Dysembryoplastic Neuroepithelial Tumor: A Benign but Complex Tumor of the Cerebral Cortex

Ultrahigh-field imaging (7 Tesla) in DNET: Unmasking microstructural imaging characteristics - A case report

Commercial ultrahigh-field 7 Tesla (T) MRI has been approved for clinical brain imaging, including applications in epilepsy and brain tumors. Increasing magnetic field strength offers significant advantages over lower-field MRI due to improved spatial resolution, signal-to-noise ratio, and contrast-to-noise ratio. These improvements provide better anatomical delineation and gray-white matter tissue-contrast differentiation. We present a case of a presumed dysembryoplastic neuroepithelial tumor (DNET) imaged at 7 T MRI of the second generation, which revealed an unprecedented level of detail of the complex and intricate tumor architecture. Insights of its different components correlate closely with its known histopathological features. These tumors are unique among low-grade neoplasms due to their distinct clinical presentation, imaging features, and histopathological architecture. DNETs are rare, typically occurring in young patients with refractory epilepsy, and are classified by their well-defined histological subtypes. We review the various MRI patterns of DNET, which have been shown to correlate with histological subtypes and the extent of the epileptogenic zone. Complete tumor resection is essential for long-term control and recurrence prevention, emphasizing the importance of precise preoperative visualization of the tumor and its surrounding tissue. In this case, 7 T images demonstrated superior lesion conspicuity and clearer boundaries, highlighting the advantages of ultrahigh-field MRI in defining the full extent of the lesion. Although 7 T MRI is not yet widely available, it has started to gain an important role in the management of epilepsy, particularly for cases requiring detailed structural analysis.

Nuclear Medicine Imaging in Epilepsy

Approximately one-third of patients with focal epilepsy have medically refractory focal epilepsy (MRFE), which significantly impacts their quality of life. Once a seizure focus is identified and determined to be in the noneloquent cortex, it can be surgically resected with the goal of freedom from seizures and minimal neurocognitive deficit. During noninvasive (phase I) presurgical planning, functional (nuclear) imaging and structural imaging are complementary in the accurate localization of the epileptogenic zone (EZ). PET and SPECT are complementary functional imaging modalities. Fluorine 18-fluorodeoxyglucose PET shows hypometabolism in the EZ, while SPECT radiotracers are used to assess regional cerebral perfusion. Functional imaging plays a more important role in patients with nonlesional epilepsy (approximately one-third of patients with MRFE), in patients with multiple lesions, or in the setting of electrophysiologic-structural discordance. Nuclear medicine imaging also helps in evaluating the functional integrity of the rest of the brain and unmasking abnormalities that are not apparent at structural imaging before surgery. During invasive (phase II) evaluation, the EZ seen at functional imaging helps in guiding intracranial electrode placement. This review of nuclear medicine imaging of epilepsy is focused on the radiotracers used, imaging acquisition and postprocessing, commonly encountered causes of MRFE in adults and children, radiologic appearances of MRFE, imaging artifacts, and interpretation pitfalls. The goal is to guide radiologists in optimally performing and interpreting these studies for effective multidisciplinary discussions of these complex patient cases. ©RSNA, 2025 Supplemental material is available for this article.

Imaging of pediatric glioneuronal and neuronal tumors

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

An imaging review of the hippocampus and its common pathologies

The hippocampus is a complex structure located in the mesial temporal lobe that plays a critical role in cognitive and memory-related processes. The hippocampal formation consists of the dentate gyrus, hippocampus proper, and subiculum, and its importance in the neural circuitry makes it a key anatomic structure to evaluate in neuroimaging studies. Advancements in imaging techniques now allow detailed assessment of hippocampus internal architecture and signal features that has improved identification and characterization of hippocampal abnormalities. This review aims to summarize the neuroimaging features of the hippocampus and its common pathologies. It provides an overview of the hippocampal anatomy on magnetic resonance imaging and discusses how various imaging techniques can be used to assess the hippocampus. The review explores neuroimaging findings related to hippocampal variants (incomplete hippocampal inversion, sulcal remnant and choroidal fissure cysts), and pathologies of neoplastic (astrocytoma and glioma, ganglioglioma, dysembryoplastic neuroepithelial tumor, multinodular and vacuolating neuronal tumor, and metastasis), epileptic (mesial temporal sclerosis and focal cortical dysplasia), neurodegenerative (Alzheimer's disease, progressive primary aphasia, and frontotemporal dementia), infectious (Herpes simplex virus and limbic encephalitis), vascular (ischemic stroke, arteriovenous malformation, and cerebral cavernous malformations), and toxic-metabolic (transient global amnesia and opioid-associated amnestic syndrome) etiologies.