Linear accelerator radiosurgery using 90 gray for essential trigeminal neuralgia: results and dose volume histogram analysis

OBJECTIVE: To evaluate treatment of essential trigeminal neuralgia with 90 Gy delivered by a linear accelerator dedicated to radiosurgery. METHODS: This is a retrospective case series of 25 patients with essential trigeminal neuralgia treated from March 1999 to March 2001. All were treated with 90 Gy by means of a 5-mm collimator directed to the nerve root entry zone. Patient follow-up (range, 8-52 mo; median, 18 mo) was completed by an uninvolved party. Dose volume histograms of the brainstem were developed for the 20, 30, and 50% isodose lines by means of radiosurgery planning software. RESULTS: All patients obtained good to excellent pain relief with treatment. Nineteen (76%) of 25 patients achieved excellent pain relief (pain-free without medication). Six patients (24%) achieved good pain relief (50-90% reduction of pain with or without medication). Median time to pain relief was 2 months. Eight patients (32%) experienced relapse 4 to 13 months after treatment. Eight patients (32%) developed facial numbness, but none developed painful numbness. Mean brainstem volume within the 50% isodose line and occurrence of numbness was statistically significant (P = 0.03). There was no correlation between brainstem volume treated and outcome. CONCLUSION: Dedicated linear accelerator-based stereotactic radiosurgery that uses a 5-mm collimator to deliver 90 Gy to the nerve root entry zone is a safe and effective method for the treatment of essential trigeminal neuralgia. Care should be taken to limit brainstem volume included in the 50% isodose line in the treatment plan to avoid facial numbness.     

Stereotactic radiosurgery for primary trigeminal neuralgia using the Leksell Gamma unit

OBJECTIVE: Previous papers have reported Gamma Knife radiosurgery to be a safe, effective method for primary trigeminal neuralgia. Since November 1996, we have treated primary trigeminal neuralgia using the Leksell Gamma Knife at the Tianjin Medical University. The present study reports clinical results of Gamma Knife radiosurgery in the treatment of trigeminal neuralgia in 80 cases. METHODS: The mean patient age was 67 years (range 32-92), the mean duration of facial pain was 7.6 years (range 1.5-29). The male:female ratio was 31:49. The right side of the face was involved in 45 patients (56.25%) and the left side in 30 cases (37.5%), with bilateral involvement in 5 cases (6.25%). Under local anesthesia, all patients underwent stereotactic MRI to identify the trigeminal nerve. A single isocenter, using a 4-mm collimator, was positioned at the sensory root of the trigeminal nerve entry zone of the pons, 4-6 mm from the brainstem surface, so that no more than the 20% isodose was administered to the brainstem. The maximum dose was between 70 and 90 Gy, with a mean of 75.6 Gy. For bilateral trigeminal neuralgia, two separate matrices were employed, and bilateral Gamma Knife radiosurgery was performed on the same day. RESULTS: Follow-up ranged from 12 to 43 months (mean 23.7 months). Neurological evaluation indicated excellent response in 42 cases (52.5%), good response in 25 cases (31.25%), effective response in 8 cases (10%), so the total pain control rate was 93.75%. The latency from Gamma Knife surgery to pain relief ranged from 1 to 120 days (mean 22 days). Among the 75 patients 7 with pain control experienced pain recurrence 5-26 months after being completely free from pain. A second Gamma Knife radiosurgery was performed in 7 recurrent cases and 5 patients with treatment failure. A maximal dose ranging from 70 to 80 Gy was given (mean 74.2 Gy). After a mean follow-up of 18 months (8-33 months), 9 patients achieved excellent results, and 2 had good results. The latency interval to pain relief ranged from 1 to 120 days (mean 15 days). Nine patients developed new facial numbness, while no other complication appeared in the remainder of the patients. CONCLUSIONS: Gamma Knife radiosurgery is a safe and effective method in the treatment of trigeminal neuralgia once diagnosis is established.     

