gms | German Medical Science

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge
7th Congress of the European Skull Base Society held in association with
the 13th Congress of the German Society of Skull Base Surgery

18. - 21.05.2005, Fulda, Germany

Vestibular schwannomas: microsurgery after partial removal and stereoradiosurgery

Meeting Contribution

  • Eduard Zverina - Dept. of ORL, Head and Neck Surgery, 1st Faculty of Medicine, Charles University, University Hospital Motol, Prague, Czech Republic
  • Jan Betka - Dept. of ORL, Head and Neck Surgery, 1st Faculty of Medicine, Charles University, University Hospital Motol, Prague, Czech Republic
  • Jiri Skrivan - Dept. of ORL, Head and Neck Surgery, 1st Faculty of Medicine, Charles University, University Hospital Motol, Prague, Czech Republic
  • Jan Kluh - Dept. of ORL, Head and Neck Surgery, 1st Faculty of Medicine, Charles University, University Hospital Motol, Prague, Czech Republic
  • Josef Kraus - Dept. of Pediatric Neurology, 2nd Faculty of Medicine , Charles University, University Hospital Motol, Prague, Czech Republic
  • Jiri Lisy - Dept. of Pediatric Neurology, 2nd Faculty of Medicine , Charles University, University Hospital Motol, Prague, Czech Republic

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge. 7th Congress of the European Skull Base Society held in association with the 13th Congress of the German Society of Skull Base Surgery. Fulda, 18.-21.05.2005. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc05esbs32

DOI: 10.3205/05esbs32, URN: urn:nbn:de:0183-05esbs325

Published: January 27, 2009

© 2009 Zverina et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Abstract

The aim of this work is a comparison of results in two groups: primary radical removal of vestibular schwannoma (VS) and secondary radical removal following unsuccessful partial surgery and/or gamma knife stereoradiosurgery (GKS) and assessing the favorable one. Between 1997 and 2004, 106 patients with VS were operated on, 8 (7.5%) were after previous subtotal/partial resection and/or unsuccessful GKS. All VS from both groups were microsurgically removed by the same retromastoideal approach using intraoperative nerve monitoring. From primarily treated group 96% ended with good or satisfactory n. VII function and in 7.5% with useful hearing; group with previous subtotal partial resection and/or GKS ended without hearing and only in 25% with satisfactory function n. VII. The worst results of management of VS both microsurgically and by GKS are after previous partial resection. Total removal of VS after subtotal/partial resection and/or stereoradiosurgery is much more difficult. The subtotal/partial resection of VS should be therefore avoided. In all operated patients after GKS a living, biologically active tumour has been proved histologically. Only minimal regressive changes have been observed. This finding unambiguously proves that the stereoradiosurgery did not devitalize tumour as expected. Growing tumours (VS) should be treated by a primary radical microsurgery.

Keywords: acoustic neuroma, vestibular schwannoma, gamma knife stereoradiosurgery, stereoradiosurgery, stereotactic radiosurgery


Text

Introduction

There is an overall agreement that growing acoustic neuroma – vestibular schwannoma (VS) should be treated [1], [2], [3], [4], [5], [6], [7]. There is a competition between microsurgical removal and stereotactic radiosurgery – gamma knife stereoradiosurgery (GKS) [8], [9], [10]. Opinions were published that “stereotactic radiosurgery will replace surgical resection as a preferred management strategy for a majority of patients with vestibular schwannomas” or “radiosurgery achieves sterilization of the tumor” or “Radiosurgery proved to be a safe and effective alternative to additional microsurgery in patients in whom the initial microsurgical removal failed. Stereotactic radiosurgery should be considered for all patients who have a regrowth or progression of previously surgically treated vestibular schwannomas” [8], [9], [10]. In the Czech Rep. with its 10 mil. inhabitants, 120 VS occur yearly, i.e. 1.2 VS/100,000 inhabits./year, which corresponds to general statistics [1], [2], [3]. Since 1992 patients are being treated by GKS. According to the statistics of the Czech Neurosurgical Society, in the recent years of 2001–2004 about 60 patients (50% of all) were treated by GKS. Further 50%, mostly large VS, were treated microsurgically. On the contrary, most of small VS are treated by GKS. There is an increasing number, up to 20% of VS, treated by GKS after previous subtotal/partial removal [9]. The aim of this work is a comparison of results in two groups: primary radical removal of VS and secondary radical removal following partial surgery and/or GKS and assessing the favorable one.

