Radiosurgery effects and adverse effects in symptomatic eloquent brain-located Cavernomas

In this study, the dose schedule efficacy, safety and late adverse effects of stereotactic radiosurgery (SRS) were evaluated for patients with symptomatic cavernomas who were not eligible for surgery and treated with SRS. Between January 2013 and December 2018, 53 patients with cavernomas were treated using SRS with the CyberKnife® system. Patients' diseases were deeply located or were in subcortical functional brain regions. In addition to bleeding, 23 (43.4%) patients had epilepsy, 12 (22.6%) had neurologic symptoms and 16 patients (30.2%) had severe headaches. The median volume was 741 (range, 421-1351) mm3, and the median dose was 15 (range, 14-16) Gy in one fraction. After treatment, six (50%) of 12 patients with neurologic deficits still had deficits. Rebleeding after treatment developed in only two (3.8%) patients. The drug was completely stopped in 14 (60.9%) out of 23 patients who received epilepsy treatment, and the dose of levetiracetam decreased from 2000 mg to 1000 mg in four (17.3%) of nine patients. Radiologically, complete response (CR) was observed in 13 (24.5%) patients, and partial responses (PR) were observed in 32 (60.2%) patients. Clinical response of CR was observed in 30 (56.6%) patients, PR was observed in 16 (30.2%), stable disease (SD) was observed in three (5.7%) and four (7.5%) patients progressed. In conclusion, SRS applied in the appropriate dose schedule may be an effective and reliable method in terms of symptom control and prevention of rebleeding, especially in patients with inoperable cavernomas.

Stereotactic radiosurgery as the initial management option for small-volume hypothalamic hamartomas with intractable epilepsy: a 35-year institutional experience and systematic review

OBJECTIVE

Young patients with hypothalamic hamartomas (HHs) often present with intractable epilepsy. Currently there are no established management guidelines for HH. The authors retrospectively reviewed their single-institution experience to delineate the role of stereotactic radiosurgery (SRS).

METHODS

Seven patients with HHs (4 females; median age 13.7 years, range 2.5-25 years) with no prior resection underwent SRS between 1987 and 2022. The clinical history, epilepsy profile, radiographic findings, and neurological outcomes were characterized. HH topographical types were classified according to the Régis classification. Outcome measures included Engel seizure classification, HH response, and the need for additional surgical interventions.

RESULTS

All patients had Engel class IV epilepsy. A Leksell Gamma Knife was used to deliver a median margin dose of 18 Gy (range 16-20 Gy) to a median hamartoma volume of 0.37 cm3 (range 0.20-0.89 cm3). Seizure reduction was confirmed in 6 patients, and 2 patients had regression of their hamartoma. Two patients underwent resection and/or laser interstitial thermal therapy after SRS. At follow-up, 1 patient was seizure free, 4 patients achieved Engel class II, 1 patient had Engel class III, and 1 patient had Engel class IV seizure outcomes.

CONCLUSIONS

SRS as the initial management option for HH was associated with a low risk of adverse effects. In this institutional series reviewing small-volume HHs treated with SRS, no adverse radiation effect was detected, and the majority of patients experienced seizure reduction. SRS should be considered as the first-line treatment for seizure control in patients with small-volume HHs.

Gamma knife radiosurgery for refractory epilepsy caused by hypothalamic hamartomas

BACKGROUND

Hypothalamic hamartomas are associated with precocious puberty and chronic epilepsy characterized by gelastic seizures. The seizure disorder is usually refractory to most antiepileptic drugs. Gamma knife surgery has emerged as an alternative to microsurgical removal or radiofrequency ablation to improve seizure control. We present our experience with radiosurgery in 4 patients afflicted by this disorder.

METHODS

Using gamma knife radiosurgery, 4 patients with intractable gelastic seizures and complex epilepsy were managed. Patient age varied from 5 to 29 years. The duration of symptoms was 4-28 years. A conformal radiosurgery plan was designed with a mean of 4.25 isocenters to cover the hamartoma at the 50% isodose line. A mean margin dose of 17.5 Gy was used. The clinical outcome was evaluated with the Engel scale.

RESULTS

No complication occurred. After a median follow-up of 22 months, 3 patients had shown some improvement, with 2 attaining Engel class II status.

CONCLUSION

Gamma knife surgery is a promising alternative to microsurgical removal for patients with refractory epilepsy caused by hypothalamic hamartomas.

