects were identified. The medial orbitotomy incision was made between the caruncle and plica semilunaris, extended superiorly and inferiorly. An extended Harris (lid crease) incision was made to expose the lateral orbital rim and the subperiosteal flap was elevated. Tumor was evident lateral to the optic nerve and superior to the lateral rectus. The orbital portion of the tumor was reflected toward the ethmoid sinus. Endoscopic anterior and posterior ethmoidectomy, posterior septectomy and sphenoidotomy were undertaken and gross total resection of the meningioma was achieved. Nasoseptal flap, split thickness calvarial graft (Figure 5C) and pericranial flap were used for reconstruction. Histopathology confirmed a World Health Organization (WHO) Grade II chordoid meningioma, with no invasion of surrounding brain parenchyma. The patient was discharged on day 8 postoperatively, with normal vision. Recurrence was identified 8 months postoperatively on the floor of the cranial fossa and proton radiotherapy commenced.

Discussion

Orbital invasion is an independent risk factor for disease-specific death and local recurrence in sinonasal malignancy.^5,6 Cross-sectional imaging aids in surgical planning and identifying patients at risk of orbital invasion but is not accurate enough to replace intraoperative assessment in equivocal cases.⁷ The positive predictive value for orbital invasion has been shown to be as low as 48.8% for CT and 47.5% for MRI.⁸ The use of endonasal surgery for advanced sinonasal malignancy has increased in the last decade,⁵ but one of the challenges that remains is the assessment for orbital involvement from a medial aspect. A medial transorbital approach in conjunction with a cranioendoscopic resection maintains the benefit of avoiding a Weber-Ferguson incision while allowing for accurate assessment of the medial orbital wall and periorbita for tumor invasion using tactile feedback. If orbital invasion is identified, orbital exenteration can be avoided if the tumor can be dissected free from orbital fat.⁶ This is achievable via the medial transorbital incision, as demonstrated in Case 3, and allows for early intraoperative decision-making regarding management of the orbit. In our case series, we showed negative margins can be achieved while protecting the globe and rectus muscles, as demonstrated by a return to normal vision and eye movements in 75% (3/4) patients. The remaining patient had only a mild diplopia on downgaze, which continues to improve. The medial transorbital approach is preferable to a Lynch incision as it avoids facial scarring and preservers medial structures such as the canaliculus and medial canthal tendon, which may be disrupted by the Lynch incision.

Further benefits of the medial transorbital approach in cranioendosopic surgery include hemostasis, by allowing for cauterization of the anterior and posterior ethmoid arteries. The transconjunctival incision can also be extended superiorly to aid in the dissection of tumors that extend intracranially or in cases where the neurosurgical dissection of a tumor is encroaching on the superior orbit. Effective medial orbital wall reconstruction can be more easily achieved with this approach, as in Case 4 when AlloDerm was used for reconstruction.

While our case series showed no major complications, the risks of a medial transorbital approach include diplopia from granulation formation, lacrimal injury, medial canthal tendon injury, and medial canthus scarring or disfigurement. Scarring and diplopia can be avoided by keeping the incision medial to the conjunctiva of the globe, and the lacrimal sac should not be encountered with adequate retraction.

One patient with WHO Grade II chordoid meningioma had recurrence in the floor of cranial fossa 8 months post-operatively. The location of recurrent disease indicates that the medial transorbital approach was not contributory to the recurrence. Chordoid meningiomas are known to have high rates of recurrence, with 5- and 10-year progression free survival of 67.5% and 54.4% respectively (9).

Overall comparison of local recurrence rates between our series (25%) and others is limited by heterogeneity of tumor pathology and extent of disease. However, a similar local recurrence rate of 30% (16/54) was found in a series of 54 patients that underwent standard of care open approach orbital preservation surgery (via lateral rhinotomy, Weber-Ferguson or midfacial degloving) in the management of sinonasal malignancy encroaching on the orbit (10). The same series reported post-operative impairment of eye function in 37% (20 of 54) and a nonfunctional eye in 9% (5 of 54), in comparison to one patient with diplopia on downgaze in our series (1 of 4; 25%) (10).

Conclusion

Based on our experience, the cranioendoscopic approach with a medial transorbital incision has multiple benefits in managing locally advanced disease originating from the sinonasal cavity or meninges. It avoids the need for a Weber-Ferguson incision with associated facial scarring and allows for accurate assessment for orbital involvement and safe dissection of disease while protecting the globe and rectus muscles. This leads to preservation of eye function while ensuring an oncological resection.

• Medial transorbital approach is an effective adjunct in advanced sinonasal tumors

• Advantages include early assessment for orbital involvement and no facial scars

• This allows for preservation of orbital function and an oncological resection