Novel Application of Steroid Eluting Stent in Petrous Apex Cholesterol Granuloma

Abstract

Objective  This study describes the safety and efficacy of mometasone furoate eluting stents in the management of petrous apex cholesterol granuloma approached through an endonasal endoscopic route and assesses the restenosis rate.

Methods  Consecutive patients undergoing endoscopic endonasal marsupialization of a petrous apex cholesterol granuloma at a tertiary referral center who had a mometasone furoate eluting stent placed intraoperatively were reviewed in a retrospective fashion. Postoperative endoscopy was used to determine success of surgery and stenting.

Results  Five patients were included in the study, three were primary cases and two patients had revision surgeries performed. The steroid eluting stent was placed successfully and safely in all patients with no dural or vascular injuries. The average follow-up duration was 10.6 months. There was no restenosis in three patients and one patient had an immediate restenosis that was debrided in clinic (revision case). This was patent at the 16 months follow-up. One patient also developed stenosis, 4 months after surgery due to sphenoid sinusitis.

Conclusion  Mometasone furoate eluting stents are safe and effective in the primary management of petrous apex cholesterol granuloma. Further studies are needed to assess their efficacy in revision cases and for long term results.

Introduction

Cholesterol granulomas are the most commonly occurring lesion in the petrous apex. Although traditional approaches required infracochlear, transtemporal, or middle fossa approaches, if the lesion is abutting the posterolateral wall of the sphenoid sinus, it can be approached in a transsphenoidal fashion to drain and marsupialize the lesion into the nasal cavity. The endonasal endoscopic approach to the petrous apex has been well described and is commonly performed today. ^{1 2 3} Despite successful drainage, cholesterol granuloma recurrence has been reported in up to 60% of cases due to difficulties in maintaining a patent opening into the cyst. ⁴

Multiple methods for marsupialization of the cyst with the use of different stenting technique and for different periods of time have been reported. The use of silicone tubes and sinonasal mucosa has been successful in preventing stenosis or occlusion of the cyst opening into the nasal cavity. ^{1 5 6} Simple attempts at curetting the epithelium at the cyst opening to create a permanent ventilation system has also been described. ³ Although the isolated use of silicone T-tube has been reported, Shibao et al described a technique for placement of a vascularized nasoseptal flap into the cyst cavity, followed by an insertion of a 7 mm silicone T-tube to maintain patency. ⁷ In this case series, patency has been reported in up to 24 months after surgery, even when the T-tube was removed.

PROPEL Mini (Intersect; Menlo Park, CA, U.S.A.) is a mometasone furoate eluting stents that provides a method for local drug delivery into the sinonasal cavity to reduce inflammation and promote sinus patency. ^{8 9 10} This study describes the application of Propel stents into cholesterol granuloma openings following a standard endoscopic transsphenoidal approach to promote cyst patency and prevent future recurrence. Although there are three available sizes, the PROPEL Mini stent was used for its favorable shape and size.

Methods

This study was approved by the Institutional Review Board at Duke University Medical Center. The Duke Enterprise Data Unified Content Explorer (DEDUCE) was utilized to identify all patients who underwent endoscopic endonasal decompression a petrous apex granuloma through a endonasal endoscopic approach. Surgeries were performed between January 1, 2014 and December 31, 2017 at Duke University Hospital. Only those who had a Propel stent placed into the cholesterol granuloma cavity were included for review. A retrospective review of electronic medical records was performed to collect data on clinical and operative details, including age, gender, presenting symptoms, size of granuloma, postoperative restenosis, or occlusion, need for revision surgery and resolution of clinical symptoms. Patients with incomplete records were excluded from the review. Descriptive analysis was performed to report the findings.

Surgical Technique

Surgeries were performed by an otolaryngology team (R.A.H. and D.W.J.) in conjunction with endoscopic skull base neurosurgeons (A.R.Z., P.J.C., and A.F.). A transsphenoidal approach was most frequently used to provide endonasal access to the cholesterol granuloma. This approach requires a wide sphenoidotomy with resection of the intersinus septum to create a common sphenoid cavity. Rescue flaps are raised bilaterally to expose the sphenoid rostrum and to preserve the pedicle to the nasoseptal flap in case a cerebrospinal fluid (CSF) leak is encountered. The sphenoid rostrum is resected down to the level of the sphenoid floor and a posterior septectomy is performed to allow for a bi-nostril approach to the petrous apex. The mucosa from the common sphenoid cavity is removed and a 4-mm angled diamond burr is used to enter the petrous apex with assistance from intraoperative image guidance system. The cholesterol granuloma opening is enlarged to facilitate cyst irrigation with normal saline following cyst decompression. The opening is enlarged to be greater than 4 mm to accommodate a PROPEL Mini stent. The stent measures 16 mm in length and as much of the stent as possible is inserted into the cavity to prevent stent displacement ( Fig. 1 ). Gelfoam (Pfizer; New York City, NY, U.S.A.) soaked in thrombin or Nasopore (Stryker; Kalamazoo, MI, U.S.A.) packing is placed around the propel stent without obstructing the outflow tract.