Influence of ionizing radiation on the course of kindled epileptogenesis

Several clinical and experimental reports suggest that low-dose irradiation of an established epileptic focus can reduce the occurrence of spontaneous seizures. Conversely, some recent reports suggest that under some conditions low-dose irradiation may have disinhibitory effects on seizure expression. Here, we have investigated mechanistic aspects of this phenomenon in the kindling model of epilepsy by applying focal irradiation at various points during kindling development. Rats were kindled to stage 5 by afterdischarge-threshold electrostimulation of the left amygdala. Treatment groups were irradiated using a collimated X-ray beam (18 MV) either prior to kindling, at kindling stage 3, or at kindling stage 5, by exposure of the left amygdala to a single-fraction central-axis dose of 25 Gy. Generalized seizure thresholds (GSTs) were subsequently assayed at weekly intervals for 10 weeks and at monthly intervals for an additional 3 months, along with the severity of the evoked seizures. Irradiation produced no significant effects on seizure threshold, but did produce persistent changes in seizure severity which varied as a function of the timing of irradiation. Relative to sham irradiated controls, the occurrence of stage 6 seizures was significantly increased by irradiation prior to kindling, but was unaffected by irradiation at kindling stage 3, and significantly reduced by irradiation at kindling stage 5. Quantitative immunohistochemical assays for neuron and astrocyte densities within the amygdala and hippocampus revealed only subtle changes in neuronal density within the dentate granule cell layer. These results are discussed in relation to mechanisms of seizure- and radiation-induced plasticity.

FLAIR-/T1-/T2-co-Registration for Image-Guided Diagnostic and Resective Epilepsy Surgery

OBJECTIVE

For technical reasons, T2-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) sequences do not allow morphological orientation with high anatomic resolution, but they may show small epileptogenic lesions. Considering the peculiarities of diagnostic and resective epilepsy surgery the present study focused on the co-registration of various magnetic resonance sequences for guided epilepsy surgery.

METHODS

Fifty patients (24 men; 26 women) aged 2 to 74 years (mean, 32 yr), in whom epileptogenic lesions were not readily identifiable on three-dimensional T1-weighted MRI scans underwent additional two-dimensional T2-weighted and FLAIR sequences before diagnostic and/or resective epilepsy surgery. FLAIR and/or T2-weighted images were co-registered to the T1-weighted data set and were displayed on the navigation station on site for guided invasive diagnostics and for resection according to an individualized resection plan. Postoperative MRI scanning was routinely performed for assessment of resection extent.

RESULTS

Co-registered T1- and FLAIR-/T2-images allowed for image-guided intraoperative identification of all lesions (n = 50). Control MRI scans revealed that complete resection was performed as planned before the operation in 49 patients and incomplete resection was performed in one patient. Preliminary seizure outcome with a mean follow up of 14 months (range, 7-24 mo) was assigned according to the Engel classification: Class I, 78%; Class II, 12%; Class III, 4%; Class IV, 6%.

CONCLUSION

Image guidance on the basis of image fusion/co-registration of T1- and FLAIR-/T2-images allows for intraoperative identification of otherwise poorly visible lesions on standard MRI sequences in good spatial resolution. Recall of this information during surgery from the navigation system's screen assists in achieving the goal of precise electrode placement, or complete resection of the lesion as well as of the perilesional epileptogenic tissue and improves the surgeon's intraoperative orientation.

Effects of kindling and irradiation on neuronal density in the rat dentate gyrus

Low-dose radiosurgery is presently in use as a treatment modality for focal epilepsy, but the mechanisms underlying the associated changes in seizure expression are poorly understood. We investigated whether total and parvalbumin expressing (PV+) neuronal densities within the hippocampus and amygdala are affected by analogous focal irradiation in amygdala-kindled rats. Adult rats were kindled by electrical stimulation through 10 stage 5 seizures. The kindled amygdala was then focally irradiated at 18 or 25 Gy, and generalized seizure thresholds were subsequently monitored for approximately 6 months. Histological and immunohistochemical assays of total and PV+ neuronal densities were performed bilaterally throughout the hippocampus and within the basolateral amygdala. PV+ neuronal densities were unaffected by kindling or irradiation in these regions. Kindling selectively reduced neuronal densities in the dentate granule cell layer, and medial CA3 pyramidal cell layer. Irradiation at 25 Gy, but not at 18 Gy, prevented or reversed this kindling-associated reduction in density.

Emerging surgical and radiotherapeutic techniques for treating epilepsy

PURPOSE OF REVIEW

Recent advances in epilepsy surgery have developed a resurgence of interest in the use of surgical techniques for the treatment of intractable epilepsy.

RECENT FINDINGS

More invasive procedures such as hemispherectomy and multiple subpial transection have become more popular. Disconnective techniques such as multiple subpial transection have provided a surgical option for patients whose epileptogenic zone resides in the eloquent cortex. Alternatively, new minimally invasive neurostimulation therapies have been introduced to preserve maximal cerebral tissue. Radiosurgery has been recently utilized in the treatment of epilepsy with preliminary promising results.

