Radiosurgery for epilepsy associated with cavernous malformation: retrospective study in 49 patients

Epilepsy associated with cerebral cavernous malformations managed with stereotactic radiosurgery: an international, multicenter study

OBJECTIVE

Stereotactic radiosurgery (SRS) has been proposed as an alternative to resection for epilepsy control in patients with cerebral cavernous malformations (CCM) located in critical areas.

METHODS

This multicentric, retrospective study evaluated seizure control in patients with a solitary CCM and a history of at least one seizure prior to SRS.

RESULTS

109 patients (median age at diagnosis 28.9 years, interquartile range (IQR) 16.4 years] were included. Prior to SRS, 2 (1.8%) were seizure-free without medication, 35 (32.1%) were seizure-free with antiseizure medications (ASM), 17 (15.6%) experienced an improvement of at least 50% in seizure frequency/intensity with ASM, and 55 (50.5%) experienced an improvement of less than 50% in seizure frequency/intensity with ASM. At a median follow-up of 3.5 years post-SRS (IQR: 4.9), 52 (47.7%) patients were Engel class I, 13 (11.9%) class II, 17 (15.6%) class III, 22 (20.2%) class IVA or IVB and 5 (4.6%) class IVC. For the 72 patients who had seizures despite medication prior to SRS, a delay > 1.5 years between epilepsy presentation and SRS decreased the probability to become seizure-free, HR 0.25 (95% CI 0.09-0.66), p = 0.006. The probability of achieving Engel I at the last follow-up was 23.6 (95% CI 12.7-33.1) and 31.3% (95% CI 19.3-50.8) at 2 and 5 years respectively. 27 patients were considered as having drug-resistant epilepsy. At a median follow-up of 3.1 years (IQR: 4.7), 6 (22.2%) of them were Engel I, 3 (11.1%) Engel II, 7 (25.9%) Engel III, 8 (29.6%) Engel IVA or IVB and 3 (11.1%) Engel IVC.

INTERPRETATION

47.7% of patients managed with SRS for solitary CCM presenting with seizures achieved Engel class I at the last follow-up.

Role of Genetics and Surgical Interventions for the Management of Cerebral Cavernous Malformations (CMM)

Cerebral cavernous malformations (CCMs) are comprised of tissue matter within the brain possessing anomalous vascular architecture. In totality, the dilated appearance of the cavernomatakes on a mulberry-like shape contributed by the shape and relation to vascular and capillary elements. Analyzing its pathophysiology along with its molecular and genetic pathways plays a vital role in whether or not a patient receives GKRS, medical management, or Surgery, the most invasive of procedures. To avoid neurological trauma, microsurgical resection of cavernomas canbe guided by the novel clinical application of a 3D Slicer with Sina/MosoCam. When cavernomas present in deep lesions with poor accessibility, gamma knife stereotactic radiosurgery (GKSR) is recommended. For asymptomatic and non-multilobal lesions, medical and symptom management is deemed standard, such as antiepileptic therapy. The two-hit hypothesis serves to explain the mutations in three key genes that are most pertinent to the progression of cavernomas: CCM1/KRIT1, CCM2/Malcavernin, and CCM3/PDCD10. Various exon deletions and frameshift mutations can cause dysfunction in vascular structure through loss and gain of function mutations. MEKK3 and KLF2/4 are involved in a protein kinase signaling cycle that promotes abnormal angiogenesis and cavernoma formation. In terms of potential treatments, RhoKinase inhibitors have shown to decrease endothelial to mesenchymal transition and CCM lesion development in mice models. All in all, understanding the research behind the molecular genetics in CCMs can foster personalized medicine and potentially create new neurosurgical and medicative treatments.

Approach Selection Strategies for Repeat Resection of Brain Cavernous Malformations: Cohort Study

BACKGROUND

Neurosurgical management of cerebral cavernous malformations (CMs) often benefits from using skull base approaches. Although many CMs are cured by resection, residual or recurrent disease may require repeat resection.

OBJECTIVE

To review approach selection strategies for reoperation of CMs to aid decision-making for repeat procedures.

METHODS

In this retrospective cohort study, a prospectively maintained single-surgeon registry was queried for patients with CMs who underwent repeat resection from January 1, 1997, to April 30, 2021.

RESULTS

Of 854 consecutive patients, 68 (8%) underwent 2 operations; 40 had accessible data on both. In most reoperations (33/40 [83%]), the index approach was repeated. In most reoperations using the index approach (29/33 [88%]), that approach was deemed ideal (no equivalent or superior alternative), whereas in some (4/33 [12%]), the alternative approach was deemed unsafe because of conformation of the tract. Among patients with reoperations using an alternative approach (7/40 [18%]), 2 with index transsylvian approaches underwent bifrontal transcallosal approaches, 2 with index presigmoid approaches underwent extended retrosigmoid revisions, and 3 with index supracerebellar-infratentorial approaches underwent alternative supracerebellar-infratentorial trajectory revisions. Among patients with reoperations with an alternative approach considered or selected (11/40 [28%]), 8 of 11 patients had a different surgeon for the index resection than for the repeat resection. The extended retrosigmoid-based approaches were used most often for reoperations.

CONCLUSION

Repeat resection of recurrent or residual CMs is a challenging neurosurgical niche at the intersection of cerebrovascular and skull base disciplines. Suboptimal index approaches may limit surgical options for repeat resection.

Outcome of intracerebral cavernoma treated by Gamma Knife radiosurgery based on a double-blind assessment of treatment indication

BACKGROUND

The benefit and the risk profile of Gamma Knife radiosurgery (GKRS) for intracerebral cavernoma remains incompletely defined in part due to the natural history of low incidence of bleeding and spontaneous regression of this vascular malformation. In this study, we retrieved cases from a prospectively collected database to assess the outcome of intracerebral cavernoma treated with GKRS using a double blinded review process for treatment.

METHODS

From 2003 to 2018, there were 94 cases of cavernoma treated by GKRS in the doubly blinded assessments by two experienced neurological and approved for GKRS treatment. All the patients received GKRS with margin dose of 11-12 (Gray) Gy and afterwards were assessed for neurological outcome, radiologic response, and quality of life.

