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Mandal R, Budde R, Lawlor GL, Irazoqui P. Utilizing multimodal imaging to visualize potential mechanism for sudden death in epilepsy. Epilepsy Behav 2021; 122:108124. [PMID: 34237676 PMCID: PMC8429091 DOI: 10.1016/j.yebeh.2021.108124] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 05/20/2021] [Accepted: 05/31/2021] [Indexed: 12/28/2022]
Abstract
Sudden death in epilepsy or SUDEP is a fatal condition that accounts for more than 4000 deaths each year. Limited clinical and preclinical data on sudden death suggest critical contributions from autonomic, cardiac, and respiratory pathways. A potential mechanism for such sudden and severe cardiorespiratory dysregulation may be linked to acid reflux-induced laryngospasm. Here, we expand on our previous investigations and utilize a novel multimodal approach to provide visual evidence of acid reflux-initiated cardiorespiratory distress and subsequent sudden death in seizing rats. We used systemic kainic acid to acutely induce seizure activity in Long Evans rats, under urethane anesthesia. We recorded electroencephalography (EEG), electrocardiography (ECG), chest plethysmography, and esophageal pH signals through a multimodal recording platform, during simultaneous fast MRI scans of the rat stomach and esophagus. MRI images, in correlation with electrophysiology data were used to identify seizure progression, stomach acid movement up the esophagus, cardiorespiratory changes, and sudden death. In all cases of sudden death, esophageal pH recordings alongside MRI images visualized stomach acid movement up the esophagus. Severe cardiac (ST segment elevation), respiratory (intermittent apnea) and brain activity (EEG narrowing due to hypoxia) changes were observed only after acid reached larynx, which strongly suggested onset of laryngospasm following acid reflux. The complementary information coming from electrophysiology and fast MRI scans provided insight into the mechanism of esophageal reflux, laryngospasm, obstructive apnea, and subsequent sudden death in seizing animals. The results carry clinical significance as it outlines a potential mechanism that may be relevant to SUDEP in humans.
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Affiliation(s)
| | - Ryan Budde
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Georgia L. Lawlor
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
| | - Pedro Irazoqui
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA,School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
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Biggs EN, Budde R, Jefferys JGR, Irazoqui PP. Ictal activation of oxygen-conserving reflexes as a mechanism for sudden death in epilepsy. Epilepsia 2021; 62:752-764. [PMID: 33570173 PMCID: PMC9153691 DOI: 10.1111/epi.16831] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 01/04/2021] [Accepted: 01/11/2021] [Indexed: 01/05/2023]
Abstract
OBJECTIVE To test the hypothesis that death with physiological parallels to human cases of sudden unexpected death in epilepsy (SUDEP) can be induced in seizing rats by ictal activation of oxygen-conserving reflexes (OCRs). METHODS Urethane-anesthetized female Long-Evans rats were implanted with electrodes for electrocardiography (ECG), electrocorticography (ECoG), and respiratory thermocouple; venous and arterial cannulas; and a laryngoscope guide and cannula or nasal cannula for activation of the laryngeal chemoreflex (LCR) or mammalian diving reflex (MDR), respectively. Kainic acid injection, either systemic or into the ventral hippocampus, induced prolonged acute seizures. RESULTS Reflex challenges during seizures caused sudden death in 18 of 20 rats-all MDR rats (10) and all but two LCR rats (8) failed to recover from ictal activation of OCRs and died within minutes of the reflexes. By comparison, 4 of 4 control (ie, nonseizing) rats recovered from 64 induced diving reflexes (16 per rat), and 4 of 4 controls recovered from 64 induced chemoreflexes (16 per rat). Multiple measures were consistent with reports of human SUDEP. Terminal central apnea preceded terminal asystole in all cases. Heart and respiratory rate fluctuations that paralleled those seen in human SUDEP occurred during OCR-induced sudden death, and mean arterial pressure (MAP) was predictive of death, showing a 17 or 15 mm Hg drop (MDR and LCR, respectively) in the 20 s window centered on the time of brain death. OCR activation was never fatal in nonseizing rats. SIGNIFICANCE These results present a method of inducing sudden death in two seizure models that show pathophysiology consistent with that observed in human cases of SUDEP. This proposed mechanism directly informs previous findings by our group and others in the field; provides a repeatable, inducible animal model for the study of sudden death; and offers a potential explanation for observations made in cases of human SUDEP.
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Affiliation(s)
- Ethan N. Biggs
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Ryan Budde
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - John G. R. Jefferys
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Department of Pharmacology, Oxford University, Oxford, UK
| | - Pedro P. Irazoqui
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
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Hutson TN, Rezaei F, Gautier NM, Indumathy J, Glasscock E, Iasemidis L. Directed Connectivity Analysis of the Neuro-Cardio- and Respiratory Systems Reveals Novel Biomarkers of Susceptibility to SUDEP. IEEE OPEN JOURNAL OF ENGINEERING IN MEDICINE AND BIOLOGY 2020; 1:301-311. [PMID: 34223181 PMCID: PMC8249082 DOI: 10.1109/ojemb.2020.3036544] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/16/2020] [Accepted: 11/02/2020] [Indexed: 01/11/2023] Open
Abstract
Goal: Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality and its pathophysiological mechanisms remain unknown. We set to record and analyze for the first time concurrent electroencephalographic (EEG), electrocardiographic (ECG), and unrestrained whole-body plethysmographic (Pleth) signals from control (WT - wild type) and SUDEP-prone mice (KO- knockout Kcna1 animal model). Employing multivariate autoregressive models (MVAR) we measured all tri-organ effective directional interactions by the generalized partial directed coherence (GPDC) in the frequency domain over time (hours). When compared to the control (WT) animals, the SUDEP-prone (KO) animals exhibited (p < 0.001) reduced afferent and efferent interactions between the heart and the brain over the full frequency spectrum (0-200Hz), enhanced efferent interactions from the brain to the lungs and from the heart to the lungs at high (>90 Hz) frequencies (especially during periods with seizure activity), and decreased feedback from the lungs to the brain at low (<40 Hz) frequencies. These results show that impairment in the afferent and efferent pathways in the holistic neuro-cardio-respiratory network could lead to SUDEP, and effective connectivity measures and their dynamics could serve as novel biomarkers of susceptibility to SUDEP and seizures respectively.
