Elson L So

Royal Melbourne Hospital, Melbourne, Victoria, Australia

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Publications (163)636.56 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: Objective: To compare the yield of epileptiform abnormalities on 30-minute recordings with those greater than 45 minutes. Methods: We performed a prospective observational cross-sectional study of all outpatient routine EEGs comparing the rate of interictal epileptiform discharges (IEDs) and clinical events during the initial 30 minutes (routine) with those occurring in the remaining 30-60 minutes (extended). A relative increase of 10% was considered clinically significant. Results: EEGs from 1,803 patients were included; overall EEG duration was 59.4 minutes (SD ±6.5). Of 426 patients with IEDs at any time during the EEG, 81 (19.1%, 95% confidence interval 15.6-23) occurred only after the initial 30 minutes. The rate of late IEDs was not associated with age, indication, IED type, or sleep deprivation. Longer recording times also increased event capture rate by approximately 30%. Conclusions: The yield of IED and event detection is increased in extended outpatient EEGs compared to 30-minute studies.
    No preview · Article · Mar 2016 · Neurology
  • [Show abstract] [Hide abstract] ABSTRACT: Based on previous fMRI and SPECT studies, it has been suggested seizures may be preceded by increased cerebral blood flow. Recently, we demonstrated transcutaneous regional cerebral oxygen saturation (rSO2) sensors are feasible for use in patients undergoing video EEG monitoring. We reanalyzed our data to determine if seizures were consistently marked by increased cerebral oxygenation. Patients with histories of generalized tonic clonic seizures (GTCS) were recruited into our study. All subjects were evaluated with continuous 30-channel scalp EEG and 2 rSO2 sensors placed on each side of the forehead. We calculated the mean rS02 value for the 1 hour epochs in the non-ictal (2 hours prior to seizure onset) and pre-ictal (1 hour prior to onset) periods. Seven primary/secondarily GTCS from 5 patients were captured. The mean rSO2 value in the non-ictal period was 75.6+/-5.7%. This increased to 76.0+/-6% in the pre-ictal period (p = 0.032). Four of the 7 GTCS (57.1%) were marked by ≥3 sequential rSO2 values in the pre-ictal period that were ≥3 SDs greater than the mean non-ictal rSO2 value. Three GTCS (42.9%) were marked by sustained cerebral hyperemia for ≥15 consecutive readings. Our results suggest increased cerebral blood flow could be noninvasively used to predict seizure occurrence.
    No preview · Article · Sep 2014 · Epilepsy Research
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    [Show abstract] [Hide abstract] ABSTRACT: Objective: To determine the outcome of implanting fewer electrodes over the hemisphere with less supporting presurgical localizing data. Methods: We retrospectively reviewed our epilepsy surgery database at Mayo Clinic, Rochester, Minnesota, between January 1, 1999, and December 31, 2011, to identify patients who had an asymmetric number of electrode contacts implanted in each hemisphere for seizure localization. We scored each presurgical noninvasive data point (0, 0.5, or 1) to predict the likelihood of identifying seizure onset in the hemisphere with fewer intracranial electrode contacts (HFEC). An aggregate score was obtained for each patient. Results: Thirteen (37%) of 35 patients had HFEC-onset seizures on intracranial electroencephalography (iEEG). The following factors predicted HFEC-onset seizures: (1) temporal lobe epilepsy (p = 0.02); (2) interictal scalp electroencephalographic discharges at the HFEC (p = 0.04); and (3) both interictal and ictal scalp EEG discharges at the HFEC (p = 0.01). The median (range) aggregate score was 2 (1-3) for patients with HFEC-onset seizures recorded on iEEG and 1 (0-3) for patients without HFEC-onset seizures (p = 0.001). Using this scoring model, the odds ratio of identifying HFEC-onset seizures on iEEG was 6.4 for each one-point increment in the aggregate score. The area under the receiver operating characteristic curve for this model was 0.84, suggesting excellent ability of the aggregate score to discriminate between patients with and without HFEC-onset seizures on iEEG. Significance: Implanting electrodes on the basis of limited supporting presurgical data may be useful in selected patients, especially those with temporal lobe epilepsy, interictal scalp discharges involving the HFEC, or both interictal and ictal scalp discharges involving the HFEC. In addition, our proposed scoring system may be helpful in selecting patients with complicated epilepsy for implantation of an asymmetric number of intracranial electrodes in the hemispheres.
