Electroencephalographic recordings of focal seizures in patients affected by periventricular nodular heterotopia: role of the heterotopic nodules in the genesis of epileptic discharges

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.

Human periventricular nodular heterotopia shows several interictal epileptic patterns and hyperexcitability of neuronal firing

Periventricular nodular heterotopia (PNH) is a malformation of cortical development that frequently causes drug-resistant epilepsy. The epileptogenicity of ectopic neurons in PNH as well as their role in generating interictal and ictal activity is still a matter of debate. We report the first in vivo microelectrode recording of heterotopic neurons in humans. Highly consistent interictal patterns (IPs) were identified within the nodules: (1) Periodic Discharges PLUS Fast activity (PD+F), (2) Sporadic discharges PLUS Fast activity (SD+F), and (3) epileptic spikes (ES). Neuronal firing rates were significantly modulated during all IPs, suggesting that multiple IPs were generated by the same local neuronal populations. Furthermore, firing rates closely followed IP morphologies. Among the different IPs, the SD+F pattern was found only in the three nodules that were actively involved in seizure generation but was never observed in the nodule that did not take part in ictal discharges. On the contrary, PD+F and ES were identified in all nodules. Units that were modulated during the IPs were also found to participate in seizures, increasing their firing rate at seizure onset and maintaining an elevated rate during the seizures. Together, nodules in PNH are highly epileptogenic and show several IPs that provide promising pathognomonic signatures of PNH. Furthermore, our results show that PNH nodules may well initiate seizures.

The analysis of 18 F-FDG PET/MRI, electroencephalography, and semiology in patients with gray matter heterotopia: A pilot study

OBJECTIVES

To describe ¹⁸ F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (¹⁸ F-FDG PET/MRI) along with semiology and electroencephalography (EEG) in patients with gray matter heterotopia (GMH); to evaluate the concordance between ¹⁸ F-FDG PET/MRI and clinical epileptogenic zone (EZ).

MATERIALS & METHODS

GMH (subcortical heterotopia [SCH] and periventricular nodular heterotopia [PNH]) patients with epilepsy who underwent ¹⁸ F-FDG PET/MRI were retrospectively enrolled. Two radiologists evaluated brain MRI, while two nuclear medicine specialists assessed the ¹⁸ F-FDG PET. The SUVmax values of visually hypometabolic cortical areas were compared to the contralateral cortex using a SUVmax threshold value of 10%; the SUVmax values of GMH lesions were compared with that of the right precentral gyrus. The cortex or GMH with hypometabolism on ¹⁸ F-FDG PET/MRI was considered representative of the EZ. The clinical EZ was identified using EEG and semiology.

RESULTS

Thirty patients (19 PNH; 11 SCH) with a mean age of 28.46 ± 9.52 years were enrolled. The heterotopic nodules were ametabolic in 3 patients (10%), hypometabolic in 16 (33.33%), isometabolic in 13 (26.66%), and hypermetabolic in 4 (10%). ¹⁸ F-FDG PET/MRI demonstrated hypometabolism in the cortex and GMH in 22/30 (73.33%) and 16/30 (53.33%). We could identify a clinical EZ in 18 patients, and 15 out of 18 (83.33%) had concordant ¹⁸ F-FDG PET/MRI findings.

CONCLUSION

Heterotopic nodules in GMH patients show different metabolic patterns on ¹⁸ F-FDG PET/MRI, with nearly three-quarters of the patients having cortical hypometabolism. ¹⁸ F-FDG PET/ MRI findings are mostly concordant with the clinical EZ.

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.

PET MRI Coregistration in Intractable Epilepsy and Gray Matter Heterotopia

A 25-year-old woman with intractable seizures underwent FDG PET/MRI for seizure focus localization. MRI demonstrated bilateral carpetlike nodular subependymal gray matter and asymmetrical focal dilatation in the right temporal horn. PET/MRI showed increased FDG within subependymal gray matter with significant hypometabolism in right anterior temporal lobe. EEG and ictal semiology confirmed the right temporal seizure origin. This case highlights the importance of identification of gray matter heterotopia on FDG PET/MRI.

Nodule excitability in an animal model of periventricular nodular heterotopia: c-fos activation in organotypic hippocampal slices

OBJECTIVE

Aberrations in brain development may lead to dysplastic structures such as periventricular nodules. Although these abnormal collections of neurons are often associated with difficult-to-control seizure activity, there is little consensus regarding the epileptogenicity of the nodules themselves. Because one common treatment option is surgical resection of suspected epileptic nodules, it is important to determine whether these structures in fact give rise, or essentially contribute, to epileptic activities.

