Functional neuroimaging in startle epilepsy: Involvement of a mesial frontoparietal network

Comparing late-onset epileptic spasm outcomes after corpus callosotomy and subsequent disconnection surgery between post-encephalitis/encephalopathy and non-encephalitis/encephalopathy

OBJECTIVE

We aimed to analyze the efficiency of corpus callosotomy (CC) and subsequent disconnection surgeries in patients with late-onset epileptic spasms (LOES) by comparing post-encephalitis/encephalopathy (PE) and non-encephalitis/encephalopathy (NE). We hypothesized these surgeries can control potential focal onset epileptic spasms (ES) in the NE group but not in the PE group.

METHODS

We retrospectively included 23 patients (12 with PE and 11 with NE) who initially underwent CC and subsequent disconnection surgeries (five NE). We compared the clinical courses, seizure types, MRI, video-EEG, epilepsy surgery, and seizure outcomes between the two groups.

RESULTS

The median age of LOES onset in the PE group was 2.8 (range 1.0-10.1 years) and 2.9 years (range 1.1-12.6) in the NE group. Bilateral MRI abnormalities were observed in both groups (PE, n = 12; NE, n = 3; P < 0.05). The PE group presented ES alone (n = 2), ES + focal seizures (FS) (n = 3), ES + generalized seizures (GS) (n = 3), and ES + FS + GS (n = 4) in addition to stimulus-induced startle seizures (SS) (n = 8) (mean 3.1 seizure types/patient). The NE group presented ES alone (n = 1), ES + FS (n = 2), and ES + FS + GS (n = 8) (mean 2.7 seizure types/patient). In the PE group, CC stopped ES (n = 1) and SS (n = 1) and achieved <50% SS (n = 3). In the NE group, CC achieved immediate ES-free status (n = 2) and < 50% ES (n = 1), and additional disconnection surgeries subsided all seizure types (n = 3) based on lateralized interictal/ictal EEG findings. LOES was significantly remitted by surgery in the NE group (6/11 [55%]) compared with the PE group (1/12 [8%]) (P < 0.05).

SIGNIFICANCE

LOES is a drug-resistant, focal/generalized/unknown onset ES. Lateralization of ES in NE could be achieved after CC and eliminated by further disconnection surgeries because of potential focal onset ES. LOES in PE had little benefit from CC for generalized onset ES. However, CC might reduce SS in patients in the PE group with multiple seizure types.

Startle-Induced Epileptic Spasms: A Clinical and Video-EEG Study

Objective

This study aimed to delineate the detailed characteristics of startle-induced epileptic spasms (ES) and explore the brain regions where startle-induced ES originated.

Methods

Among 581 patients with ES registered in our database, 30 were diagnosed with startle-induced ES according to video-electroencephalogram (EEG) and seizure semiology and were included in this study. Patients' clinical characteristics and ictal high-frequency oscillations (HFOs) were analyzed.

Results

Mean age at the onset of startle-induced ES was 28.1 months. Half of the patients had structural etiology, two of whom were diagnosed with co-existing structural and genetic etiologies. The focal neuroimaging abnormalities were predominant in the frontal cortex (9/15, 60.0%). Fifteen patients (50%) had prominent interictal epileptiform discharges in the frontal and anterior temporal. Ictal HFOs counts of the startle-induced ES in the anterior region were significantly higher than those in the posterior regions (p &lt; 0.05). Five patients (16.7%) became seizure-free ≥6 months, and ten (33.3%) showed startle-induced ES cessation ≥6 months. All patients except one had mild to severe psychomotor developmental delay after the onset of seizures.

Conclusion

Patients with startle-induced ES typically had brain lesions and showed drug-resistant. The neuroimaging and EEG findings, including ictal HFOs, support that startle-induced ES often originates from the frontal cortex.

Startle Seizures and Diffuse Leukoencephalopathy After Resolution of Herpes Simplex Virus 1 Encephalitis in a Child

We describe a unique clinical presentation of a child after the acute phase of herpes simplex virus 1 (HSV1) encephalitis. A 17-month-old boy first presented with HSV1 encephalitis and was promptly treated with antiviral medication. Seven months later, he was re-admitted for startle seizures. Magnetic Resonance Imaging of the brain showed diffuse confluent leukoencephalopathy. This constellation of symptoms has not been previously reported in HSV1 encephalitis. In conclusion, we showed that brain injury due to HSV1 encephalitis can be associated with the development of startle seizures and diffuse white matter injury in the post-acute phase.

