Top 25 Cited Gamma Knife® Surgery Articles - Volume 111

Object. The purpose of this study was to assess the durability and completeness of pain relief in patients treated using stereotactic gamma knife surgery (GKS) for trigeminal neuralgia (TN).

Methods. Thirty-eight patients with refractory TN were treated with stereotactic GKS. All patients received a prescription radiation dose of 35, 40, or 45 Gy to the 50% isodose surface through a 4-mm collimator helmet. The group was assessed regularly based on physician-directed interviews for a median follow up of 24 months (range 6–27 months). Pain relief was classified as excellent (no pain without medication), good (well-controlled pain with continued medication), fair (decreased but residual pain with continued medication), or poor (unimproved or increased pain with the same or increased medication).

Three months after treatment, pain relief was good or excellent in 71% of patients. By 24 months post-GKS, 50% of the original cohort had poor pain relief, 21% continued to have either excellent or good relief, 3% had fair relief, and 26% had not reached the 24-month follow up. Based on their status at the last follow up, 29% of patients had excellent and 16% had good pain relief. Thirty-seven percent experienced facial numbness, which was dose related. In addition, there was a significantly higher rate of complete pain relief in patients who had facial numbness following treatment (p = 0.003).

Conclusions. Stereotactic GKS is an effective treatment in patients with TN; however, the durability of pain relief and the time to treatment response are limiting factors. As with other types of ablative treatment, facial numbness is strongly associated with better treatment response.

Object. Hypothalamic hamartoma is a nonneoplastic malformative mass of neurons and glia in the region of the hypothalamus. Because of its location, open surgery is associated with high morbidity and mortality rates. Gamma knife surgery (GKS) may be an efficient and safe treatment approach, which produces little morbidity. The authors describe the results of GKS in three patients with hypothalamic hamartomas.

Methods. All patients were male, aged 3, 12, and 15 years. The lesions were classified according to the Valdueza scale: one was Type IIb and two were Type IIa. The patients presented with gelastic seizures (15–20 per day), generalized epilepsy, behavioral abnormalities, and alterations of the sleep cycle. Precocious puberty was present in one patient. The Type IIb tumor had a volume of 1.8 cm³, and the Type IIa tumors were 597 mm³ and 530.1 mm³. The lesions received 12.5 Gy, 14 Gy, and 15 Gy, respectively, to the 50% isodose line. The patients were followed for 30 to 50 months. After 3 months, all patients showed improvement of their sleep, behavior, and epilepsy. At the present time, these patients are receiving low-dose antiepileptic agents and have achieved adequate social development and school integration.

Conclusions. Gamma knife surgery appears to be a good, safe, and effective option for the treatment of selected hypothalamic hamartomas. No morbidity or mortality was associated with these three cases.

Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.

Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm³ (range 0.04–23.1 cm³). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.

A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.

Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Object. The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs).

Methods. Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T₂-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05).

Conclusions. Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

Object. Gamma knife surgery (GKS) has been a safe and effective treatment for vestibular schwannomas in both the short and long term, although less is known about long-term outcomes in the past 10 years. The aim of this study was to clarify long-term outcomes in patients with vestibular schwannomas treated using GKS based on techniques in place in the early 1990s.

Methods. Eighty patients harboring a vestibular schwannoma (excluding neurofibromatosis Type 2) were treated using GKS between May 1991 and December 1993. Among these, 73 patients were assessed; seven were lost to follow up. The median duration of follow up was 135 months. The mean patient age at the time of GKS was 56 years old. The mean tumor volume was 6.3 cm³, and the mean maximal and marginal radiation doses applied to the tumor were 28.4 and 14.6 Gy, respectively. Follow-up magnetic resonance images were obtained in 71 patients. Forty-eight patients demonstrated partial tumor remission, 14 had tumors that remained stable, and nine demonstrated tumor enlargement or radiation-induced edema requiring resection. Patients with larger tumors did not fare as well as those with smaller lesions. The actuarial 10-year progression-free survival rate was 87% overall, and 93% in patients with tumor volumes less than 10 cm³. No patient experienced malignant transformation.