RESULTS

The median age of the patients was 48 (15-85) years with median follow up of 77 (26-180) months post SRS. The mean target volume was 1.93 ± 3.45 cc. In those who has pre-SRS epilepsy, 7 of 16 (43.7%) achieved seizure freedom (Engel I/II) and 9 of 16 (56.3%) achieved decreased seizures (Engel III) after SRS. Rebleeding occurred in 2 cases (2.1%) at 13 and 52 months post SRS. The radiologic assessment demonstrated 20 (21.3%) cases of decreased cavernoma volume, 69 (73.4%) were stable, and 5 (7.3%) increased size. Eighty-seven of 94 (92.5%) cases at the last follow up achieve improvement in their quality of life, but 7 cases (7.4%) showed a deterioration. In statistical analysis, the effective seizure control class (Engel I/II) was highly correlated with patient harboring a single lesion (p < 0.05) and deep seated location of the cavernoma (p < 0.01). New neurological deficits were highly correlated with decreased mental (p < 0.001) and physical (p < 0.05) components of quality of life testing, KPS (p < 0.001), deep seated location (p < 0.01), and increased nidus volume (p < 0.05). Quality of life deterioration either in physical component (p < 0.01), mental component (p < 0.01), and KPS (p < 0.05) was highly correlated with increased cavernoma volume.

CONCLUSION

Low margin dose GKRS for intracerebral cavernoma offers reasonable seizure control and improved quality of life while conferring a low risk of treatment complications including adverse radiation effect.

Treatment of Cerebral Cavernous Malformations Presenting With Seizures: A Systematic Review and Meta-Analysis

Background: Cerebral cavernous malformations (CCMs) presenting with seizures can be treated with neurosurgery or radiosurgery, but the ideal treatment remains unclear. Currently, there is no adequate randomized controlled trial comparing surgical treatment and radiotherapy for epileptogenic CCMs. Therefore, we conducted a systematic review and meta-analysis of available data from published literature to compare the efficacy and safety of neurosurgery and radiosurgery for epileptogenic CCMs. Methods: We performed a comprehensive search of the Ovid MEDLINE, Web of Science, PubMed, China Biological Medicine and China National Knowledge Infrastructure databases for studies published between January 1994 and October 2019. The search terms were as follows: "epilepsy," "seizures," "brain cavernous hemangioma," "cerebral cavernous malformation," "cerebral cavernous hemangioma," "hemangioma, cavernous, central nervous system." Two researchers independently extracted the data and reviewed all the articles. We compared the advantages and disadvantages of the two treatments. Results: A total of 45 studies were included in our analysis. Overall, the seizure control rate was 79% (95% CI: 75-83%) for neurosurgery and 49% (95% CI: 38-59%) for radiosurgery. In the neurosurgery studies, 4.4% of patients experienced permanent morbidity, while no patients in the radiotherapy studies had permanent morbidity. In addition, the results of subgroup analysis showed that ethnicity, CCMs location and average lesion number are likely significant factors influencing the seizure outcome following treatment. Conclusions: The epilepsy control rate after neurosurgery was higher than that after radiosurgery, but neurosurgery also had a relatively higher rate of permanent morbidity.

[Functional stereotactic radiosurgery: Indications and perspectives]

Stereotactic radiosurgery (SRS) is a non-invasive technique that enables to create brain focal lesions with a high precision and localization. Thus, functional brain disorders can be treated by SRS in case of pharmacoresistance or inoperability. To date, treatment of trigeminal neuralgia is the most described and known indication. Other indications will be developed in the future like movement disorders, refractory epilepsy, obsessive compulsive disorder and severe depression. We present here a review of actual and future indications of functional brain SRS with their level of evidence. All these SRS treatments have to be strictly conducted by trained teams with an excellent collaboration between radiation physicists, medical physicists, neurosurgeons, neurologists, psychiatrists and probably neuroradiologists.

Contemporary radiosurgery of cerebral cavernous malformations: Part 2. Treatment outcome for hemispheric lesions

OBJECTIVE

The role of radiosurgery (RS) in treating superficial cavernous malformations (CMs) is insufficiently studied in part because of the disappointing results of early experimental attempts as compared to the mostly safe and effective microsurgery. Nonetheless, because of lesion- or treatment-specific factors, a therapeutic alternative may be required. In this study, the authors aimed to assess the safety of RS in treating superficial CMs and to analyze its long-term effect on hemorrhage rates and epilepsy control.

METHODS

The authors conducted a retrospective analysis of 96 patients with 109 CMs located in the cerebral or cerebellar hemispheres and treated with RS between 1995 and 2014. A median of 15 Gy (range 10-25 Gy) was given to the 50% prescription isodose level, lesion volume was 604 mm3 (4-8300 mm3), and the prescription isodose volume was 638.5 mm3 (4-9500 mm3). Outcomes were compared to those of 206 deep-seated lesions reported on in another study. Ninety-five patients had available follow-up, which was a median of 7 years (1-21 years). Median patient age was 42 years (0.5-77) at presentation and 45 (3-80) at treatment. Seventy-one CMs presented with symptomatic hemorrhage, and 52 caused seizures.

RESULTS

In the nonhemorrhagic group (37 lesions), one bleed occurred during the follow-up period, for an annual bleed rate of 0.4% per lesion. The lifetime annual bleed rate of CMs having a single hemorrhage prior to treatment was 2.5%. The rebleed rate in the single-bleed group decreased from 1.8% within the first 2 years after RS to 0.7% thereafter. The pretreatment rebleed rate for lesions having multiple bleeds prior to RS was 14.15%, which fell to 3.85% for the first 2 years after RS and declined to 1.3% thereafter. Multivariate analysis showed younger age, deep lesion location, and multiple pretreatment hemorrhages as significant predictors of posttreatment hemorrhage.Pretreatment hemorrhages led to permanent deficits in 41.4% of the cases with a single bleed and in 46.1% of cases with multiple bleeds. Only mild (modified Rankin Scale score 1) and a low rate of permanent neurological deficits were caused either by posttreatment hemorrhages (4.3%) or by radiation (2%).The rate of improvement in epilepsy was 84.9% after RS in patients with at least one seizure prior to treatment, not depending on the presence of hemorrhage or the time interval between presentation and treatment. Favorable outcome occurred in 81% of patients whose seizures were not controlled with antiepileptic medication prior to RS.

CONCLUSIONS

Radiosurgery for superficial CMs is safe and appears to be effective, offering a real treatment alternative to surgery for selected patients. Given their relatively benign natural history, superficial CMs require further study to verify the long-term benefit of RS over the lesions' natural history.

