Acta Oto-Laryngologica. 2015; Early Online, 1–6

ORIGINAL ARTICLE

Staged resection for vestibular schwannoma

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YASUOMI KUNIMOTO1, LORENZO LAUDA2, MAURIZIO FALCIONI2, ABDELKADER TAIBAH2, KENSAKU HASEGAWA1 & MARIO SANNA2 1

Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Tottori University, Tottori, Japan and Gruppo Otologico, Piacenza, Italy

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Abstract Conclusion: Surgery remains the preferred option for large vestibular schwannoma (VS). The presence of unpredictable intraoperative difficulties may convince the operator to suspend the surgery to avoid risks to patient life. Additional surgeries may be mandatory and are better performed using a transcochlear approach. High rates of complications, poor facial nerve results, and a percentage of incomplete removals should be expected in such unfavorable cases. Objectives: To review the results for nine cases of huge VS treated by staged resection. Method: A retrospective case review was performed for all nine patients who underwent staged resection of VS at the Gruppo Otologico between 1984–2012. The decision to perform staged surgery was always made intra-operatively after encountering unpredicted difficulties. Results: The nine patients represented 0.3% of all patients who underwent VS surgery during the same period. Mean tumor size was 4.7 cm (range = 3.0–6.6 cm). Two cases required three surgeries, resulting in a total of 20 operations. In addition, two cases required pre-operative ventriculoperitoneal shunt and one required temporary tracheotomy. After the final stage of surgery, complete removal had been achieved in six of the nine patients. The facial nerve was never preserved anatomically.

Keywords: Large vestibular schwannoma, facial palsy, transcochlear approach

Introduction Vestibular schwannoma (VS) resection remains a great challenge to neurosurgeons and otologists. Even if new treatment options have been introduced for small and medium-sized tumors [1], surgery remains the preferred solution for large tumors (> 3 cm in maximum diameter) [2,3]. Total or sub-total removal may be selected in accordance with the individual features of the case. In cases involving large lesions, unpredictable difficulties may be encountered during tumor removal, making it extremely risky to continue surgery. Suspending the surgery may be advisable in these rare situations, even if a significant amount of lesion remains present, to allow planning of a second stage for ultimate tumor removal. Staged resection is not a new concept in VS surgery, and was first advocated by Sheptak [4] in

1979 as an additional option in the presence of huge VS. However, few reports on staged resection have been published since then [5,6]. Our experience with staged resection is reported herein, and the advantages and disadvantages of this technique are considered. Patients and methods Data were collected from the medical charts of 2980 patients with VS who underwent surgery performed either by the senior author (M.S.) or under his direct supervision between 1984–2012. The inclusion criterion was the necessity to stop the first surgery due to unpredicted difficulties while a large volume of tumor remained in place (minimum diameter = 1.5 cm), with the consequent necessity for second surgery. As a definition, we did not consider staged resection to

Correspondence: Yasuomi Kunimoto, Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Tottori University, 86 Nishi-machi, yonago, Tottori 6838503, Japan. Tel: +81 859 38 6627. Fax: +81 859 38 6629. E-mail: [email protected]

(Received 31 January 2015; accepted 30 March 2015) ISSN 0001-6489 print/ISSN 1651-2251 online  2015 Informa Healthcare DOI: 10.3109/00016489.2015.1040170

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include those patients who required second surgery because of regrowth of residual tumor after planned partial removal. Pre-operative tumor size, reasons for suspending the first surgery, surgical approaches adopted, interval between stages, completeness of the final removal, post-operative facial nerve (FN) function, and complications were summarized and reviewed. Only one case was affected by neurofibromatosis type 2. Tumor size was measured as the maximal diameter within the cerebellopontine angle (CPA) [7]. Facial function was assessed according to the HouseBrackmann (HB) grading scale. Final function was evaluated at least 1 year after the last surgery. Intraoperative FN monitoring was routinely used in all surgeries. Results Between 1984–2012, a total of 2980 patients underwent surgery for VS at our institution. Among these, only nine cases required staged resection, representing 0.3% of the overall series and 4.6% of tumors larger than 3 cm. Mean age in this group at the time of first surgery was 30.1 years (range = 18-45 years). No preponderance of sex or side was apparent. Mean tumor diameter at the first surgery was 4.7 cm (range = 3.0–6.6 cm). Only one patient had undergone previous surgery elsewhere and was deemed to have residual tumor. No patients had previously undergone radiotherapy. Three patients required ventriculo-peritoneal shunt insertion before the first surgery at our institution in order to control obstructive hydrocephalus. Four of the nine patients showed residual tumor after the second-stage surgery. Of these, two patients were treated by third-stage surgery at our institution because they were young and had a residual tumor that was considered too large for stereotactic radiotherapy. The remaining two patients were treated at other institutions; one died after an attempt to remove the last tumor remnant, while the other was lost to follow-up. These two patients treated at other institutions were, thus, excluded from postoperative analysis. Mean duration of follow-up for the remaining seven patients after the final surgery was 50.7 months (range = 14–115 months). Mean interval between stages was 21.5 weeks (range = 3–40 weeks). Reasons for stopping the first surgery were excessive bleeding, inability to establish a correct cleavage plane between the tumor and brainstem or cerebellum, and modifications of vital parameters when trying to manipulate the residual lesion. In one 19-year-old male patient, the first surgery was suspended before beginning tumor removal due to the reddish, pulsatile aspect of the lesion and was followed by arteriography with embolization before the second surgery.