    Full-text · Article · Sep 2014 · Epilepsia
  • [Show abstract] [Hide abstract] ABSTRACT: We evaluated the outcomes of intracranial electroencephalography (iEEG) recording and subsequent resective surgery in patients with magnetic resonance imaging (MRI) − negative temporal lobe epilepsy (TLE). Thirty-two patients were identified from the Mayo Clinic Epilepsy Surgery Database (Arizona, Florida, and Minnesota). Eight (25.0%) had chronic iEEG monitoring that recorded neocortical temporal seizure onsets; 12 (37.5%) had mesial temporal seizure onsets; 5 (15.6%) had independent neocortical and mesial temporal seizure onsets; and 7 (21.9%) had simultaneous neocortical and mesial seizure onsets. Neocortical temporal lobe seizure semiology was the only factor significantly associated with neocortical temporal seizure onsets on iEEG. Only 33.3% of patients who underwent lateral temporal neocorticectomy had an Engel class 1 outcome, whereas 76.5% of patients with iEEG-guided anterior temporal lobectomy that included the amygdala and the hippocampus had an Engel class 1 outcome. Limitations in cohort size precluded statistical analysis of neuropsychological test data.
    No preview · Article · Jul 2014 · Epilepsy research
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    [Show abstract] [Hide abstract] ABSTRACT: Purpose: We aimed to determine the yield of revising intracranially implanted electrodes and the factors contributing to the yield. Methods: Patients were identified from the Mayo Clinic Epilepsy Surgery Database between 1997 and 2010. Twenty patients had revision of intracranial electrode placements because initial implantation did not localize seizure onset adequately. Results: Seizures were captured in 18 of 20 patients who underwent intracranial electrode revision, of which 10 (55.6%) showed localized seizure onset that led to a surgical resection. Seizures were improved in 9 of 10 patients who underwent resection; of these, five were seizure free. The only factors found to be statistically significant in localizing ictal onset zone after revised implantation were prior focal scalp interictal discharges and an initial intracranial EEG showing ictal onset at the edge of the electrode grid. No permanent complication was associated with revised implantation, but one patient had transient apraxia of the right foot. Conclusions: Revised implantation could be useful in selected patients with inadequate seizure localization on initial intracranial EEG. Resective surgery was performed in 50% of patients who underwent revision of intracranial electrodes with the majority of these patients experiencing an improvement in seizure control.
