1
|
Swain CC, Wischmeier JN, Neifer AE, Lloyd EAR, Neifer KL, Kile KB, Burkett JP. Hereditary convulsions in an outbred prairie vole line. Epilepsy Res 2023; 195:107202. [PMID: 37540927 PMCID: PMC10529651 DOI: 10.1016/j.eplepsyres.2023.107202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 07/09/2023] [Accepted: 07/31/2023] [Indexed: 08/06/2023]
Abstract
Patients with epilepsy are significantly burdened by the disease due to long-term health risks, the severe side effect profiles of anti-epileptic drugs, and the strong possibility of pharmacoresistant refractory seizures. New animal models of epilepsy with unique characteristics promise to further research to address these ongoing problems. Here, we characterize a newly developed line of prairie voles (Microtus ochrogaster, UTol:HIC or "Toledo" line) that presents with a hereditary, adult-onset, handling-induced convulsion phenotype. Toledo voles were bred for four generations and tested to determine whether the observed phenotype was consistent with epileptic seizures. Toledo voles maintained a stable 22 % incidence of convulsions across generations, with an average age of onset of 12-16 weeks. Convulsions in Toledo voles were reliably evoked by rodent seizure screens and were phenotypically consistent with murine seizures. At the colony level, Toledo voles had a 7-fold increase in risk for sudden unexpected death from unknown causes, which parallels sudden unexpected death in epilepsy (SUDEP) in human patients. Finally, convulsions in Toledo voles were reduced or prevented by treatment with the anti-epileptic drug levetiracetam. Taken in combination, these results suggest that convulsions in Toledo voles may be epileptic seizures. The Toledo prairie vole strain may serve as a new rodent model of epilepsy in an undomesticated, outbred species.
Collapse
Affiliation(s)
- Caroline C Swain
- University of Toledo College of Medicine and Life Sciences, Toledo, OH 43614, USA
| | - James N Wischmeier
- University of Toledo College of Natural Sciences and Mathematics, Toledo, OH 43606, USA
| | - Asha E Neifer
- University of Toledo College of Natural Sciences and Mathematics, Toledo, OH 43606, USA
| | | | - Kari L Neifer
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH 43614, USA
| | - Kara B Kile
- Department of Physics, University of Toledo College of Natural Sciences and Mathematics, Toledo, OH 43606, USA
| | - James P Burkett
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH 43614, USA.
| |
Collapse
|
2
|
Fisher RS, Acharya JN, Baumer FM, French JA, Parisi P, Solodar JH, Szaflarski JP, Thio LL, Tolchin B, Wilkins AJ, Kasteleijn-Nolst Trenité D. Visually sensitive seizures: An updated review by the Epilepsy Foundation. Epilepsia 2022; 63:739-768. [PMID: 35132632 DOI: 10.1111/epi.17175] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 01/10/2022] [Accepted: 01/12/2022] [Indexed: 12/19/2022]
Abstract
Light flashes, patterns, or color changes can provoke seizures in up to 1 in 4000 persons. Prevalence may be higher because of selection bias. The Epilepsy Foundation reviewed light-induced seizures in 2005. Since then, images on social media, virtual reality, three-dimensional (3D) movies, and the Internet have proliferated. Hundreds of studies have explored the mechanisms and presentations of photosensitive seizures, justifying an updated review. This literature summary derives from a nonsystematic literature review via PubMed using the terms "photosensitive" and "epilepsy." The photoparoxysmal response (PPR) is an electroencephalography (EEG) phenomenon, and photosensitive seizures (PS) are seizures provoked by visual stimulation. Photosensitivity is more common in the young and in specific forms of generalized epilepsy. PS can coexist with spontaneous seizures. PS are hereditable and linked to recently identified genes. Brain imaging usually is normal, but special studies imaging white matter tracts demonstrate abnormal connectivity. Occipital cortex and connected regions are hyperexcitable in subjects with light-provoked seizures. Mechanisms remain unclear. Video games, social media clips, occasional movies, and natural stimuli can provoke PS. Virtual reality and 3D images so far appear benign unless they contain specific provocative content, for example, flashes. Images with flashes brighter than 20 candelas/m2 at 3-60 (particularly 15-20) Hz occupying at least 10 to 25% of the visual field are a risk, as are red color flashes or oscillating stripes. Equipment to assay for these characteristics is probably underutilized. Prevention of seizures includes avoiding provocative stimuli, covering one eye, wearing dark glasses, sitting at least two meters from screens, reducing contrast, and taking certain antiseizure drugs. Measurement of PPR suppression in a photosensitivity model can screen putative antiseizure drugs. Some countries regulate media to reduce risk. Visually-induced seizures remain significant public health hazards so they warrant ongoing scientific and regulatory efforts and public education.