Arteriography was performed in an additional case in which the surgery was interrupted for excessive bleeding, but, in that case, embolization was considered too risky due to the presence of arteriovenous shunts. At the first surgery, the enlarged translabyrinthine approach (ETLA) was selected in seven of the nine cases (77.8%), while a modified transcochlear approach was adopted in the remaining two cases in whom a wide operative field was preferred because one case had been previously operated on elsewhere and the other case involved a patient with neurofibromatosis type 2. The modified transcochlear approach was used in nine of the 11 second or third surgeries (81.8%), with the ETLA reserved for the remaining two surgeries. Although eight patients presented with preoperative FN function HB I, another, who had already been operated on elsewhere, presented with complete palsy. The FN was never identified at the brainstem at the first surgery, due to the presence of the residual lesion. All patients displayed complete facial palsy after the first surgery (with the exception of the case in which the first surgery was stopped after the approach). After final-stage surgery, all cases showed interruption of the FN. Four of seven patients underwent hypoglossal-facial anastomosis at our institutions; three of these recovered to HB III and one recovered to grade IV. One additional patient underwent hypoglossal-facial anastomosis at another institution and recovered to grade IV. The remaining patients declined additional treatment. After the final-stage surgery, complete removal was achieved in six of the nine patients. One patient with a small remnant still present was initially followed and then treated with stereotactic radiotherapy because of tumor re-growth, while the last two cases still had a residual lesion larger than 1 cm; one was lost to follow-up, while the other was treated at another hospital and died after the surgery. Three post-operative complications were seen among the total of 20 operations performed on the nine patients in this study; two patients developed lower cranial nerve palsy (one requiring temporary tracheotomy); and the other developed subcutaneous abdominal hematoma that required surgical evacuation. Details of the cases are summarized in (Table I). Discussion Complete agreement on the best treatment for VS has not yet been reached. Radiological monitoring, stereotactic radiotherapy and microsurgery each present advantages and disadvantages, depending on the specific case [1]. However, due to the significant compression on the brainstem and cerebellum, surgical

Staged resection for VS

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Table I. The details of staged cases. Age

Size* (mm)

19

50

ETLA, TC, TC

3, 30

total

bleeding



VI (III)

embolization

45

48

ETLA, ETLA

18

sub-total

unclear plane vital signs change



VI

lost to follow-up

Approach

Interval (weeks)

Final removal

Reason for residual

Pre-op V-P shunt

Final HB

Notes

39

40

ETLA, TC

26

total

unclear plane



VI (III)



34

30

ETLA, TC

22

total

high JB



VI (III)

abdominal hematoma

28**

55

TC, TC

20

sub-total

bleeding unclear plane

yes

VI

LCN palsy with tracheotomy death after additional surgery at another institution

18

66

ETLA, TC, TC

23, 18

near-total

bleeding unclear plane



VI (IV)***

arteriography LCN palsy radiation after 3rd op

28

50

ETLA, ETLA

34

total

deep incuneation into CPA



VI



27

40

ETLA, TC

40

total

bleeding

yes

VI (IV)



33

45

TC, TC

22

total

bleeding

yes

VI

NF2

ETLA, enlarged translabyrinthine approach; TC, transcochlear approach; LCN, lower cranial nerves; CPA, cerebellopontine angle; HB, House-Brackmann, () , HB grade at least 1 year after VII–XII anastomosis; V-P, ventriculo-peritoneal shunt. *tumor size at the first surgery. **previous surgery at another institution. ***hypoglossal-facial anastomosis performed at another institution.

