Faculty Bibliography

To preserve postoperative language, electrical stimulation mapping is often conducted prior to surgery involving the language-dominant hemisphere. Object naming is the task most widely used to identify language cortex, and sites where stimulation elicits naming difficulty are typically spared from resection. In clinical practice, sites classified as positive undergo no further testing regarding the underlying cause of naming failure. Word production is a complex function involving multiple mechanisms that culminate in the identification of the target word. Two main mechanisms, i.e., semantic and phonological, underlie the retrieval of stored information regarding word meaning and word sounds, and naming can be hampered by disrupting either of these. These two mechanisms are likely mediated by different brain areas, and therefore, stimulation-identified naming sites might not be functionally equivalent. We investigated whether further testing at stimulation-identified naming sites would reveal an anatomical dissociation between these two mechanisms. In 16 patients with refractory temporal lobe epilepsy (TLE) with implanted subdural electrodes, we tested whether, despite inability to produce an item name, patients could reliably access semantic or phonological information regarding objects during cortical stimulation. We found that stimulation at naming sites in superior temporal cortex tended to impair phonological processing yet spared access to semantic information. By contrast, stimulation of inferior temporal naming sites revealed a greater proportion of sites where semantic access was impaired and a dissociation between sites where stimulation spared or disrupted semantic or phonological processing. These functional-anatomical dissociations reveal the more specific contribution to naming provided by these cortical areas and shed light on the often profound, interictal word-finding deficit observed in temporal lobe epilepsy. Additionally, these techniques potentially lay the groundwork for future studies to determine whether particular naming sites that fall within the margins of the desired clinical resection might be resected without significant risk of decline.

With an increasing focus on quality metrics, hospital length of stay (LOS) in the U.S. has garnered significant scrutiny. To help establish evidence-based benchmarks for epilepsy monitoring unit (EMU) metrics, we evaluated the impact of multiple variables on LOS through a retrospective analysis of 905 consecutive inpatient adult EMU admissions. The most common reasons for admission were event characterization (n=494), medication adjustment (n=189), and presurgical evaluation (n=96). Presurgical evaluations experienced a longer average LOS (aLOS) of 7.1days versus patients admitted for other indications (p<0.001). Patients with symptomatic generalized epilepsy (n=22) had a longer aLOS (6.9days) than patients with other types of epilepsy/events (p<0.001). Patients admitted on two or fewer antiepileptic drugs (AEDs) had a shorter aLOS than patients admitted on three or more AEDs (4.3days vs 6.3days, respectively; p<0.001). A history of previous invasive epilepsy management was associated with a longer aLOS than those without (6.2days vs 4.7days, respectively; p<0.0001). Epilepsy monitoring unit aLOS is influenced by admission indication, epilepsy classification, medication burden, and having had prior invasive management. Multiple variables should be considered when analyzing LOS EMU metrics, arguing against a "one size fits all" approach.

PURPOSE OF REVIEW/OBJECTIVE:This article discusses targeted special issues in epilepsy, including epilepsy in the elderly and immuncompromised populations and bone health in epilepsy. Although this is a broad and diverse set of topics, common themes can be identified by focusing on elderly patients and patients who are immunocompromised that provide a valuable framework for other groups. RECENT FINDINGS/RESULTS:An increasing incidence of epilepsy has been reported in patients 65 years of age and older. As people age, physiologic changes can alter antiepileptic drug metabolism, which can significantly impact dosing requirements and tolerability. Side effects of antiepileptic drugs may pose a significant challenge given the relatively high frequency of comorbid illnesses. When evaluating and treating immunocompromised patients, a broad range of potential etiologies for new-onset or worsening seizures must be considered. When choosing an antiepileptic drug, drug-drug interactions, the potential for increased side effects, and the overall impact of treatments on the underlying illness must be considered. The most recent findings and recommendations pertaining to bone health assessment and maintenance in various populations with epilepsy are summarized. SUMMARY/CONCLUSIONS:Treating epilepsy and seizures in special populations requires taking a broad view of patients' overall health status, including potentially complex treatment regimens and a unique predisposition to adverse events.

Objective: To characterize efficacy and risks of diagnostic bilateral intracranial electroencephalography (bICEEG) in treatment-resistant epilepsy (TRE) patients with poorly lateralized epileptogenic zone (EZ) on non-invasive studies. Background: Patients with TRE are candidates for epilepsy surgery if the EZ is localized and deemed resectable. For cases with discordant non-invasive studies, bICEEG may definitively lateralize the EZ to identify surgical candidates. Methods: We retrospectively reviewed all 208 bICEEG cases at New York University (NYU) between 1994 and 2013. Endpoints included: progress to resection, Engel outcome, and peri-operative complications. Results: Of 208 patients, 19 were lost to follow-up. For 60[percnt], bICEEG lateralized the EZ and they progressed to therapeutic resection or further regional ICEEG. Subdural and depth electrodes were routinely used together but only the number of depth electrodes positively correlated with progress to resection and depth electrode use was not greater in temporal lobe cases. Forty-eight percent who progressed to resection were seizure free at last follow-up (mean 5.4yrs) compared with 13[percnt] of patients who did not have resection (mean 5.6yrs). Pre-operative seizure frequency greater than 1/day was associated with worse post-operative seizure control. The most common complication was infection requiring surgical intervention; occurrence was 3.1[percnt]. Rates of superficial infection, DVT, pulmonary embolism, stroke, and hemorrhage were each below 1[percnt]. Conclusions: At NYU, 60[percnt] of patients with TRE who underwent bICEEG progressed to EZ resection and 48[percnt] of these cases were seizure free. The risks of bICEEG monitoring are similar to our unilateral invasive monitoring. We conclude that bICEEG extends the benefit of epilepsy surgery to poorly lateralized TRE patients. Future analysis will determine the relative predictive value of seizure semiology, vEEG monitoring, MRI, MEG, and PET to progress to resection and Engel outcome in this series; as well as determine how depth electrodes augment subdural monitoring

