Radiosurgery for the treatment of dominant hemisphere periventricular heterotopia and intractable epilepsy in a series of three patients

Laser Ablation of Periventricular Nodular Heterotopia for Medically Refractory Epilepsy

OBJECTIVE

Periventricular nodular heterotopia (PVNH) is the most common neuronal heterotopia, frequently resulting in pharmaco-resistant epilepsy. Here, we characterize variables that predict good epilepsy outcomes following surgical intervention using stereo-electroencephalography (SEEG) -informed magnetic resonance-guided laser interstitial thermal therapy (MRgLITT).

METHODS

A retrospective review of consecutive cases from a single high-volume epilepsy referral center identified patients who underwent SEEG evaluation for PVNH to characterize the intervention and outcomes.

RESULTS

Thirty-nine patients underwent SEEG-guided MRgLITT of the seizure onset zone (SoZ) in PVNH and associated epileptic tissue. PVNH and polymicrogyria (PMG) were densely sampled with a mean of 16.5 (SD = 2)/209.4 (SD = 36.9) SEEG probes/recording contacts per patient. Ablation principally targeted just the PVNH and cortex that was abnormal on imaging was ablated (5 patients) only if implicated in the SoZ. Volumetric analyses revealed a high percentage of PVNH SoZ ablation (96.6%, SD = 5.3%) in unilateral and bilateral (92.9%, SD = 7.2%) cases. Mean follow-up duration was 31.4 months (SD = 20.9). Seizure freedom (ILAE 1) was excellent: unilateral PVNH without other imaging abnormalities, 80%; PVNH with mesial temporal sclerosis (MTS) or PMG, 63%; bilateral PVNH, 50%. SoZ ablation percentage significantly impacted surgical outcomes (p < 0.001).

INTERPRETATION

PVNH plays a central role in seizure genesis as revealed by dense recordings and selective targeting by LITT. MRgLITT represents a transformative technological advance in PVNH-associated epilepsy with seizure control outcomes consistent with those seen in focal lesional epilepsies. In localized unilateral cases and otherwise normal imaging, PVNH ablation without invasive recordings may be considered, and this approach deserves to be explored further. ANN NEUROL 2024;96:1174-1184.

Stereotactic radiosurgery for medically refractory non-lesional epilepsy: A case-based Radiosurgery Society (RSS) practice review

INTRODUCTION

Medically refractory epilepsy (MRE) occurs in about 30 % of patients with epilepsy, and the treatment options available to them have evolved over time. The classic treatment for medial temporal lobe epilepsy (mTLE) is anterior temporal lobectomy (ATL), but an initiative to find less invasive options has resulted in treatments such as neuromodulation, ablative procedures, and stereotactic radiosurgery (SRS). SRS has been an appealing non-invasive option and has developed an increasing presence in the literature over the last few decades. This article provides an overview of SRS for MRE with two example cases, and we discuss the optimal technique as well as the advantages, alternatives, and risks of this therapeutic option.

CASES

We present two example cases of patients with MRE, who were poor candidates for invasive surgical treatment options and underwent SRS. The first case is a 65-year-old female with multiple medical comorbidities, whose seizure focus was localized to the left temporal lobe, and the second case is a 19-year-old male with Protein C deficiency and medial temporal lobe sclerosis. Both patients underwent SRS to targets within the medial temporal lobe, and both achieve significant improvements in seizure frequency and severity.

DISCUSSION

SRS has generally been shown to be inferior to ATL for seizure reduction in medically refractory mTLE. However, there are patients with epilepsy for which SRS can be considered, such as patients with medical comorbidities that make surgery high risk, patients with epileptogenic foci in eloquent cortex, patients who have failed to respond to surgical management, patients who choose not to undergo surgery, and patients with geographic constraints to epilepsy centers. Patients and their physicians should be aware that SRS is not risk-free. Patients should be counseled on the latency period and monitored for risks such as delayed cerebral edema, visual field deficits, and radiation necrosis.

Surgical treatment of epilepsy in a patient with bilateral periventricular nodular heterotopia: A case report

Background

Periventricular nodular heterotopia (PNH) is a rare pathological condition characterized by the presence of nodules of gray matter located along the lateral ventricles of the brain. The condition typically presents with seizures and other neurological symptoms, and various methods of surgical treatment and postoperative outcomes have been described in the literature.

Case Description

We present a case study of a 17-year-old patient who has been experiencing seizures since the age of 13. The patient reported episodes of loss of consciousness and periodic freezing with preservation of posture. Two years later, the patient experienced his first generalized tonic-clonic seizure during nocturnal sleep and was subsequently admitted to a neurological department. A magnetic resonance imaging scan of the brain with an epilepsy protocol (3 Tesla) confirmed the presence of an extended bilateral subependymal nodular heterotopy at the level of the temporal and occipital horns of the lateral ventricles, which was larger on the left side, and a focal subcortical heterotopy of the right cerebellar hemisphere. The patient underwent a posterior quadrant disconnection surgery, which aimed to isolate the extensive epileptogenic zone in the left temporal, parietal, and occipital lobes using standard techniques. As of today, 6 months have passed since the surgery and there have been no registered epileptic seizures during this period following the surgical treatment.

Conclusion

Although PNHs can be extensive and located bilaterally, surgical intervention may still be an effective way to achieve seizure control in selected cases.

Stereo-EEG Evaluation and Surgical Treatment in Patients With Drug-Resistant Focal Epilepsy Associated With Nodular Heterotopia

PURPOSE

Nodular heterotopia (NH) is a common cause of drug-resistant epilepsy. Only limited studies detail the treatment of NH with laser interstitial thermal therapy and none analyze the relation between epileptogenicity and NH location.

