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–40)  median margin dose (range) 20 (18–20) Gamma knife surgery was performed using the Leksell gamma knife models (Elekta Instrument AB, Stockholm, Sweden). Treatment planning was performed using KULA or Leksell GammaPlan (Elekta Instruments AB) and stereotactic computerized tomography or MR images. The treatment protocol calls for the irradiation of the enhanced mass with a margin dose of 20 Gy. In cystic tumors only the mural nodule is targeted. In this series, all tumor margins were covered by the 50% isodose. Twenty-eight tumors received 20 Gy to the

.76.1.0038 37. Seo Y , Fukuoka S , Takanashi M , et al : Gamma knife surgery for angiographically occult vascular malformations. Stereotact Funct Neurosurg (suppl 1) 64 : 98 – 109 , 1995 Seo Y, Fukuoka S, Takanashi M, et al: Gamma knife surgery for angiographically occult vascular malformations. Stereotact Funct Neurosurg (suppl 1) 64: 98–109, 1995 8584845 10.1159/000098769 38. Strugar J , Rothbart D , Harrington W , et al : Vascular permeability factor in brain metastases: correlation with

of recurrence and possibly defines the need for adjuvant therapy. 5 Radiotherapy after resection of benign and AMs continues to be controversial. 3 Because of the rarity of AMs and differences in the way they were classified, the literature on the role of radiation is difficult to interpret. As a result, the treatment has largely been extrapolated from data on both benign and malignant meningiomas. Gamma knife surgery has proven beneficial in the treatment of benign meningiomas, both as an adjunct to subtotal resection and as a primary treatment for selected

after GKS, the cyst remained the same size. Illustrative Case Case 1 This 22-year-old woman with VHL disease underwent a partial excision of her largest cystic hemangioblastoma. Gamma knife surgery was subsequently performed for 12 small solid tumors, one small cystic tumor, and the one surgical remnant. The dose delivered to the tumor margin was 17.5 Gy at the 70% isodose (an 8-mm collimator) for the two large-volume lesions and 17.4 Gy at the 60% isodose line (a 4-mm collimator) for the two small solid lesions. At 6 years, progressive headache

, and GKS was performed as a supportive treatment. In recent years, with refined MR imaging techniques, the detection rate of cavernous hemangiomas has increased. Most occult vascular malformations are reported as cavernous hemangioma. We describe the results of GKS for cavernous hemangiomas. Clinical Material and Methods Between October 1994 and December 2002, GKS was performed in 65 patients with cavernous hemangiomas. Forty-two cases underwent follow-up MR imaging. Gamma knife surgery was conducted after injection of a local anesthestic. Stereotactic MR

S ince GKS was introduced in the 1960s as a less invasive treatment method for functional disorder, the indication has been extended to many kinds of intracranial diseases. Intracranial meningiomas are one of the common indications for GKS, especially those located at the skull base. 4, 5, 7, 8 Gamma knife surgery has not, however, been commonly performed for superficially located meningiomas because it is relatively easy to resect such tumors and there is a high incidence of complications associated with peritumoral edema after GKS. 1, 3, 11, 14–17 Recently

Table 3 and Fig. 4 . Side effects appeared in six patients (32%) after a median latency of 21 months (range 1–72 months). Fig. 4. A Kaplan—Meier curve showing the rates of sensory impairment after the second GKS. Discussion Gamma knife surgery for TN has come to be seen as a rewarding treatment method. The initial overall success rate was 96% in our patients and 80% of them were pain free after GKS. Moreover, the results reported by different authors are fairly similar, and the success rate is generally excellent or very good. The

radiotherapy after either embolization or surgery in one each. All of these treatments had failed to obliterate the AVMs. Gamma knife surgery was the primary treatment in the remaining 19 patients (59%). At the time of GKS, 19 patients (59%) demonstrated no neurological deficits, and the others showed some clinical symptoms caused by past hemorrhage or prior treatment sequelae. There was headache in five, seizures in three, motor weakness in four, recent memory disturbance in three, aphasia in two, and a sensory disturbance in one. The location of the AVM nidus within the

treated with repeated GKS when their volumes increased after the initial treatment. Treatment Parameters Gamma knife surgery was performed using the Leksell gamma unit (Model U; Elekta Instruments, Inc., Norcross, GA) before July 2001 and the Leksell gamma unit C after July 2001. All patients were treated by the senior author (L.S.). Forty patients without a history of WBRT received prescription doses between 18 and 24 Gy; 142 patients with a history of WBRT received margin doses between 14 and 18 Gy. In three cases of repeated GKS for refractory brain

M eningioma is a common type of benign intracranial tumor but it is not always easily removed by surgery. Gamma knife surgery has become an important treatment modality for meningioma, especially in cases of skull base lesions. 3–6, 8, 10–13, 15–17, 20–22 Recently, however, it has become known that GKS may occasionally be associated with cyst formation following treatment for vestibular schwannoma 7 and arteriovenous malformation. 14 In addition, peritumoral edema occurs after GKS in approximately 10% of hemispheric tumors, such as convexity or parasagittal