    Full-text · Article · Jun 2014 · Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society
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    [Show abstract] [Hide abstract] ABSTRACT: IMPORTANCE Scalp electroencephalography (EEG) and intraoperative electrocorticography (ECoG) are routinely used in the evaluation of magnetic resonance imaging-negative temporal lobe epilepsy (TLE) undergoing standard anterior temporal lobectomy with amygdalohippocampectomy (ATL), but the utility of interictal epileptiform discharge (IED) identification and its role in outcome are poorly defined. OBJECTIVES To determine whether the following are associated with surgical outcomes in patients with magnetic resonance imaging-negative TLE who underwent standard ATL: (1) unilateral-only IEDs on preoperative scalp EEG; (2) complete resection of tissue generating IEDs on ECoG; (3) complete resection of opioid-induced IEDs recorded on ECoG; and (4) location of IEDs recorded on ECoG. DESIGN, SETTING, AND PARTICIPANTS Data were gathered through retrospective medical record review at a tertiary referral center. Adult and pediatric patients with TLE who underwent standard ATL between January 1, 1990, and October 15, 2010, were considered for inclusion. Inclusion criteria were magnetic resonance imaging-negative TLE, standard ECoG performed at the time of surgery, and a minimum follow-up of 12 months. Univariate analysis was performed using log-rank time-to-event analysis. Variables reaching significance with log-rank testing were further analyzed using Cox proportional hazards. MAIN OUTCOMES AND MEASURES Excellent or nonexcellent outcome at time of last follow-up. An excellent outcome was defined as Engel class I and a nonexcellent outcome as Engel classes II through IV. RESULTS Eighty-seven patients met inclusion criteria, with 48 (55%) achieving an excellent outcome following ATL. Unilateral IEDs on scalp EEG (P = .001) and complete resection of brain regions generating IEDs on baseline intraoperative ECoG (P = .02) were associated with excellent outcomes in univariate analysis. Both were associated with excellent outcomes when analyzed with Cox proportional hazards (unilateral-only IEDs, relative risk = 0.31 [95% CI, 0.16-0.64]; complete resection of IEDs on baseline ECoG, relative risk = 0.39 [95% CI, 0.20-0.76]). Overall, 25 of 35 patients (71%) with both unilateral-only IEDs and complete resection of baseline ECoG IEDs had an excellent outcome. CONCLUSIONS AND RELEVANCE Unilateral-only IEDs on preoperative scalp EEG and complete resection of IEDs on baseline ECoG are associated with better outcomes following standard ATL in magnetic resonance imaging-negative TLE. Prospective evaluation is needed to clarify the use of ECoG in tailoring temporal lobectomy.
    Full-text · Article · Apr 2014
  • [Show abstract] [Hide abstract] ABSTRACT: To evaluate a trial of immunotherapy as an aid to diagnosis in suspected autoimmune epilepsy. We reviewed the charts of 110 patients seen at our autoimmune neurology clinic with seizures as a chief complaint. Twenty-nine patients met the following inclusion criteria: (1) autoimmune epilepsy suspected based on the presence of ≥1 neural autoantibody (n = 23), personal or family history or physical stigmata of autoimmunity, and frequent or medically intractable seizures; and (2) initiated a 6- to 12-week trial of IV methylprednisolone (IVMP), IV immune globulin (IVIg), or both. Patients were defined as responders if there was a 50% or greater reduction in seizure frequency. Eighteen patients (62%) responded, of whom 10 (34%) became seizure-free; 52% improved with the first agent. Of those receiving a second agent after not responding to the first, 43% improved. A favorable response correlated with shorter interval between symptom onset and treatment initiation (median 9.5 vs 22 months; p = 0.048). Responders included 14/16 (87.5%) patients with antibodies to plasma membrane antigens, 2/6 (33%) patients seropositive for glutamic acid decarboxylase 65 antibodies, and 2/6 (33%) patients without detectable antibodies. Of 13 responders followed for more than 6 months after initiating long-term oral immunosuppression, response was sustained in 11 (85%). These retrospective findings justify consideration of a trial of immunotherapy in patients with suspected autoimmune epilepsy. This study provides Class IV evidence that in patients with suspected autoimmune epilepsy, IVMP, IVIg, or both improve seizure control.