Gamma knife surgery for trigeminal neuralgia: outcomes and prognostic factors

OBJECT: Microvascular decompression (MVD) and percutaneous ablation surgery have historically been the treatments of choice for medically refractory trigeminal neuralgia (TN). Gamma knife surgery (GKS) has been used as an alternative, minimally invasive treatment in TN. In the present study, the authors evaluated the long-term results of GKS in the treatment of TN. METHODS: From 1996 to 2003, 151 cases of TN were treated with GKS. In this group, radiosurgery was performed once in 136 patients, twice in 14 patients, and three times in one patient. The types of TN were as follows: 122 patients with typical TN, three with atypical TN, four with multiple sclerosis-associated TN, and seven with TN and a history of a cavernous sinus tumor. In each case, the chosen radiosurgical target was located 2 to 4 mm anterior to the entry of the trigeminal nerve into the pons. The maximal radiation doses ranged from 50 to 90 Gy. The median age of the patients was 68 years (range 22-90 years), and the median time from diagnosis to GKS was 72 months (range 1-276 months). The median follow up was 19 months (range 2-96 months). Clinical outcomes and postradiosurgical magnetic resonance (MR) imaging studies were analyzed. Univariate and multivariate analyses were performed to evaluate factors that correlated with a favorable, pain-free outcome. The mean time to relief of pain was 24 days (range 1-180 days). Forty-seven, 45, and 34% of patients were pain free without medication at the 1-, 2-, and 3-year follow ups, respectively. Ninety, 77, and 70% of patients experienced some improvement in pain at the 1-, 2-, and 3-year follow ups, respectively. Thirty-three (27%) of 122 patients with initial improvement subsequently experienced pain recurrence a median of 12 months (range 2-34 months) post-GKS. Among those whose symptoms recurred, 14 patients underwent additional GKS, six MVD, four glycerol injection, and one patient a percutaneous radiofrequency rhizotomy. Twelve patients (9%) suffered the onset of new facial numbness post-GKS. Changes on MR images post-GKS were noted in nine patients (7%). On univariate analysis, right-sided neuralgia (p = 0.0002) and a previous neurectomy (p = 0.04) correlated with a pain-free outcome; on multivariate analysis, both rightsided neuralgia (p = 0.032) and patient age (p = 0.05) were statistically significant. New onset of facial numbness following GKS correlated with undergoing more than one GKS (p = 0.002). CONCLUSIONS: At the last follow up, GKS effected pain relief in 44% of patients. Some degree of pain improvement at 3 years post-GKS was noted in 70% of patients with TN. Although less effective than MVD, GKS remains a reasonable treatment option for those unwilling or unable to undergo more invasive surgical approaches and offers a low risk of side effects.     

Gamma Knife surgery and trigeminal schwannoma: is it possible to preserve cranial nerve function?

OBJECT: The current study was undertaken to evaluate the tumor control rate and functional outcome after Gamma Knife surgery (GKS) in patients with a trigeminal schwannoma. The conditions associated with the development of cranial neuropathies after radiosurgery were scrutinized. METHODS: The authors reviewed the clinical records and radiological data in 22 consecutive patients who received GKS for a trigeminal schwannoma. The median tumor volume was 4.1 ml (0.2-12.0 ml), and the mean tumor margin dose was 13.3 +/- 1.3 Gy at an isodose line of 49.9 +/- 0.6% (mean +/- standard deviation). The median clinical follow-up period was 46 months (range 24-89 months), and the median length of imaging follow-up was 37 months (range 24-79 months). RESULTS: Tumor growth control was achieved in 21 (95%) of the 22 patients. Facial pain responded best to radiosurgery, with two thirds of patients showing improvement. However, only one third of patients with facial hypesthesia improved. Six patients (27%) experienced new or worsening cranial neuropathies after GKS. Ten patients (46%) showed tumor expansion after radiosurgery, and nine of these also showed central enhancement loss. Loss of central enhancement, tumor expansion, and a tumor in a cavernous sinus were found to be significantly related to the emergence of cranial neuropathies. CONCLUSIONS: The use of GKS to treat trigeminal schwannoma resulted in a high rate of tumor control and functional improvement. Cranial neuropathies are bothersome complications of radiosurgery, and tumor expansion in a cavernous sinus after radiosurgery appears to be the proximate cause of the complication. Loss of central enhancement could be used as a warning sign of cranial neuropathies, and for this vigilant patient monitoring is required.     