Materials and methods

Our study is a retrospective analysis of the group of 106 patients operated in the years 1997–2004. Eight patients (7.5%) were operated on for a growth of VS after previous partial/subtotal resection and/or unsuccessful GKS. Microsurgical radical removal of VS was done in the dept. of ORL, head and neck surgery by the same team of otolaryngologist and a neurosurgeon. The neurosurgical experience consists of over 700 VS operated since the year 1983 [7]. Patients were operated by a retromastoideal posterior fossa approach in a semi-sitting or supine position by standard technique [4], [5], [6], [7], [11], [12]. Previous subtotal/partial resection were done in other depts. Previous GKS were done in the Dept. of Stereotactic and Radiation Neurosurgery Na Homolce Hospital, Prague, Czech Republic [9]. Grading of the hearing loss was made according to Gardner-Robertson [1]. Function of the facial nerve assessed according to House-Brackmann scale and by electromyography [1], [6]. Four grades of VS size by MRI were described according to the Hannover Medical School [5], [6]: The 1st grade: intrameatal , the 2nd grade: spreading into the cerebellopontine angle (CPA), the 3rd grade: filling completely CPA, the 4th grade: compressing and dislocating nerve structures of CPA. In NF2 patients receiving auditory brainstem implant (ABI), the position of the electrode plate was checked by an electrically evoked brainstem responses audiometry – EBERA [12]. A postoperative imaging check was made 1 week, 1 month, 6 months after surgery and then every 1–2 years.

Results

From 1997 till 2004, 106 patients with VS were operated on, 8 (7.5%) were after previous subtotal/partial resection and/or unsuccessful GKS. Follow-up period ranged from 7 months to 8 years. Age range of patients was 19–72 years (mean 47 years). Females represented 65%, males 35%. Out of the group, there were 3 VS of the 1st grade, 8 VS of the 2nd grade, 25 VS of the 3rd grade and 70 VS of the 4th grade. Majority of tumors – 95 (90%) – were large VS of the 3rd and 4th. In 5 cases, patients suffered from NF2, 2 of them were unsuccessfully treated by GKS.

In primarily treated group VS were totally removed in all (100%) patients. No recurrence was found. Cochlear function: good and serviceable hearing (grades I–II) was achieved only in small VS of the 1st–2nd grade in eight patients (7.5%). Facial nerve function according to House-Brackmann shows nearly normal function in small VS and good or spontaneous recovery of function in large VS in 102 patients (96%). In 4 cases, the facial nerve had to be sutured in the CPA, either directly or with the nerve graft according to Samii or Dott with satisfactory results [4], [7], [11]. Cross anastomosis with other nerves (i.e. with n. XII) was not necessary.

After a previous subtotal/partial removal and/or GKS we achieved total removal only in 87.5%, in one case the radicality was uncertain. The total removal was technically much more difficult because of arachnoideal adhesions. Histological results; we found in all 8 (100%) patients after SR histological growing and viable tumor. Only some regression changes could be found. Hearing was not maintained in any case. It was impossible to preserve normal function of n. VII in any patient and partial function only in 25%. In 4 cases n. VII had to be anatomically interrupted, the proximal stump was damaged or absent and patient had to be treated by cross anastomosis using side-to-end technique.