Collapse
Affiliation(s)
- Robert S Fisher
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Jayant N Acharya
- Department of Neurology, Penn State Health, Hershey, Pennsylvania, USA
| | - Fiona Mitchell Baumer
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Jacqueline A French
- NYU Comprehensive Epilepsy Center, Epilepsy Foundation, New York, New York, USA
| | - Pasquale Parisi
- Department of Neuroscience, Mental Health, and Sensory Organs, Sapienza University, Rome, Italy
| | - Jessica H Solodar
- American Medical Writers Association-New England Chapter, Boston, Massachusetts, USA
| | - Jerzy P Szaflarski
- Department of Neurology, Neurobiology and Neurosurgery, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, USA
| | - Liu Lin Thio
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Benjamin Tolchin
- Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA
| | | | | |
Collapse
|
3
|
Aceves-Serrano L, Neva JL, Doudet DJ. Insight Into the Effects of Clinical Repetitive Transcranial Magnetic Stimulation on the Brain From Positron Emission Tomography and Magnetic Resonance Imaging Studies: A Narrative Review. Front Neurosci 2022; 16:787403. [PMID: 35264923 PMCID: PMC8899094 DOI: 10.3389/fnins.2022.787403] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 02/01/2022] [Indexed: 12/14/2022] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a therapeutic tool to alleviate symptoms for neurological and psychiatric diseases such as chronic pain, stroke, Parkinson’s disease, major depressive disorder, and others. Although the therapeutic potential of rTMS has been widely explored, the neurological basis of its effects is still not fully understood. Fortunately, the continuous development of imaging techniques has advanced our understanding of rTMS neurobiological underpinnings on the healthy and diseased brain. The objective of the current work is to summarize relevant findings from positron emission tomography (PET) and magnetic resonance imaging (MRI) techniques evaluating rTMS effects. We included studies that investigated the modulation of neurotransmission (evaluated with PET and magnetic resonance spectroscopy), brain activity (evaluated with PET), resting-state connectivity (evaluated with resting-state functional MRI), and microstructure (diffusion tensor imaging). Overall, results from imaging studies suggest that the effects of rTMS are complex and involve multiple neurotransmission systems, regions, and networks. The effects of stimulation seem to not only be dependent in the frequency used, but also in the participants characteristics such as disease progression. In patient populations, pre-stimulation evaluation was reported to predict responsiveness to stimulation, while post-stimulation neuroimaging measurements showed to be correlated with symptomatic improvement. These studies demonstrate the complexity of rTMS effects and highlight the relevance of imaging techniques.
Collapse
Affiliation(s)
- Lucero Aceves-Serrano
- Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada
- *Correspondence: Lucero Aceves-Serrano,
| | - Jason L. Neva
- École de Kinésiologie et des Sciences de l’Activité Physique, Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
- Centre de Recherche de l’Institut Universitaire de Gériatrie de Montréal, Montréal, QC, Canada
| | - Doris J. Doudet
- Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
4
|
The baboon in epilepsy research: Revelations and challenges. Epilepsy Behav 2021; 121:108012. [PMID: 34022622 PMCID: PMC8238811 DOI: 10.1016/j.yebeh.2021.108012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 04/17/2021] [Indexed: 11/23/2022]
Abstract
The baboon offers a natural model for genetic generalized epilepsy with photosensitivity. In this review, we will summarize some of the more important clinical, neuroimaging, and elctrophysiological findings form recent work performed at the Southwest National Primate Research Center (SNPRC, Texas Biomedical Research Institute, San Antonio, Texas), which houses the world's largest captive baboon pedigree. Due to the phylogenetic proximity of the baboon to humans, many of the findings are readily translatable, but there may be some important differences, such as the mutlifocality of the ictal and interictal epileptic discharges (IEDs) on intracranial electroencephalography (EEG) and greater parieto-occipital connectivity of baboon brain networks compared to juvenile myoclonic epilepsy in humans. Furthermore, there is still limited knowledge of the natural history of the epilepsy, which could be transformative for research into epileptogenesis in genetic generalized epilepsy (GGE) and sudden unexpected death in epilepsy (SUDEP).
Collapse
|
5
|
Saravanan C, Flandre T, Hodo CL, Lewis AD, Mecklenburg L, Romeike A, Turner OC, Yen HY. Research Relevant Conditions and Pathology in Nonhuman Primates. ILAR J 2021; 61:139-166. [PMID: 34129672 DOI: 10.1093/ilar/ilab017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 02/12/2021] [Accepted: 03/05/2021] [Indexed: 12/13/2022] Open
Abstract
Biomedical research involving animal models continues to provide important insights into disease pathogenesis and treatment of diseases that impact human health. In particular, nonhuman primates (NHPs) have been used extensively in translational research due to their phylogenetic proximity to humans and similarities to disease pathogenesis and treatment responses as assessed in clinical trials. Microscopic changes in tissues remain a significant endpoint in studies involving these models. Spontaneous, expected (ie, incidental or background) histopathologic changes are commonly encountered and influenced by species, genetic variations, age, and geographical origin of animals, including exposure to infectious or parasitic agents. Often, the background findings confound study-related changes, because numbers of NHPs used in research are limited by animal welfare and other considerations. Moreover, background findings in NHPs can be exacerbated by experimental conditions such as treatment with xenobiotics (eg, infectious morphological changes related to immunosuppressive therapy). This review and summary of research-relevant conditions and pathology in rhesus and cynomolgus macaques, baboons, African green monkeys, common marmosets, tamarins, and squirrel and owl monkeys aims to improve the interpretation and validity of NHP studies.
