Luis Schiappacasse

Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach: planned subtotal resection followed by gamma knife radiosurgery

ObjectiveTo perform planned subtotal resection followed by gamma knife surgery (GKRS) in a series of patients with large vestibular schwannoma (VS), aiming at an optimal functional outcome for facial and cochlear nerves.MethodsPatient characteristics, surgical and dosimetric features, and outcome were collected prospectively at the time of treatment and during the follow-up.ResultsA consecutive series of 32 patients was treated between July 2010 and June 2016. Mean follow-up after surgery was 29xa0months (median 24, range 4–78). Mean presurgical tumor volume was 12.5xa0cm3 (range 1.47–34.9). Postoperative status showed normal facial nerve function (House–Brackmann I) in all patients. In a subgroup of 17 patients with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 16 (94.1%) retained serviceable hearing. Among them, 13 had normal hearing (Gardner–Robertson class 1) before surgery, and 10 (76.9%) retained normal hearing after surgery. Mean duration between surgery and GKRS was 6.3xa0months (range 3.8–13.9). Mean tumor volume at GKRS was 3.5xa0cm3 (range 0.5–12.8), corresponding to mean residual volume of 29.4% (range 6–46.7) of the preoperative volume. Mean marginal dose was 12xa0Gy (range 11–12). Mean follow-up after GKRS was 24xa0months (range 3–60). Following GKRS, there were no new neurological deficits, with facial and hearing functions remaining identical to those after surgery in all patients. Three patients presented with continuous growth after GKRS, were considered failures, and benefited from the same combined approach a second time.ConclusionOur data suggest that large VS management, with planned subtotal resection followed by GKRS, might yield an excellent clinical outcome, allowing the normal facial nerve and a high level of cochlear nerve functions to be retained. Our functional results with this approach in large VS are comparable with those obtained with GKRS alone in small- and medium-sized VS. Longer term follow-up is necessary to fully evaluate this approach, especially regarding tumor control.

Commissioning of the Leksell Gamma Knife® Icon™

Purpose: The Leksell Gamma Knife (LGK) Icon has been recently introduced to provide Gamma Knife technology with frameless stereotactic treatments which use an additional cone‐beam CT (CBCT) imaging system and a motion tracking system (IFMM, Intra‐Fraction Motion Management). The system was commissioned for the treatment unit itself as well as the imaging system. Methods: The LGK Icon was calibrated using an A1SL ionization chamber. EBT3 radiochromic films were employed to independently check the machine calibration, to measure the relative output factors (ROFs) and to collect dose distributions. Coincidence between CBCT isocenter and radiological focus was evaluated by means of EBT3 films. CBCT image quality was investigated in terms of spatial resolution, contrast‐to‐noise ratio (CNR), and uniformity for the two presets available (low dose and high dose). Computed Tomography Dose Index (CTDI) was also measured for both presets. Results: The absolute dose rate of the LGK Icon was 3.86 ± 0.09 Gy/min. This result was confirmed by EBT3 readings. ROF were found to be 0.887 ± 0.035 and 0.797 ± 0.032 for the 8 mm and 4 mm collimators, respectively, which are within 2% of the Monte Carlo‐derived ROF values. Excellent agreement was found between calculated and measured dose distribution with the gamma pass rate >95% of points for the nine dose distributions analyzed with 3%/1 mm criteria. CBCT isocenter was found to be within 0.2 mm with respect to radiological focus. Image quality parameters were found to be well within the manufacturers specifications with the high‐dose preset being superior in terms of CNR and uniformity. CTDI values were 2.41 mGy and 6.32 mGy, i.e. −3.6% and 0.3% different from the nominal values for the low‐dose and high‐dose presets, respectively. Conclusions: The LGK Icon was successfully commissioned for clinical use. The use of the EBT3 to characterize the treatment unit was demonstrated to be feasible. The CBCT imaging system operates well within the manufacturers specifications and provides good geometrical accuracy.