METHODS

To study the excitability of aberrant nodules, we have examined c-fos activation in organotypic hippocampal slice cultures generated from an animal model of periventricular nodular heterotopia created by treating pregnant rats with methylazoxymethanol acetate. Using this preparation, we have also attempted to assess tissue excitability when the nodule is surgically removed from the culture. We then compared c-fos activation in this in vitro preparation to c-fos activation generated in an intact rat treated with kainic acid.

RESULTS

Quantitative analysis of c-fos activation failed to show enhanced nodule excitability compared to neocortex or CA1 hippocampus. However, when we compared cultures with and without a nodule, presence of a nodule did affect the excitability of CA1 and cortex, at least as reflected in c-fos labeling. Surgical removal of the nodule did not result in a consistent decrease in excitability as reflected in the c-fos biomarker.

SIGNIFICANCE

Our results from the organotypic culture were generally consistent with our observations on excitability in the intact rat-as seen not only with c-fos but also in previous electrophysiologic studies. At least in this model, the nodule does not appear to be responsible for enhanced excitability (or, presumably, seizure initiation). Excitability is different in tissue that contains a nodule, suggesting altered network function, perhaps reflecting the abnormal developmental pattern that gave rise to the nodule.

Location of periventricular nodular heterotopia is related to the malformation phenotype on MRI

BACKGROUND AND PURPOSE

Periventricular nodular heterotopia are common malformations of cortical development that are associated with many clinical syndromes and with many different neuroimaging phenotypes. The purpose of this study was to determine whether specific malformation phenotypes may be related to location, side, or number of PNH as assessed by MR imaging.

MATERIALS AND METHODS

MR images of 200 patients previously diagnosed with PNH were retrospectively analyzed. PNH were classified according to their location along the ventricles (anterior, posterior, or diffuse), side (unilateral or bilateral), and number of nodules (<5, 6-10, or >10). The cerebrum, brain stem and cerebellum were analyzed to assess associated anomalies. Associations between PNH location and the presence of other anomalies were tested by using Fisher exact test and χ2 test.

RESULTS

Posterior PNH were significantly associated with malformations of the cerebral cortex, diminished white matter volume, and mid-/hindbrain anomalies. Diffuse PNH were associated with diminished white matter volume, callosal "anomalies," and the presence of megacisterna magna. Unilateral PNH were strongly associated with cortical malformations.

CONCLUSIONS

Certain malformation complexes are associated with PNH in specific locations: posterior PNH with cerebral cortical and mid-/hindbrain malformations and diffuse PNH with callosal anomalies and megacisterna magna. Knowledge of these associations should allow more directed analyses of brain MR imaging in patients with PNH. In addition, knowledge of these associations may help to direct studies to elucidate the causes of these malformation complexes.

A case report of surgically treated drug resistant epilepsy associated with subependymal nodular heterotopia

Subependymal nodular heterotopia (SNH) is a cortical development malformation that is commonly associated with medically resistant epilepsy. Cases of SNH are challenging to treat surgically because there are typically multiple nodules, which may be involved in epileptogenesis. Moreover, dual pathology may exist in these patients. Here, we present a case with unilateral subependymal heterotopic nodules associated with ipsilateral hippocampal atrophy. Invasive and non-invasive work-ups revealed that the hippocampus was the actual ictal onset zone and that the SNH was not involved. An anterior temporal lobectomy was carried out, and postoperative seizure outcome was class Ia at the end of 2 years. The case demonstrates that SNH may not play a major role in patients with dual pathology. However, direct electroencephalography (EEG) recording from areas of SNH and other possible epileptogenic regions is indispensable in defining the ictal onset zone and avoiding poor surgical outcomes.

Incidence of hydrocephalus and the need to ventriculoperitoneal shunting in premature infants with intraventricular hemorrhage: risk factors and outcome

OBJECTIVE

To investigate the associated risk factors for ventriculoperitoneal (VP) shunting in infantile hydrocephalus following intraventricular hemorrhage (IVH) in premature infants.

METHODS

A historical cohort study was conducted, consisting of 97 premature infants in whom the diagnosis of IVH was previously made by cranial ultrasound and were referred to pediatric neurosurgery clinic and/or neonatal intensive care unit of Children's Hospital Medical Center in Tehran, Iran, from April 2004 to March 2009. Among the patients, those who were followed up for at least 6 months after the diagnosis of IVH were included in the study, and data regarding signs and symptoms of increased intracranial pressure, cranial ultrasound, non-surgical treatment (CSF drainage and/or acetazolamide), and shunt requirement were extracted. Patients who required VP shunting were followed up for at least 6 months thereafter considering shunt infection.