Conclusions. Gamma knife surgery remained an effective treatment for vestibular schwannomas for longer than 10 years. Although treatment failures usually occurred within 3 years after GKS, it is necessary to continue follow up in patients to reveal delayed tumor recurrence.

Object. The authors evaluated the long-term efficacy of gamma knife surgery (GKS) in patients with trigeminal schwannomas.

Methods. Fifty-six patients, 31 women and 25 men (mean age 42 years), underwent GKS for trigeminal schwannomas. Fourteen had previously undergone surgery, and GKS was the primary treatment in the remaining 42 patients. The mean target volume was 8.7 cm³ (range 0.8–33 cm³); the mean maximum dose was 27 Gy (range 20–40 Gy); the mean tumor margin dose was 13.3 Gy (range 10–15 Gy); and the mean follow-up period was 68 months (range 27–114 months).

Disappearance of the tumor occurred in seven patients. An obvious decrease in tumor volume was observed in 41 patients, four tumors remained unchanged, and four tumors progressed at 5, 26, 30, and 60 months, respectively. One patient with disease progression died of tumor progression at 36 months after GKS. The tumor growth control rate in this group was 93% (52 of 56 cases).

Mild numbness or diplopia was relieved completely in 14 patients. Improvement of other neurological deficits was demonstrated in 25 patients. Trigeminal nerve dysfunction was either unchanged or slightly worse in 13 patients after GKS. Four patients experienced mild symptom deterioration related to tumor progression.

Conclusions. Radiosurgery proved to be an effective treatment for small- and medium-sized trigeminal schwannomas. Some larger tumors are also suitable for radiosurgery if there is no significant brainstem compression.

Object. The purpose of the study was to define the therapeutic profile of outpatient gamma knife surgery (GKS) for vestibular schwannoma (VS) by using sequential tumor volumetry to quantify changes following treatment.

Methods. A total of 111 patients met the inclusion criteria. The median follow-up duration was 7 years (range 5–9.6 years). Thirty-seven patients (33%) had undergone surgery before GKS and 10 (9%) had neurofibromatosis Type 2 (NF2). The median VS volume was 1.6 cm³ (range 0.08–8.7 cm³).

The actuarial 6-year tumor control rate after a single GKS treatment was 95%. Tumor swelling was observed in 43 patients (38.7%). Recurrence was significantly associated with NF2 (p < 0.003) and the reduced dose (p < 0.03) delivered to these tumors. The incidence of facial nerve neuropathy was mainly determined by surgery prior to GKS (p < 0.0001). Facial nerve radiation toxicity was mild and transient. No permanent facial nerve toxicity was observed. Trigeminal neuropathy occurred in 13 patients, and this was correlated with the VS volume (p < 0.02). The median hearing loss was −10 dB (range + 20 dB to −70 dB). The risk of hearing loss was correlated with age and transient tumor swelling (p < 0.05) but not with dose parameters or NF2.

Conclusions. Outpatient GKS is feasible, effective, and safe. Its therapeutic profile compares favorably with that of microsurgery.

Object. Lung carcinoma is the leading cause of death from cancer. More than 50% of those with small cell lung cancer develop a brain metastasis. Corticosteroid agents, radiotherapy, and resection have been the mainstays of treatment. Nonetheless, median survival for patients with small cell lung carcinoma metastasis is approximately 4 to 5 months after cranial irradiation. In this study the authors examine the efficacy of gamma knife surgery for treating recurrent small cell lung carcinoma metastases to the brain following tumor growth in patients who have previously undergone radiation therapy, and they evaluate factors affecting survival.

Methods. A retrospective review of 27 patients (47 recurrent small cell lung cancer brain metastases) undergoing radiosurgery was performed. Clinical and radiographic data obtained during a 14-year treatment period were collected. Multivariate analysis was utilized to determine significant prognostic factors influencing survival.