    No preview · Article · Apr 2014 · Neurology
  • Elson L So · Ricky W Lee
    [Show abstract] [Hide abstract] ABSTRACT: This study discusses the challenges of MRI-negative epilepsy surgery, and the strategies in using advanced MRI and functional imaging tests and their associated postsurgical outcome. Several methods for processing MRI postacquisition data have identified either previously undetectable or overlooked MRI abnormalities. The resection of these abnormalities is associated with excellent postsurgical seizure control. There have been major advances in functional imaging as well, one of which is the application of statistical parametric mapping analysis for comparing patient data against normative data. This approach has specifically improved the usefulness of both PET and single-photon emission computed tomography in MRI-negative epilepsy surgery evaluation. One other development of importance is that of PET-MRI coregistration, which has recently been shown to be superior to conventional PET. More recent publications on magnetoencephalography have added to the literature of its use in MRI-negative epilepsy surgery evaluation, which up to now remains somewhat limited. However, recent data now indicate that single magnetoencephalography cluster is associated with better chance of concordance with intracranial EEG localization, and with excellent postsurgical seizure control if completely resected. Advanced MRI and functional imaging and subsequent intracranial EEG confirmation of the seizure-onset zone are essential to make MRI-negative epilepsy surgery possible and worthwhile for the patient.
    No preview · Article · Feb 2014 · Current opinion in neurology
  • [Show abstract] [Hide abstract] ABSTRACT: To evaluate the benefit of statistical SPECT processing over traditional subtraction methods, we compared ictal-interictal SPECT analyzed by statistical parametric mapping (SPM) (ISAS), statistical ictal SPECT coregistered to MRI (STATISCOM), and subtraction ictal-interictal SPECT coregistered with MRI (SISCOM) in patients with MRI-negative focal temporal lobe epilepsy (nTLE) and extratemporal lobe epilepsy (nETLE). We retrospectively identified 49 consecutive cases of drug-resistant focal epilepsy that had a negative preoperative MRI and underwent interictal and ictal SPECT prior to resective epilepsy surgery. Interictal and ictal SPECT scans were analyzed using SISCOM, ISAS, and STATISCOM to create hyperperfusion and hypoperfusion maps for each patient. Reviewers blinded to clinical data and the SPECT analysis method marked the site of probable seizure origin and indicated their confidence in the localization. In nTLE and nETLE, the hyperperfusions detected by STATISCOM (71% nTLE, 57% nETLE) and ISAS (67% nTLE, 53% nETLE) were more often colocalized with surgery resection site compared to SISCOM (38% nTLE, 36% nETLE). In nTLE, localization of the hyperperfusion to the region of surgery was associated with an excellent outcome for STATISCOM (p = 0.005) and ISAS (p = 0.027), but not in SISCOM (p = 0.071). This association was not present in nETLE for any method. In an unselected group of patients with normal MRI and focal epilepsy, SPM-based methods of SPECT processing showed better localization of SPECT hyperperfusion to surgical resection site and higher interobserver agreement compared to SISCOM. These results show the benefit of statistical SPECT processing methods and further highlight the challenge of nETLE.
    No preview · Article · Feb 2014 · Neurology
  • No preview · Article · Oct 2013 · Journal of the Neurological Sciences
  • [Show abstract] [Hide abstract] ABSTRACT: Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in people with chronic refractory epilepsy. Very rarely, SUDEP occurs in epilepsy monitoring units, providing highly informative data for its still elusive pathophysiology. The MORTEMUS study expanded these data through comprehensive evaluation of cardiorespiratory arrests encountered in epilepsy monitoring units worldwide. Between Jan 1, 2008, and Dec 29, 2009, we did a systematic retrospective survey of epilepsy monitoring units located in Europe, Israel, Australia, and New Zealand, to retrieve data for all cardiorespiratory arrests recorded in these units and estimate their incidence. Epilepsy monitoring units from other regions were invited to report similar cases to further explore the mechanisms. An expert panel reviewed data, including video electroencephalogram (VEEG) and electrocardiogram material at the time of cardiorespiratory arrests whenever available. 147 (92%) of 160 units responded to the survey. 29 cardiorespiratory arrests, including 16 SUDEP (14 at night), nine near SUDEP, and four deaths from other causes, were reported. Cardiorespiratory data, available for ten cases of SUDEP, showed a consistent and previously unrecognised pattern whereby rapid breathing (18-50 breaths per min) developed after secondary generalised tonic-clonic seizure, followed within 3 min by transient or terminal cardiorespiratory dysfunction. Where transient, this dysfunction later recurred with terminal apnoea occurring within 11 min of the end of the seizure, followed by cardiac arrest. SUDEP incidence in adult epilepsy monitoring units was 5·1 (95% CI 2·6-9·2) per 1000 patient-years, with a risk of 1·2 (0·6-2·1) per 10 000 VEEG monitorings, probably aggravated by suboptimum supervision and possibly by antiepileptic drug withdrawal. SUDEP in epilepsy monitoring units primarily follows an early postictal, centrally mediated, severe alteration of respiratory and cardiac function induced by generalised tonic-clonic seizure, leading to immediate death or a short period of partly restored cardiorespiratory function followed by terminal apnoea then cardiac arrest. Improved supervision is warranted in epilepsy monitoring units, in particular during night time. Commission of European Affairs of the International League Against Epilepsy.