Jaw Immobilization for Gamma Knife Surgery in Patients with Mandibular Lesions: A Newly, Innovative Approach

Background: The purpose of our report is to describe an innovative system used for mandibular immobilization during Gamma Knife surgery (GKS) procedures. It is based on an approach originally developed in Marseille in extracranial lesions, close to or involving the mandible, which may imply a certain degree of movement during the therapeutic image acquisitions and/or GKS treatment. Methods: The maxillofacial surgeon applied bone titanium self-tapping monocortical screws (4; 2 mm diameter, 10 mm length) between roots of the teeth in the fixed gingiva (upper and lower maxillae) the day before GKS (local anesthesia, 5-10 min time). Two rubber bands were sufficient for the desired tension required to undergo GKS. We further proceeded with application of the Leksell stereotactic G frame and carried out the usual GKS procedure. Results: The mean follow-up period was 2.3 years (range 0.6-3). Three patients have been treated with this approach: 2 cases with extracranial trigeminal schwannomas involving the mandibular branch, with decrease in tumor size on MR follow-up; 1 case with residual paracondylian mandibular arteriovenous malformation following partial embolization, completely obliterated at 7 months (digital subtraction angiography programmed 1 year after treatment). Conclusions: Jaw immobilization appears to be a quick, minimally invasive, safe and accurate adjunctive technique to enhance GKS targeting precision.

Letter: Cystic Vestibular Schwannomas Respond Best to Radiosurgery

To the Editor: We have read with great interest the recent articles published inNeurosurgery, related to the response after radiosurgery (RS) for cystic vestibular schwannomas (VSs).1,2 During the past 20 yr, a noteworthy reflection and dilemma have been ongoing whether surveillance, microsurgery, or RS should be performed in patients with newly diagnosed VSs.3 Particularly, tumor volume and cystic component have been considered related to tumor response and control after RS.1 VSs (small to medium size tumors) represent nowadays a common indication of RS and particularly of GammaKnife surgery (GKS). The former is related to high rates of tumor control, ranging between 89% and 98%4-7 at 5 yr, with facial nerve preservation rates between 84% and 100%.3,4,6,8-12 The prescribed doses are currently low, ranging between 11 and 13 Gy in most of the

Gamma knife radiosurgery for arteriovenous malformations: general principles and preliminary results in a Swiss cohort

INTRODUCTIONnArteriovenous malformations (AVMs) are a type of vascular malformation characterised by an abnormal connection between arteries and veins, bypassing the capillary system. This absence of capillaries generates an elevated pressure (hyperdebit), in both the AVM and the venous drainage, increasing the risk of rupture. Management modalities are: observation, microsurgical clipping, endovascular treatment and radiosurgery. The former can be used alone or in the frame of a multidisciplinary approach. We review our single-institution experience with gamma knife radiosurgery (GKR) over a period of 5 years.nnnMATERIALS AND METHODSnThe study was open-label, prospective and nonrandomised. Fifty-seven consecutive patients, benefitting from 64 GKR treatments, were included. All were treated with Leksell Gamma Knife Perfexion (Elekta Instruments, AB, Sweden) between July 2010 and August 2015. All underwent stereotactic multimodal imaging: standard digital subtraction angiography, magnetic resonance imaging and computed tomography angiography. We report obliteration rates, radiation-induced complications and haemorrhages during follow-up course.nnnRESULTSnThe mean age was 46 years (range 13-79 years). The mean follow-up period was 36.4 months (median 38, range 12-75 months). Most common pretherapeutic clinical presentation was haemorrhage (50%). The most common Pollock-Flickinger score was between 1.01 and 1.5 (46%) and Spetzler-Martin grade III (46%). In 39 (60.1%) of cases, GKR was performed as upfront therapeutic option. The mean gross target volume (GTV) was 2.3 ml (median 1.2, range 0.03-11.3 ml). Mean marginal dose was 22.4 Gy (median 24, range 18-24 Gy). The mean prescription isodose volume (PIV) was 2.9 ml (median 1.8, range 0.065-14.6 ml). The overall obliteration rates (all treatments combined) at 12, 24, 36, 48 and 60 months were 4.8, 16.9%, 37.4, 63.6 and 78.4%, respectively. The main predictive factors for complete obliteration were: higher mean marginal dose (23.3 vs 21.0 Gy), lower GTV (mean 1.5 vs 3.5 ml) and absence of previous embolisation (at 60 months 61.8% prior embolisation compared with 82.4% without prior embolisation) (for all p <0.05). Eight (14%) patients experienced complications after GKR. Overall definitive morbidity rate was 3.1%. No patient died from causes related to GKR. However, during the obliteration period, one case of extremely rare fatal haemorrhage occurred.nnnCONCLUSIONnRadiosurgery is a safe and effective treatment modality for intracranial AVMs in selected cases. It can be used as upfront therapy or in the frame of a combined management. Obliteration rates are high, with minimal morbidity. The treatment effect is progressive and subsequent and regular clinical and radiological follow-up is needed to evaluate this effect.