removal is universally accepted as the treatment of choice in cases of large (> 3 cm) VS [2,3,8]. In addition in these large VSs, radiotherapy entails the risk of transient VS swelling, which can lead to increased compression of the brainstem [9]. Total tumor removal with minimal post-operative morbidity is usually the aim of surgery, but small tumor remnants may be deliberately left behind to reduce neurological risks [10,11]. Because they usually show a very low growth rate and rarely require additional surgery when smaller than 1 cm, these small residuals may be followed-up radiologically or treated by stereotactic radiotherapy [12]. The ETLA has been described as a safe and effective approach for VS removal, with a low incidence of morbidity, particularly for large tumors [13]. The main advantage when compared to the retrosigmoid approach is represented by the possibility of achieving a direct route to the tumor and lateral cistern, allowing both tumor debulking and evacuation of cerebrospinal fluid with consequent reductions of intracranial pressure, before performing any manipulation of the cerebellum. For these reasons, ETLA is preferred for all cases of large VS at our institution [14]. At our institution, staged resection is never selected pre-operatively. However, occasionally, when treating a huge VS, this option may be chosen intraoperatively in the event of unpredicted difficulties. These may be represented by excessive bleeding from the tumor, or difficulties establishing a cleavage plane

when dissecting the tumor from the most delicate neurological areas, particularly the brainstem. With huge lesions, in fact, some tumor components may be strongly adherent to or wedged into the pons; sometimes even the pia mater may be absent. In such situations, attempts to manipulate these remnants can produce such modifications to the vital parameters (mainly in the form of bradycardia) that suspending the surgery becomes advisable. In all these situations, the amount of tumor left may be as much as half the original size, or at any rate more than 1.5 cm in diameter, and a second-stage surgery may be considered. In such residual cases, additional treatment options are determined based on the size of the residual tumor and the age, general condition, and symptoms of the patient. In the management of large VS, the combination of sub-total resection and radiotherapy might represent a valid treatment strategy [9]. Arguments against this combined technique might be that the patient is not completely cured in one operative session and that radiotherapy might induce malignant transformation of surrounding tissues. The risk of malignant transformation over a 5– 30-year period is estimated to be ~ 1:1000 [15]. At our institution, additional surgical removal is usually adopted in patients younger than 60 years old and in good general condition [10], as demonstrated by the mean age of staged cases in this series (30.1 years). In fact, in our experience, residual lesions in young patients usually display a high growth rate.

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Staged brain-tumor surgery is not a new concept. Such procedures have been carried out for many years, particularly with certain supratentorial gliomas, meningiomas and arteriovenous malformations [4]. Even for VS removal, staged surgeries have already been sporadically reported [4,6]. Actually, the first reported translabyrinthine approach was a staged resection undertaken because of excessive bleeding [16,17]. Some authors have suggested routine adoption of staged resection in the presence of tumors larger than 3 cm [18]. We have never followed this policy and always try to achieve complete removal of the tumor during the first surgery, but staged resection may offer some advantages in complicated cases. First, by attacking and debulking the lateral part of the tumor in the first-stage surgery, some of the blood supply from the anterior inferior cerebellar artery is interrupted. Pathological analysis has revealed that spontaneous thrombosis occurs within the tumor vasculature [5]. This leaves the residual tumor mass dependent only on feeders from the medial surface, and the tumor, thus, often becomes relatively avascular. However, severe bleeding can sometimes be seen even at the second surgery, making the operation much more difficult. In addition to decreased vascularity, significant reduction of the tumor mass partially decompressing the posterior fossa allows the brainstem to shift laterally toward its original position and push the residual tumor laterally into the vacant space of the CPA, improving surgical access [5]. The reduction in tumor pressure on the brainstem often improves the possibility of establishing a clear cleavage plane with the tumor (Figure 1). Despite the potential advantages obtained during the first operation by ETLA, the second-stage surgery is always very demanding. In fact, the surgical field is obliterated by fat and landmark identification is difficult, as is initial identification of a cleavage plane. This may be at least partially overcome by adopting a transotic (TO) or transcochlear (TC) approach. The TO and TC approaches both include removal of the external auditory canal, middle ear, and cochlea. In this way, the approach is extended anteriorly and, more importantly, the surgeon has the possibility of reaching the tumor at its anterior surface, which usually remains untouched during the first stage. This greatly facilitates the identification of both landmarks and the correct cleavage plane. That is the great benefit and reason we prefer TO or TC approaches for staged surgery. The choice between these two approaches is made based on FN function after the first surgery. When already in the presence of FN palsy (as in every case of the present series), the TC