    No preview · Article · Sep 2013 · The Lancet Neurology
  • [Show abstract] [Hide abstract] ABSTRACT: Although the pathophysiologic mechanism of sudden unexpected death in epilepsy (SUDEP) is unknown, autonomic dysfunction is thought to be the most likely. It has been hypothesized that respiratory depression resulting in SUDEP may be secondary to postictal generalized electroencephalography suppression (PGES). We sought to determine the characteristics of PGES in children. This included whether PGES was associated with ictally mediated autonomic changes and potential increased risk of SUDEP. Children admitted to our Pediatric Epilepsy Monitoring Unit between 3/2009 and 10/2011 were prospectively recruited. Clinical and electrophysiological data from children with PGES were compared to those without PGES. Data included the occurrence of peri-ictal tachycardia, bradycardia, and hypoxemia. Potential SUDEP risk was assessed using SUDEP-7 Inventory scores. Thirty seven children with 168 seizures were analyzed. PGES was observed following 27/168 (16.1%) seizures in 12/37 (32.4%) children. Only primary and secondarily generalized tonic clonic seizures were marked by PGES. PGES was significantly associated with peri-ictal tachycardia (p=0.019) and hypoxemia (p=0.005). Children with PGES had significantly higher SUDEP-7 Inventory scores than those without PGES (4.2±1.3 versus 2.8±1.4, p=0.007). SUDEP-7 scores were not significantly different between children with and without peri-ictal tachycardia (3.4±1.3 versus 2.5±1.6, p=0.12), bradycardia (4±2 versus 2.9±1.4, p=0.45), or hypoxemia (3.4±1.5 versus 2.4±1.3, p=0.051). Based on our data, PGES is not rare in children. Children with PGES may be at greater risk for SUDEP as measured by the SUDEP-7 Inventory.
    No preview · Article · Jun 2013 · Epilepsy research
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    [Show abstract] [Hide abstract] ABSTRACT: IMPORTANCE A focal lesion detected by use of magnetic resonance imaging (MRI) is a favorable prognostic finding for epilepsy surgery. Patients with normal MRI findings and extratemporal lobe epilepsy have less favorable outcomes. Most studies investigating the outcomes of patients with normal MRI findings who underwent (nonlesional) extratemporal epilepsy surgery are confined to a highly select group of patients with limited follow-up. OBJECTIVE To evaluate noninvasive diagnostic test results and their association with excellent surgical outcomes (defined using Engel classes I-IIA of surgical outcomes) in a group of patients with medically resistant nonlesional extratemporal epilepsy. DESIGN A retrospective study. SETTING Mayo Clinic, Rochester, Minnesota. PARTICIPANTS From 1997 through 2002, we identified 85 patients with medically resistant extratemporal lobe epilepsy who had normal MRI findings. Based on a standardized presurgical evaluation and review at a multidisciplinary epilepsy surgery conference, some of these patients were selected for intracranial electroencephalographic (EEG) monitoring and epilepsy surgery. EXPOSURE Nonlesional extratemporal lobe epilepsy surgery. MAIN OUTCOMES AND MEASURES The results of noninvasive diagnostic tests and the clinical variables potentially associated with excellent surgical outcome were examined in patients with a minimum follow-up of 1 year (mean follow-up, 9 years). RESULTS Based on the noninvasive diagnostic test results, a clear hypothesis for seizure origin was possible for 47 of the 85 patients (55%), and 31 of these 47 patients (66%) proceeded to intracranial EEG monitoring. For 24 of these 31 patients undergoing long-term intracranial EEG (77%), a seizure focus was identified and surgically resected. Of these 24 patients, 9 (38%) had an excellent outcome after resective epilepsy surgery. All patients with an excellent surgical outcome had at least 10 years of follow-up. Univariate analysis showed that localized interictal epileptiform discharges on scalp EEGs were associated with an excellent surgical outcome. CONCLUSIONS AND RELEVANCE Scalp EEG was the most useful test for identifying patients with normal MRI findings and extratemporal lobe epilepsy who were likely to have excellent outcomes after epilepsy surgery. Extending outcome analysis beyond the resective surgery group to the entire group of patients who were evaluated further highlights the challenge that these patients pose. Although 9 of 24 patients undergoing resective surgery (38%) had excellent outcomes, only 9 of 31 patients undergoing intracranial EEG (29%) and only 9 of 85 patient with nonlesional extratemporal lobe epilepsy (11%) had long-term excellent outcomes.