Collapse
Affiliation(s)
- Chandra Saravanan
- Novartis, Novartis Institutes for BioMedical Research, Preclinical Safety, Cambridge, Massachusetts 02139, USA
| | - Thierry Flandre
- Novartis, Novartis Institutes for BioMedical Research, Preclinical Safety, Basel, Switzerland
| | - Carolyn L Hodo
- The University of Texas MD Anderson Cancer Center, Michale E. Keeling Center for Comparative Medicine and Research, Bastrop, Texas, USA
| | - Anne D Lewis
- Oregon National Primate Research Center, Beaverton, Oregon, USA
| | | | | | - Oliver C Turner
- Novartis, Novartis Institutes for BioMedical Research, Preclinical Safety, East Hanover, New Jersey, USA
| | - Hsi-Yu Yen
- Covance Preclinical Services GmbH, Münster 48163, Germany
| |
Collapse
|
6
|
Effects of ketamine on EEG in baboons with genetic generalized epilepsy. Epilepsy Res 2019; 154:50-54. [PMID: 31048260 DOI: 10.1016/j.eplepsyres.2019.04.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 04/12/2019] [Accepted: 04/17/2019] [Indexed: 11/21/2022]
Abstract
Ketamine, a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, used as an anesthetic has been reported to induce seizures both in humans and baboons predisposed to epilepsy. In this study, we aimed to characterize the acute effects of ketamine on scalp (sc-EEG) and intracranial EEG (ic-EEG) in the baboon, which offers a natural model of genetic generalized epilepsy (GGE). We evaluated the electroclinical response to ketamine in three epileptic baboons. The raw EEG data were analyzed within 10 min of intramuscular ketamine (5-6 mg/kg) administration. Earliest EEG changes occurred after 30 s in sc-EEG and after 15 s in ic-EEG of ketamine administration. These initial changes involved increased paroxysmal fast activity (PFA) followed by slowing, the latter emerging first occipitally, and then spreading more anteriorly. Generalized spike-and-wave discharges (GSWDs) were evident on both sc-EEG and ic-EEG within two minutes, but focal occipital discharges were already increased on ic-EEG after 15 s. Occipital slowing emerged on ic-EEG after 30 s, before spreading fronto-centrally and orbito-frontally. By 60-120 seconds post-injection, ic-EEG demonstrated a parieto-occipital burst suppression (BS), which was not noted on sc-EEG. Ketamine waves and seizures, especially if the latter were subclinical, also appeared earlier on ic-EEG. This study highlights the anesthetic and proconvulsant effects of ketamine originate in the occipital lobes before fronto-central regions. We speculate that NMDAR concentration difference in cortical regions, such as the occipital and frontal cortices, are mainly involved in the expression of ketamine's EEG effects, both physiological and epileptic.
Collapse
|
7
|
Szabó CÁ, Salinas FS, Papanastassiou AM, Begnaud J, Ravan M, Eggleston KS, Shade R, Lutz C, De La Garza M. High-frequency burst vagal nerve simulation therapy in a natural primate model of genetic generalized epilepsy. Epilepsy Res 2017; 138:46-52. [PMID: 29059589 PMCID: PMC5856459 DOI: 10.1016/j.eplepsyres.2017.10.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/24/2017] [Accepted: 10/10/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE Since the approval of Vagal Nerve Stimulation (VNS) Therapy for medically refractory focal epilepsies in 1997, it has been also reported to be effective for a wide range of generalized seizures types and epilepsy syndromes. Instead of conventional VNS Therapy delivered at 20-30Hz signal frequencies, this study evaluates efficacy and tolerability of high-frequency burst VNS in a natural animal model for genetic generalized epilepsy (GGE), the epileptic baboon. METHODS Two female baboons (B1 P.h. Hamadryas and B2 P.h. Anubis x Cynocephalus) were selected because of frequently witnessed generalized tonic-clonic seizures (GTCS) for VNS implantation. High-frequency burst VNS Therapy was initiated after a 4-5 week baseline; different VNS settings (0.25, 2 or 2.5mA, 300Hz, 4 vs 7 pulses, 0.5-2.5s interburst interval, and intermittent stimulation for 1-2 vs for 24h per day) were tested over the subsequent 19 weeks, which included a 4-6 week wash-out period. GTCS frequencies were quantified for each setting, while seizure duration and postictal recovery times were compared to baseline. Scalp EEG studies were performed at almost every setting, including intermittent light stimulation (ILS) to evaluate photosensitivity. Pre-ILS ictal and interictal discharge rates, as well as ILS responses were compared between trials. The Novel Object test was used to assess potential treatment effects on behavior. RESULTS High-frequency burst VNS Therapy reduced GTCS frequencies at all treatment settings in both baboons, except when output currents were reduced (0.25mA) or intermittent stimulation was restricted (to 1-2h/day). Seizure duration and postictal recovery times were unchanged. Scalp EEG studies did not demonstrate treatment-related decrease of ictal or interictal epileptic discharges or photosensitivity, but continuous treatment for 120-180s during ILS appeared to reduce photoparoxysmal responses. High-frequency burst VNS Therapy was well-tolerated by both baboons, without cardiac or behavioral changes. Repetitive muscle contractions involving the neck and left shoulder girdle were observed intermittently, most commonly at 0.5 interburst intervals, but these were transient, resolving with a few cycles of stimulation and not noted in wakefulness. CONCLUSIONS This preclinical pilot study demonstrates efficacy and tolerability of high-frequency burst VNS Therapy in the baboon model of GGE. The muscle contractions may be due to aberrant propagation of the stimulus along the vagal nerve or to the ansa cervicalis, but can be reduced by minimal adjustment of current output or stimulus duration.
Collapse
Affiliation(s)
- C Á Szabó
- Department of Neurology, UT Health San Antonio, San Antonio, TX, United States; South Texas Comprehensive Epilepsy Center, University Health System, San Antonio, TX, United States.