Stereotactic radiosurgery for idiopathic trigeminal neuralgia

OBJECT: Each year a greater number of patients with trigeminal neuralgia (TN) undergo radiosurgery, including a large number of patients who are candidates for microvascular decompression (MVD). METHODS: The case characteristics and outcomes of 117 consecutive patients who underwent radiosurgery were retrieved from a prospectively maintained database. The mean patient age was 67.8 years; and the majority (58%) of patients had undergone surgery previously. The dependent variable for all analyses of facial pain was complete pain relief without medication (excellent outcome). Median follow-up duration was 26 months (range 1-48 months). The actuarial rate of achieving and maintaining an excellent outcome was 57% and 55% at 1 and 3 years, respectively, after radiosurgery. A greater percentage of patients who had not previously undergone surgery achieved and maintained excellent outcomes (67% at 1 and 3 years) than that of patients who had undergone prior surgery (51% and 47% at 1 and 3 years, respectively; relative risk [RR] = 1.77, 95% confidence interval [CI] 1.01-3.13, p = 0.04). New persistent trigeminal dysfunction was noted in 43 patients (37%). Tolerable numbness or paresthesias occurred in 29 patients (25%), whereas bothersome dysesthesias developed in 14 patients (12%). Only a radiation dose of 90 Gy correlated with new trigeminal deficits or dysesthesias (RR = 3.10, 95% CI 1.64-5.81, p < 0.001). Excellent outcomes in patients with new trigeminal dysfunction were achieved and maintained at rates of 76% and 74% at 1 and 3 years, respectively, after radiosurgery, compared with respective rates of 46% and 42% in patients who did not experience postradiosurgery trigeminal dysfunction (RR = 4.53, 95% CI 2.03-9.95, p < 0.01). CONCLUSIONS: Radiosurgical treatment provides complete pain relief for the majority of patients with idiopathic TN. There is a strong correlation between the development of new facial sensory loss and achievement and maintenance of pain relief after this procedure. Because the long-term results of radiosurgery still remain unknown, MVD should continue to be the primary operation for medically fit patients with TN.     

Dedicated linear accelerator radiosurgery for the treatment of trigeminal neuralgia

OBJECT: In this study the authors evaluate the efficacy of and complications associated with dedicated linear accelerator (LINAC) radiosurgery for trigeminal neuralgia (TN). METHODS: Between August 1995 and February 2001, 60 patients whose median age was 66.1 years (range 45-88 years) were treated with dedicated LINAC radiosurgery for TN. Forty-one patients (68.3%) had essential TN, 12 (20%) had secondary facial pain, and seven (11.7%) had atypical features. Twenty-nine patients (48.3%) had undergone previous surgical procedures. Radiation doses varied between 70 and 90 Gy (mean 83.3 Gy) at the isocenter, with the last 35 patients (58.3%) treated with a 90-Gy dose. A 5-mm collimator was used in 45 patients (75%) and a 7.5-mm collimator in 15 patients (25%). Treatment was focused at the nerve root entry zone. At last follow up (mean follow-up period 23 months, range 2-70 months), 36 (87.8%) of the 41 patients with essential TN had sustained significant pain relief (good plus excellent results). Twenty-three patients (56.1%) were pain free without medication (excellent outcome), 13 (31.7%) had a 50 to 90% reduction in pain with or without medication (good outcome), and five (12.2%) had minor improvement or no relief. Of 12 patients with secondary facial pain, significant relief was sustained in seven patients (58.3%); worse results were found with atypical pain. Fifteen (25%) of the 60 patients experienced new numbness postprocedure; no other significant complications were found. Pain relief was experienced at a mean of 2.7 months (range 0-12 months). CONCLUSIONS: Dedicated LINAC radiosurgery is a precise and effective treatment for TN.     