    Full-text · Article · Jun 2013
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    [Show abstract] [Hide abstract] ABSTRACT: C ontinuous EEG Monitoring is becoming a commonly used tool in assessing brain function in critically ill patients. However, there is no uniformly accepted nomenclature for EEG patterns fre-quently encountered in these patients such as periodic discharges, fluctuating rhythmic patterns, and combinations thereof. Similarly, there is no consensus on which patterns are associated with ongoing neuronal injury, which patterns need to be treated, or how aggres-sively to treat them. The first step in addressing these issues is to standardize terminology to allow multicenter research projects and to facilitate communication. To this end, we gathered a group of electro-encephalographers with particular expertise or interest in this area in order to develop standardized terminology to be used primarily in the research setting. One of the main goals was to eliminate terms with clinical connotations, intended or not, such as "triphasic waves," a term that implies a metabolic encephalopathy with no relationship to seizures for many clinicians. We also avoid the use of "ictal," "interictal" and "epileptiform" for the equivocal patterns that are the primary focus of this report. A standardized method of quantifying interictal discharges is also included for the same reasons, with no attempt to alter the existing definition of epileptiform discharges (sharp waves and spikes [Noach-tar et al 1999]). Finally, we suggest here a scheme for categorizing background EEG activity. The revisions proposed here were based on solicited feedback on the initial version of the Report [Hirsch LJ et al 2005], from within and outside this committee and society, including public presentations and discussion at many venues. Inter-and intra-observer agreement between expert EEG readers using the initial version of the terminology was found to be moderate for major terms but only slight to fair for modifiers. [Gerber PA et al 2008] A second assessment was performed on an interim version after extensive changes were introduced. This assessment showed significant improvement with an inter-rater agreement almost perfect for main terms (k = 0.87, 0.92) and substantial agreement for the modifiers of amplitude (93%) and frequency (80%) (Mani R, et al, 2012). Last, after official posting on the ACNS Website and solicitation of com-ment from ACNS members and others, additional minor additions and revisions were enacted. To standardize terminology of periodic and rhythmic EEG patterns in the critically ill in order to aid communication and future research involving such patterns. Our goal is to avoid terms with clinical connotations and to define terms thoroughly enough to maximize inter-rater reliability. Not included in this nomenclature:
    Full-text · Dataset · Mar 2013
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    [Show abstract] [Hide abstract] ABSTRACT: Continuous EEG Monitoring is becoming a commonly used tool in assessing brain function in critically ill patients. However, there is no uniformly accepted nomenclature for EEG patterns fre-quently encountered in these patients such as periodic discharges, fluctuating rhythmic patterns, and combinations thereof. Similarly, there is no consensus on which patterns are associated with ongoing neuronal injury, which patterns need to be treated, or how aggres-sively to treat them. The first step in addressing these issues is to