Fig. 1.

(A) PROPEL Mini stent is inserted into the cholesterol granuloma cyst opening following decompression and irrigation of the cyst cavity. (B) Intraoperative image of the cavity opening immediately after placement of the PROPEL mini stent.

Results

The DEDUCE search yielded five patients who underwent propel stent placement following endonasal endoscopic approach for resection of petrous apex cholesterol granuloma. No patients were excluded from this review due to incomplete records. No additional patients underwent endonasal endoscopic surgery for cholesterol granuloma during the study period. The mean age of the patients undergoing surgery was 40.6 years old and 80% of the patients were male. The mean follow-up duration was 10.6 months. Tinnitus was the most common presenting symptom (three-fifth), followed by headaches (two-fifth). Primary surgery was most frequently performed and two patients had secondary revision surgeries performed ( Table 1 ). Primary surgeries for these two patients (patients 2 and 5) were previously performed by the authoring team and did not utilize the PROPEL Mini stent. Patient 2 previously underwent a right temporal craniotomy with partial resection of the petrous tip in 2005, followed by a transnasal microscopic partial resection of the cholesterol granuloma without postoperative stent placement in 2015. Patient 5 also has a history of recurrence following two prior surgeries. Initial surgery was performed in 2009 for which he underwent a right middle fossa craniotomy with resection of the cholesterol granuloma and obliteration with a temporoparietal fascia flap. He subsequently recurred in 2015 and was treated with an endonasal endoscopic transpterygoid/middle fossa approach for resection of the cholesterol granuloma but this required closure with a nasoseptal flap due to a CSF leak secondary to an iatrogenic dural defect along the middle cranial fossa. Endoscopic transsphenoidal approach to the petrous apex was performed in 4 patients as described above, and one patient (patient 5) had an endoscopic infrapetrosal approach performed as a revision surgery ( Fig. 2 ). The PROPEL Mini stent was easily placed into the cyst opening following decompression and irrigation of the cholesterol granuloma with normal saline in all patients. Half of the stent was inside the cyst and the other half was placed outside. There were no incidences involving vascular or dural injuries due to the implant. CSF leaks were not encountered in all patients. Patency of the petrous apex was assessed during routine endoscopic exams performed during postoperative visits. Although complete stenosis or symptom recurrence are the primary criteria for postoperative imaging, postoperative computed tomography (CT) scan was obtained for patient 5 due to his distance precluding a follow-up visit for endoscopy. All patients undergoing primary surgery had no concerns for postoperative stenosis at the 3 months follow-up ( Fig. 3 ). However, Patient 1 developed stenosis of the petrous apiceotomy due to sphenoid sinusitis that was identified at the 7 months follow-up visit. This was noted on endoscopy and required medical management without surgical intervention. A one year repeat magnetic resonance imaging (MRI) did not show any recurrence with a stable size of the lesion and the patient remained asymptomatic. Of the two patients undergoing revision surgery, patient 2 experienced immediate restenosis with a fibrinous layer that required postoperative debridement in clinic at 10 days following surgery. This was identified on endoscopy at the first postoperative visit ( Fig. 4 ). The opening was patent at the16 month follow-up visit and did not require further debridement.

Table 1. Patient demographics.

Patient	Age/sex (y/[M/F])	Presenting symptoms	Revision surgery?	Postop stenosis	Size (cm)	Follow–up (mo)	Resolution of symptoms
1	23/M	Tinnitus, aural fullness, headaches	No	Yes, due to sphenoid sinusitis	4.6 × 2.5 × 3.0	16	yes
2	39/M	Hearing loss, CN VII palsy	Yes, previously in 2009 and 2015	Transient	6.1 × 3.4 × 2.5	16	no
3	26/M	Tinnitus, facial hypesthesia	No	No	3.2 × 2.9 × 3.9	3	yes
4	47/F	Dizziness, headaches	No	No	2.1 × 1 × 0.7	15	partial
5	68/M	Tinnitus	Yes, previously in 2009 and 2015	No	4.3 × 3.7 × 2.5	3	yes

Abbreviations: CN, cranial nerve; F, female; M, male; mo, month; Postop, postoperative.