Image-guided radiosurgery of head and neck cancers

OBJECTIVES: Radiosurgery precisely delivers a single high dose or a few fractionated doses of radiation to a localized tumor via the stereotactic approach. Some head and neck sites are suitable for radiosurgery since there is minimal or no organ motion. The clinical studies were carried out to determine the accuracy of stereotactic radiosurgery and to demonstrate the effectiveness of radiosurgery in head and neck cancers. MATERIALS AND METHODS: Thirteen patients were treated with either single-dose or fractionated radiosurgery to the tumor. All patients except one with cancer of the lip had received prior treatments including surgery, radiotherapy, and chemotherapy for the primary cancers. The dose ranged 12 to 18 Gy for single-dose radiosurgery and 30 Gy in 5 or 6 fractions twice a week for fractionated radiosurgery. Tumor localization was achieved via the stereotactic approach. RESULTS: Accuracy of radiosurgery was within 1.5 mm. Despite the recurrent disease from previous heavy treatments, 9 patients (70%) showed a significant response (complete or >50% tumor reduction) to radiosurgery, and 3 patients had stable disease. Complete tumor response was achieved in 6 patients. All patients had excellent pain relief with functional and cosmetic preservation. There was no acute and subacute radiation toxicity detected clinically during the minimal follow-up of 6 months. CONCLUSION: Image-guided radiosurgery is effective in achieving the local tumor control and pain relief. Radiosurgery provided excellent functional and cosmetic preservation with minimal complication. The results indicate the potential of radiosurgery in the treatment of recurrent and selected primary head and neck cancers.     

La radiochirurgie dans le traitement de la névralgie trigéminale : résultats à long terme et influence des nuances techniques

Stereotactic radiosurgery is an alternative to conventional surgery for the treatment of trigeminal neuralgia. To better define the safety of radiosurgery and optimal technical choices, we reviewed our patient records and the literature. A total of 334 patients presenting with trigeminal neuralgia were treated between December 1992 and September 2005. A minimum of 1 year of follow-up was available for 262 patients. The mean age was 68 years (range: 30-90); 128 patients were male and 134 female. A neurovascular conflict was clearly visualized on MRI in 167 patients. Twenty-one had a past history of multiple sclerosis and 110 had already received conventional surgical treatment for trigeminal neuralgia. The intervention consisted of gamma knife radiosurgery (GKS) to the retrogasserian cisternal portion of the Vth cranial nerve. The median maximal dose used was 85 Gy (range: 70-90). Actuarial curves show a plateau at 5 years for both the risk of hypoesthesia and recurrence. At 5 years, 58% of the patients remain pain-free and 83% have no trigeminal nerve disturbance. The median delay for pain cessation was 15 days. The initial pain-relief rate was 89%. None of the complications reported for the other techniques were observed. Patient selection (typical versus atypical, age, past surgery, multiple sclerosis) and details of operative technique (maximum dose, volume of nerve treated, target location, etc.) had a major influence on the probability of pain relief and toxicity risk. The details of operative technique are turning out to have a major influence on the clinical results. In our experience, high-dose (80-90 Gy) retrogasserian (7-8 mm from the brainstem) GKS provides the patient with a better chance of long-term pain relief and a lower risk of trigeminal nerve functional disturbance. GKS applied to the cisternal anterior trigeminal nerve using high doses provided safe and effective treatment for trigeminal neuralgia over the long term.     