standardize terminology to allow multicenter research projects and to facilitate communication. To this end, we gathered a group of electro-encephalographers with particular expertise or interest in this area in order to develop standardized terminology to be used primarily in the research setting. One of the main goals was to eliminate terms with clinical connotations, intended or not, such as "triphasic waves," a term that implies a metabolic encephalopathy with no relationship to seizures for many clinicians. We also avoid the use of "ictal," "interictal" and "epileptiform" for the equivocal patterns that are the primary focus of this report. A standardized method of quantifying interictal discharges is also included for the same reasons, with no attempt to alter the existing definition of epileptiform discharges (sharp waves and spikes [Noach-tar et al 1999]). Finally, we suggest here a scheme for categorizing background EEG activity. The revisions proposed here were based on solicited feedback on the initial version of the Report [Hirsch LJ et al 2005], from within and outside this committee and society, including public presentations and discussion at many venues. Inter-and intra-observer agreement between expert EEG readers using the initial version of the terminology was found to be moderate for major terms but only slight to fair for modifiers. [Gerber PA et al 2008] A second assessment was performed on an interim version after extensive changes were introduced. This assessment showed significant improvement with an inter-rater agreement almost perfect for main terms (k = 0.87, 0.92) and substantial agreement for the modifiers of amplitude (93%) and frequency (80%) (Mani R, et al, 2012). Last, after official posting on the ACNS Website and solicitation of com-ment from ACNS members and others, additional minor additions and revisions were enacted. To standardize terminology of periodic and rhythmic EEG patterns in the critically ill in order to aid communication and future research involving such patterns. Our goal is to avoid terms with clinical connotations and to define terms thoroughly enough to maximize inter-rater reliability. Not included in this nomenclature:
    Full-text · Article · Feb 2013 · Journal of Clinical Neurophysiology
  • No preview · Article · Jan 2013 · Epilepsy Currents
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    [Show abstract] [Hide abstract] ABSTRACT: Cerebral oximetry has not been explored in patients experiencing seizures in the epilepsy monitoring unit (EMU). The purpose of our study was to evaluate the feasibility of periictal measurement of cerebral oxygenation using noninvasive cerebral tissue oximetry and to determine whether there was evidence of cerebral hypoxemia during generalized seizures. Cerebral oxygen saturation findings were subsequently correlated with sudden unexpected death in epilepsy (SUDEP) risk factors. We prospectively evaluated six patients admitted to our EMU with histories of generalized tonic-clonic seizures (GTCS) with prolonged scalp electroencephalography (EEG) and two regional cerebral oxygen saturation (rSO(2) ) sensors. Minimum rSO(2) values were recorded in the 5 min preceding seizure onset, during the seizure, and in the 5 min following seizure offset. SUDEP risk was assessed using the SUDEP-7 Inventory. Cerebral oximetry was well tolerated, with a mean duration of rSO(2) monitoring of 81.1 h. Cerebral oxygen saturation data were available from at least one sensor in 9 (90%) of 10 seizures; only 6 (60%) of 10 seizures had useable periictal digital pulse oximetry data. GTCS were associated with significantly lower minimum ictal (p = 0.003) and postictal (p = 0.004) %rSO(2) values than the minimum preictal value. Patients with at least one seizure with a %rSO(2) decrease of ≥20% tended to have higher SUDEP-7 Inventory scores (mean SUDEP-7 Inventory score 7 ± 2.8) versus patients without recorded desaturations (4.3 ± 0.5, p = 0.08). Larger studies are needed to determine the value of cerebral oximetry in the identification of patients at risk of SUDEP.