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Affiliation(s)
- T. Noah Hutson
- Department of Biomedical EngineeringLouisiana Tech UniversityRustonLA71272USA
| | - Farnaz Rezaei
- Department of Mathematics and StatisticsLouisiana Tech UniversityRustonLA71272USA
| | - Nicole M. Gautier
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences CenterShreveportLA71130USA
| | - Jagadeeswaran Indumathy
- Department of PhysiologyJawaharlal Institute of Postgraduate Medical Education and ResearchPuducherryIndia
| | - Edward Glasscock
- Department of Biological SciencesSouthern Methodist UniversityDallasTX75275USA
| | - Leonidas Iasemidis
- Department of Biomedical EngineeringLouisiana Tech UniversityRustonLA71272USA
- Center for Biomedical Engineering and Rehabilitation ScienceLouisiana Tech UniversityRustonLA71272USA
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Budde RB, Pederson DJ, Biggs EN, Jefferys JGR, Irazoqui PP. Mechanisms and prevention of acid reflux induced laryngospasm in seizing rats. Epilepsy Behav 2020; 111:107188. [PMID: 32540771 PMCID: PMC7541801 DOI: 10.1016/j.yebeh.2020.107188] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 05/04/2020] [Accepted: 05/23/2020] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Recent animal work and limited clinical data have suggested that laryngospasm may be involved in the cardiorespiratory collapse seen in sudden unexpected death in epilepsy (SUDEP). In previous work, we demonstrated in an animal model of seizures that laryngospasm and sudden death were always preceded by acid reflux into the esophagus. Here, we expand on that work by testing several techniques to prevent the acid reflux or the subsequent laryngospasm. METHODS In urethane anesthetized Long Evans rats, we used systemic kainic acid to acutely induce seizure activity. We recorded pH in the esophagus, respiration, electrocorticography activity, and measured the liquid volume in the stomach postmortem. We performed the following three interventions to attempt to prevent acid reflux or laryngospasm and gain insights into mechanisms: fasting animals for 12 h, severing the gastric nerve, and electrical stimulation of either the gastric nerve or the recurrent laryngeal nerve. RESULTS Seizing animals had significantly more liquid in their stomach. Severing the gastric nerve and fasting animals significantly reduced stomach liquid volume, subsequent acid reflux, and sudden death. Laryngeal nerve stimulation can reverse laryngospasm on demand. Seizing animals are more susceptible to death from stomach acid-induced laryngospasm than nonseizing animals are to artificial acid-induced laryngospasm. SIGNIFICANCE These results provide insight into the mechanism of acid production and sudden obstructive apnea in this model. These techniques may have clinical relevance if this model is shown to be similar to human SUDEP.
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Affiliation(s)
- Ryan B. Budde
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Daniel J. Pederson
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
| | - Ethan N. Biggs
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - John G. R. Jefferys
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA,Department of Pharmacology, Oxford University, Oxford, UK,Department of Biochemistry, Oxford University, Oxford, UK
| | - Pedro P. Irazoqui
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA,Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
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Budde RB, Arafat MA, Pederson DJ, Lovick TA, Jefferys JGR, Irazoqui PP. Acid reflux induced laryngospasm as a potential mechanism of sudden death in epilepsy. Epilepsy Res 2018; 148:23-31. [PMID: 30336367 PMCID: PMC6276113 DOI: 10.1016/j.eplepsyres.2018.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 08/22/2018] [Accepted: 10/07/2018] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Recent research suggests that obstructive laryngospasm and consequent respiratory arrest may be a mechanism in sudden unexpected death in epilepsy. We sought to test a new hypothesis that this laryngospasm is caused by seizures driving reflux of stomach acid into the larynx, rather than spontaneous pathological activity in the recurrent laryngeal nerve. APPROACH We used an acute kainic acid model under urethane anesthesia to observe seizure activity in Long-Evans rats. We measured the pH in the esophagus and respiratory activity. In a subset of experiments, we blocked acid movement up the esophagus with a balloon catheter. MAIN RESULTS In all cases of sudden death, terminal apnea was preceded by a large pH drop from 7 to 2 in the esophagus. In several animals we observed acidic fluid exiting the mouth, sometimes in large quantities. In animals where acid movement was blocked, sudden deaths did not occur. No acid was detected in controls. SIGNIFICANCE The results suggest that acid movement up the esophagus is a trigger for sudden death in KA induced seizures. The fact that blocking acid also eliminates sudden death implies causation. These results may provide insight to the mechanism of SUDEP in humans.
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Affiliation(s)
- Ryan B Budde
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, US
| | - Muhammad A Arafat
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, US
| | - Daniel J Pederson
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, US
| | - Thelma A Lovick
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, US; School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - John G R Jefferys
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, US; Department of Pharmacology, Oxford University, Oxford, UK; Department of Biochemistry, Oxford University, Oxford, UK
| | - Pedro P Irazoqui
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, US; Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, US.
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Lonsdale D. Sudden infant death syndrome and abnormal metabolism of thiamin. Med Hypotheses 2015; 85:922-6. [DOI: 10.1016/j.mehy.2015.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 09/09/2015] [Indexed: 11/25/2022]
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