Repeat radiosurgery for refractory trigeminal neuralgia

OBJECTIVE: Stereotactic radiosurgery has become an important and minimally invasive alternative for patients with refractory trigeminal neuralgia. When a second procedure is necessary, the outcomes are unknown. The degree of pain relief and morbidity after repeat radiosurgery were studied. METHODS: Thirty-one patients underwent a second gamma knife radiosurgery procedure because of unsatisfactory or unsustained relief of pain after the first procedure. Twenty-seven patients were assessable at median follow-up periods of 42.7 and 20.4 months after the first and second procedures, respectively. Most patients had undergone multiple previous operations of other types (microvascular decompression, radiofrequency rhizotomy, glycerol rhizotomy, balloon compression). The median target doses of the first and second radiosurgeries were 75 and 64 Gy, respectively. All patients were evaluated by a physician who did not participate in patient treatment. RESULTS: After the first radiosurgical procedure, 13 patients had an excellent response initially (complete relief without any medication), 3 had a good response (complete relief with some medication), 7 had a fair response (>50% relief), and 4 had a poor response (<50% pain relief or treatment failure). Repeat radiosurgery was performed in patients with recurrent or residual pain. After the second radiosurgical procedure, 5 patients had an excellent response, 8 had a good response, 10 had a fair response, and 4 had a poor response. Thirteen patients (48%) achieved complete pain relief (with or without medication). Two patients (7.4%) experienced new sensory symptoms after the first radiosurgical procedure, and three (12.7%, actuarial) experienced new sensory symptoms after the second procedure. CONCLUSION: Repeat radiosurgery provided a similar rate of pain relief as the first procedure, despite a modest dose reduction. The risk of new sensory symptoms was increased, but no other morbidity was identified. For patients who experience recurrent pain and choose to undergo a second procedure, our current procedure is to deliver a maximum dose of 50 to 60 Gy to a trigeminal target anterior to the root entry zone near the entrance of the nerve beneath the petrous dura.     

Trigeminal schwannomas: results of gamma knife surgery in 37 cases

OBJECT: Information on outcomes of Gamma Knife surgery (GKS) for patients harboring trigeminal schwannomas is limited because these tumors are rare. The authors evaluated tumor control and functional outcomes in patients who underwent GKS for trigeminal schwannomas to clarify the efficacy of this treatment. METHODS: Forty-two patients with trigeminal schwannomas but no evidence of neurofibromatosis Type 2 were treated with GKS at Komaki City Hospital between November 1991 and December 2003. Of these, 37 patients were assessed. The mean tumor volume in these patients was 10 cm3. The mean maximum radiation dose directed to the tumor was 27.9 Gy and the mean dose directed to the tumor margin was 14.2 Gy. The mean follow-up period was 54 months. In four patients (11%) there was complete tumor remission; in 20 (54%) there was partial tumor remission; in eight (22%) the disease remained stable; and in five (14%) the tumor enlarged or uncontrollable facial pain developed with radiation-induced edema requiring resection. The actuarial 5- and 10-year tumor control rates were both 84%. With respect to functional outcomes, 40% of patients noted an improvement in their symptoms, and one patient experienced new symptoms despite good tumor control. CONCLUSIONS: Gamma Knife surgery was a safe and effective treatment for a select group of patients harboring trigeminal schwannomas. Large tumors that compress the brainstem and cause deviation of the fourth ventricle should first be removed surgically and any remnant should be treated by GKS.     

Boost Gamma Knife surgery during multimodality management of adult medulloblastoma

