Low-dose radiosurgery or hypofractionated stereotactic radiotherapy as treatment option in refractory epilepsy due to epileptogenic lesions in eloquent areas – Preliminary report of feasibility and safety

Innovative minimally invasive options to treat drug-resistant epilepsies

Despite the regular discovery of new molecules, one-third of epileptic patients are resistant to antiepileptic drugs. Only a few can benefit from resective surgery, the current gold standard. Although effective in 50-70% of cases, this therapy remains risky, costly, and can be associated with long-term cognitive or neurological side effects. In addition, patients are increasingly reluctant to have a craniotomy, emphasizing the need for new less invasive therapies for focal drug-resistant epilepsies. Here, we review different minimally invasive approaches already in use in the clinic or under preclinical development to treat drug-resistant epilepsies. Localized thermolesion of the epileptogenic zone has been developed in the clinic using high-frequency thermo-coagulations or magnetic resonance imaging-guided laser or ultrasounds. Although less invasive, they have not yet significantly improved the outcomes when compared with resective surgery. Radiosurgery techniques have been used in the clinic for the last 20years and have proven efficiency. However, their efficacy is not better than resective surgery, and various side effects have been reported as well as the potential risk of sudden unexpected death associated with epilepsy. Recently, a new strategy of radiosurgery has emerged using synchrotron-generated X-ray microbeams: microbeam radiation therapy (MRT). The low divergence and high-flux of the synchrotron beams and the unique tolerance to MRT by healthy brain tissues, allows a precise targeting of specific brain regions with minimal invasiveness and limited behavioral or functional consequences in animals. Antiepileptic effects over several months have been recorded in animal models, and histological and synaptic tracing analysis suggest a reduction of neuronal connectivity as a mechanism of action. The possibility of transferring this approach to epileptic patients is discussed in this review.

Radiomodulation in Mixed, Complex Cancer Pain by Triple Target Irradiation in the Brain: A Preliminary Experience

Introduction

Up to 30% of terminally ill cancer patients experiencing intense pain might be refractory to opioid treatment. Complex cancer pain can be a mixture of somatic, visceral, and neuropathic pain with few or no effective alternatives to ameliorate pain. Radiosurgery to treat refractory pain in cancer has been reported with different degrees of success. Radiomodulation in pain could be defined as a fast (<72 h), substantial (>50%) pain relief by focal irradiation to a peripheric, and/or central mediated pain circuitry. Based on our previous experience, mixed, refractory cancer pain is usually unresponsive to single target irradiation of the hypophysis. We treated three patients using a multi-target approach.

Methods

Three terminally ill oncological patients experiencing refractory, complex, mixed pain from bone, abdomen, thorax, and brachial plexus were treated with triple target irradiation which consisted of irradiating with a maximum dose (Dmax) of 90 Gy to the hypophysis using either an 8 mm collimator with gamma ray (Infini) (Shenzhen, China: Masep Medical Company) or a 7.5 circular collimator with Cyberknife (Sunnyvale, CA: Accuray Inc.), the other two targets were the mesial structures of the thalamus bilaterally using a 4 mm collimator with Infini and the 5 mm circular collimator with CK delivering 90 Gy Dmax to each region. Patients had a VAS of 10 despite the best medical treatment.

A correlation was made between the 45 Gy and 20 Gy isodose curves of the two different technologies to the Morel stereotactic atlas of the thalamus and basal ganglia for further understanding of dose distribution reconstructions in accordance with the São Paulo-Würzburg atlas of the Human Brain Project were performed. Lastly, a scoping review of the literature regarding radiosurgery for oncological pain was performed.

Results

Radiomodulation effect was achieved in all patients; case 1 had a VAS of five at 72 h, three at 15 days, and three at the time of death (21 days after treatment). Case 2 had a VAS of six at 72 h, five at 15 days, and four at the time of death (29 days after treatment). Case 3 had a VAS of five at 72 h, six at 15 days, and six at the time of death (30 days). Morphine rescues for cases 1 and 2 were reduced to 84%, and 70% for case 3. Overall, there were no adverse effects to treatment although excessive sleepiness was reported by one patient. After reading the title and abstract, only 14 studies remained eligible for full-text evaluation, and only nine studies met inclusion criteria after full-text reading. For most reports (seven), the target was the hypophysis and in two reports, the target was the thalamus either with single or bilateral irradiation.

Conclusions

In complex, for refractory oncological pain of mixed nature (nociceptive, neuropathic, and visceral), very few, if any, treatment alternatives are currently available. We provide a small proof of concept that multitarget intracranial radiosurgery might be effective in ameliorating pain in this population. The doses administered per target are the lowest that have shown effectiveness thus far, a different strategy might be needed as opposed to single target “large” dose approach that has been tried in the past for complex mixed refractory oncological pain. By no means, in our experience, these treatments traduce in elimination of pain, clinical results might make pain to be more bearable and respond better to pain medication.

Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy for Epilepsy: Systematic Review of Technique, Indications, and Outcomes

BACKGROUND

For patients with focal drug-resistant epilepsy (DRE), surgical resection of the epileptogenic zone (EZ) may offer seizure freedom and benefits for quality of life. Yet, concerns remain regarding invasiveness, morbidity, and neurocognitive side effects. Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has emerged as a less invasive option for stereotactic ablation rather than resection of the EZ.