| | - F S Salinas
- Research Imaging Institute, UT Health San Antonio, San Antonio, TX, United States
| | - A M Papanastassiou
- South Texas Comprehensive Epilepsy Center, University Health System, San Antonio, TX, United States; Department of Neurosurgery, UT Health San Antonio, San Antonio, TX, United States
| | - J Begnaud
- LivaNova, Houston, TX, United States
| | - M Ravan
- LivaNova, Houston, TX, United States
| | | | - R Shade
- Southwest National Primate Research Center, Texas Biomed, San Antonio, TX, United States
| | - C Lutz
- Southwest National Primate Research Center, Texas Biomed, San Antonio, TX, United States
| | - M De La Garza
- Southwest National Primate Research Center, Texas Biomed, San Antonio, TX, United States
| |
Collapse
|
8
|
Ákos Szabó C, Salinas FS, Li K, Franklin C, Leland MM, Fox PT, Laird AR, Narayana S. Modeling the effective connectivity of the visual network in healthy and photosensitive, epileptic baboons. Brain Struct Funct 2016; 221:2023-33. [PMID: 25749860 PMCID: PMC5558201 DOI: 10.1007/s00429-015-1022-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 02/27/2015] [Indexed: 12/13/2022]
Abstract
The baboon provides a model of photosensitive, generalized epilepsy. This study compares cerebral blood flow responses during intermittent light stimulation (ILS) between photosensitive (PS) and healthy control (CTL) baboons using H 2 (15) O-PET. We examined effective connectivity associated with visual stimulation in both groups using structural equation modeling (SEM). Eight PS and six CTL baboons, matched for age, gender and weight, were classified on the basis of scalp EEG findings performed during the neuroimaging studies. Five H 2 (15) O-PET studies were acquired alternating between resting and activation (ILS at 25 Hz) scans. PET images were acquired in 3D mode and co-registered with MRI. SEM demonstrated differences in neural connectivity between PS and CTL groups during ILS that were not previously identified using traditional activation analyses. First-level pathways consisted of similar posterior-to-anterior projections in both groups. While second-level pathways were mainly lateralized to the left hemisphere in the CTL group, they consisted of bilateral anterior-to-posterior projections in the PS baboons. Third- and fourth-level pathways were only evident in PS baboons. This is the first functional neuroimaging study used to model the photoparoxysmal response (PPR) using a primate model of photosensitive, generalized epilepsy. Evidence of increased interhemispheric connectivity and bidirectional feedback loops in the PS baboons represents electrophysiological synchronization associated with the generation of epileptic discharges. PS baboons demonstrated decreased model stability compared to controls, which may be attributed to greater variability in the driving response or PPRs, or to the influence of regions not included in the model.
Collapse
Affiliation(s)
- C Ákos Szabó
- Department of Neurology, South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center San Antonio, 8300 Floyd Curl Drive, San Antonio, TX, 78229-7883, USA.
| | - Felipe S Salinas
- Research Imaging Institute, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Karl Li
- Research Imaging Institute, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Crystal Franklin
- Research Imaging Institute, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - M Michelle Leland
- Laboratory Animal Research, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Peter T Fox
- Research Imaging Institute, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
- South Texas Veterans Administration Medical Center, San Antonio, TX, USA
| | - Angela R Laird
- Department of Physics, Florida International University, Miami, FL, USA
| | - Shalini Narayana
- Department of Pediatrics, Le Bonheur's Children's Hospital, University of Tennessee, Memphis, TN, USA
- Neuroscience Institute, Le Bonheur's Children's Hospital, Memphis, TN, USA
| |
Collapse
|
9
|
Salinas FS, Franklin C, Narayana S, Szabó CÁ, Fox PT. Repetitive Transcranial Magnetic Stimulation Educes Frequency-Specific Causal Relationships in the Motor Network. Brain Stimul 2016; 9:406-414. [PMID: 26964725 DOI: 10.1016/j.brs.2016.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 01/13/2016] [Accepted: 02/06/2016] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Repetitive transcranial magnetic stimulation (rTMS) has the potential to treat brain disorders by modulating the activity of disease-specific brain networks, yet the rTMS frequencies used are delivered in a binary fashion - excitatory (>1 Hz) and inhibitory (≤1 Hz). OBJECTIVE To assess the effective connectivity of the motor network at different rTMS stimulation rates during positron-emission tomography (PET) and confirm that not all excitatory rTMS frequencies act on the motor network in the same manner. METHODS We delivered image-guided, supra-threshold rTMS at 3 Hz, 5 Hz, 10 Hz, 15 Hz and rest (in separate randomized sessions) to the primary motor cortex (M1) of the lightly anesthetized baboon during PET imaging. Each rTMS/PET session was analyzed using normalized cerebral blood flow (CBF) measurements. Path analysis - using structural equation modeling (SEM) - was employed to determine the effective connectivity of the motor network at all rTMS frequencies. Once determined, the final model of the motor network was used to assess any differences in effective connectivity at each rTMS frequency. RESULTS The exploratory SEM produced a very well fitting final network model (χ(2) = 18.04, df = 21, RMSEA = 0.000, p = 0.647, TLI = 1.12) using seven nodes of the motor network. 5 Hz rTMS produced the strongest path coefficients in four of the seven connections, suggesting that this frequency is the optimal rTMS frequency for stimulation the motor network (as a whole); however, the premotor cerebellum connection was optimally stimulated at 10 Hz rTMS and the supplementary motor area caudate connection was optimally driven at 15 Hz rTMS. CONCLUSION(S) We have demonstrated that 1) 5 Hz rTMS revealed the strongest path coefficients (i.e. causal influence) on the nodes of the motor network, 2) stimulation at "excitatory" rTMS frequencies did not produce increased CBF in all nodes of the motor network, 3) specific rTMS frequencies may be used to target specific none-to-node interactions in the stimulated brain network, and 4) more research needs to be performed to determine the optimum frequency for each brain circuit and/or node.
Collapse
Affiliation(s)
- Felipe S Salinas
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States.
| | - Crystal Franklin
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Shalini Narayana
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - C Ákos Szabó
- Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Peter T Fox
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| |
Collapse
|
10
|
Salinas FS, Szabó CÁ. Resting-state functional connectivity in the baboon model of genetic generalized epilepsy. Epilepsia 2015; 56:1580-9. [PMID: 26290449 DOI: 10.1111/epi.13115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVE The baboon provides a natural model of genetic generalized epilepsy (GGE). This study compares the intrinsic connectivity networks of epileptic and healthy control baboons using resting-state functional magnetic resonance imaging (rs-fMRI) and data-driven functional connectivity mapping. METHODS Twenty baboons, matched for gender, age, and weight, were classified into two groups (10 epileptic [EPI], 10 control [CTL]) on the basis of scalp electroencephalography (EEG) findings. Each animal underwent one MRI session that acquired one 5-min resting state fMRI scan and one anatomic MRI scan-used for registration and spatial normalization. Using independent component analysis, we identified 14 unique components/networks, which were then used to characterize each group's functional connectivity maps of each brain network. RESULTS The epileptic group demonstrated network-specific differences in functional connectivity when compared to the control animals. The sensitivity and specificity of the two groups' functional connectivity maps differed significantly in the visual, motor, amygdala, insular, and default mode networks. Significant increases were found in the occipital gyri of the epileptic group's functional connectivity map for the default mode, cingulate, intraparietal, motor, visual, amygdala, and thalamic regions. SIGNIFICANCE This is the first study using resting-state fMRI to demonstrate intrinsic functional connectivity differences between epileptic and control nonhuman primates. These results are consistent with seed-based GGE studies in humans; however, our use of a data-driven approach expands the scope of functional connectivity mapping to include brain regions/networks comprising the whole brain.