Stereotactic radiosurgery of intracranial cavernous malformations

Despite increasing worldwide experience, the role of stereotactic radiosurgery (SRS) in the management of cerebral cavernous malformations (CMs) remains controversial. Microsurgical excision of easily accessible CMs is typically safe; therefore, removal remains the gold standard for most of the symptomatic hemispheric lesions. However, there is now sufficient evidence supporting the use of SRS for the difficult cases. Waiting for the cumulative morbidity of the natural history to justify intervention does not serve the patient's interest, therefore, we argue for early radiosurgical intervention. Carefully designed randomized controlled trials might resolve controversies concerning the role of SRS in treating cerebral CMs.

Microsurgical or radiosurgical management of intracranial cavernomas

Cranial cavernous malformations (CCMs) constitute a heterogeneous group of lesions that tend to change dynamically over time with related periods of repeated exacerbation and alternating periods of remission. The decision on their management is based on estimating the inherent risk of further morbidity and the risk/benefit related to the particular treatment mode. Incidentally detected CCMs or lesions in asymptomatic patients presenting without major hemorrhage are best followed up. Complete resection of a CCM is the only healing option and is indicated for symptomatic or hemorrhagic lesions. In the large published series 83-92 % of the patients improved or remained unchanged after surgery, with only 8-11 % showing significant deterioration. For most patients, quality of life is improved. Analysis of the risk/benefit ratio for radiosurgery shows that it should not be regarded as an alternative option: It confers limited protection against bleeding and is related to a certain morbidity risk. In the subgroup of patients with symptomatic or hemorrhagic CCMs in locations that preclude surgical resection with acceptable risks, we recommend follow-up. The senior author is following a group of more than 80 such patients, and the vast majority remain free of hemorrhage and symptoms.

Gamma knife radiosurgery of brain cavernomas

PURPOSE

Radiosurgery of cavernomas should prevent rebleeding, growth of the lesion, and deterioration of clinical symptoms. However, there is no direct diagnostic tool to verify the endpoints of treatment. At present, the positive effects of radiosurgery are identified by clinical observation and analysis of imaging changes on magnetic resonance imaging during a sufficiently long follow-up period.

METHODS

Between 1992 and 2000, a total of 112 patients with brain cavernomas were treated with Gamma Knife radiosurgery at our center. In all, 59 patients experienced bleeding before radiosurgery; the remainder did not. The median age of patients was 42 years, the median volume of the cavernomas was 0.9 cm(3), and the median applied marginal dose was 16 Gy.

RESULTS

After a 2-year latent interval after treatment (median follow-up 84 months), the risk of bleeding in the group of patients with bleeding before radiosurgery had decreased from 3.7 % to 0.2 %. For the patients without bleeding before radiosurgery, the annual risk of bleeding was 0.8 %. The cavernoma size decreased in 53.0 % of cases and increased in 6.4 %. Epilepsy, if present before the treatment, was alleviated in 45 % of cases. The risks of temporary or permanent morbidity caused by radiosurgery were 14.6 % and 0.9 %, respectively.

CONCLUSION

Radiosurgery of cavernomas was associated with a low risk of permanent morbidity. The risk of rebleeding after the 2-year latent interval after radiosurgery had decreased. Treatment of cavernomas with no history of bleeding was halted at our center.

The outlook for adults with epileptic seizure(s) associated with cerebral cavernous malformations or arteriovenous malformations

Cerebral cavernous malformations (CCMs) and arteriovenous malformations (AVMs) are common: their asymptomatic prevalence on brain magnetic resonance imaging (MRI) is 1 in 625 and 1 in 2,000, respectively. The risk of epileptic seizure(s) for people with AVMs and CCMs affects their domestic, social, and professional lives, and may influence their decisions about treatment. This article summarizes the seizure risks for people with AVMs and CCMs, gleaned from published original articles indexed in OVID Medline and Embase before 1 January 2012. In the absence of prior intracranial hemorrhage and nonhemorrhagic focal neurologic deficit, a population-based study in Scotland, United Kingdom, found that the 5-year risks of first seizure were 8% for AVM and 4% for CCM; presentation with intracranial hemorrhage or focal neurologic deficit raised this risk for AVM (23%) but not for CCM (6%). Features associated with the occurrence of epileptic seizures for CCM are lesion multiplicity and cortical CCM location, whereas for AVM the most consistently reported associations are younger age, temporal location, cortical involvement, and nidus diameter >3 cm. In the absence of prior intracranial hemorrhage and nonhemorrhagic focal neurologic deficit, the 5-year risk of developing epilepsy following a first seizure is 58% for AVM and 94% for CCM, though there is no difference in the chance of achieving 2-year seizure freedom in this time frame (45% AVM vs. 47% CCM). Observational case series describe encouraging differences in seizure frequency before and after AVM and CCM treatment, but the shortage of studies demonstrating dramatic effects in comparison to concurrent control groups justifies the need for more controlled studies, ideally with randomized treatment allocation when the benefits of AVM or CCM treatment are uncertain.

Surgical management of cavernous malformations presenting with drug-resistant epilepsy

Cerebral cavernous malformations (CMs) are dynamic lesions characterized by continuous size changes and repeated bleeding. When involving cortical tissue, CMs pose a significant risk for the development of drug-resistant epilepsy, which is thought to be result of an altered neuronal network caused by the lesion itself and its blood degradation products. Preoperative evaluation should comprise a complete seizure history, neurological examination, epilepsy-oriented MRI, EEG, video-EEG, completed with SPECT, PET, functional MRI, and/or invasive monitoring as needed. Radiosurgery shows variable rates of seizure freedom and a high incidence of complications, thus microsurgical resection remains the optimal treatment for CMs presenting with drug-resistant epilepsy. Two thirds of patients reach Engel I class at 3-year follow-up, regardless of lobar location. Those with secondarily generalized seizures, a higher seizure frequency, and generalized abnormalities on preoperative or postoperative EEG, show poorer outcomes, while factors such as gender, duration of epilepsy, lesion size, age, bleeding at the time of surgery, do not correlate consistently with seizure outcome. Electrocorticography and a meticulous removal of all cortical hemosiderin - beyond pure lesionectomy - reduce the risk of symptomatic recurrences.

Radiosurgery for epilepsy: clinical experience and potential antiepileptic mechanisms

Stereotactic radiosurgery, well established in the noninvasive treatment of focal lesions that are otherwise difficult to access through open surgery, is an emerging technology in the treatment of focal epileptic lesions. Recent studies suggest that seizures from hypothalamic hamartomas and mesial temporal lobe epilepsy remit at clinically significant rates with radiosurgery, but large variations among different studies have raised questions about appropriate treatment protocols and mechanisms. Proposed anticonvulsant mechanisms include neuromodulatory effects or ischemic necrosis of epileptic tissue. An ongoing trial that directly compares efficacy, morbidities, and cost of radiosurgery versus open surgery for mesial temporal lobe epilepsy is underway.