SUMMARY

In this analysis, the authors will attempt to review the more recent surgical approaches and their indications for the treatment of medically intractable epilepsy. For patients with the epileptogenic zone in the noneloquent cortex, seizure focus resection remains the most reasonable approach to therapy.

Radiosurgical treatment of intractable epilepsy with low radiation dose

OBJECTIVE

To localize the epileptic foci with positron emission tomography (PET), and study the principles of target definition and method to determine the optimal range of exposure in radiosurgery for intractable epilepsy.

METHODS

This study included 176 patients with intractable epilepsy, who received linear accelerator radiosurgery after (18)F-FDG PET for epileptic foci localization. The patients were divided according to different peripheral doses used in the treatment into Group A in which radiation dose of 9 to 11 Gy was used, Group B with 11 to 13 Gy and Group C with exposure to over 13 Gy. Follow-up study was conducted in all the patients for a period ranging from 3 to 16 months, during which the frequency of seizure after treatment was recorded to evaluate the therapeutic effect.

RESULTS

The seizure frequency significantly decreased after radiosurgical treatment in all the groups, but between the groups, the decrement evinced no significant difference. According to Wieser's classification of the effect after operation, 46.9% cases belonged to grade I to II and 41.5% to grade III to IV. Obvious complications were not observed, nor did disability or mortality occurred in these cases.

CONCLUSIONS

Stereotactic radiosurgery with low radiation dose under the guidance of PET provides a safe, effective and minimally invasive surgical approach for patients with intractable epilepsy, and peripheral radiation doses of 9 to 11 Gy for the epileptic foci localized by PET is sufficient to ensure good clinical outcome.

[The delayed effects of modulated and non-modulated electromagnetic field on epileptiformic activity in rats]

The modifying influence of the weak electromagnetic field on the development of the audiogenic spasmodic activity in rats was shown. The decrease of lifetime of experimental rats exposed to electromagnetic fields with different parameters and development of tumours (in one set of experiments) was found.

Variations in the natural history and survival of patients with supratentorial low-grade astrocytomas

Data from 55 consecutive patients with low-grade astrocytomas treated between 1982 and 1990 were analyzed to determine specific outcome factors, including time to recurrence, incidence of anaplastic transformation, and survival. Gender, type of symptoms, contrast enhancement, and timing of radiation therapy were not significant in determining outcome. Patients who had symptoms for > 2 years and underwent gross-total resection of the tumor, with age as a continuous variable, were associated with significantly longer time to recurrence and survival. Within the population of patients with low-grade astrocytomas, patients with chronic epilepsy clearly had the best prognoses. There were no tumor recurrences or deaths in 27 patients with chronic epilepsy, regardless of the extent of surgery and without the use of radiotherapy. Ten-year survival was 100% for 31 patients who underwent gross-total tumor resection, regardless of the length of preoperative symptoms. Immediate postoperative radiotherapy did not prolong the time to recurrence, reduce the incidence of transition to more malignant tumors at recurrence, or increase the length of survival when compared with delayed radiotherapy. Because recurrence with a high-grade lesion caused 92% of the mortality in our series, the benefit in patients who underwent aggressive surgery seems to result from a significant decrease in the risk of recurrence when compared with patients who underwent anything less than gross-total resection. Our data also suggest that variability in the natural history of low-grade astrocytomas has a strong influence in determining survival and that tumors associated with chronic epilepsy are much less likely to become more malignant over time.

Seizures in patients with supratentorial oligodendroglial tumours. Clinicopathological features and management considerations

In this study of 34 consecutive histologically confirmed oligodendroglial brain tumours (15 oligoastrocytoma, 12 oligodendroglioma, 7 anaplastic oligodendroglioma) twenty five patients (75%) presented with symptoms related to seizures. Although the seizure incidence was lowest in anaplastic oligodendroglioma (57%) it was not statistically different from either pure (75%) or mixed (80%) oligodendroglial tumours. Patients with seizures had a significantly lower age (p < 0.001) at diagnosis (median 36 years) than those without seizures (57 years). The types of seizure disorder, that were present for a median of 15 months prior to surgery, were variable with 32% having generalised, 36% partial and 32% mixed patterns. There were no significant differences between either the type or incidence of seizures and the particular cerebral location of the oligodendroglial tumour. Twenty four of the patients presenting with seizures underwent surgery (5 stereotactic biopsy, 5 stereotactic guided resection and 14 conventional craniotomy and resection) without intraoperative electrocorticography (ECoG). Eighteen (75%) of these patients also had postoperative radiotherapy (40 to 54 Gy in 30 fractions. Following these treatments the percentage of patients fit free at 6, 12, and 24 months were 67%, 56%, and 53%, respectively. Median time to first post operative seizure was 32 weeks (range 5 weeks to 5.3 years). After a median follow up time of 30 months 20 of the 25 patients who presented with seizures were still alive. Eight (40%) were seizure free and three other patients (15%) had experienced less than three postoperative seizures in follow-up periods ranging from 42 to 62 months. Although the numbers of patients on preoperative (87%) and postoperative (83%) anticonvulsant medications were similar, some had their medications either withdrawn (17%) or reduced (4%) whilst others had it introduced (12%) after interventional management. Only five (20%) patients who presented with seizures, compared to 6 (67%) who had not presented with seizures had died during median follow-up of 28 months. Three of nine patients (33%), who were initially seizure free, developed seizures between 25 and 36 months after initial surgery and radiotherapy. This study (i) confirms the high incidence of epilepsy in supratentorial oligodendroglial tumours; (ii) has shown that seizures associated with these tumours are significantly more common in younger patients; (iii) suggests that younger age, but not the presence of seizures, is a significant independent prognostic variable; (iv) that seizure control following a second operation is generally disappointing and (v) suggests that tumour resection and radiotherapy often facilitate control of the seizures by anticonvulsants. Because of the multiple clinicopathological and management variables involved a prospective study would be required to assess the optimal management of patients with seizure disorders associated with oligodendroglial brain tumours.