OBJECTIVES: Seizures are often accompanied by ictal tachycardia, which, when pronounced, is one of the cardiac arrhythmias associated with sudden unexpected death in epilepsy (SUDEP). We examined the relationship between the lateralization and localization of seizure onset and development of ictal tachycardia. METHODS: We identified patients who underwent bi-hemispheric intracranial EEG recording over a period of 18months. Two to four consecutive seizures were reviewed for each patient. RESULTS: Fifty-seizures from 19 consecutive patients were analyzed. Forty seizures (80%) developed tachycardia (>20% increase from baseline), but laterality at seizure onset did not predict its occurrence (p=0.168). Bi-laterality at ictal onset was associated with early ictal tachycardia (<10s) (p=0.0208). Seizures out of sleep developed tachycardia faster (mean 19.7s vs. 68.2s, p=0.0067), but the state of alertness was not predictive of the development of tachycardia within 10s of seizure onset. Temporal and/or orbito-frontal lobe involvement was associated with tachycardia when compared to any other lobar combinations at ictal onset (p=0.0073). CONCLUSION: Laterality at seizure onset does not predict the occurrence of ictal tachycardia. Involvement of the temporal and orbito-frontal cortex, spread to the contralateral hemisphere and state of alertness, may define the degree and rate of autonomic changes. SIGNIFICANCE: Our results help clarify the autonomic control during seizures and offer potential use for future studies in SUDEP risk and automatic seizure detection.

OBJECTIVE: Epilepsy surgery is the most effective treatment for select patients with drug-resistant epilepsy. In this article, we aim to provide an accurate understanding of the current epidemiologic characteristics of this intervention, as this knowledge is critical for guiding educational, academic, and resource priorities. METHODS: We profile the practice of epilepsy surgery between 1991 and 2011 in nine major epilepsy surgery centers in the United States, Germany, and Australia. Clinical, imaging, surgical, and histopathologic data were derived from the surgical databases at various centers. RESULTS: Although five of the centers performed their highest number of surgeries for mesial temporal sclerosis (MTS) in 1991, and three had their highest number of MTS surgeries in 2001, only one center achieved its peak number of MTS surgeries in 2011. The most productive year for MTS surgeries varied then by center; overall, the nine centers surveyed performed 48% (95% confidence interval [CI] -27.3% to -67.4%) fewer such surgeries in 2011 compared to either 1991 or 2001, whichever was higher. There was a parallel increase in the performance of surgery for nonlesional epilepsy. Further analysis of 5/9 centers showed a yearly increase of 0.6 +/- 0.07% in the performance of invasive electroencephalography (EEG) without subsequent resections. Overall, although MTS was the main surgical substrate in 1991 and 2001 (proportion of total surgeries in study centers ranging from 33.3% to 70.2%); it occupied only 33.6% of all resections in 2011 in the context of an overall stable total surgical volume. SIGNIFICANCE: These findings highlight the major aspects of the evolution of epilepsy surgery across the past two decades in a sample of well-established epilepsy surgery centers, and the critical current challenges of this treatment option in addressing complex epilepsy cases requiring detailed evaluations. Possible causes and implications of these findings are discussed.

Focal cortical dysplasia (FCD) is the most common cause of pediatric epilepsy and the third most common lesion in adults with treatment-resistant epilepsy. Advances in MRI have revolutionized the diagnosis of FCD, resulting in higher success rates for resective epilepsy surgery. However, many patients with histologically confirmed FCD have normal presurgical MRI studies ('MRI-negative'), making presurgical diagnosis difficult. The purpose of this study was to test whether a novel MRI postprocessing method successfully detects histopathologically verified FCD in a sample of patients without visually appreciable lesions. We applied an automated quantitative morphometry approach which computed five surface-based MRI features and combined them in a machine learning model to classify lesional and nonlesional vertices. Accuracy was defined by classifying contiguous vertices as "lesional" when they fell within the surgical resection region. Our multivariate method correctly detected the lesion in 6 of 7 MRI-positive patients, which is comparable with the detection rates that have been reported in univariate vertex-based morphometry studies. More significantly, in patients that were MRI-negative, machine learning correctly identified 14 out of 24 FCD lesions (58%). This was achieved after separating abnormal thickness and thinness into distinct classifiers, as well as separating sulcal and gyral regions. Results demonstrate that MRI-negative images contain sufficient information to aid in the in vivo detection of visually elusive FCD lesions.