Ictal 18F-FDG PET/MRI in a Patient With Cortical Heterotopia and Focal Epilepsy

An Independent Seizure-Onset Zone in Medial Temporal Lobe Found by 18 F-FDG PET Imaging Besides Epileptogenic Periventricular Nodular Heterotopia

ABSTRACT

A 23-year-old man with drug-resistant epilepsy was admitted for presurgical evaluation. The epileptogenic zone could not be derived from seizure semiology and scalp electroencephalographic monitoring definitely. MRI showed periventricular nodular heterotopia in occipital horn of left lateral ventricle with high FDG uptake on interictal 18 F-FDG PET scan, whereas the hypometabolic zone in the left medial temporal lobe was also found on PET with no abnormality on MRI. Stereoelectroencephalographic implantation was performed to identify the seizure-onset zone. Two independent epileptogenic foci located in periventricular nodular heterotopia and left hippocampus were validated by stereoelectroencephalographic monitoring and the outcome of subsequent thermocoagulation.

Clinical and Instrumental Characterization of Patients With Late-Onset Epilepsy

Epilepsy is classically considered a childhood disease. However, it represents the third most frequent neurological condition in the elderly, following stroke, and dementia. With the progressive aging of the general population, the number of patients with Late-Onset Epilepsy (LOE) is constantly growing, with important economic and social consequences, in particular for the more developed countries where the percentage of elderly people is higher. The most common causes of LOE are structural, mainly secondary to cerebrovascular or infectious diseases, brain tumors, trauma, and metabolic or toxic conditions. Moreover, there is a growing body of evidence linking LOE with neurodegenerative diseases, particularly Alzheimer's disease (AD). However, despite a thorough characterization, the causes of LOE remain unknown in a considerable portion of patients, thus termed as Late-Onset Epilepsy of Unknown origin (LOEU). In order to identify the possible causes of the disease, with an important impact in terms of treatment and prognosis, LOE patients should always undergo an exhaustive phenotypic characterization. In this work, we provide a detailed review of the main clinical and instrumental techniques for the adequate characterization of LOE patients in the clinical practice. This work aims to provide an easy and effective tool that supports routine activity of the clinicians facing LOE.

Three Different FDG Patterns in Periventricular Nodular Heterotopia Correlated to Video Stereoelectroencephalography

ABSTRACT

A 40-year-old woman with a drug-resistant focal epilepsy underwent cerebral FDG PET in phase 1 presurgical epilepsy study. MRI essentially showed multiple periventricular nodular heterotopias. The stereoelectroencephalography coupled to MRI and FDG PET helped to define the anatomofunctional correlation of the epileptogenic zone network. This procedure brought to light 3 distinct patterns of FDG consumption, corresponding to different anatomoelectroclinical features. This pattern was already found in a previous FDG PET reflecting a "stable" permanent intralesional intercritical stereoelectroencephalography activity, an electrical "signature" of the lesion. Finally, functional imaging improved thermocoagulation in this patient and emphasized the use of FDG in drug-resistant epilepsy.

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.

Value of Multimodal Imaging Approach to Diagnosis of Neurosarcoidosis

Background: Neurosarcoidosis is a highly variable condition with many clinical and radiological manifestations, that can lead to difficult identification of isolated central nervous system (CNS) forms, because it could mimic inflammatory, infective or neoplastic disorders. Conventional magnetic resonance imaging (MRI) is gold standard to evaluate CNS involvement in neurosarcoidosis, despite the reported high sensitivity but low specificity in the diagnosis. Case presentation: Here, we describe a 52-year-old man that presented to our hospital with a 10-year history of focal seizures, progressive cognitive decline and motor impairment. Neurological examination revealed ataxic gait, bilateral telekinetic and postural tremor, brisk reflexes, left extensor plantar response and hypoesthesia to the right side of body. Brain 3T-magnetic resonance imaging (MRI) showed a leukoencephalopathy with multifocal nodular lesions hyperintense on T2/ fluid attenuated inversion recovery (FLAIR) weighted images involving basal ganglia, periventricular and deep white matter. The interpretation of this pattern on conventional MRI was unclear, opening a challenge on the differential diagnosis between inflammatory, infective or neoplastic disorders. Thus, to better understand the nature of these nodules, single-voxel ¹H-magnetic resonance spectroscopy (¹H-MRS), contrast enhanced computed tomography (CT) scan and fluorine-18-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG-PET)/3T-MRI were performed. The parenchymal multifocal lesions exhibited slight N-acetyl-aspartate/creatine reduction without abnormal peaks on ¹H-MRS, enhancement after the administration of contrast agent on CT and hypermetabolism on ¹⁸F-FDG-PET/3T-MRI. All these findings excluded primary neoplasms, metastasis, neurotuberculosis, neurocysticercosis and brain abscess, strongly suggesting a diagnosis of neurosarcoidosis. Therefore, a whole-body ¹⁸F-FDG-PET/CT was performed in order to identify subclinical extraneural sarcoidosis localizations, and a hypermetabolic nodule of the left lung upper lobe was found. Subsequently, a biopsy documented the presence of systemic sarcoidosis, supporting a diagnosis of probable neurosarcoidosis. Conclusions: This case demonstrated that a multimodal neuroimaging approach can provide different but complementary evidences to suspect sarcoidosis, especially in apparently CNS isolated forms.