The Changing Paradigm for the Surgical Treatment of Large Vestibular Schwannomas

Objective Planned subtotal resection followed by Gamma Knife surgery (GKS) in patients with large vestibular schwannoma (VS) has emerged during the past decade, with the aim of a better functional outcome for facial and cochlear function. Methods We prospectively collected patient data, surgical, and dosimetric parameters of a consecutive series of patients treated by this method at Lausanne University Hospital during the past 8 years. Results A consecutive series of 47 patients were treated between July 2010 and January 2018. The mean follow‐up after surgery was 37.5 months (median: 36, range: 0.5‐96). Mean presurgical tumor volume was 11.8 mL (1.47‐34.9). Postoperative status showed normal facial nerve function (House‐Brackmann I) in all patients. In a subgroup of 28 patients, with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 26 (92.8%) retained serviceable hearing. Nineteen had good or excellent hearing (Gardner‐Robertson class 1) before surgery, and 16 (84.2%) retained it after surgery. Mean duration between surgery and GKS was 6 months (median: 5, range: 3‐13.9). Mean residual volume as compared with the preoperative one at GKS was 31%. Mean marginal dose was 12 Gy (11‐12). Mean follow‐up after GKS was 34.4 months (6‐84). Conclusion Our data show excellent results in large VS management with a combined approach of microsurgical subtotal resection and GKS on the residual tumor, with regard to the functional outcome and tumor control. Longer term follow‐up is necessary to fully evaluate this approach, especially regarding tumor control.

Gamma Knife radiosurgery for glossopharyngeal neuralgia: A study of 21 patients with long-term follow-up:

Objective Glossopharyngeal neuralgia (GPN) is a very rare condition, affecting the patient’s quality of life. We report our experience in drug-resistant, idiopathic GPN, treated with Gamma Knife radiosurgery (GKRS), in terms of safety and efficiency, on a very long-term basis. Methods The study was opened, self-controlled, non-comparative and bicentric (Marseille and Lausanne University Hospitals). Patients treated with GKRS between 2003 and 2015 (models C, 4C and Perfexion) were included. A single 4-mm isocentre was positioned in the cisternal portion of the glossopharyngeal nerve, with a targeting based both on magnetic resonance imaging (MRI) and computed tomography (CT). The mean maximal dose delivered was 81.4u2009±u20096.7u2009Gy (medianu2009=u200985u2009Gy, rangeu2009=u200960–90u2009Gy at the 100% isodose line). Results Twenty-one patients (11 women, 10 men) benefited from 25 procedures. The mean follow-up period was 5.2u2009±u20093 years (rangeu2009=u20090.9–12.1 years). Seventeen (81%) were initially pain-free after GKRS. At three months, six months and one year after radiosurgery, the percentage of patients with good outcome (BNI classes I to IIIA) was 87.6%, 100% and 81.8%, respectively. Ten cases (58.8%) from the initial pain-free ones had a recurrence, after a mean period of 13.6u2009±u200910.4 months (rangeu2009=u20093.1–36.6 months). Only three patients (14.2%) had recurrences (two for each one of them) requiring further surgeries. Three patients underwent a second GKRS procedure; one case needed a third GKRS. The former procedures were performed at 7, 17, 19 and 30 months after the first one, respectively. Furthermore, two patients needed additional interventions. At last follow-up, 17 cases (80.9%) were still pain-free without medication. The actuarial pain relief without new surgery was 83%. A transient complication (paraesthesia of the edge of the tongue) was seen in one case (4.8%). Conclusion GKRS is a valuable, minimally invasive, surgical alternative for idiopathic GPN, with a very high short- and long-term efficacy and without permanent complications. A quality imaging, including T2 CISS/Fiesta MRI and bone CT acquisitions for good visualisation of the nerve and the other bony anatomic landmarks, is essential for targeting accuracy and successful therapy.