Illustrative cases

Case 1: Radical removal of small VS (2nd–3rd gr.) after unsuccessful GKS

Female, 54 years, in 7/2000 irradiated by GKS for intrameatal VS of 1st gr. on the left side (25 Gy at the center, 14 Gy at the margin, 1 Gy to the brainstem). Two years after GKS the patient lost hearing, developed tinnitus, dizziness, n.VII weakness and n.V neuropathy. According to the MRI the VS volume increased from 1st to 3rd grade. In 9/2002 VS was radically removed by standard retromastoideal approach. Removing was technically difficult because of the scarred tissue, n.VIII was anatomically damaged. N.VII was anatomically preserved but without satisfactory function (House-Brackmann gr. 5).

Case 2: Removal of large VS (4th gr.) after unsuccessful GKS.

Female, 61 years, in 4/2002 irradiated by GKS for VS of 3rd gr. on the left side (24 Gy at the VS center, 12 Gy at the margin). The patient lost hearing, developed tinnitus, dizziness and n.V neuropathy. Two and a half years after GKS tumor volume increased up to 20% (from 3rd to 4th gr.). In 8/2004 VS was removed by retromastoideal approach. Removing was technically difficult. The total removal was uncertain; n.VIII and n.VII were anatomically interrupted. Proximal stump of n.VII was damaged. It was necessary to use cross hypoglosso-facial anastomosis.

Case 3: Radical removal of large VS (4th gr.) after unsuccessful partial resection and GKS.

Male, 51 years, four years ago VS of 3rd–4th gr. on the right side was subtotally removed in another dept. Two years ago was irradiated by GKS because of an increasing volume of VS. After the partial resection and GKS the volume of VS increased nearly twice (from 8cm³ to 14cm³) and patient deteriorated. Retromastoideal radical removal was extremely difficult due to arachnoideal adhesions, revascularization, and scarred tissue. Status of patient slowly improved except for the hearing and facial nerve function. N.VII was anatomically preserved but without satisfactory function (House-Brackmann gr. 5)

Auditory brainstem implant (ABI) was implanted to five patients with NF2. All implantees are users; one of them understands whole sentences without lip-reading [12].

Majority of operated patients from both groups returned into their previous social activity. From primarily treated group 96% ended with good or satisfactory n. VII function and in 7.5% with useful hearing; group with previous subtotal partial resection and/or GKS ended without hearing and only in 25% with satisfactory function n. VII.

Conclusion

Stereoradiosurgical treatment of VS comes out of a premise, that a spatially concentrated gamma irradiation devitalizes the tumour, biologically kills it or minimally stops its growth.

All eight patients had to be operated upon microsurgically after a standard GKS for a tumour regrowth and a clinically expressed progression of symptoms (deterioration of functions of cranial nerves VIII, VII, V, the cerebellum and brainstem).

In all operated patients after GKS a living, biologically active tumour has been proved histologically. Only minimal regressive changes have been observed. This finding unambiguously proves that the stereoradiosurgery did not devitalize tumour as expected.

The tumour growth after GKS occurred in this group of patients after a sole previous irradiation and after irradiation indicated after previous subtotal/partial microsurgical resection of tumour.

A rationale that VS cannot be microsurgically only diminished (in order not to damage function of the VII. and VIII. cranial nerves) and a remnant of tumour is destroyed by stereoradiosurgery showed to be false.

If we compare results of a microsurgical total VS removal in a group of patients operated primarily with a group of patients operated after subtotal/partial resection and stereoradiosurgery, it can be said, that a surgery is far more difficult and results are much worse, especially from a point of view of function of the VII and VIII nerves.

Growing tumours (VS) should be treated by a primary radical microsurgery.

Acknowledgements

This work was supported by grants IGA MZ CR, NR 8437-3/2005 and NR 8113-4/2004.

Thanks for data concerning irradiations to R. Liscak M.D. Ph.D., head of Dept. of Stereotactic and Radiation Neurosurgery Na Homolce Hospital, Prague, Czech Republic.


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