Energy landscape of resting magnetoencephalography reveals fronto-parietal network impairments in epilepsy

Juvenile myoclonic epilepsy (JME) is a form of idiopathic generalized epilepsy. It is yet unclear to what extent JME leads to abnormal network activation patterns. Here, we characterized statistical regularities in magnetoencephalograph (MEG) resting-state networks and their differences between JME patients and controls by combining a pairwise maximum entropy model (pMEM) and novel energy landscape analyses for MEG. First, we fitted the pMEM to the MEG oscillatory power in the front-oparietal network (FPN) and other resting-state networks, which provided a good estimation of the occurrence probability of network states. Then, we used energy values derived from the pMEM to depict an energy landscape, with a higher energy state corresponding to a lower occurrence probability. JME patients showed fewer local energy minima than controls and had elevated energy values for the FPN within the theta, beta, and gamma bands. Furthermore, simulations of the fitted pMEM showed that the proportion of time the FPN was occupied within the basins of energy minima was shortened in JME patients. These network alterations were highlighted by significant classification of individual participants employing energy values as multivariate features. Our findings suggested that JME patients had altered multistability in selective functional networks and frequency bands in the fronto-parietal cortices.

Quantitative Analysis of [18F]FFMZ and [18F]FDG PET Studies in the Localization of Seizure Onset Zone in Drug-Resistant Temporal Lobe Epilepsy

BACKGROUND

Positron emission tomography (PET) imaging in epilepsy is an in vivo technique that allows the localization of a possible seizure onset zone (SOZ) during the interictal period. Stereo-electro-encephalography (SEEG) is the gold standard to define the SOZ. The objective of this research was to evaluate the accuracy of PET imaging in localizing the site of SOZ compared with SEEG.

METHODS

Seven patients with refractory temporal lobe epilepsy (Ep) and 2 healthy controls (HC) underwent 2 PET scans, one with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) and another with 2'-[18F]fluoroflumazenil (FFMZ), acquired 1 day apart. FDG was acquired for 10 min (static scan) 1 h after administration. An FFMZ scan was acquired for 60 min from radiopharmaceutical administration in a dynamic mode. Each brain PET image was segmented using a standard template implemented in PMOD 3.8. The pons was used as the reference region for modeling of the nondisplaceable binding potential (BPND)for FFMZ, and to obtain uptake ratios for FDG. SEEG studies of patients were performed as a part of their surgical evaluation to define the SOZ.

RESULTS

Well-defined differences between HC and Ep were found with both radiopharmaceuticals, showing the utility to identify abnormal brain regions using quantitative PET imaging. Lateralization of the SOZ findings by PET (lower uptake/binding in a specific brain hemisphere) matched in 86% for FFMZ and 71% for FDG with SEEG data.

CONCLUSION

Quantitative PET imaging is an excellent complementary tool that matches reasonably well with SEEG to define SOZ in presurgical evaluation.

Multiple Stereoelectroencephalography-Guided Radiofrequency Thermocoagulations for Polymicrogyria With Startle Seizures: A Case Report

The best results of stereoelectroencephalography (SEEG)-guided radiofrequency thermocoagulation (RF-TC) were observed in epilepsies with more limited lesions, but this procedure is rarely used in a wide range of brain malformation. We report a rare case of polymicrogyria (PMG) combined with drug-resistant startle seizures. Presurgical monitoring was performed using SEEG owing to the large lesion and complexity of PMG. According to the intracranial electrode results, the seizure onset was extensive, with the onset starting earlier in the cingulate sulcus and insular pole than in other sites of the other electrodes. Multi-point and multi-step SEEG-guided RF-TC was used for diffuse lesion and functional protection. RF-TC was first applied to the cingulate sulcus and insular pole, and our patient was rendered free from startle seizures after 2 weeks. Two weeks of observation helped us to observe the efficacy of RF-TC and the changes of SEEG, so as to make the next TC scheme. The patient still had spontaneous seizures after the first treatment. RF-TC was then applied to other sites involved earlier. Finally, the patient reached Engel class IIa for a follow-up period of 1 year. There were no additional startle seizures, and important functional areas were protected.

A study of perfusion changes with Insula Epilepsy using SPECT

PURPOSE

The non-invasive localisation of insular lobe epilepsy is a challenge. We aimed to determine if ictal SPECT is a reliable adjunctive test in insular cases and to explore its role in the tailoring of intracranial strategies.

METHOD

From a dataset of patients who underwent SEEG between December 2012 and December 2016, we collected patients with focal insular onset epilepsy. We examined semiology, EEG, PET and SPECT hyperperfusion pattern with SISCOM. We also reviewed relevant literature.

RESULTS

5 patients were identified, 4 females, from a dataset of 51 patients. Median age of seizure onset was 8 years old (8 months to 10 years). All patients had an ictal SPECT during pre-surgical work-up: median injection time was 7 s (3-17 sec) from clinical onset, and median seizure duration was 42 s (11-85 sec). Insula cortex showed focal hyperaemia in four patients, all bilateral, with the greatest hyperperfusion contralateral to the ictal onset in two cases, using SISCOM threshold at 1.5 standard deviation. Other sites with hyperaemia included basal ganglia and middle temporal gyrus. The SEEG confirmed insular onset seizures in all the cases. All patients had epilepsy surgery and were seizure free at 21 to 50 months follow up. The results from the literature review showed frequent hyperperfusion in structures outside insula and frequently over the contralateral hemisphere.