Advances in the radiosurgical treatment of epilepsy

Radiosurgery is the precise application of focused radiation to a targeted volume area within the brain, which has been identified on MRI. With recent advances, radiosurgical treatment is now being evaluated as an alternative treatment to open resective surgery for intractable epilepsy. Recent prospective trials suggest that radiosurgery may be an effective and safe treatment for medically intractable epilepsy associated with mesial temporal sclerosis, cavernous malformations, and hypothalamic hamartomas.

Arcuate fasciculus tractography integrated into Gamma Knife surgery

Object

To prevent speech disturbances after Gamma Knife surgery (GKS), the authors integrated arcuate fasciculus (AF) tractography based on diffusion tensor (DT) MR imaging into treatment planning for GKS.

Methods

Arcuate fasciculus tractography was retrospectively integrated into planning that had been previously performed by neurosurgeons and radiation oncologists. This technique was retrospectively applied to 12 patients with arteriovenous malformations adjacent to the AF. Diffusion tensor images were acquired before the frame was affixed to the patient's head and DT tractography images of the AF were created using the authors' original software. The data from DT tractography and stereotactic 3D imaging studies obtained after frame fixation were transported to a treatment planning workstation for GKS and coregistered so that the delivered doses and incidence of posttreatment aphasia could be assessed.

Results

The AF could not be depicted in 2 patients who initially presented with motor aphasia caused by hemorrhaging from arteriovenous malformations. During the median follow-up period of 29 months after GKS, aphasia developed in 2 patients: 30 Gy delivered to the frontal portion of the AF caused conduction aphasia in 1 patient, and 9.6 Gy to the temporal portion led to motor aphasia in the other. Speech dysfunction was not observed after a maximum radiation dose of 10.0–16.8 Gy was delivered to the frontal fibers in 4 patients, and 3.6–5.2 Gy to the temporal fibers in 3.

Conclusions

The authors found that administration of a 10-Gy radiation dose during GKS was tolerated in the frontal but not the temporal fibers of the AF. The authors recommend confirmation of the dose by integration of AF tractography with GKS, especially in lesions located near the temporal language fibers.

Radiosurgery for angiographically occult vascular malformations

The use of radiosurgery for angiographically occult vascular malformations (AOVMs) is a controversial treatment option for those that are surgically inaccessible or located in eloquent brain. To determine the efficacy of this treatment, the authors reviewed the literature reporting hemorrhage rates, seizure control, and radiation-induced morbidity. They found overall hemorrhage rates of 2-6.4%, overall postradiosurgery hemorrhage rates of 1.6-8%, and stratified postradiosurgery hemorrhage rates of 7.3-22.4% in the period immediately to 2 years after treatment; these latter rates declined to 0.8-5.2% > 2 years after treatment. Of 291 patients presenting with seizure across 16 studies, 89 (31%) attained a seizure-free status and 102 (35%) had a reduction in seizure frequency after radiosurgery. Overall radiation-induced morbidity ranged from 2.5 to 59%, with higher complication rates in patients with brainstem lesion locations. Researchers applying mean radiation doses of 15-16.2 Gy to the tumor margin saw both low radiation-induced complication rates (0-9.1%) and adequate hemorrhage control (0.8-5.2% > 2 years after treatment), whereas mean doses >or= 16.5 Gy were associated with higher total radiation-induced morbidity rates (> 17%). Although the use of stereotactic radiosurgery remains controversial, patients with AOVMs located in surgically inaccessible areas of the brain may benefit from such treatment.

[Radiosurgery for drug-resistant epilepsies: state of the art, results and perspectives]

BACKGROUND

There is growing interest in the use of radiosurgery in epilepsy. We analyzed our experience in this field in an attempt to define the potential of radiosurgery in epileptology.

MATERIAL AND METHODS

[corrected] Our local clinical experience (134 patients), accumulated over the last 15 years, mainly includes treatment of temporal lobe epilepsy without space-occupying lesions (59 patients), including 53 with pure MTLE, 61 cases of hypothalamic hamartoma, two cases of callosotomy, and 12 other types of epilepsy.

RESULTS

The analysis of our material, as well as other clinical and experimental data, suggest that the use of radiosurgery is beneficial only to patients in whom a strict preoperative definition of the extent of the epileptogenic zone (or network) has been achieved and strict rules of dose planning have been applied. As soon as these principles are not observed, the risk of treatment failure and/or side effects increases dramatically. Long-term outcome data are now available and published for MTLE but not yet for other types of epilepsy. Long-term safety and efficacy in MTLE are comparable to surgical resection but radiosurgery has the advantage of sparing verbal memory in patients operated by Gamma Knife (GK) on the dominant side. In small hamartomas, the efficacy is comparable to microsurgery but with a dramatic reduction in risk.

CONCLUSION

The vast amount of clinical materiel and long-term evaluation now support the use of GK surgery in small hypothalamic hamartomas and MTLE when the patient is at risk of verbal memory loss.

[Role of radiosurgery in the management of intracranial cavernomas. Review of the literature]

From a review of the literature dealing with radiosurgery of cavernous malformations, we have analyzed its impact on hemorrhagic risk, epilepsy, histological modifications, morbidity and potential indications of treatment. Radiosurgery could significantly reduce the hemorrhagic risk, in a selected population with a high risk of hemorrhage, after an interval of about 2 years, but cannot provide protection against rebleeding. As for epilepsy related to the lesion, a significant reduction of seizures has been observed in certain cases, with better control in case of recent evolution and simple seizures linked to the site of the vascular malformation. Histologic lesions are vascular fibrosis, fibrinoid necrosis and ferrugination, without good correlation with results of CT scan or MRI. Morbidity of radiosurgery seems higher compared to other diseases with similar doses and target volumes. The rate of transient complications was about 25%, with permanent sequelae in 5 to 10% of patients. This would be due to a radiosensitizing effect of the hemosiderin halo around the lesion. Radiosurgery can be proposed for non-surgical lesions with a high risk of hemorrhage, nevertheless the superiority of the technique over conservative treatment has to be proven. Without long-term prospective studies, the efficiency of RS for cavernomas remains questionable and subject to debate. New imaging methods proving the obstruction of the cavernous malformation are needed.

