O. Schröttner

Gamma knife surgery in mesial temporal lobe epilepsy: a prospective multicenter study.

Summary:  Purpose: This article is the first prospective documentation of the efficacy and safety of gamma knife surgery (GKS) in the treatment of drug‐resistant epilepsies of mesial temporal lobe origin.

Radiosurgery for Epilepsy Associated with Cavernous Malformation: Retrospective Study in 49 Patients

OBJECTIVEMicrosurgical resection of a cavernous malformation (CM) with or without associated cortical resection can provide efficient treatment of drug-resistant associated epilepsy. To explore the potential alternative role of radiosurgery and to evaluate its safety and efficacy for this indication, we conducted a retrospective multicenter study. METHODSWe retrospectively reviewed the files of patients with long-lasting drug-resistant epilepsy, presumably caused by CM, who were treated by gamma knife (GK) surgery for the control of their epilepsy in five centers (Marseilles, Komaki City, Prague, Graz, and Sheffield). A satisfactory follow-up was available for 49 patients (mean follow-up period, 23.66 ± 13 mo). The mean duration of epilepsy before the GK procedure was 7.5 (±9.3) years. The mean frequency of seizures was 6.9/month (±14). The mean marginal radiation dose was 19.17 Gy ± 4.4 (range, 11.25–36). Among the 49 patients, 17 (35%) had a CM located in or involving a highly functional area. RESULTSAt the last follow-up examination, 26 patients (53%) were seizure-free (Engel’s Class I), including 24 in Class IA (49%) and 2 patients with occasional auras (Class IB, 4%). A highly significant decrease in the number of seizures was achieved in 10 patients (Class IIB, 20%). The remaining 13 patients (26%) showed little or no improvement. The mediotemporal site was associated with a higher risk of failure. One patient bled during the observation period, and another experienced radiation-induced edema with transient aphasia. Postradiosurgery excision was performed in five patients, and a second radiosurgical treatment was carried out in one patient. CONCLUSIONThis series is the first to specifically evaluate the capability of GK surgery to safely and efficiently treat epilepsy associated with CM. Seizure control can be reached when a good electroclinical correlation exists between CM location and epileptogenic zone. Although we do not recommend GK surgery for prevention of bleeding for a CM that has not bled previously, our findings suggest that GK surgery can be proposed for the treatment of epilepsy when the CM is located in a highly functional area.

Incidence of radiation retinopathy after high-dosage single-fraction gamma knife radiosurgery for choroidal melanoma

OBJECTIVE To investigate the incidence and clinical findings of radiation retinopathy after single-fraction high-dose gamma knife radiosurgery for choroidal melanoma. DESIGN Retrospective noncomparative interventional case series. PARTICIPANTS Thirty-two patients with choroidal melanoma. METHODS Review of charts, color fundus photographs, and fluorescein angiograms of 32 choroidal melanoma patients after radiosurgery. All patients were treated with the Leksell gamma knife in one fraction with a marginal dose between 40 and 80 Gy (median, 50 Gy) and were followed for at least 24 months (or until enucleation because of complications secondary to radiation). MAIN OUTCOME MEASURES Any clinical feature of radiation retinopathy and neovascular glaucoma. RESULTS During a mean follow-up of 38 months (range, 6-81 months) we found radiation retinopathy in 84% of our patients. The most common findings in these patients were intraretinal hemorrhages with an incidence of 70%, macular edema and capillary nonperfusion in 63%, and hard exudates in 52% of the patients. Less common were microaneurysms in 30% and retinal neovascularization in 22%. The time of onset of the various radiation-associated retinal findings ranged between 1 and 22 months. Forty-seven percent of all patients developed neovascular glaucoma. In our study there was no correlation between radiation dosage applied and clinical findings. CONCLUSIONS Single-fraction high-dose Leksell gamma knife radiosurgery of choroidal melanomas with a median marginal dose of 50 Gy is highly associated with early radiation retinopathy and with neovascular glaucoma.