Upfront Gamma Knife surgery for facial nerve schwannomas: retrospective case series analysis and systematic review

IntroductionFacial nerve schwannomas are rare tumors and account for less than 2% of intracranial neurinomas, despite being the most common tumors of the facial nerve. The optimal management is currently under debate and includes observation, microsurgical resection, radiosurgery (RS), and fractionated radiotherapy. Radiosurgery might be a valuable alternative, as a minimally invasive technique, in symptomatic patients and/or presenting tumor growth.MethodsWe review our series of four consecutive cases, treated with Gamma Knife surgery (GKS) between July 2010 and July 2017 in Lausanne University Hospital, Switzerland. Clinical and dosimetric parameters were assessed. Radiosurgery was performed using Leksell Gamma Knife Perfexion. We additionally performed a systematic review, which included 23 articles and 193 treated patientsxa0from the current literrature.ResultsThe mean age at the time of the GKS was 44.25xa0years (median 43.5, range 34–56). Mean follow-up period was 31.8xa0months (median 36, range 3–60). Two cases presented with facial palsy and other two with hemifacial spasm. Pretherapeutically, House–Brackmann (HB) grade was II for one case, III for two, and VI for one. The mean gross tumor volume (GTV) was 0.406xa0ml (median 0.470xa0ml, range 0.030–0.638xa0ml). The mean marginal prescribed dose was 12xa0Gy at the mean 54% isodose line (median 50%, range 50–70). The mean prescription isodose volume (PIV) was 0.510xa0ml (median 0.596xa0ml, range 0.052–0.805xa0ml). The mean dose received by the cochlea was 4.2xa0Gy (median 4.1xa0Gy, range 0.1–10). One patient benefited from a staged-volume GKS. At last follow-up, tumor volume was stable in one and decreased in three cases. Facial palsy remained stable in two patients (one HB II and one HB III) and improved in two (from HB III to II and from HB VI to HB III). Regarding hemifacial spasm, both patients presenting one pretherapeutically had a decrease in its frequency and intensity after GKS. All patients kept stable Gardner–Robertson class 1 at last follow-up.ConclusionIn our experience, RS and particularly GKS, using standard, yet low doses of radiation, appear to be a safe and effective therapeutic option in the management of these rare tumors. The results as from our systematic review are also encouraging with satisfactory rates of clinical stabilization and/or improvement and high rate of tumor control. Complications are infrequent and mostly transient.

Radiosurgery in trochlear and abducens nerve schwannomas: case series and systematic review