Collapse
Affiliation(s)
- Felipe S Salinas
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, Texas, U.S.A
| | - C Ákos Szabó
- Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, U.S.A
| |
Collapse
|
11
|
Epileptic baboons have lower numbers of neurons in specific areas of cortex. Proc Natl Acad Sci U S A 2013; 110:19107-12. [PMID: 24191031 DOI: 10.1073/pnas.1318894110] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epilepsy is characterized by recurrent seizure activity that can induce pathological reorganization and alter normal function in neocortical networks. In the present study, we determined the numbers of cells and neurons across the complete extent of the cortex for two epileptic baboons with naturally occurring seizures and two baboons without epilepsy. Overall, the two epileptic baboons had a 37% average reduction in the number of cortical neurons compared with the two nonepileptic baboons. The loss of neurons was variable across cortical areas, with the most pronounced loss in the primary motor cortex, especially in lateral primary motor cortex, representing the hand and face. Less-pronounced reductions of neurons were found in other parts of the frontal cortex and in somatosensory cortex, but no reduction was apparent in the primary visual cortex and little in other visual areas. The results provide clear evidence that epilepsy in the baboon is associated with considerable reduction in the numbers of cortical neurons, especially in frontal areas of the cortex related to motor functions. Whether or not the reduction of neurons is a cause or an effect of seizures needs further investigation.
Collapse
|
12
|
Salinas FS, Narayana S, Zhang W, Fox PT, Szabó CÁ. Repetitive transcranial magnetic stimulation elicits rate-dependent brain network responses in non-human primates. Brain Stimul 2013; 6:777-87. [PMID: 23540281 DOI: 10.1016/j.brs.2013.03.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 03/01/2013] [Accepted: 03/04/2013] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Transcranial magnetic stimulation (TMS) has the potential to treat brain disorders by tonically modulating firing patterns in disease-specific neural circuits. The selection of treatment parameters for clinical repetitive transcranial magnetic stimulation (rTMS) trials has not been rule based, likely contributing to the variability of observed outcomes. OBJECTIVE To utilize our newly developed baboon (Papio hamadryas anubis) model of rTMS during position-emission tomography (PET) to quantify the brain's rate-response functions in the motor system during rTMS. METHODS We delivered image-guided, suprathreshold rTMS at 3 Hz, 5 Hz, 10 Hz, 15 Hz and rest (in separate randomized sessions) to the primary motor cortex (M1) of the lightly anesthetized baboon during PET imaging; we also administered a (reversible) paralytic to eliminate any somatosensory feedback due to rTMS-induced muscle contractions. Each rTMS/PET session was analyzed using normalized cerebral blood flow (CBF) measurements; statistical parametric images and the resulting areas of significance underwent post-hoc analysis to determine any rate-specific rTMS effects throughout the motor network. RESULTS The motor system's rate-response curves were unimodal and system wide--with all nodes in the network showing highly similar rate response functions--and an optimal network stimulation frequency of 5 Hz. CONCLUSION(S) These findings suggest that non-invasive brain stimulation may be more efficiently delivered at (system-specific) optimal frequencies throughout the targeted network and that functional imaging in non-human primates is a promising strategy for identifying the optimal treatment parameters for TMS clinical trials in specific brain regions and/or networks.
Collapse
Affiliation(s)
- Felipe S Salinas
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
| | | | | | | | | |
Collapse
|
13
|
Szabó CÁ, Knape KD, Leland MM, Williams JT. Electroclinical phenotypes in a pedigreed baboon colony. Epilepsy Res 2013; 105:77-85. [PMID: 23499213 DOI: 10.1016/j.eplepsyres.2013.02.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 02/06/2013] [Accepted: 02/12/2013] [Indexed: 11/19/2022]
Abstract
This is the first large-scale epidemiological study evaluating the prevalence of interictal epileptic discharges (IEDs) and photosensitivity (PS) recorded by scalp EEG in a natural nonhuman-primate model of photosensitive, generalized epilepsy. Scalp EEG was used to characterize electroclinical phenotypes in a large baboon pedigree housed at the Southwest National Primate Research Center at the Texas Biomedical Research Institute (Texas Biomed) based upon IEDs and photosensitivity. Scalp EEG studies including intermittent light stimulation (ILS) were performed in 671 baboons. Clinical histories were available for 531 (79%) of the animals. The EEG studies lasted 53 (±11) min, during which the baboons were lightly sedated with intramuscular ketamine doses of 5.6 (±0.8) mg. The animals were further classified according to electroclinical phenotypes recorded by scalp EEG: presence or absence of IEDs, seizures and photoparoxysmal or photoconvulsive responses. Effects of age, gender, and species on EEG phenotypes were compared using (Chi-square, two-sided, α<0.05). Sensitivity and specificity of IEDs and photosensitivity to detect a history of seizures was calculated. Generalized IEDs and photosensitivity were identified in 324 (49%) and 156 (23%) pedigreed baboons, respectively. Only photosensitivity was associated with gender, significantly increased in males. Otherwise, while IEDs were marginally more prevalent among males, there were no other significant associations of IEDs or photosensitivity with age or subspecies. Photosensitivity was significantly associated with IEDs, with demonstrating a possible association with gender and subspecies. Of 531 baboons with histories of clinical events, 91 (17%) had witnessed seizures and 269 (51%) were asymptomatic. IEDs demonstrated sensitivity and specificity of 62% and 57%, and photosensitivity of 40% and 83%, for prediction of seizures, respectively. While these EEG findings mirror the high prevalence of seizures in the colony, the sensitivity and specificity of scalp EEG may have been affected by ketamine's ability to lower the threshold for IEDs and seizures, particularly in animals predisposed to epilepsy. Photosensitivity provides a specific biological marker for epilepsy in future epidemiological, genetic, behavioral and histopathological studies.