Treatment of Epileptogenic Cavernomas: Surgery versus Radiosurgery

BACKGROUND

Epilepsy is the most common symptom of cavernoma. Although microsurgery is the mainstay treatment for epileptogenic cavernoma, this procedure may cause severe complications for some lesions. This report aimed to study if linear accelerator (LINAC) radiosurgery was an alternative treatment modality for epileptogenic cavernoma.

METHODS

In this retrospective study, 29 patients were diagnosed with epileptogenic cavernomas from September 1995 to March 2005. Fifteen patients were treated with surgical excision and 14 with LINAC radiosurgery. The evaluation of epilepsy control was according to Engel's classification.

RESULTS

In the surgical group, 13 (86.7%) of 15 patients had a class I seizure-free outcome. In the radiosurgery group, class I control was achieved in 9 (64.3%) of 14 patients. However, there was no significant difference in the results of treatment between the two groups.

CONCLUSIONS

LINAC radiosurgery is an alternative treatment for epileptogenic cavernomas, especially when the lesions are located in the central regions or eloquent areas of the brain.

[Epileptogenicity and evaluation of epileptic risk]

Epilepsy is the more frequent clinical manifestation of hemispheric cavernomas in 50 to 75% of symptomatic cases; the annual risk of a first seizure is evaluated from 1.5 to 2.5%. As for all epileptogenic lesions, many questions arise: Is the pathologic tissue or the perilesional cortex responsible for the epileptic symptoms? Is the risk related with the topography of the lesion? Is the prognosis of the epilepsy related with the number of seizures? Can the epilepsy become drug-resistant? Can surgical treatment cure the epilepsy? When surgery is indicated, should lesionectomy alone or lesionectomy plus perilesional tissue resection be performed? The iron and the hemosiderin deposits induce metabolic perturbations and tissue reorganization (gliosis and sclerosis) around the cavernoma. These cortical modifications seem to be responsible for the epileptic discharges but this is difficult to demonstrate. Epileptic discharges have been recorded in the perilesional tissue in only one study of the literature. Drug therapy can usually control the seizures, but it appears that surgery is more effective when the epilepsy is recent and the seizures are not too frequent. For these reasons it would appear licit to propose the resection of the lesion when the surgical risk is not too great. In case of drug-resistant epilepsy, the same function-targeted surgical strategy may be used as for the management of any severe epilepsy.

X-ray scalpel - a new device for targeted x-ray brachytherapy and stereotactic radiosurgery

The basic design and performance of a novel x-ray scalpel device for interstitial radiosurgery are reported. The x-ray scalpel is comprised of a capillary optics collimator conjugated with a high brilliance microfocus x-ray tube and a thin hollow needle (tip) attached to the collimator. The device is capable of producing a high dose rate (about 140 Gy min(-1) in water-like absorber at the exit window), 0.7 mm diameter, quasi-parallel beam that can be delivered to a targeted site by a minimally invasive procedure. Contrary to insertable x-ray tubes or radionuclides used in brachytherapy and complying with the 1/r(2) radiation attenuation law, the dose rate for a quasi-parallel beam decreases with distance as mu exp(-mu r), where mu is the energy-dependent linear attenuation coefficient in the exposed medium. Moreover, the shape, energy and the dose attenuation curve of the x-ray beam can be adjusted. Two versions of the x-ray scalpel device (5.4 keV and 20.2 keV) are described. We present results from our first test of the x-ray scalpel as a controllable source of focal radiation for producing radiation necrosis in rat brain tissue. Irradiation was transdurally delivered to the rat cerebral cortex for 10 min at a dose rate of 20 Gy min(-1).

Gamma knife radiosurgery targeting protocols for the experiments with small animals

BACKGROUND/AIMS

Manipulation of brain functions via Gamma Knife (GK) irradiation would have numerous applications in clinical and experimental neurology.

METHODS

Alteration of brain functions in the unilaterally irradiated striatum was indexed through monitoring freely moving rat behaviors. Spontaneous activity and rotations on the apomorphine test, which can detect dopaminergic function imbalance, were indexed employing our behavior tracking system. The spatial distribution of necrotic lesions was explored using serial sections, and was assumed to represent the real foci of the GK target.

RESULTS

Distinct behavioral alterations corresponded to the precise locations of the lesions in various areas of the basal ganglia. Displacement of the irradiation sites in the anteromedial direction increased spontaneous activity, and posterolateral shift provoked circling behavior on the apomorphine test.

CONCLUSION

Accurate positioning of the target is crucial for experimental GK irradiation locally focused on domains of a small brain such as that of the rat. Here, we propose a protocol for converting the 'intended' focus, based on brain map coordinates, to a 'planned' focus on the MR imaging coordinate system with the Régis-Valliccioni stereotactic frame.

LINAC radiosurgery for intracranial cavernous malformation: 10-year experience

BACKGROUND

The annual hemorrhage rate of intracranial cavernous malformation (CM) is reported to range from 0.23% to 1.1%. Because of the low hemorrhage rate, operating on a deep symptomatic lesion with or without hemorrhage is considered controversial. For the prevention of hemorrhage, radiosurgery is an alternative method, targeting smaller lesions and delivering higher doses of radiation. Linear accelerator (LINAC) radiosurgery, aside from the gamma knife (GK), is not often discussed in the treatment of CM.

PATIENTS AND METHODS

From 1995 to 2005, 30 patients presenting with hemorrhage or seizures, aged 14-79 years (mean 24.0 years) with single (27 patients) or multiple (three patients) CMs received LINAC radiosurgery at our institute. Six patients received LINAC radiosurgery following craniotomy for residual lesions revealed by the follow-up MRI. The temporal lobe was the most common site for CM in this series (n=8), followed by the brain stem (n=7). Thirty patients received 34 radiosurgery treatments with peripheral doses ranging from 800 cGy to 2200 cGy. The mean follow-up time was 59.9 months (range 1-122 months).

RESULTS

One patient re-bled post-radiosurgery (0.67% in 149.75 observation-years). Two patients had asymptomatic post-LINAC edema (6.7%). Those three patients were symptom-free during the follow-up period.

CONCLUSION

We suggest that LINAC radiosurgery is a relatively safe technique for treating deep or residual CM, although the actual effectiveness for CM obliteration is not known.