Cavernous Sinus Meningiomas – What Is the Strategy: Upfront or Adjuvant Gamma Knife Surgery?

43 patients with meningiomas of the cavernous sinus form the basis of this study. Two patients were treated with microsurgery alone, 17 patients were treated by Gamma Knife radiosurgery (GKRS) as a primary treatment modality, and 24 patients underwent a combined treatment of microsurgery followed by GKRS. Therefore, in 17 patients the diagnosis rested on clinical and radiological criteria alone. Cranial nerve disorders (CND) related to open surgical treatment were infrequent in this material (3 of 13 patients) due to deliberate strategies of partial or subtotal resection aimed at sparing cranial nerves from surgical maneuvers. In contrast, 6 of 11 patients, admitted for GKRS from other institutions suffered from considerable CND after open surgery and showed only partial improvement after GKRS. In all GKRS cases, no radiation-related complications were seen after a follow-up of 18–62 months (mean 39 months). Moreover, in all cases tumor control was obtained with a stable tumor volume in 63%, reduction of volume in 34.5% and a disappearance of tumor in 2.5%. GKRS is not only an additional treatment for meningiomas involving the cavernous sinus, but may be offered to the patient as an alternative primary treatment.

Radiation Sensitivity of Visual and Oculomotor Pathways

Adverse effects of stereotactic radiosurgery on cranial nerves, especially the optic nerve and its pathways, are not yet sufficiently understood. 29 patients who underwent Gamma Knife radiosurgery for benign skull base tumors were reviewed. In all of them, parts of the visual pathways and/or other cranial nerves in the middle cranial fossa received significant doses of radiation. The dose given was correlated with neuro-ophthalmological findings during a follow-up period of 6-24 months. Cranial nerves III, IV and VI within the cavernous sinus, exposed to a dose from 4.5 to 30 Gy, did not develop signs of a neuropathy. Neither did the trigeminal nerve which received between 5 and 20 Gy. In patients with normal neuro-ophthalmological findings prior to radiosurgery, the visual pathways tolerated a dose between 7.5 to 15 Gy. However, in a group of patients with visual deficits before treatment and where the visual fibers received between 6 and 16.6 Gy, 31% deteriorated afterwards. These results indicate that the visual pathways are more at risk for radiation damage than the other cranial nerves in the region and that they may be even more vulnerable to radiation if prior to radiosurgery their function has been compromised by tumor or previous surgery.

Radiosurgery in Lesional Epilepsy: Brain Tumors

The purpose of this study was to examine the effects of different doses of radiation to the brain tissue immediately adjacent to tumors which were associated with epilepsy. From April 1992 to December 1995, 26 patients with medically intractable tumor epilepsy (mean duration 6.9 years, range: 1–27 years) have been treated with Gamma Knife radiosurgery (GKRS). Clinical and imaging controls were available for 24 patients with a mean follow-up of 2.25 years (range: 1–4.4 years). Tumor control had been achieved in all patients. The patients were divided into two groups according to the volume of tissue outside the tumor which had received 10 Gy or more. This volume was assessed by measuring the ratio of the tumor and the ratio of the volume within the isodose containing 10 Gy (10G/Tum ratio). 54 percent of all the 24 patients achieved an excellent result according to the Engel classification (class I or II). The patients were divided into two groups. In group I were 12 patients, and the 10G/Tum ratio was 3 or less. In group II there were 12 patients and the 10G/Tum ratio was more than 3. In group I the mean value for the 10G/Tum ratio was 2 (range 0.86 to 2.9). In group II the mean value of the ratio was 11.1 (range 3.13 to 63.2). In group I only 42% of patients achieved an excellent result compared with 66% in group II. Moreover, the location of the tumor had an effect on the results, in that temporal tumors were associated with excellent results in 64% of cases as opposed to 40% in extratemporal tumors. Finally, if the epilepsy had lasted for 2.5 years or less there were excellent results in 70% of patients, as opposed to 43% excellent results for patients who had suffered epilepsy for more than 2.5 years.