Collapse
Affiliation(s)
- C Ákos Szabó
- South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center, San Antonio, TX 78229, USA.
| | | | | | | |
Collapse
|
14
|
Szabó CÁ, Salinas FS, Leland MM, Caron JL, Hanes MA, Knape KD, Xie D, Williams JT. Baboon model of generalized epilepsy: continuous intracranial video-EEG monitoring with subdural electrodes. Epilepsy Res 2012; 101:46-55. [PMID: 22480914 PMCID: PMC3398162 DOI: 10.1016/j.eplepsyres.2012.02.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/03/2012] [Accepted: 02/27/2012] [Indexed: 11/21/2022]
Abstract
The baboon provides a natural non-human primate model for photosensitive, generalized epilepsy. This study describes an implantation procedure for the placement of subdural grid and strip electrodes for continuous video-EEG monitoring in the epileptic baboon to evaluate the generation and propagation of ictal and interictal epileptic discharges. Subdural grid, strip and depth electrodes were implanted in six baboons, targeting brain regions that were activated in functional neuroimaging studies during photoparoxysmal responses. The baboons were monitored with continuous video-EEG monitoring for 2-21 (mean 9) days. Although the animals were tethered, the EEG signal was transmitted wirelessly to optimize their mobility. Spontaneous seizures, interictal epileptic discharges (IEDs), and responses to intermittent light stimulation (ILS) were assessed. Due to cortical injuries related to the electrode implantation and their displacement, the procedure was modified. Habitual myoclonic and generalized tonic-clonic seizures were recorded in three baboons, all associated with a generalized ictal discharge, but were triggered multiregionally, in the frontal, parietal and occipital cortices. IEDs were similarly expressed multiregionally, and responsible for triggering most generalized spike-and-wave discharges. Generalized photoparoxysmal responses were activated only in one baboon, while driving responses recorded in all three photosensitive baboons were 2.5 times the stimulus rate. In contrast to previous intracranial investigations in this model, generalized ictal and interictal epileptic discharges were triggered by parietal and occipital, in addition to the frontocentral cortices. Furthermore, targeted visual areas responded differently to ILS in photosensitive than nonphotosensitive baboons, but further studies are required before mechanisms can be implicated for ILS-induced activation of the epileptic networks.
Collapse
Affiliation(s)
- C Ákos Szabó
- South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center at San Antonio, TX 78229, USA.
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Szabó CÁ, Salinas FS, Narayana S. Functional PET Evaluation of the Photosensitive Baboon. Open Neuroimag J 2011; 5:206-15. [PMID: 22276085 PMCID: PMC3257183 DOI: 10.2174/1874440001105010206] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 02/03/2011] [Accepted: 02/14/2011] [Indexed: 11/22/2022] Open
Abstract
The baboon provides a unique, natural model of epilepsy in nonhuman primates. Additionally, photosensitivity of the epileptic baboon provides an important window into the mechanism of human idiopathic generalized epilepsies. In order to better understand the networks underlying this model, our group utilized functional positron emission tomography (PET) to compare cerebral blood flow (CBF) changes occurring during intermittent light stimulation (ILS) and rest between baboons photosensitive, epileptic (PS) and asymptomatic, control (CTL) animals. Our studies utilized subtraction and covariance analyses to evaluate CBF changes occurring during ILS across activation and resting states, but also evaluated CBF correlations with ketamine doses and interictal epileptic discharge (IED) rate during the resting state. Furthermore, our group also assessed the CBF responses related to variation of ILS in PS and CTL animals. CBF changes in the subtraction and covariance analyses reveal the physiological response and visual connectivity in CTL animals and pathophysiological networks underlying responses associated with the activation of ictal and interictal epileptic discharges in PS animals. The correlation with ketamine dose is essential to understanding differences in CBF responses between both groups, and correlations with IED rate provides an insight into an epileptic network independent of visual activation. Finally, the ILS frequency dependent changes can help develop a framework to study not only spatial connectivity but also the temporal sequence of regional activations and deactivations related to ILS. The maps generated by the CBF analyses will be used to target specific nodes in the epileptic network for electrophysiological evaluation using intracranial electrodes.
Collapse
Affiliation(s)
- C Ákos Szabó
- South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | | | | |
Collapse
|
16
|
Functional neuroimaging of the baboon during concurrent image-guided transcranial magnetic stimulation. Neuroimage 2011; 57:1393-401. [PMID: 21664276 DOI: 10.1016/j.neuroimage.2011.05.065] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 04/29/2011] [Accepted: 05/21/2011] [Indexed: 01/15/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) has well-established applications in basic neuroscience and promising applications in neurological and psychiatric disorders. However the underlying mechanisms of TMS-induced alterations in brain function are not well understood. As a result, treatment design parameters are determined ad hoc and not informed by any coherent theory or model. Once the mechanisms underlying TMS's modulatory effects on brain systems are better understood and modeled, TMS's potential as a therapeutic and/or investigative tool will be more readily explored and exploited. An animal model is better suited to study different TMS variables, therefore we developed a baboon model to facilitate testing of some of the current theoretical models of TMS interactions with brain regions. We have demonstrated the feasibility of this approach by successfully imaging cerebral blood flow (CBF) changes with H(2)(15)O positron emission tomography imaging during high-frequency, suprathreshold repetitive TMS in the primary motor cortex of five healthy, adult baboons.