    Full-text · Article · Oct 2012 · Epilepsia
  • Elson L So · Terrence J O'Brien
    No preview · Article · Sep 2012 · Handbook of Clinical Neurology
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    [Show abstract] [Hide abstract] ABSTRACT: Purpose. To investigate EEG and SPECT in the surgical outcome of patients with normal MRI (nonlesional) and extratemporal lobe epilepsy. Methods. We retrospectively identified 41 consecutive patients with nonlesional extratemporal epilepsy who underwent epilepsy surgery between 1997 and 2007. The history, noninvasive diagnostic studies (scalp EEG, MRI, and SPECT) and intracranial EEG (iEEG) monitoring was reviewed. Scalp and iEEG ictal onset patterns were defined. The association of preoperative studies and postoperative seizure freedom was analyzed using Kaplan-Meier analysis, log-rank test, and Cox proportional hazard. Results. Thirty-six of 41 patients had adequate information with a minimum of 1-year followup. Favorable surgical outcome was identified in 49% of patients at 1 year, and 35% at 4-year. On scalp EEG, an ictal onset pattern consisting of focal beta-frequency discharge (>13-125 Hz) was associated with favorable surgical outcome (P = 0.02). Similarly, a focal fast-frequency oscillation (>13-125 Hz) on iEEG at ictal onset was associated with favorable outcome (P = 0.03). Discussion. A focal fast-frequency discharge at ictal onset identifies nonlesional MRI, extratemporal epilepsy patients likely to have a favorable outcome after resective epilepsy surgery.
    Full-text · Article · Jun 2012
  • [Show abstract] [Hide abstract] ABSTRACT: Objective To describe clinical characteristics and immunotherapy responses in patients with autoimmune epilepsy. Design Observational, retrospective case series. Setting Mayo Clinic Health System. Patients Thirty-two patients with an exclusive (n = 11) or predominant (n = 21) seizure presentation in whom an autoimmune etiology was suspected (on the basis of neural autoantibody [91%], inflammatory cerebrospinal fluid [31%], or magnetic resonance imaging suggesting inflammation [63%]) were studied. All had partial seizures: 81% had failed treatment with 2 or more antiepileptic drugs and had daily seizures and 38% had seizure semiologies that were multifocal or changed with time. Head magnetic resonance imaging was normal in 15 (47%) at onset. Electroencephalogram abnormalities included interictal epileptiform discharges in 20; electrographic seizures in 15; and focal slowing in 13. Neural autoantibodies included voltage-gated potassium channel complex in 56% (leucine-rich, glioma-inactivated 1 specific, 14; contactin-associated proteinlike 2 specific, 1); glutamic acid decarboxylase 65 in 22%; collapsin response-mediator protein 5 in 6%; and Ma2, N -methyl-D-aspartate receptor, and ganglionic acetylcholine receptor in 1 patient each. Intervention Immunotherapy with intravenous methylprednisolone; intravenous immune globulin; and combinations of intravenous methylprednisolone, intravenous immune globulin, plasmapheresis, or cyclophosphamide. Main Outcome Measure Seizure frequency. Results After a median interval of 17 months (range, 3-72 months), 22 of 27 (81%) reported improvement postimmunotherapy; 18 were seizure free. The median time from seizure onset to initiating immunotherapy was 4 months for responders and 22 months for nonresponders (P < .05). All voltage-gated potassium channel complex antibody–positive patients reported initial or lasting benefit (P < .05). One voltage-gated potassium channel complex antibody–positive patient was seizure free after thyroid cancer resection; another responded to antiepileptic drug change alone. Conclusion When clinical and serological clues suggest an autoimmune basis for medically intractable epilepsy, early-initiated immunotherapy may improve seizure outcome.
    No preview · Article · Mar 2012 · Archives of neurology