Radiosurgery for epilepsy

Radiosurgery is an emerging therapeutic approach for the treatment of medically intractable epileptogenic foci. A favourable seizure outcome was first reported in studies of the effects of radiosurgery in the treatment of arteriovenous malformations and tumours. Radiosurgery has since been applied to the treatment of complex partial seizures with mesial-temporal-lobe onset. Nearly simultaneously, experimental evidence supporting the usefulness of radiosurgery to improve or abolish seizures has confirmed that stereotactic irradiation can preferentially affect epileptogenic versus normal cortex. Further work is clearly needed, but this technique might become an important approach in the management of mesial-temporal and extratemporal epilepsy, especially if refractory seizures arise from eloquent cortex or surgically challenging regions of brain.

Gamma knife surgery for epilepsy related to hypothalamic hamartomas

OBJECTIVE

Drug resistant epilepsy associated with hypothalamic hamartoma (HH) can be cured by microsurgical resection of the lesion. Morbidity and mortality risks of microsurgery in this area are significant. Gamma Knife Surgery's (GKS) reduced invasivity seems to be well adapted. In view of the severity of the disease and risks of surgical resection it is crucial to evaluate GKS for this indication. A first retrospective study has shown a very good safety and efficacy level but for a more reliable evaluation a prospective study would be required.

METHODS

Between Oct 1999 and July 2002, 30 patients with HH and associated severe epilepsy were included. Seizure semiology (video EEG) and frequency, behavioural disturbances, neuropsychological performance, endocrinological status, sleep electroclinical abnormalities, MR imaging, and visual function were systematically evaluated before and after GKS (6, 12, 18, 24, 36 months). Twenty patients had experienced precocious puberty at a median age of 3,7 (0-9). Range of maximum diameter was from 7,5 to 23 mm with only 3 larger than 18 mm. The median marginal dose was 17 gy (14-20).

RESULTS

Sufficient follow up for final evaluation is not yet available. Only 6 patients have a follow-up of more than 12 months and 19 more than 6 months. However a lot of very dramatic changes did occur during that period in this group. Among the 19 patients with more than 6 months of follow-up, a lot had already experienced an increase of gelastic seizures around 3 months (3), an improvement in their seizure rate (18), behaviour (9), sleep (3), and EEG background activity (3), a cessation of partial complex seizures (7). No complications have occurred till now except one patient experiencing at 5 months a hyperthermia without infection and concomitant increase of gelastic seizures both ceasing suddenly and spontaneously after 15 days.

CONCLUSION

Our first results indicate that GKS is as effective as microsurgical resection and very much safer. GKS also allows to avoid the vascular risk related to radiofrequency lesioning or stimulation. The disadvantage of radiosurgery is its delayed action. Longer follow-up is mandatory for a serious evaluation of the role of GKS. Results are faster and more complete in patients with smaller lesions inside the 3rd ventricle (grade II). The early effect on subclinical discharges turns out to play a major role in the dramatic improvement of sleep quality, behaviour, developmental acceleration at school.

Management of supratentorial cavernous malformations: craniotomy versus gammaknife radiosurgery

OBJECTIVE

Although craniotomy is the preferred treatment for symptomatic solitary supratentorial cavernous malformation (CM), radiosurgery is also an option. Our aim was to see which of these strategies was the most effective and under what circumstances.

METHODS

Of the 46 patients with solitary supratentorial CM that we retrospectively studied, 24 presented with seizures, 16 with focal neurological deficits due to intracerebral hemorrhage, and 6 with both seizures and bleeding. Sixteen were treated with craniotomy and 30 with gammaknife radiosurgery (GKRS). The main outcome measures for comparing craniotomy with GKRS were the proportion of postoperative seizure-free patients and the proportion of patients in whom no rebleeding occurred.

RESULTS

Of patients presenting with seizures with/without bleeding, a significantly higher proportion of the craniotomy group than the GKRS group became and remained seizure-free (11/14 [79%] versus 4/16 [25%]; P < 0.002), and of those presenting with bleeding with/without seizures, a somewhat (though nonsignificantly) higher proportion did not rebleed (4/4 [100%] versus 12/18 [67%]) after surgery. The remaining 2 of the 16 craniotomy patients did not rebleed and had no residual tumor at follow up. Twelve of the 30 GKRS patients had evidence of tumor regression at follow up.

CONCLUSION

In the clinical management of solitary supratentorial CM, craniotomy for lesionectomy resulted in better seizure control and rebleeding avoidance than GKRS.

The effect of gamma knife irradiation on functions of striatum in rats

Object. An animal model has been developed to study the effect of gamma knife surgery(GKS) on cerebral function.

Methods. A rat was fixed in a newly developed Régis—Valliccioni frame that enables the target region to be planned directly on the magnetic resonance images. The left striatum was irradiated with 150 Gy via a 4-mm collimator of the Leksell gamma knife. Apomorphine (dopamine agonist) was administered to elicit a circling behavior (apomorphine test) after the GKS so as to examine the time course of the changes in dopaminergic functions of irradiated striatum. After a series of behavioral analyses, irradiated brains were subjected to histological examination.

Necrosis was observed in the irradiated area surrounded by hemorrhage and gliosis. The distance between the histologically estimated and planned centers of the irradiation areas was 1.0 ± 0.5 mm. The extent of the distance was due to errors along dorsoventral axis. The distribution of the irradiation areas influenced the activity and the circling behaviors in apomorphine test, which was suggestive of involvement of the nigrostriatal pathway.

Conclusions. Targeting by using the Régis—Valliccioni frame was very accurate compared with targeting with coordinates based on brain maps used hitherto. Although targeting improved the accuracy, further effort will still be necessary to reduce errors along dorsoventral axis. The apomorphine test indicated a reduced dopaminergic function of the irradiated area including striatum, which accompanied histological changes after a high dose of irradiation (150 Gy).

Gamma knife surgery of brain cavernous hemangiomas

Object.The authors conducted a study to record more detailed information about the natural course and factors predictive of outcome following gamma knife surgery (GKS) for cavernous hemangiomas.

Methods.One hundred twelve patients with brain cavernous hemangiomas underwent GKS between 1993 and 2000. The median prescription dose was 16 Gy. One hundred seven patients were followed for a median of 48 months (range 6–114 months). The rebleeding rate was 1.6%, which is not significantly different with that prior to radiosurgery (2%). An increase in volume was observed in 1.8% of cases and a decrease in 45%. Perilesional edema was detected in 27% of patients, which, together with the rebleeding, caused a transient morbidity rate of 20.5% and permanent morbidity rate of 4.5%. Before radiosurgery 39% of patients suffered from epilepsy and this improved in 45% of them. Two patients with brainstem cavernous hemangiomas died due to rebleeding. Rebleeding was more frequent in female middle-aged patients with a history of bleeding, a larger lesion volume, and a prescription dose below 13 Gy. Edema after GKS occurred more frequently in patients who had surgery, a larger lesion volume, and in those in whom the prescription dose was more than 13 Gy.