Collapse
|
17
|
Abstract
BACKGROUND A comprehensive survey of the prevalence of congenital anomalies in baboons has not been previously reported. We report the congenital anomalies observed over a 26-year period in a large captive baboon colony. METHODS A computer search was performed for all baboon congenital anomalies identified at necropsy and recorded on necropsy submissions. RESULTS We identified 198 congenital anomalies in 166 baboons from 9972 necropsies (1.66% of total necropsies). The nervous, urogenital, musculoskeletal, and cardiovascular systems were most commonly affected. The most common organs affected were the brain, bone, heart, testicle, kidney, penis, aorta, and skeletal muscle. The most frequent congenital anomalies were blindness, seizures, and hydrocephalus. CONCLUSIONS The baboon has an overall frequency of congenital anomalies similar to humans and other non-human primates. Although the most frequently affected systems are similar, congenital anomalies involving the digestive system appear to be less common in the baboon.
Collapse
Affiliation(s)
- Benjamin Fox
- Southwest National Primate Research Center at the Texas Biomedical Research Institute, San Antonio, TX 78245-0549, USA
| | | | | | | |
Collapse
|
18
|
Szabó CA, Kochunov P, Knape KD, McCoy KJM, Leland MM, Lancaster JL, Fox PT, Williams JT, Rogers J. Cortical sulcal areas in baboons (Papio hamadryas spp.) with generalized interictal epileptic discharges on scalp EEG. Epilepsy Res 2011; 93:91-5. [PMID: 21256716 DOI: 10.1016/j.eplepsyres.2010.10.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 09/09/2010] [Accepted: 10/31/2010] [Indexed: 11/18/2022]
Abstract
Brain MRI studies in people with idiopathic generalized epilepsies demonstrate regional morphometric differences, though variable in magnitude and location. As the baboon provides an excellent electroclinical and neuroimaging model for photosensitive generalized epilepsy in humans, this study evaluated MRI volumetric and morphometric differences between baboons with interictal epileptic discharges (IEDs) on scalp EEG and baboons with normal EEG studies. Seventy-seven baboons underwent high-resolution brain MRI and scalp EEG studies. The scans were acquired using an 8-channel primate head coil (Siemens TRIO 3T scanner, Erlangen, Germany). After spatial normalization, sulcal measurements were obtained by object-based-morphology methods. One-hour scalp EEG studies were performed in animals sedated with ketamine. Thirty-eight (22F/16M) baboons had normal EEGs (IED-), while 39 (22F/17M) had generalized IEDs (IED+). The two groups were compared for age, total brain volume, and sulcal areas (Hotelling's Trace) as well as between-subjects comparison of 11 individual sulcal areas (averaged between left and right hemispheres). There were no differences between IED- and IED+ groups with respect to age or total brain (gray or white matter) volume, and multivariate tests demonstrated a marginally significant decrease of sulcal areas in IED+ baboons (p=0.075). Tests of between-subjects effects showed statistically significant decreases in the intraparietal (p=0.002), central (p=0.03) and cingulate sulci (p=0.02), and marginal decreases involving the lunate (p=0.07) and superior temporal sulci (p=0.08). Differences in sulcal areas in IED+ baboons may reflect global developmental abnormalities, while decreases of areas of specific sulci reflect anatomical markers for potential generators or cortical nodes of the networks underlying spontaneous seizures and photosensitivity in the baboon.
Collapse
Affiliation(s)
- C A Szabó
- Department of Neurology, UTHSCSA, San Antonio, TX, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Matos G, Andersen ML, Tufik S. Sudden unexpected death in epilepsy: The obscure role of sleep. J Neurol Sci 2010. [DOI: 10.1016/j.jns.2010.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
20
|
Szabó CA, Knape KD, Leland MM, Feldman J, McCoy KJM, Hubbard GB, Williams JT. Mortality in captive baboons with seizures: a new model for SUDEP? Epilepsia 2009; 50:1995-8. [PMID: 19389147 DOI: 10.1111/j.1528-1167.2009.02073.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Because the baboon is a model of primary generalized epilepsy, we were interested in mortality of captive animals with a history of witnessed seizures. Causes of natural death were investigated in 46 seizure baboons (SZ) and 78 nonepileptic controls (CTL), all of which underwent a complete pathologic examination at the Southwest Foundation for Biomedical Research (SFBR) in San Antonio. SZ animals died at a younger age than the control baboons (p < 0.001). Almost all epileptic baboons that died suddenly without an apparent cause (SZ-UKN), had pulmonary congestion or edema without evidence of trauma, systemic illness, or heart disease, compared to nine controls (12%) (p < 0.001), most of which demonstrated evidence of a concurrent illness. Serosanguineous bronchial secretions were found in 15 SZ-UKN baboons (58%), but in only three controls (4%) (p < 0.001). Chronic multifocal fibrotic changes in myocardium were noted in only three (12%) of SZ-UKN baboons and one control baboon. Based upon these results, untreated seizures appear to reduce the life expectancy of captive baboons. Sudden unexpected death in epilepsy (SUDEP) may be a common cause of natural death in epileptic baboons.