OBJECTIVE

To provide an introduction to MRgLITT for epilepsy, including historical development, surgical technique, and role in therapy.

METHODS

The development of MRgLITT is briefly recounted. A systematic review identified reported techniques and indication-specific outcomes of MRgLITT for DRE in human studies regardless of sample size or follow-up duration. Potential advantages and disadvantages compared to available alternatives for each indication are assessed in an unstructured review.

RESULTS

Techniques and outcomes are reported for mesial temporal lobe epilepsy, hypothalamic hamartoma, focal cortical dysplasia, nonlesional epilepsy, tuberous sclerosis, periventricular nodular heterotopia, cerebral cavernous malformations, poststroke epilepsy, temporal encephalocele, and corpus callosotomy.

CONCLUSION

MRgLITT offers access to foci virtually anywhere in the brain with minimal disruption of the overlying cortex and white matter, promising fewer neurological side effects and less surgical morbidity and pain. Compared to other ablative techniques, MRgLITT offers immediate, discrete lesions with real-time monitoring of temperature beyond the fiber tip for damage estimates and off-target injury prevention. Applications of MRgLITT for epilepsy are growing rapidly and, although more evidence of safety and efficacy is needed, there are potential advantages for some patients.

Insular Cortex Surgery for the Treatment of Refractory Epilepsy

Focal epilepsy originating from the insular cortex is rare. One reason is the small amount of cortical tissue compared with other lobes of the brain. However, the incidence of insular epilepsy might be underestimated because of diagnostic difficulties. The semiology and the surface EEG are often not meaningful or even misleading, and elaborated imaging might be necessary. The close connections of the insular cortex with other potentially epileptogenic areas, such as the temporal lobe or frontal/central cortex, is increasingly recognized as possible reason for failure of epilepsy surgery for temporal or extratemporal seizures. Therefore, some centers consider invasive EEG recording of the insular cortex not only in case of insular epilepsy but also in other focal epilepsies with nonconclusive results from the presurgical work-up. The surgical approach to and resection of insular cortex is challenging because of its deep location and proximity to highly eloquent brain structures. Over the last decades, technical adjuncts like navigation tools, electrophysiological monitoring and intraoperative imaging have improved the outcome after surgery. Nevertheless, there is still a considerable rate of postoperative transient or permanent deficits, in some cases as unavoidable and calculated deficits. In most of the recent series, seizure outcome was favorable and comparable with extratemporal epilepsy surgery or even better. Up to now, the data volume concerning long-term follow-up is limited. This review focusses on the surgical challenges of resections to treat insular epilepsy, on prognostic factors concerning seizure outcome, on postoperative deficits and complications. Moreover, less invasive surgical techniques to treat epilepsy in this highly eloquent area are summarized.

Lesion focused radiofrequency thermocoagulation of bottom-of-sulcus focal cortical dysplasia type IIb: Conceptional considerations with regard to the epileptogenic zone

Small bottom-of-sulcus focal cortical dysplasias (BOS-FCD) type IIb are intrinsically epileptogenic lesions often responsible for pharmacoresistant epilepsy. They are increasingly well demarcated in vivo from surrounding cortex and white matter by 3 T magnetic resonance imaging (MRI). These facts and frequent seizure freedom after just narrow resections allow questioning the classical concept of epilepsy surgery in which the epileptogenic lesion is generally considered only one part of the epileptogenic zone and the resection volume categorically has to exceed lesion limits. This study approaches this question by analyzing procedures of strongly lesion focused stereotactic radiofrequency thermocoagulation (L-RFTC) applied to BOS-FCD IIb. Seven patients with BOS-FCD IIb were treated, three had invasive EEG recordings prior to L-RFTC, all had intraoperative stereotactic EEG-recordings. Perilesional epileptic discharges (PLD) were documented in all patients. Coagulation was planned based on MRI, the maximum extension beyond lesion limits due to PLD was 4.8 mm. Although in all patients other areas of PLD remained uncoagulated, seizure freedom was achieved in four of five patients with complete lesion coagulation. In summary, due to the minimal extensions of lesion coagulations, current experience with L-RFTC of BOS-FCD IIb is not yet sufficient to rebut the significance of PLD. It encourages, however, further research on even stronger MRI guidance and possibly even ignorance of PLD in BOS-FCD IIb. It appears possible that in some BOS-FCD IIB the complete epileptogenic zone (according to Lüders) might lie inside the MRI visible lesion. This would influence the understanding of the concept of cortical zones.

Successful Treatment of a Drug-Resistant Epilepsy by Long-term Transcranial Direct Current Stimulation: A Case Report

Transcranial direct current stimulation (tDCS) is a reemerged noninvasive cerebral therapy used to treat patients with epilepsy, including focal cortical dysplasia, with controversial results. We present a case of a 28-year-old female with left frontal cortical dysplasia refractory to antiepileptic drugs, characterized by 10–15 daily right tonic hemi-body seizures. The patient received a total of seven sessions of cathodal tDCS (2 mA, 30 min). The first three sessions were applied over three consecutive days, and the remaining four sessions of tDCS were given each at 2-week intervals. At the 1-year follow-up, the patient reported to have a single seizure per month and only mild adverse events.