Radiation-Induced Edema after Gamma Knife Treatment for Meningiomas

A retrospective study was performed to analyze some parameters in a consecutive series of 35 Gamma Knife treatments in 34 patients with benign meningiomas. The minimum dose to the tumors was never less than 12 Gy. The follow-up period was from 1 to 3 years. A semiquantitative method of tumor volume assessment was used to measure the tumor response to treatment. The presence and clinical significance of postradiation edema were noted. Even in this short follow-up period, 11 of the 35 tumors were reduced in volume. No tumors increased in size. Edema developed preferentially in nonbasal tumors, especially those around the midline and sagittal sinus. In all but one case where radiation-induced edema was observed was the margin tumor dose 18 Gy or more. It is suggested that doses of 18 Gy or more should probably be avoided in the Gamma Knife treatment of meningiomas and that the greatest care should be taken in selecting non-skull base tumors for this form of treatment.

Efficacy and safety of radiosurgical callosotomy: a retrospective analysis.

Summary:  Purpose: Anterior callosotomy is a surgical option for the treatment of generalized tonic or atonic seizures associated with drop attacks. Besides open surgery, a radiosurgical callosal disconnection using the gamma knife (GK) also can be performed, but reliable data about tolerability and efficacy are sparse.

Cranial Nerve Preservation after Radiosurgery of Vestibular Schwannomas

Radiosurgery is a management approach used to treat patients with vestibular schwannomas. The goals are long-term tumour growth control, maintenance of cranial nerve function and prevention of new deficiencies. We sought to determine long-term outcomes measuring the potential benefits against the neurological risks of primary radiosurgery. Gamma Knife radiosurgery was applied as a treatment modality for 289 patients with vestibular schwannomas from April 1992 to April 2002. The long-term results of 100 patients who underwent radiosurgery were evaluated. 60 patients received a primary treatment, 40 other cases presented with previously performed subtotal microsurgical resection or recurrence of disease (12-96 months, median 39). The median treatment volume was 3.4 ccm and the median dose to the tumour margin was 13 Gy. The median patient follow-up time was 76 months (range 60-120 months). Four tumours progressed after primary radiosurgery. Tumour control rate was 96%. Useful hearing (Gardner-Robertson I/II) was preserved in 16 patients (55%). Clinical neurological improvement occurred in 50%. Adverse effects comprised neurological symptoms (incomplete facial palsy) (House-Brackman II/III) in six cases (four recovered completely), mild transient trigeminal neuropathy in five cases, and morphological changes displaying rapid enlargement of preexisting macrocysts in two patients and tumour growth in two other patients. Microsurgical resection was performed in four cases (4%) and two patients underwent a shunting procedure because of hydrocephalus formation (2%). In patients who had undergone previous microsurgery, no new cranial nerve deficit was observed. Radiosurgery is an effective method for growth control of vestibular schwannomas and is associated with both a low mortality rate and a good quality of life. Accordingly, for the preservation of cranial nerve function radiosurgery is a useful method for the management of properly selected patients and is comparable to microsurgery.

Thalamotomy and Caudatotomy with the Gamma Knife as a Treatment for Parkinsonism with a Comment on Lesion Sizes

Radiosurgery with the Gamma Knife was performed in 12 patients with parkinsonism. In 9 patients small lesions were created in the head of the caudate nucleus bilaterally. Two patients underwent radiosurgical thalamotomy, and 1 patient was treated with caudatotomy and thalamotomy. After a follow-up period of 1-12 months, 9 patients of the caudatotomy group and all patients with thalamotomies showed clear benefit. There was no complication or side effect that could be related to the treatment. Pre- and postoperative testing was performed with the Unified Parkinson Rating Scale and with objective motor tasks. Caudatotomy proved to be an effective treatment for bradykinesia and rigidity, while tremor was ameliorated by thalamotomy. Functional neurosurgery with the Gamma Knife would seem to be a good alternative to open procedures with low morbidity and no mortality. Advantages and drawbacks of radiosurgical techniques for the treatment of parkinsonism are discussed.