Video EEG is also useful in capturing and verifying auras. For example, forced turning of the head and eyes with neck extension localizes to the contralateral frontal eye fields and can be the first indication of frontal lobe epilepsy Video EEG is also helpful in confirming whether stereotypic, episodic behaviors are a manifestation of seizure activity or are nonepileptic. If rapid seizure spread is present, localization of the initial epileptic zone may be limited, and additional modalities may be necessary to augment localization. In specific regard to infantile spasms, video EEG should be of sufficient length to capture wakefulness, sleep, and wakening 18 ; hour video EEG monitoring has the best chance of capturing epileptic spasms and detecting hypsarrhythmia A single lesion on MRI corresponding to an EEG epileptogenic focus is a common situation with a potentially straightforward surgical plan, but more complex scenarios are frequently encountered.
For example, in patients with tuberous sclerosis complex, several cortical tubers may be present on imaging, making it more difficult to determine the epileptogenic lesion noninvasively.
Pediatric Epilepsy Surgery
In addition, adult patterns of myelination do not appear until 18 months of age 20 , and it is often difficult to resolve subtle abnormalities including focal cortical dysplasia in infants. Finally, while MRI is a widely available diagnostic modality, barriers do exist. Strict contraindications include cochlear implants and cardiac pacemakers, and images can be degraded by presence of dental braces, ventricular shunts, and any patient motion.
Any image degradation can be detrimental when attempting to detect subtle abnormalities on high-resolution scans. Classically, fMRI has been used to map motor, speech, auditory, and visual areas with the goal of avoiding them during surgical resection. Areas of activation are identified by blood-oxygen-level-dependent BOLD response or increased blood flow to an identified region while performing a specific task.
It is critical that the specific tasks used during fMRI are appropriate to the age and education level of the patient, as responses are partially dependent on this 21 and responses may be attenuated by tasks that are too simple or too complex 22 , Functional MRI is limited in terms of seizure localization, as only a few case reports exist of patients incidentally having a seizure while undergoing BOLD sequence imaging. More commonly, reflexive seizures, those that occur following a stimulus, such as flashing lights or excessive heat, can be provoked during imaging for localization purposes, as increased blood flow will be present to the epileptogenic region.
MEG is a more recent noninvasive method of epileptic focus identification. This modality is limited by regional availability and cost, but has some advantages in comparison to EEG. PET using fluorine 18 fluorodeoxyglucose FDG is a study of brain metabolism and has a role in epileptogenic focus localization, especially when structural MRI is unrevealing.
Hypometabolism occurs at an epileptic focus in an interictal state and is the result of neuronal loss, decreased synaptic activity, or decreased activity of blood—brain barrier glucose transport receptors 37 - Because of the typical infrequency of seizure activity, the test is typically performed in an interictal state, but EEG is usually performed concurrently to determine whether seizure activity occurs during the examination.
If a seizure occurs during the study, the EEG can correlate areas of possible glucose hypermetabolism and the epileptic focus. One limitation of FDG-PET imaging is that the area of glucose hypometabolism, or functional deficit zone, is often larger than the focal epileptic zone It is critical to note that regions of hypometabolism cannot differentiate the primary epileptogenic zone from secondary foci To conduct the study, children are admitted to the hospital, and long-term video EEG is placed.
A seizure is confirmed by EEG and at that time the radioisotope is injected, and imaging is completed within subsequent hours.
Interictal imaging is completed at a separate time for digital subtraction to identify areas of hypermetabolism during seizure onset. However, technical details may confound interpretation of the results, including the length of time between seizure onset and radioisotope administration, during which propagation of the seizure may occur. Intracranial EEG is an invasive measure to identify an epileptic zone that incorporates subdural EEG strip, grid, and depth electrode placement via craniotomy and stereotactic depth electrode insertion Figure 1.
Pediatric Epilepsy Surgery
Intracranial EEG is often required if lateralization or localization of an epileptic focus has not been identified using noninvasive methods and also facilitates cortical stimulation mapping of functionally eloquent cortex. Although this modality is the gold standard of epileptic focus localization, limitations exist. For example, general anesthesia, the definitive treatment of status epilepticus, is required for intracranial electrode placement and has a variable impact on seizure activity Stereo EEG SEEG , which involves the placement of multiple often bilateral depth electrodes, is commonly used in children in whom accurate lateralization or localization cannot be achieved with noninvasive diagnostic means.
In one report from a single institution, 18 children underwent depth electrode placement because scalp EEG results were unclear or indicated discordant localization of an epileptic focus. All patients who underwent resection were seizure-free at the one-year time point Subdural strip electrodes have a similar goal of lateralization or localization but can be placed through burr holes only.