OBJECT: The aim of this paper was to determine prognostic factors for adult medulloblastoma treated with boost Gamma Knife surgery (GKS) following resection and craniospinal irradiation. METHODS: The authors performed a retrospective analysis of 12 adult patients with histologically proven medulloblastoma or supratentorial primitive neuroectodermal tumor who between February 1991 and December 2004 underwent >or=1 sessions of GKS for posttreatment residual or recurrent tumors (6 tumors in each group). Before GKS, all patients had undergone a maximal feasible resection followed by craniospinal irradiation. Nine patients also received systemic chemotherapy. Stereotactic radiosurgery was applied to residual and recurrent posterior fossa tumor as well as to foci of intracranial medulloblastoma metastases. The median time interval from initial diagnosis and resection to the first GKS treatment was 24 months (range 2-37 months). The mean GKS-treated tumor volume was 9.4 cm3 (range 0.5-39 cm3). RESULTS: Following adjunctive radiosurgery, 5 patients had no evidence of tumor on magnetic resonance (MR) imaging, 3 patients had stable tumor burden on MR imaging, and 4 patients had evidence of tumor progression locally with or without intracranial metastases. All patients with tumor progression died. Eight patients survive with a mean cumulative follow-up of 72.4 months (range 21-152 months). No acute radiation toxicity or delayed radiation necrosis was observed among any of the 12 patients. The majority of patients who achieved tumor eradication (80%) and tumor stabilization (67%) after GKS had residual tumor as the reason for their referral for GKS. The best outcomes were attained in patients with residual disease who were younger, had smaller tumor volumes, had no evidence of metastatic disease, and had received higher cumulative GKS doses. CONCLUSIONS: Single or multiple GKS sessions were a well-tolerated, feasible, and effective adjunctive treatment for posterior fossa residual or recurrent medulloblastoma as well as intracranial metastatic medulloblastoma in adult patients.     

Gamma Knife surgery for skull base chordomas and chondrosarcomas

OBJECT: The purpose of this study was to evaluate radiosurgical outcomes in skull base chordomas and chondrosarcomas, and to determine which tumors are appropriate for stereotactic radiosurgery as adjuvant therapy following maximum tumor resection. METHODS: Thirty-seven patients (48 lesions) were treated using Gamma Knife surgery (GKS); 27 had chordomas, seven had chondrosarcomas, and three had radiologically diagnosed chordomas. The mean tumor volume was 20 ml, and the mean maximum and marginal doses were 28 and 14 Gy, respectively. The mean follow-up period was 97 months from diagnosis and 59 months from GKS. RESULTS: The actuarial 5- and 10-year survival rates after GKS were 80 and 53%, respectively. The actuarial 5- and 10-year local tumor control (LTC) rates after single or multiple GKS sessions were 76 and 67%, respectively. All patients with low-grade chondrosarcomas achieved good LTC. A tumor volume of less than 20 ml significantly affected the high rate of LTC (p = 0.0182). No patient had adverse radiation effects, other than one in whom facial numbness worsened despite successful tumor control. CONCLUSIONS: As an adjuvant treatment after resection, GKS is a reasonable option for selected patients harboring skull base chordomas or chondrosarcomas with a residual tumor volume of less than 20 ml. Dose planning with a generous treatment volume to avoid marginal treatment failure should be made at a marginal dose of at least 15 Gy to achieve long-term tumor control.     

Failure of low-dose radiosurgery to control temporal lobe epilepsy.

Radiosurgical treatment of intractable epilepsy has emerged as a noninvasive alternative to resection. Although gamma knife surgery (GKS) reportedly is effective when the radiation dose is sufficient to cause a destructive reaction in the targeted medial temporal lobe, the optimal target area and dose distribution are largely unknown. Some investigators have suggested that focused irradiation from a nondestructive dose is also effective. In this article the authors report two cases of medial temporal lobe epilepsy in which the patients underwent GKS performed using a 50% marginal dose of 18 Gy covering the amygdala. hippocampal head and body, and parahippocampal gyrus. In both cases this procedure failed to control seizures. Both patients became seizure free after undergoing anterior temporal lobectomy 30 and 16 months, respectively, after radiosurgery.     