METHODS

We retrospectively studied nine patients with drug-resistant epilepsy and NH who underwent stereoelectroencephalography and subsequent epilepsy surgery. Nodular heterotopia in the frontal lobes or along the bodies of the lateral ventricles was classified as anterior NH. Nodular heterotopia in the trigones, temporal or occipital horns, or temporal lobes was classified as posterior NH. Nodular heterotopia in both anterior and posterior locations was classified as diffuse NH. Interictal and ictal stereoelectroencephalography were analyzed, and patients were followed postoperatively to assess outcomes.

RESULTS

Of the six patients who underwent nine laser interstitial thermal therapy procedures either in isolation or in combination with other surgical therapies, four patients were Engel Ia, one was Engel IIb, and one was Engel IIIa, with an average follow-up of 22.8 months. All patients with posterior NH had interictal epileptiform abnormalities and seizures originating from the posterior NH. None of the patients with anterior NH had epileptiform activity recorded from their NH.

CONCLUSION

Laser interstitial thermal therapy alone or in combination with other surgical therapies is an effective treatment in those with drug-resistant epilepsy because of NH, even in those with extensive NH and broad seizure onset. We observed a trend suggesting that posterior NH are more likely to be epileptogenic compared with anterior NH and recommend that in patients with anterior NH, alternative epilepsy etiologies and stereoelectroencephalography implantation strategies be considered.

Role of High-Frequency Oscillation in Locating an Epileptogenic Zone for Radiofrequency Thermocoagulation

Radiofrequency thermocoagulation (RFTC) has been proposed as a first-line surgical treatment option for patients with drug-resistant focal epilepsy (DRE) that is associated with gray matter nodular heterotopia (GMNH). Excellent results on seizures have been reported following unilateral RFTC performed on ictal high-frequency-discharge, fast-rhythm, and low-voltage initiation areas. Complex cases (GMNH plus other malformations of cortical development) do not have good outcomes with RFTC. Yet, there is little research studying the effect of high-frequency oscillation in locating epileptogenic zones for thermocoagulation on unilateral, DRE with bilateral GMNH. We present a case of DRE with bilateral GMNH, treated using RFTC on unilateral GMNH and the overlying cortex, guided by stereotactic electroencephalogram (SEGG), and followed up for 69 months. Twenty-four-hour EGG recordings, seizure frequency, post-RFTC MRI, and neuropsychological tests were performed once yearly. To date, this patient is seizure-free, the electroencephalogram is normal, neuropsychological problems have not been found, and the trace of RFTC has been clearly identified on MRI. His dosage of antiepileptic medication has, furthermore, been significantly reduced. It is concluded that RFTC on unilateral DRE with bilateral GMNH may achieve good long-term effects, lasting up to, and perhaps longer than, 69 months. Ictal high-frequency oscillation (fast ripple) inside the heterotopia and the overlying cortex may be the key to this successful effect.

Treatment of Epilepsy Associated with Periventricular Nodular Heterotopia

PURPOSE OF REVIEW

Epilepsy associated with periventricular nodular heterotopia (PNH), a developmental malformation, is frequently drug-resistant and requires focal therapeutic intervention. Invasive EEG study is usually necessary to delineate the epileptogenic zone, but constructing an accurate hypothesis to define an appropriate electrode implantation scheme and the treatment is challenging. This article reviews recent studies that help understanding the epileptogenicity and potential therapeutic options in PNH.

RECENT FINDINGS

New noninvasive diagnostic and intracerebral EEG analytic tools demonstrated that cortical hyperexcitability and aberrant connectivity (between nodules and cortices and among nodules) are likely mechanisms causing epilepsy in most patients. The deeply seated PNH, if epileptogenic, are ideal target for stereotactic ablative techniques, which offer concomitant ablation of multiple regions with relatively satisfactory seizure outcome. Advance in diagnostic and analytic tools have enhanced our understanding of the complex epileptogenicity in PNH. Development in stereotactic ablative techniques now offers promising therapeutic options for these patients.

[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.

Heterotopia or overlaying cortex: What about in-between?

We describe a patient with unilateral periventricular nodular heterotopia (PNH) and drug-resistant epilepsy, whose SEEG revealed that seizures were arising from the PNH, with the almost simultaneous involvement of heterotopic neurons ("micronodules") scattered within the white matter, and subsequently the overlying cortex. Laser ablation of heterotopic nodules and the adjacent white matter rendered the patient seizure free. This case elucidates that "micronodules" scattered in white matter between heterotopic nodules and overlying cortex might be another contributor in complex epileptogenicity of heterotopia. Detecting patient-specific targets in the epileptic network of heterotopia creates the possibility to disrupt the pathological circuit by minimally invasive procedures.

IMAGING DIAGNOSIS-MAGNETIC RESONANCE IMAGING OF A NEURONAL HETEROTOPIA IN THE BRAIN OF A CAT

A domestic shorthair kitten was presented for evaluation and further treatment of seizures. Magnetic resonance imaging of the brain revealed a large multilobulated mass in the third ventricle extending into the right lateral ventricle with secondary obstructive hydrocephalus. The mass was homogeneously isointense to gray matter on T2W, T2-FLAIR, T2^* W, T1W, and ADC images, and hyperintense on DW-EPI. There was no appreciable contrast enhancement. Seizures were managed medically and with subsequent ventriculoperitoneal shunt placement. Clinical status later deteriorated and the cat was euthanized. Histopathology confirmed that the mass was the result of neuronal heterotopia. To the authors' knowledge this is the first report of neuronal heterotopia in a cat.