Regardless of the technique, intracranial surveys often require subsequent craniotomy and grid placement for more precise localization once regional seizure onset is identified.
Craniotomy with insertion of large subdural electrode arrays requires general localization of the epileptic zone, either based on concordant noninvasive data or from a previous intracranial survey operation. Various electrode combinations are available, including dense grid electrodes 5 mm between platinum contacts or double-sided interhemispheric grid electrodes.
In certain cases, interictal recordings under total intravenous anesthesia in the operating room are sufficient to make surgical decisions. Frequently, however, staged craniotomy with long-term seizure monitoring to capture ictal onset and allow cortical stimulation mapping of functional eloquent cortex is required 46 , Nearly two decades ago, Davies and colleagues described their experience using MRI to evaluate subdural and depth electrodes without complication At our institution, an MRI is completed on postoperative day 1 to verify grid location and to identify possible surgical complications including hemorrhage or ischemia Figure 1.
The advantages to grid placement include dense electrode coverage in the absence of a structural lesion identified by MRI, resolution of discordant noninvasive testing, evaluating the relationship of a structural lesion to an epileptic zone, evaluation of patients with dual pathology or multifocal epilepsy, and extraoperative awake cortical stimulation mapping to identify primary cortex and map eloquent function The risks of staged craniotomy and placing large electrode arrays include intracranial hemorrhage, compression of cortical vascular structures causing cerebral edema and ischemia, as well as cerebrospinal fluid leak and meningitis.
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Epilepsy surgery requires a multidisciplinary team including a pediatric epileptologist, a pediatric neurosurgeon, and a neuropsychologist. The Introduction provides an excellent avenue for the subsequent chapters on invasive and noninvasive epilepsy diagnostics, including a very detailed and elaborate section on structural and functional imaging of the brain. This includes, e. The subdivision of the first section on Preoperative Assessment in electrophysiology, neuroimaging, neuropsychological, and cognitive assessment, respectively, is very logical and useful.
What I do not Skip to main content. Advertisement Hide. Oguz Cataltepe, George I.
Tests Before Surgery | Epilepsy Foundation
The authors present numerous approaches for managing temporal lobe epilepsy and extratemporal lobe epilepsy and guide clinicians through various surgical techniques for hemispherectomy, disconnection procedures, neuromodulation, and more. Highlights: Complete coverage of the selection of surgical candidates, including young patients with congenital or early lesions Detailed discussion of the latest surgical techniques such as hippocampal transection, cortical and deep brain stimulation and radiosurgery Comprehensive presentation of all major hemispherectomy and hemispherotomy techniques More than illustrations, including 85 in full-color, to elucidate key concepts Ideal for pediatric neurosurgeons, epilepsy surgeons and pediatric epileptologists, this authoritative text is also a valuable reference for clinicians, residents, and fellows in neurology, neuroradiology, neuropsychology, and neurophysiology with an interest in pediatric epilepsy surgery.
The definitive guide to surgical management of epilepsy in pediatric patients This fully revised and updated second edition of Pediatric Epilepsy Surgery, edited by internationally renowned pediatric neurosurgeons and epilepsy surgery experts O uz Cataltepe and George Jallo, fills a void in the literature, encompassing the full spectrum of topics related to the surgical treatment of intractable epilepsy and seizures in children.
The prodigiously illustrated book and its accompanying videos feature contributions from distinguished specialists in several different countries across a wide range of disciplines. From epidemiology, genetics, pathology, preoperative electrophysiological assessment and neuroimaging to state-of-the-art surgical approaches, this remarkable resource covers the full depth and breadth of surgical management of pediatric epilepsy.
Topics include awake anesthesia, intracranial stimulation and mapping techniques, temporal and extratemporal epilepsy surgery techniques, insular, multilobar and hemispheric surgery approaches, and diverse disconnection, neuromodulation, and ablative procedures. Insights are provided on postoperative issues including seizure control, neuropsychological and psychosocial outcomes, surgical failure and re-operation, and much more.
Key Features A review of topographic anatomy of the cerebral cortex and white matter with numerous illustrations provides enhanced understanding of eloquent anatomy. Discussion of cutting-edge techniques such as stereo-electroencephalography, multi-modality imaging and tractography, endoscopic and laser ablation approaches in hypothalamic hamartomas, peri-insular quadrantotomy, and various hemispherotomy approaches. Overview of common cortical stimulation and mapping techniques including magnetic and electrical stimulation modalities, functional MRI, and the WADA test.