Experimental and clinical studies on the putative therapeutic efficacy of cerebral irradiation (radiotherapy) in epilepsy

1. The majority of the published literature on the radiotherapeutic treatment of epilepsy suffers because it has involved neither radiotherapists nor epileptologists. 2. Papers have either been written describing an incidental beneficial effect (these suffer from being retrospective analyses) or by enthusiasts (where one must question patient selection). In addition there are a small number of very detailed and useful individual case reports. 3. Despite the reservations it would appear that radiation can have beneficial effects on seizures, and this effect has been described for a wide variety of conditions using a wide variety of treatment modalities. 4. There are grounds for prospective clinical trials to test the putative therapeutic efficacy of cerebral irradiation. However, it is essential that these are carried out by a group involving an established epilepsy surgery programme and a radiotherapy department conversant with the complex issues involved in focussed radiation treatment.

Effect of cranial irradiation on seizure frequency in adults with low-grade astrocytoma and medically intractable epilepsy

We report the effect of cranial irradiation on seizure frequency in five adults with unresected (biopsy-proven) cerebral hemisphere low-grade astrocytoma and medically intractable epilepsy. Seizures were refractory to standard antiepileptic drugs for 7 months to 27 years. Treatment with 5,400 cGy to 6,120 cGy focal radiation reduced seizure frequency by more than 90% in three patients (one of whom became seizure-free) and by more than 75% (but less than 90%) in one patient. One patient had no response. Brain CT or MRI showed a partial tumor response to radiation in three of the four patients with reduced seizure frequency. In three patients, the reduced seizure frequency continued to the most recent follow-up of 1 to 1.5 years. In the patient who became seizure-free, seizures recurred at 8.2 years and were associated with tumor progression. Irradiation can reduce seizure frequency in some patients with unresected cerebral hemisphere low-grade astrocytoma and medically intractable epilepsy.

[Proton stereotaxic therapy of epilepsy due to cerebral arteriovenous aneurysms]

The authors estimated the influence of proton-beam stereotaxic therapy on a course of epileptic fits in cerebral arteriovenous aneurysms (AVA). A stable disappearance of epileptic fits was noted in 16 of 29 patients (56%), in 12 of them (41%) positive angiography results were noted. The calculated D and V fields of irradiation for 16 patients without fits and for 13 patients with epileptic fits after proton-beam stereotaxic therapy have shown that with D being the same, the effect depends upon a fraction of an AVA irradiated area.

Relief of epilepsy by radiosurgery of cerebral arteriovenous malformations

129 patients with inoperable cerebral arteriovenous malformations (AVM) were treated by stereotactic proton beam irradiation. Symptomatic epilepsy was present in 29 patients (22.5%) before the treatment. It was markedly relieved by the radiosurgery leading to cessation of the seizures in 16 patients, the persisting seizure-free follow-up period ranging from 2 to 8 years (mean 4.5 years). In no case was the epilepsy worsened by radiosurgery. The positive effect on epilepsy was not strictly dependent on the angiographic result, suggesting that the ionizing radiation by itself could lead to inhibition of epileptic activity around the AVM.

Epileptogenic cerebral low-grade tumors: effect of interstitial stereotactic irradiation on seizures

15 patients with various types of surgically inaccessible epileptogenic cerebral neuroepithelial tumors were treated with stereotactic interstitial irradiation. Epilepsy was improved in all cases, being abolished in 6 and markedly reduced in another 7. The effects which became apparent soon after the radioisotope implant persisted. Possible mechanisms of the phenomenon are discussed.