The effects of stereotactic radiosurgery on secondary facial pain

Twenty-seven patients with tumor-related secondary facial pain were treated by stereotactic radiosurgical procedures between November 1991 and October 1998. They had 14 meningiomas, 11 schwannomas (one trigeminal, 10 vestibular), one nasopharyngeal cancer and one chordoma. The mean maximum dose administered was 26.4 Gy (range 16 to 35 Gy) and the margin of the tumor was encompassed within the 45 to 90% isodose. The patients were analyzed based on their pain relief with a mean follow-up duration of 32.1 months. In 24 patients (85.7%), there was initial pain improvement after radiosurgery, but half had recurrent pain. A pain response was obtained in 12 cases (pain response rate = 42.9%), five were pain free and seven had pain reduction. On the follow-up MRI, a decrease in tumor volume of more than 20% of the preoperative volume occurred in 14 of 25 cases. The mean time interval to initial pain improvement (10.3 months) and pain response (5.7 months) were shorter than for a decrease in tumor volume (18.6 months). Tumor-related secondary facial pain was less responsive to stereotactic radiosurgery than idiopathic trigeminal neuralgia. It would seem that the mechanism of pain relief in radiosurgery is not only trigeminal root decompression secondary to tumor volume reduction, but also other mechanisms involving inactivation of abnormal electrical transmission may be involved.     

Stereotactic radiosurgery for brainstem metastases.

OBJECT: Brainstem metastases portend a dismal prognosis. Surgical resection is not part of routine management and radiation therapy has offered little clinical benefit. Radiosurgery provides a safe and effective treatment for many patients with brain metastasis, but its role in the brainstem has not been evaluated. In this study the authors examine the role of radiosurgery in the treatment of brainstem metastases. METHODS: The authors reviewed the outcomes after stereotactic radiosurgery in 26 patients with 27 brainstem metastases. Tumor locations included the pons (21 tumors) and midbrain (six tumors): 14 patients had additional tumors in other locations. Twenty patients presented with brainstem signs. The median dose to the tumor margin was 16 Gy (range 12-20 Gy). Twenty-four patients received fractionated whole-brain radiation therapy (WBRT) and 12 underwent additional chemotherapy or immunotherapy. The median follow-up time in these patients was 9.5 months (range 1-43 months). After radiosurgery, the local control rate in brainstem tumors was 95%. In one patient in whom the tumor initially decreased in size, tumor enlargement was seen 7 months later. The median survival time was 11 months after diagnosis and 9 months after radiosurgery. Thirteen patients improved, 10 were stable, and three deteriorated. Eventually, 22 patients died, 18 of progression of their extracranial disease, three of new tumor growth (including one hemorrhage into a new brain metastasis), and one of extracranial disease plus new brain tumor growth. CONCLUSIONS: Although they have slightly lower than the expected survival rates of patients with nonbrainstem tumors, patients with brainstem metastases may achieve effective palliation after stereotactic radiosurgery and WBRT.     

Glioblastoma multiforme occurring in a patient treated with gamma knife surgery. Case report and review of the literature

Stereotactic radiosurgery is being increasingly advocated as the primary modality for treatment of vestibular schwannomas (VS). This modality has been shown to arrest tumor growth, with few associated short-term morbidities, and with possibly better hearing and facial nerve preservation rates than microsurgery. Radiation-induced oncogenesis has long been recognized, although stereotactic radiosurgery de novo induction of a secondary tumor has never been clearly described. The authors report on a patient with a VS who did not have neurofibromatosis Type 2 and who underwent gamma knife surgery (GKS). This patient required microsurgical removal of the VS within 8 months because of development of a tumor cyst with associated brainstem compression and progressive hydrocephalus. The operation resulted in clinical stabilization and freedom from tumor recurrence. Seven and a half years after undergoing GKS, the patient presented with symptoms of raised intracranial pressure. Magnetic resonance imaging demonstrated a new ring-enhancing lesion in the inferior temporal lobe adjacent to the area of radiosurgery, which on craniotomy was confirmed to be a glioblastoma multiforme (GBM). Despite additional conventional external-beam radiation to the temporal lobe, the GBM has progressed. Whereas this first reported case of a GBM within the scatter field of GKS does not conclusively prove a direct causal link, it does fulfill all of Cahan's criteria for radiation-induced neoplasia, and demands increased vigilance for the potential long-term complications of stereotactic radiosurgery, and reporting of any similar cases.