Fig. 2.

Coronal view of a CT brain with contrast, demonstrating the location of the recurrent cholesterol granuloma requiring an infrapetrosal approach for decompression and mometasone eluting stent placement. CT, computed tomography.

Fig. 3.

(A) Intraoperative image of the cyst opening following PROPEL Mini stent placement in patient 4. (B) This demonstrates postoperative opening at 9 months following surgery as depicted by the black arrow. (C) It is a noncontrast axial CT view demonstrating the cholesterol granuloma (single arrow) and the internal carotid artery (double arrow) in relation to the sphenoid sinus. CT, computed tomography.

Fig. 4.

(A) Fibrinous layer forming over the PROPEL stent at 10 days postoperative follow–up; (B) the fibrinous layer was easily debrided using a suction in clinic reestablishing the cyst patency. (C) Final cyst opening at 16 months follow-up.

Discussion

Cholesterol granulomas can be easily accessed through an endoscopic transsphenoidal approach to the petrous apex when they abut the posterolateral wall of the sphenoid. Safe entrance into the cholesterol granuloma through the petrous apex can be achieved using anatomical landmarks with the help of intraoperative image guidance and the cyst opening must be maintained to prevent reaccumulation, symptom recurrence, and need for further interventions. Several methods to maintain patency of the opening have been previously described, including scraping of the epithelium, use of nasoseptal flaps, silastic tubes, and nasoseptal flaps with silicon T-tubes. ^{1 5 6} The use of steroid eluting stent to effectively treat cholesterol granulomas have not been previously described.

Eytan et al performed a systemic review of surgical outcomes following endoscopic management of petrous apex cholesterol granulomas. ¹¹ The review of 53 patients revealed 20% restenosis rates at a mean follow-up of 20 months and overall recurrence rate of 7.5%, despite 45.1% rate of postoperative stent use. A nonsignificant difference of symptomatic cyst recurrence rate was noted with (10.7%) and without (4.3%) the use of postoperative stenting, but one must consider that restenosis can be asymptomatic and may be conservatively managed. To improve postoperative outcomes, this pilot study demonstrates the feasibility of using PROPEL Mini mometasone eluting stents to facilitate surgical management of petrous apex cholesterol granulomas. These stents have been widely accepted in the field of rhinology since its introduction in 2011.

PROPEL Mini stent provides a rigid support structure to maintain cyst patency while delivering mometasone furoate to local tissues in contact with the stent. This is currently prescribed for use in the sinonasal cavity to diminish the incidence of postoperative stenosis within the nasal cavity, and to reduce the need for postoperative interventions. ¹² Its use in the treatment of cholesterol granuloma offers several advantages: (1) The stent is self-dissolving and provides rigid structural support for 30 to 45 days allowing adequate time for epithelization of the cyst opening. No further manipulation of the cyst opening is required which may cause local trauma, inflammation, and subsequent stenosis. (2) The stent placement does not add significant operative time and can be easily placed under direct visualization, with minimal manipulation. (3) Delivery of mometasone furoate can potentially reduce circumferential inflammation around the cyst opening to prevent stenosis. (4) There are no significant postoperative sequelae secondary to stent placement, unlike nasoseptal flaps which can cause obstructive crusting requiring serial debridement, or silastic stents which can cause local granulation tissue and requires eventual removal, typically after a prolonged period.

Although this study is limited in size and long term follow-up, it provides feasibility data supporting the potential use of mometasone furoate eluting stents in the surgical management of petrous apex cholesterol granuloma. Long-term outcome data are limited in this study, as our protocol is established for patients to return for follow-up at 1 week, 4 weeks, and then every 12 weeks. However, follow-up is sometimes limited due patient's distance from our facility, precluding routine surveillance visits. In return, an open line of communication is provided for patients in case of symptom recurrence requiring further evaluation. Despite this limitation, the study demonstrates that the PROPEL Mini stent can be safely deployed in petrous apiceotomies, with inherent characteristics that make it an ideal medium for use as a postoperative stent. Future studies are required to further assess the safety and efficacy profile of PROPEL Mini stents that was demonstrated through this case series.

Conclusion

Mometasone furoate eluting Propel stents may be a safe, effective alternative to silastic stents, and nasoseptal flaps to maintain cyst openings following endoscopic endonasal surgery. These stents can be easily placed without difficulty and no intraoperative and postoperative complications were encountered in all patients. Future studies are required to determine their efficacy in providing a patent opening over a prolonged period.