Conclusions.Gamma knife surgery of cavernous hemangiomas can produce an acceptable rate of morbidity, which can be reduced by using a lower margin dose. Lesion regression was observed in many patients. Radiosurgery seems to remain a suitable treatment modality in carefully selected patients.

The effect of gamma knife irradiation on functions of striatum in rats

Object.An animal model has been developed to study the effect of gamma knife surgery(GKS) on cerebral function.

Methods.A rat was fixed in a newly developed Régis—Valliccioni frame that enables the target region to be planned directly on the magnetic resonance images. The left striatum was irradiated with 150 Gy via a 4-mm collimator of the Leksell gamma knife. Apomorphine (dopamine agonist) was administered to elicit a circling behavior (apomorphine test) after the GKS so as to examine the time course of the changes in dopaminergic functions of irradiated striatum. After a series of behavioral analyses, irradiated brains were subjected to histological examination.

Necrosis was observed in the irradiated area surrounded by hemorrhage and gliosis. The distance between the histologically estimated and planned centers of the irradiation areas was 1.0 ± 0.5 mm. The extent of the distance was due to errors along dorsoventral axis. The distribution of the irradiation areas influenced the activity and the circling behaviors in apomorphine test, which was suggestive of involvement of the nigrostriatal pathway.

Conclusions.Targeting by using the Régis—Valliccioni frame was very accurate compared with targeting with coordinates based on brain maps used hitherto. Although targeting improved the accuracy, further effort will still be necessary to reduce errors along dorsoventral axis. The apomorphine test indicated a reduced dopaminergic function of the irradiated area including striatum, which accompanied histological changes after a high dose of irradiation (150 Gy).

Gamma knife surgery for cavernous hemangiomas: an analysis of 125 patients

Object. The authors sought to determine the value of gamma knife surgery (GKS) in the treatment of cavernous hemangiomas (CHs).

Methods. Between 1993 and 2002, a total of 125 patients with symptomatic CHs were treated with GKS. Ninety-seven patients presented with bleeding and 45 of these had at least two bleeding episodes. Thirteen patients presented with seizures combined with hemorrhage, and 15 patients presented with seizures alone. The mean margin dose of radiation was 12.1 Gy and the mean follow-up time was 5.4 years.

In the 112 patients who had bled the number of rebleeds after GKS was 32. These rebleeds were defined both clinically and based on magnetic resonance imaging for an annual rebleeding rate of 32 episodes/492 patient-years or 6.5%. Twenty-three of the 32 rebleeding episodes occurred within 2 years after GKS. Nine episodes occurred after 2 years; thus, the annual rebleeding rate after GKS was 10.3% for the first 2 years and 3.3% thereafter (p = 0.0038). In the 45 patients with at least two bleeding episodes before GKS, the rebleeding rate dropped from 29.2% (55 episodes/188 patient-years) before treatment to 5% (10 episodes/197 patient-years) after treatment (p < 0.0001). Among the 28 patients who presented with seizures, 15 (53%) had good outcomes (Engel Grades I and II). In this study of 125 patients, symptomatic radiation-induced complications developed in only three patients.

Conclusions. Gamma knife surgery can effectively reduce the rebleeding rate after the first symptomatic hemorrhage in patients with CH. In addition, GKS may be useful in reducing the severity of seizures in patients with CH.

Gamma knife surgery for cavernous hemangiomas: an analysis of 125 patients

Object. The authors sought to determine the value of gamma knife surgery (GKS) in the treatment of cavernous hemangiomas (CHs).

Methods. Between 1993 and 2002, a total of 125 patients with symptomatic CHs were treated with GKS. Ninety-seven patients presented with bleeding and 45 of these had at least two bleeding episodes. Thirteen patients presented with seizures combined with hemorrhage, and 15 patients presented with seizures alone. The mean margin dose of radiation was 12.1 Gy and the mean follow-up time was 5.4 years.

In the 112 patients who had bled the number of rebleeds after GKS was 32. These rebleeds were defined both clinically and based on magnetic resonance imaging for an annual rebleeding rate of 32 episodes/492 patient-years or 6.5%. Twenty-three of the 32 rebleeding episodes occurred within 2 years after GKS. Nine episodes occurred after 2 years; thus, the annual rebleeding rate after GKS was 10.3% for the first 2 years and 3.3% thereafter (p = 0.0038). In the 45 patients with at least two bleeding episodes before GKS, the rebleeding rate dropped from 29.2% (55 episodes/188 patient-years) before treatment to 5% (10 episodes/197 patient-years) after treatment (p < 0.0001). Among the 28 patients who presented with seizures, 15 (53%) had good outcomes (Engel Grades I and II). In this study of 125 patients, symptomatic radiation-induced complications developed in only three patients.

Conclusions. Gamma knife surgery can effectively reduce the rebleeding rate after the first symptomatic hemorrhage in patients with CH. In addition, GKS may be useful in reducing the severity of seizures in patients with CH.

Gamma knife surgery of brain cavernous hemangiomas

Object. The authors conducted a study to record more detailed information about the natural course and factors predictive of outcome following gamma knife surgery (GKS) for cavernous hemangiomas.

Methods. One hundred twelve patients with brain cavernous hemangiomas underwent GKS between 1993 and 2000. The median prescription dose was 16 Gy. One hundred seven patients were followed for a median of 48 months (range 6–114 months). The rebleeding rate was 1.6%, which is not significantly different with that prior to radiosurgery (2%). An increase in volume was observed in 1.8% of cases and a decrease in 45%. Perilesional edema was detected in 27% of patients, which, together with the rebleeding, caused a transient morbidity rate of 20.5% and permanent morbidity rate of 4.5%. Before radiosurgery 39% of patients suffered from epilepsy and this improved in 45% of them. Two patients with brainstem cavernous hemangiomas died due to rebleeding. Rebleeding was more frequent in female middle-aged patients with a history of bleeding, a larger lesion volume, and a prescription dose below 13 Gy. Edema after GKS occurred more frequently in patients who had surgery, a larger lesion volume, and in those in whom the prescription dose was more than 13 Gy.

Conclusions. Gamma knife surgery of cavernous hemangiomas can produce an acceptable rate of morbidity, which can be reduced by using a lower margin dose. Lesion regression was observed in many patients. Radiosurgery seems to remain a suitable treatment modality in carefully selected patients.