IntroductionSchwannomas involving the occulomotor cranial nervesxa0 (CNs; III, IV and VI), can be disabling, due to the associated diplopia and decreased quality of life and are extremely rare. We evaluated the role of Gamma Knife surgery (GKS) in these cases.MethodsFive patients with CN IV and VI schwannomas (three and two, respectively) were treated in Lausanne University Hospital between 2010 and 2015. Four benefitted from upfront GKS and one from a combined approach (planned subtotal resection followed by GKS), due to a large preoperative tumour volume (size, 3xa0×xa02xa0×xa02.5xa0cm; volume, 7.9xa0ml), with symptomatic mass effect and oedema, as well as an entrapement cyst at the brainstem interface,xa0in a young patient. Neuro-ophtalmological evaluation was performed at baseline and during each follow-up time-point. A systematic literature review is presented and compared to the present report.ResultsThe mean follow-up was 44.4xa0months (12–54). Initial clinical presentation was diplopia in four cases and cavernous sinus syndrome in one. The marginal dose was 12xa0Gy in all cases. The mean target volume was 1.51xa0cm3 (0.086–5.8). The mean prescription isodose volume (PIV) was 1.71xa0cm3 (0.131–6.7). At last follow-up, all patients presented with disappearance of the baseline symptoms. Tumour control was achieved in 100%, with decrease in volume in all cases. The systematic review analysed 11 peer-reviewed studies, with a total of 35 patients. For uniformly reported CN VI, the mean marginal radiation dose ranged between 12 and 12.5xa0Gy, with disappearance of symptoms in 12.5%, improvement in 31.25%, stabilisation in 6.25%, worsening in 12.5%. Tumour volume decreased in all cases.ConclusionsOur data suggest that first intention GKS is a safe and effective option for patients with small to medium sizexa0oculomotor schwannomas, providing a high rate of clinical alleviation and tumour control. When the initial tumour volume is too large for first intention GKS, a combined approach with plannedxa0subtotal resection followed by GKS can be performed, with favourable and comparable outcomes as in upfront GKS.

A metastatic relapse associated with hippocampal dose sparing after whole-brain radiotherapy.

Whole-brain radiation therapy (WBrt) is used in a number of clinical indications both for palliation and as a prophylactic treatment at doses usually comprised between 25 and 30 gy in 10 fractions that are considered sufficient to treat microscopic disease [1] and to offer symptomatic relief in macroscopic disease. A significant proportion of these patients have a life expectancy long enough, and ionizing radiation may have a significant impact on their quality of life. the decrease in memory function represents one of the main late side effects in patients treated with WBrt [2–5]. One of the potential important structure involved in memory is the hippocampus [6–8] and this has led a number of authors to evaluate the feasibility of hippocampal dose-sparing rt [9,10]. dosimetric studies have shown that modern rt techniques like intensity-modulated rt (iMrt) have the capacity to greatly decrease the irradiation dose on the hippocampi without compromising the dose distribution for the remaining brain [11,12]. these studies have shown that the risk of metastatic involvement of the hippocampal region is relatively low and, therefore, intra-hippocampal metastatic involvement can be considered as a rare event while a decrease of the radiation dose to the hippocampi might be associated with less midand long-term side effects [13–16]. in this context, four patients between 60 and 70 years old presenting with metastatic breast cancer (n ue035 2), sigmoid adenocarcinoma, and transitional bladder cancer were treated in our department in 2010 with hippocampal dose-sparing WBrt. the patients were treated with tomotherapy using helical iMrt and daily megavoltage computed tomography (Ct) to account for reproducibility. Among these four patients, we describe the case of a 61-year-old woman known for bilateral metachronous breast carcinoma treated by mastectomy and axillary node dissection followed by adjuvant rt in 1994 and 1999. the patient was under anti-hormonal treatment since 2009 for a metastatic disease progression limited to the lungs. in 2010, she presented a metastatic brain progression with four lesions (cerebellum and left hemispheric). She underwent surgical resection of two cerebellar masses causing obstructive cranial hypertension symptoms. Surgery went well with no postoperative complication. the resection was macroscopically complete. She was, then, referred to our department for WBrt. A total dose of 30 gy in 10 fractions was delivered to the whole brain with simultaneous integrated boost of 40 gy to the cerebellar surgical resection cavity and to the macroscopic metastatic lesions while sparing the right hippocampus (maximal point dose of the hippocampus ue031 5 mm margin ue035 20 gy). Left hippocampus was not spared, being too close to one of the metastases.