Collapse
Affiliation(s)
- C Akos Szabó
- South Texas Comprehensive Epilepsy Center, Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-7883, USA.
| | | | | | | | | | | | | |
Collapse
|
21
|
Szabó CA, Narayana S, Franklin C, Knape KD, Davis MD, Fox PT, Leland MM, Williams JT. "Resting" CBF in the epileptic baboon: correlation with ketamine dose and interictal epileptic discharges. Epilepsy Res 2008; 82:57-63. [PMID: 18801644 DOI: 10.1016/j.eplepsyres.2008.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2008] [Revised: 07/10/2008] [Accepted: 07/11/2008] [Indexed: 11/30/2022]
Abstract
BACKGROUND Photosensitive epileptic (SZ) baboons demonstrate different cerebral blood flow (CBF) activation patterns from asymptomatic controls (CTL) during intermittent light stimulation (ILS). This study compares "resting" CBF between PS and CTL animals, and CBF correlations with ketamine dose and interictal epileptic discharges (IEDs) between PS and CTL animals. METHODS Continuous intravenous ketamine was administered to eight PS and eight CTL baboons (matched for gender and weight), and maintained at subanesthetic doses (4.8-14.6 mg/kg/hr). Three resting H(2)(15)O-PET studies were attempted in each animal (CTI/Siemens HR+ scanner). Images were acquired in 3D mode (63 contiguous slices, 2.4mm thickness). PET images were co-registered with MRI images (3T Siemens Trio, T1-weighted 3D Turboflash sequence, TE/TR/TI=3.04/2100/785 ms, flip angle=13 degrees ). EEG was used to monitor depth of sedation and for quantification of IED rates. Regional CBF was compared between PS and CTL groups and correlations were analyzed for ketamine dose and IED rates. RESULTS When subsets of animals of either group, receiving similar doses of ketamine were compared, PS animals demonstrated relative CBF increases in the occipital lobes and decreases in the frontal lobes. Correlation analyses with ketamine dose confirmed the frontal and occipital lobe changes in the PS animals. The negative correlations of CBF with ketamine dose and IED rate overlapped frontally. While frontal lobe CBF was also negatively correlated with IED rate, positive correlations were found in the parietal lobe. CONCLUSIONS "Resting" CBF differs between PS and CTL baboons. Correlation analyses of CBF and ketamine dose reveal that occipital lobe CBF increases and frontal lobe in PS animals are driven by ketamine. While frontal lobe CBF decreases may be related to ketamine's propensity to activate IEDs, positive CBF correlations with IED rate suggest involvement of the parietal lobes in their generation.
Collapse
Affiliation(s)
- C Akos Szabó
- South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center, San Antonio, TX, United States.
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Abstract
Photic stimulation is part of a typical EEG in most countries, especially to check on the photoparoxysmal response (PPR). Interest in this response was enhanced in 1997 when hundreds of Japanese children had attacks while viewing a TV cartoon called "Pokemon." The overall prevalence of the PPR among patients requiring an EEG is approximately 0.8%, but 1.7% in children and 8.87% in patients with epilepsy, more often in Caucasians and females. Autosomal dominant inheritance is indicated, and this response is seen especially at the wavelength of 700 nm or at the flicker frequency of 15-18 Hz. The PPR extending beyond the stimulus carries no increased risk of seizures. Prognosis is generally good, especially after 20 years of age. Attention to PPR has been increased with the advent of video games, and the evoked seizures from these games are likely a manifestation of photosensitive epilepsy. Drug therapy has emphasized valproic acid, but Levetiracetam has also been successful in eliminating the PPR.
Collapse
Affiliation(s)
- John R Hughes
- Department of Neurology, University of Illinois, Medical Center at Chicago, Illinois 60612, USA.
| |
Collapse
|
23
|
Szabó CA, Narayana S, Kochunov PV, Franklin C, Knape K, Davis MD, Fox PT, Leland MM, Williams JT. PET imaging in the photosensitive baboon: case-controlled study. Epilepsia 2007; 48:245-53. [PMID: 17295617 DOI: 10.1111/j.1528-1167.2006.00949.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
PURPOSE The baboon (Papio hamadryas spp) offers a natural primate animal model of photosensitive generalized epilepsy. This study compared changes in cerebral blood flow (CBF) during intermittent light stimulation (ILS) between photosensitive and asymptomatic baboons. METHODS Six photosensitive, epileptic (PS) and four nonphotosensitive, asymptomatic (CTL) baboons, matched for age, gender, and weight, were selected based on previous scalp EEG evaluation. Continuous intravenous ketamine (5-13 mg/kg) was used for sedation. Subjects underwent five sequential blood-flow PET studies within 60 min with 20 mCi (15)O-labeled water. Images were acquired in 3D mode (CTI/Siemens HR+ scanner, 63 contiguous slices, 2.4-mm thickness). Three resting scans were alternated with two activation scans during ILS. ILS was performed at 25 Hz for 60 s before to 60 s after the start of an activation scan. PET images were coregistered with MRI (3T Siemens Trio, T(1)-weighted 3D Turboflash sequence; TE/TR/TI, 3.04/2,100/785 ms; flip angle, 13 degrees). PET scans were reviewed and corrected for motion artifact. Resting scans were contrasted with activation scans and averaged independently for both groups. Quantitative CBF analyses were performed for the occipital and motor cortices. RESULTS The CTL baboons showed greatest ILS-induced activation in the left middle frontal and inferior temporal gyri, left brainstem structures and right postcentral gyrus, bilateral occipital lobes, and in the posterior cingulate gyrus and cerebellum. In contrast, the PS animals showed strongest ILS activation in the right anterior cingulate and medial orbital gyri, amygdala, globus pallidum, and left inferior and superior temporal gyri. A striking finding was the absence of occipital and variable motor cortex activation in the PS animals. Deactivations were noted in the right orbitofrontal and anterior cingulate cortices in the CTL baboons and in the posterior cingulate gyrus, brainstem and cerebellum of the PS animals. CONCLUSIONS The patterns of ILS-induced CBF changes differed between CTL and PS groups. These differences of activations and inhibitions suggest involvement of specific cortical-subcortical or networks in photosensitivity.
Collapse
Affiliation(s)
- C Akos Szabó
- South Texas Comprehensive Epilepsy Center, University of Texas Health Science Center at San Antonio, Texas 78284-7883, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|