represents the largest available approach without any additional drawbacks. In addition, after wide bone removal at the level of the posterior and middle cranial fossa dura, as ordinarily performed during an ETLA, both the posterior and middle cranial fossae remain without bony containment. As a consequence, they tend to progressively prolapse anteriorly (for the posterior fossa) and inferiorly (for the middle fossa) (Figure 2). The space available for tumor removal during the second surgery is, thus, significantly narrowed. The second surgery should, thus, be planned to be performed as soon as possible in order to limit this situation. Theoretically, 16–24 weeks seems to represent the ideal timing, providing the optimal balance between the necessity to avoid significant narrowing of the surgical field and the requirements of the patient in recovering from a distressing surgery. At the same time, this interval avoids significant re-growth of the lesion, which is not uncommon in these cases. FN preservation has always been considered an issue of primary concern in VS surgery. Despite the continuous improvements in microsurgery, postoperative FN weakness remains a tangible complication and the risk of its occurrence increases with tumor size [3]. In a previous study on a series of 1151 VSs treated using the ETLA at our institution [19], anatomical interruption of the nerve was recorded in 4.2% of cases, with an additional 5.6% in whom the nerve was anatomically preserved but did not recover to better than HB grade IV. In agreement with those data, preservation of the anatomical integrity of the nerve was not possible in any of our cases requiring staged removal. Even the proximal stump of the nerve was impossible to identify at the end of the surgery, precluding any chance of immediate grafting. Due to the presence of pre-existing FN palsy, saving time by cutting the nerve and eventually performing the reconstruction at the end of surgery seems logical. In five cases, the FN was rehabilitated by further surgery through a hypoglossal-facial anastomosis. The other two patients declined to undergo additional surgery. Complications were seen in three cases, with two cases showing lower cranial nerve palsy (one requiring temporary tracheotomy) and one case showing subcutaneous abdominal hematoma requiring surgical evacuation. The lower cranial nerve can be injured during removal of large VSs, which would impinge on jugular foramen contents and cranial nerves IX, X, and XI. Acute lower cranial nerve deficits can result in dysphagia and aspiration. In cases with severe problems and risk of aspiration pneumonia, tracheostomy and percutaneous endoscopic gastrostomy can be an option. Acute and sub-acute post-operative

Staged resection for VS A

B

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D

E

Figure 1. (A) Pre-operative MRI showing a huge right-sided vestibular schwannoma deeply incuneated into the cerebellopontine angle. (B) MRI performed after the first stage showing the residual lesion adherent to the brainstem. (C) MRI performed the day before the second stage (8 months after (B)); note the re-expansion of the brainstem producing a lateral dislocation of the residual tumor. (D) MRI performed 4 days after the second stage showing the total removal; edema and evidence of blood are still visible. (E) MRI performed 1 year after the second stage with confirmation of total removal. The brainstem and cerebellum have come back to their original position.

A

B

Figure 2. (A) MRI performed 4 years after second stage showing a shift of the contents of the posterior fossa laterally due to the absence of the bony barrier originally represented by the temporal bone. (B) Coronal post-operative MRI showing the inferior prolapse of the temporal lobe consequent to the removal of the middle cranial fossa floor.

hemorrhage reportedly show frequencies of 2.2% and 1.5%, respectively. Ischemic complications may be of arterial or venous origin and may affect the brain stem or the cerebellar hemisphere. Adhesion of tumor to the brainstem and cerebellum is a cause of microtrauma of the small vessels coursing at the tumor– brain interface [20]. Consequently, meticulous care should be taken to preserve the subpial vessels. Conclusion Staged resection is not a new concept in VS surgery [4–6]. In our center, this option is never planned preoperatively, as suggested by other authors [18], but unexpected intra-operative difficulties result in the

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adoption of this strategy in a minority of our cases (0.3%, 9/2980). In these particularity difficult cases, staged resection may offer some advantages. Based on our experience, this possibility should always be mentioned to patients if a tumor larger than 3 cm in diameter is identified.

[9]

[10]

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

[11]

[12]

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Staged resection for vestibular schwannoma.

Surgery remains the preferred option for large vestibular schwannoma (VS). The presence of unpredictable intraoperative difficulties may convince the ...
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