CONCLUSIONS

This study highlights the technical limitations of SPECT when attempting to assess seizures arising from the insula. Our findings and the literature show ictal SPECT can be localising but falsely lateralising in seizures arising from the insula.

Reflex epileptic mechanisms in ictogenesis and therapeutic consequences

Recent studies of reflex epileptic mechanisms in human epilepsy using advanced methods of neurophysiology and functional neuroimaging have contributed much to elucidate pathophysiological processes of seizure generation. Whereas in lesional focal epilepsies reflex mechanisms usually relate directly to the anatomical focus, in system epilepsies they have helped to define which functional anatomical systems serving physiological function are recruited by the ictogenic mechanisms. Reflex epileptic seizures can often be prevented by avoidance or modification of triggers or by prophylactic benzodiazepine administration. Surgical options apply to focal cases. According to restricted experiences with pharmacotherapy, without controlled studies and little information on new AEDs, reflex seizures in system epilepsies appear to respond best to valproic acid and in focal epilepsies, to carbamazepine.

Slow-Wave Oscillations in Awake Healthy Subjects: Methodological and Physiological Considerations

PURPOSE

Detection of pathologic slow-wave oscillations (0.5-7 Hz) in awake subjects has gained increasing interest in clinical diagnostics. Their significance, however, is hampered by the occasional presence of slow waves in healthy subjects, as well as the abundance of artefactual signals at low measurement frequencies. The aim of this study was to assess the occurrence of slow-wave oscillations in healthy subjects and to sharpen the management of possible measurement artifacts, in order to create a normative database for neurological patients.

METHODS

The authors analyzed magnetoencephalography recordings of spontaneous brain oscillations in 139 awake healthy adults. Sources of artifacts were first identified and suppressed by temporal extension of signal space separation method, and the remaining artifact components were projected out using signal space projection. Individual amplitude spectra were compared with the channel-level average spectra over all subjects.

RESULTS

Slow-wave oscillations deviating ±2 standard deviations from the average spectrum were detected in 12 subjects (∼9%). In 10 subjects, the oscillations were considered as normal physiological phenomena. Only two subjects showed activity that could have been interpreted as pathological: one subject with widespread parietal bilateral polyrhythmic slow-wave activity and one with focal rolandic 2.7-Hz slow-wave activity.

CONCLUSIONS

The prevalence of slow-wave oscillations in a healthy adult population is low. Knowledge about their occurrence, however, is essential for interpreting their significance in brain diseases. Artifacts and benign oscillatory variants at slow frequencies have to be recognized.

A case of startle epilepsy associated with IL1RAPL1 gene deletion

BACKGROUND

Startle epilepsy is a type of reflex epilepsy in which the seizures are mainly precipitated by unexpected sensory stimuli.

PATIENT

We present an 18-month-old boy with global developmental delay and multiple episodes of loss of tone after auditory cues.

RESULTS

The neurophysiologic study (video-electroencephalographic monitoring) revealed the epileptic nature of the stimulus-induced drop attacks, and the comparative genomic hybridization analysis revealed a microdeletion encompassing the interleukin-1 receptor accessory protein like 1 (IL1RAPL1) gene. The drop attacks were refractory to initial antiepileptic treatment, but they had a satisfactory response to a synthetic adrenocorticotropic hormone analogue.

CONCLUSIONS

The IL1RAPL1 gene is located on Xp21.2-p21.3 and codes a synaptic adhesion protein involved in neuronal differentiation and synapse localization, stabilization, and maturation. The coexistence of startle epilepsy and IL1RAPL1 gene deletion in this child may not be coincidental and suggests a possible involvement of IL1RAPL1 in the dysregulation of excitatory synapses and the pathogenesis of startle epilepsy.

Seizure-free after surgery in a patient with non-lesional startle epilepsy: a case report

We present the case of a patient with startle epilepsy provoked by auditory, somatosensory and visual stimuli during video-electrocorticography (ECoG) recording. Ictal ECoG of all types of seizures triggered by the three kinds of stimuli showed that seizure onset originated from the left supplementary sensorimotor area (SSMA). The patient has been seizure-free after the cortex around the left SSMA only had been resected. Therefore, we speculate that left SSMA is the epileptogenic zone of startle epilepsy in this patient and perhaps the primary cortex to modulate the startle reflex in healthy persons.

Reflex seizures and reflex epilepsies: old models for understanding mechanisms of epileptogenesis

Reflex seizures and epilepsies represent an ancient human model to understand basic mechanisms of epilepsy. The increase of light stimulation makes this issue extremely actual and interesting. In addition, a lot of observations show the frequent occurrence of provoked seizures in malformations of cortical development and in recently defined conditions such as familial or sporadic lateral temporal epilepsy. Advances in morphological and functional neuroimaging techniques, and the possibility of their fusion with EEG (e.g., fMRI-EEG co-registration) offer a unique non-invasive opportunity to investigate cortical areas and brain networks involved in cerebral functions and in epileptic discharges.