RESULTS

All the patients were followed up for at least 1 year, except for three who died at the ages of 6 (two of them) and 7 months. Thirty five percent (35%) of patients required VP shunting, in all of whom IVH was of grade 3 or 4. The need for VP shunting in these patients was predicted only by the severity of IVH. Non-surgical treatments for IVH had no statistically significant effect on shunt requirement. Moreover, 11 of 31 patients with shunt developed shunt infection, which was significantly associated with repeated cerebrospinal fluid (CSF) drainage.

CONCLUSION

It is suggested that children with IVH, especially of higher grades, should be followed up meticulously (by signs, symptoms, and periodic cranial ultrasounds). Non-surgical treatments are considered for patients requiring VP shunting who are not good candidates for immediate surgical intervention. The only predictor for surgical intervention was the grade of IVH.

Layer I neocortical ectopia: cellular organization and local cortical circuitry

Focal cortical dysplasia (FCD) are associated with neurological disorders and cognitive impairments in humans. Molecular layer ectopia, clusters of misplaced cells in layer I of the neocortex, have been identified in patients with developmental dyslexia and psychomotor retardation. Mouse models of this developmental disorder display behavioral impairments and increased seizure susceptibility. Although there is a correlation between cortical malformations and neurological dysfunction, little is known about the morphological and physiological properties of cells within cortical malformations. In the present study we used electrophysiological and immunocytochemical analyses to examine the distribution of neuronal and non-neuronal cell types within and surrounding layer I neocortical ectopia in NXSMD/EiJ mice. We show that cells within ectopia have membrane properties of both pyramidal and a variety of non-pyramidal cell types, including fast-spiking cells. Immunocytochemical analysis for different interneuronal subtypes demonstrates that ectopia contain nonpyramidal cells immunoreactive for calbindin-D28K (CALB), parvalbumin (PARV), and calretinin (CR). Ectopia also contains astrocytes, positive for glial fibrillary acidic protein (GFAP) and oligodendrocyte precursor cells positive for NG2 proteoglycan (NG2). Lastly, we provide electrophysiological and morphological evidence to demonstrate that cells within ectopia receive input from cells within layers I, upper and deeper II/III, and V and provide outputs to cells within deep layer II/III and layer V, but not layers I and upper II/III. These results indicate that ectopia contain cells of different lineages with diverse morphological and physiological properties, and appear to cause disruptions in local cortical circuitry.

Chronic subdural electrodes in the management of epilepsy

Subdural electrodes play a very important role in the evaluation of a percentage of patients being considered for epilepsy surgery. Electrical activity at very low and very high frequencies, beyond the practical range of scalp EEG, can be recorded subdurally and may contain considerable information not available non-invasively. The recording and stimulating procedures for using chronically implanted subdural electrodes to localize the epileptogenic zone and map eloquent functions of the human cortex are well established, and complication rates are low. Complications include infections, CSF leak, and focal neurologic deficits, all of which tend to be increased with a higher number of electrodes and longer duration of recordings. Careful consideration of the risks and benefits should be coupled with a firm hypothesis about the epileptogenic zone derived from the non-invasive components of the epilepsy workup to guide the decision about whether and where to implant subdural electrodes. When they are employed to answer a specific question in an individual patient, subdural electrodes can optimize the clinical outcome of a candidate for epilepsy surgery.

Periventricular Nodular Heterotopia: Classification, Epileptic History, and Genesis of Epileptic Discharges

PURPOSE

Periventricular nodular heterotopia (PNH) is among the most common malformations of cortical development, and affected patients are frequently characterized by focal drug-resistant epilepsy. Here we analyzed clinical, MRI, and electrophysiologic findings in 54 PNH patients to reevaluate the classification of PNH, relate the anatomic features to epileptic outcome, and ascertain the contribution of PNH nodules to the onset of epileptic discharges.

METHODS

The patients were followed up for a prolonged period at the Epilepsy Center of our Institute. In all cases, we related MRI findings to clinical and epileptic outcome and analyzed interictal and ictal EEG abnormalities. In one patient, EEG and stereo-EEG (SEEG) recordings of seizures were compared.

RESULTS

We included cases with periventricular nodules, also extending to white matter and cortex, provided that anatomic continuity was present between nodules and malformed cortex. Based on imaging and clinical data, patients were subdivided into five PNH groups: (a) bilateral and symmetrical; (b) bilateral single-noduled; (c) bilateral and asymmetrical; (d) unilateral; and (e) unilateral with extension to neocortex. The latter three groups were characterized by worse epileptic outcome. No differences in outcome were found between unilateral PNH patients regardless the presence of cortical involvement. Interictal as well as ictal EEG abnormalities were always related to PNH location.

CONCLUSIONS

The distinctive clinical features and epileptic outcomes in each group of patients confirm the reliability of the proposed classification. Ictal EEG and SEEG recordings suggest that seizures are generated by abnormal anatomic circuitries including the heterotopic nodules and adjacent cortical areas.