Novel surgical treatments for epilepsy

The surgical treatment of epilepsy is expanding in an exciting and unprecedented way. This review highlights some of the recent advances in neuroimaging that have improved epilepsy surgery. In addition, novel therapies currently being evaluated in clinical trials, including gamma knife radiosurgery, deep brain stimulation, and responsive stimulation, are discussed. Further surgical developments that will be ready for human application in the near future are highlighted.

Gamma Knife Surgery in Mesial Temporal Lobe Epilepsy: A Prospective Multicenter Study

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.

METHODS

From July 1996 to March 2000, three European centers selected 21 patients with mesial temporal lobe epilepsy (MTLE) for a temporal lobectomy. The preoperative investigations included video-EEG with foramen ovale electrodes, magnetic resonance imaging, neuropsychological testing, and the ESI-55 quality-of-life questionnaire. In place of a cortectomy, radiosurgical treatment was performed by using the Leksell Gamma Knife (LGK) at a dose of 24 +/- 1 Gy at the margin. The target included the anterior parahippocampal cortex and the basal and lateral part of the amygdala and anterior hippocampus (head and body). One patient (a heavy smoker) died of a myocardial infarction. Twenty patients were available for prospective evaluation. A minimum 2-year follow-up period included clinical, neuropsychological, and radiologic evaluations.

RESULTS

At each 6-month follow-up evaluation, the frequency of seizures was significantly smaller than that at the previous visit. The median seizure frequency of 6.16 the month before treatment was reduced to 0.33 at 2 years after treatment. At 2 years, 65% of the patients (13 of 20) were seizure free. Five patients had transient side effects, including depression, headache, nausea, vomiting, and imbalance. There was no permanent neurological deficit reported except nine visual field deficits. No neuropsychological deterioration was observed 2 years after treatment. The quality of life was significantly better than that before surgery.

CONCLUSIONS

The safety and efficacy of the radiosurgical treatment of MTLEs appears good in this group of patient over short-to-middle term. Delay of the seizure cessation was the major disadvantage of GKS. A longer follow-up period is required for confirmation of these results.

Beyond pharmacotherapy: surgical management

PURPOSE

To review the recent advances in the field of temporal lobe epilepsy (TLE) surgery.

RESULTS

TLE surgery has recently demonstrated a highly significant superiority over optimal medical therapy in a randomized trial. Accordingly, a median rate of 70% of class I outcome (patients free of disabling seizures postoperatively) has emerged from the pooling of all data published since the early 1990s. In addition, successful TLE surgery appears likely to reduce the risk of seizure-related death. However, it remains largely underused and overly delayed, partly because of the legitimate fears of possible surgical complications, such as verbal memory deficits or failure to control seizures. Reasons for surgical failures are not completely understood, and include bitemporal, pseudotemporal, and temporal-plus epilepsies, as well as insufficient resection of the mesial temporal structures. Developing techniques such as intraoperative MRI, gamma-knife radiosurgery, and various types of cranial nerves or intracerebral chronic stimulation have the potential to alleviate part of the limitations of TLE surgery.

CONCLUSIONS

The overall benefit of surgical treatment in patients with drug-resistant TLE should encourage a more frequent and earlier referral of such patients to epilepsy surgery centers. Important progress toward higher rates of seizure-free outcome and lower morbidity remains to be made and may be obtained by taking advantage of the new available technologies.

Gamma-Knife radiosurgery of mesiotemporal tumour epilepsy observations and long-term results

PURPOSE

The efficacy of radiosurgery in cases of mesiotemporal tumours associated with long standing epilepsy has not clearly been documented up to now. The authors present a retrospective analysis of 19 cases treated by Gamma-Knife radiosurgery (GKRS) for mesiotemporal tumour epilepsy.

METHODS

Between 1992 and 1997 19 patients (12 male and 7 female) with a mean age of 31 years (5-72) and mesiotemporal tumour-induced epilepsy of a mean duration of 8.6 years (0.9-28) were treated by GKRS. All tumours were within the mesiotemporal structures and the pathohistology proven by biopsy or resective procedure revealed 15 (79%) low grade astrocytomas, 3 (16%) gangliogliomas and 1 (5%) cavernoma. Beside tumour control, the main aim of GKRS was alleviation of epilepsy by irradiating the presumed epileptic foci outside the tumour volume. The 50% isodose volumes surrounding the tumours measured a mean of 6.2 ccm (1.1-18 ccm). Doses given at marginal isodoses ranged from 12 to 30 Gy (mean 17.3 Gy). The outcome with respect to epileptic seizures was evaluated by the Engel classification.

RESULTS

After a follow-up (FU) of 1.7 to 9.7 years (mean 6.5 years) 11 patients (57.9%) were significantly ameliorated (Engel I and Engel II), 7 patients (36.8%) worthwhile improved (Engel III) and 1 patient (5.3%) unchanged. In 11 patients (58%) radiosurgically induced image changes were seen on MRI.

INTERPRETATION

Although microsurgical approach guided by electrocorticography (EcoG) is the state of art for treatment of mesiotemporal tumour epilepsy, GKRS can be used as a non-invasive, safe and effective alternative to resective surgery for selected cases.

Gamma Knife surgery, a neuromodulation therapy in epilepsy surgery!

INTRODUCTION

The more classical approach for Epilepsy surgery is the removal of the epileptogenic zone (ZE). We present a critical review of information in favor of a possible non-destructive effect of radiosurgery in epilepsy surgery.

MATERIAL

Clinical material of patients with epilepsies related to a lesion in highly functional areas subjected to radiosurgery with relief of the seizures and no functional worsening is available. We applied direct treatment of the EZ with good efficacy in the absence of destructive aspects on the MR and no functional deterioration (e.g. hypothalamic hamartomas). Experimental studies have shown biochemical differential effect of radiosurgery on the striatum, glial cell elimination, stem cell migration toward the target area, sprouting,... Plasticity phenomenon are induced by radiosurgery when using non necrotizing dosemetry.

DISCUSSION

There is clinical and experimental evidence of Gamma Knife capability to induce modulation in the neural system. Detailed mechanism of this modulation and dosemetric parameters enabling to induce such plasticity with no necrosis are still unknown. Subpial transection turning out actually to be quite disappointing, there is a specific rationale to test radiosurgery capability to treat EZ cortex while preserving the underlying function of this cortex when the functional risk for cortectomy is too high.