The overall median survival was 18 months after the diagnosis of brain metastases. In multivariate analysis, factors significantly affecting survival included: 1) tumor volume (p = 0.0042); 2) preoperative Karnofsky Performance Scale score (p = 0.0035); and 3) time between initial lung cancer diagnosis and development of brain metastasis (p = 0.0127). Postradiosurgical imaging of the brain metastases revealed that 62% decreased, 19% remained stable, and 19% eventually increased in size. One patient later underwent a craniotomy and tumor resection for a tumor refractory to radiosurgery and radiation therapy. In three patients new brain metastases were demonstrating on follow-up imaging.

Conclusions. Stereotactic radiosurgery for recurrent small cell lung carcinoma metastases provided effective local tumor control in the majority of patients. Early detection of brain metastases, aggressive treatment of systemic disease, and a therapeutic strategy including radiosurgery can extend survival.

Object. Management options for vestibular schwannomas (VSs) have greatly expanded since the introduction of stereotactic radiosurgery. Optimal outcomes reflect long-term tumor control, preservation of cranial nerve function, and retention of quality of life. The authors review their 15-year experience.

Methods. Between 1987 and 2002, some 829 patients with VSs underwent gamma knife surgery (GKS). Dose selection, imaging, and dose planning techniques evolved between 1987 and 1992 but thereafter remained stable for 10 years. The average tumor volume was 2.5 cm³. The median margin dose to the tumor was 13 Gy (range 10–20 Gy).

No patient sustained significant perioperative morbidity. The average duration of hospital stay was less than 1 day. Unchanged hearing preservation was possible in 50 to 77% of patients (up to 90% in those with intracanalicular tumors). Facial neuropathy risks were reduced to less than 1%. Trigeminal symptoms were detected in less than 3% of patients whose tumors reached the level of the trigeminal nerve. Tumor control rates at 10 years were 97% (no additional treatment needed).

Conclusions. Superior imaging, multiple isocenter volumetric conformal dose planning, and optimal precision and dose delivery contributed to the long-term success of GKS, including in those patients in whom initial microsurgery had failed. Gamma knife surgery provides a low risk, minimally invasive treatment option for patients with newly diagnosed or residual VS. Cranial nerve preservation and quality of life maintenance are possible in long-term follow up.

Object. The authors sought to assess the respective roles of microsurgery and gamma knife surgery (GKS) in the treatment of patients with meningiomas.

Methods. The authors culled from a 4-year prospective database data on 74 cases of meningiomas. Thirty-eight were treated with GKS and 35 with microsurgery. Simpson Grade 1 or 2 resection was achieved in 86.1% of patients who underwent microsurgery. Patients who underwent GKS received a mean margin dose of 16.4 Gy (range 14–20 Gy). The mean tumor coverage was 94.7%, and the mean conformity index was 1.76. Significant differences between the two treatment groups (GKS compared with microsurgery) included age (mean 60 compared with 50.7 years), volume (mean 7.85 cm³ compared with 44.4 cm³), treatment history (55.3% compared with 14.3%), and tumor location (cavernous sinus/petroclival, 14 compared with three). The median follow up was 21.5 months (range 1.5–50 months). In patients with benign meningiomas GKS tumor control was 96.8% with one recurrence at the margin. The recurrence rate was zero of 27 for Simpson Grade 1 or 2 resection and three of four for higher grades in those patients who underwent microsurgery. There was no procedure-related mortality or permanent major neurological morbidity. The mean Karnofsky Performance Scale score was maintained for both forms of treatment. Symptoms improved in 48.4% of patients undergoing microsurgery and 16.7% of those who underwent GKS. Transient and permanent cranial nerve morbidity was 7.9 compared with 2.9%, and 5.3 compared with 8.5% for GKS and microsurgery, respectively. In a patient satisfaction survey 93.1% of microsurgery patients and 91.2% of GKS patients were highly satisfied.

Conclusions. Both GKS and microsurgery serve important roles in the overall management of patients with meningiomas. Both are safe and effective and provide high degrees of satisfaction when used for differentially selected patients.