Faculty Bibliography

The current study examined whether mood-congruent biases in emotion processing extend to epilepsy patients with depressive symptoms and the potentially moderating effects of age of seizure onset on these biases. In addition, we examined associations between depression (Beck Depression Inventory - 2nd Edition; BDI-II) and quality of life (Quality of Life in Epilepsy - 10-item questionnaire; QOLIE-10). Data from 101 epilepsy patients were analyzed, including 61 females and 40 males. Measures included the Comprehensive Affect Testing System - Abbreviated (CATS-A), from which indices of mood-congruent bias were derived. A significant interaction between BDI-II raw scores and age of seizure onset was found for mood-congruent bias scores in the facial affect modality (beta=-0.24, p<.03). Beck Depression Inventory - 2nd Edition raw scores were significantly and positively correlated with quality of life (QOLIE-10; r=.69, p<.01). Results of the current study show that epilepsy patients with an early age of seizure onset may be most at risk for mood-congruent biases when experiencing depressive symptoms and that such symptoms have real-world implications for quality of life for persons living with epilepsy.

Despite decades of cognitive, neuropsychological and neuroimaging studies, it is unclear if letters are identified before word-form encoding during reading, or if letters and their combinations are encoded simultaneously and interactively. Here using functional magnetic resonance imaging, we show that a 'letter-form' area (responding more to consonant strings than false fonts) can be distinguished from an immediately anterior 'visual word-form area' in ventral occipito-temporal cortex (responding more to words than consonant strings). Letter-selective magnetoencephalographic responses begin in the letter-form area approximately 60 ms earlier than word-selective responses in the word-form area. Local field potentials confirm the latency and location of letter-selective responses. This area shows increased high-gamma power for approximately 400 ms, and strong phase-locking with more anterior areas supporting lexico-semantic processing. These findings suggest that during reading, visual stimuli are first encoded as letters before their combinations are encoded as words. Activity then rapidly spreads anteriorly, and the entire network is engaged in sustained integrative processing.

PURPOSE: Psychogenic nonepileptic seizures (PNES) can be challenging to diagnose, but certain clinical features can help to distinguish PNES from epileptic seizures. The purpose of this study is to assess chronic pain and prescribed pain medication use in PNES patients. METHODS: A case-controlled, retrospective analysis was performed examining pain medication use in 85 PNES patients versus an active control group of 85 patients with idiopathic generalized epilepsy (IGE). RESULTS: Chronic pain was more frequent among PNES patients (N=40) than active controls (N=10) (p<0.0001). Reported use of prescription pain medication was higher among PNES patients (N=20) versus active controls (N=6) (p=0.0048). The Positive Predictive Value of prescription pain medications for PNES patients was 76.9%. Opioid use in the PNES population was higher compared with active controls (p=0.0096). When excluding patients with a dual diagnosis of PNES and epilepsy from the latter two analyses and comparing these results to those that included this patient population, no statistically significant difference in results was found. CONCLUSIONS: Patients with PNES are more likely than those with IGE to report chronic pain disorders. A history of chronic pain and opioid use among patients with seizures raises the possibility of PNES. Among patients with PNES and chronic pain, a psychogenic etiology for pain and non-opiate pain management strategies should be considered.

Object Tuberous sclerosis complex (TSC) is a multisystem autosomal dominant disorder resulting in hamartomas of several organs. Cortical tubers are the most prominent brain lesions in TSC. Treatment-resistant epilepsy often develops early in life in patients with TSC and is associated with severe intellectual and behavioral impairments. Seizures may remit following epilepsy surgery in selected cases, yet it remains unclear whether the tuber or the perituberal cortex is the source of seizure onset. In this study, the authors reviewed the onset of seizures in patients in whom depth electrodes had been placed within or adjacent to cortical tubers. Methods After obtaining institutional review board approval, the authors retrospectively reviewed data from 12 pediatric patients with multifocal TSC and treatment-resistant epilepsy who had undergone invasive intracranial electroencephalographic monitoring. Tubers were identified on postimplantation MRI, and all depth electrodes were located. Depth electrode contacts were classified visually as either tuber/perituberal cortex or nontuber/nonperituberal cortex. Board-certified clinical neurophysiologists reviewed the seizures to identify all electrodes involved in the ictal onset. Results Among 309 recorded seizures, 104 unique ictal onset patterns were identified. Of the 11 patients with electrodes recording in a tuber, 9 had seizure onsets involving the tuber. Similarly, of the 9 patients with perituberal recording electrodes, 7 had perituberal ictal onsets. Overall, there was no difference in the percentage of contacts involved in seizure onset between the tuber and perituberal cortex. In a subset of 7 patients in whom at least 1 depth electrode contact was within the tuber and 1 was in the perituberal cortex, there was no difference between the percentage of tuber and perituberal onsets. Conclusions Findings demonstrated heterogeneity in the ictal onset patterns as well as involvement of the tuber and perituberal cortex within and between patients. Although the data are limited by the restricted region(s) sampled with intracranial electrodes, they do suggest that cortical hyperexcitability in TSC may derive from the tuber or surrounding cortex.

Making sense of the world requires us to process information over multiple timescales. We sought to identify brain regions that accumulate information over short and long timescales and to characterize the distinguishing features of their dynamics. We recorded electrocorticographic (ECoG) signals from individuals watching intact and scrambled movies. Within sensory regions, fluctuations of high-frequency (64-200 Hz) power reliably tracked instantaneous low-level properties of the intact and scrambled movies. Within higher order regions, the power fluctuations were more reliable for the intact movie than the scrambled movie, indicating that these regions accumulate information over relatively long time periods (several seconds or longer). Slow (<0.1 Hz) fluctuations of high-frequency power with time courses locked to the movies were observed throughout the cortex. Slow fluctuations were relatively larger in regions that accumulated information over longer time periods, suggesting a connection between slow neuronal population dynamics and temporally extended information processing.

Psychogenic nonepileptic seizures (PNES) are a common presentation to the emergency room and neurology department. They are often misdiagnosed and treated as epileptic seizures. Inappropriate treatment leads to poor patient outcomes and iatrogenic complications, as the underlying mechanisms and treatments are distinctly different. Most causes involve a conversion or dissociative reaction to a prior traumatic experience or abuse. Recognition of the characteristic clinical features of PNES and utilization of video-electroencephalography to confirm the diagnosis is critical. Discontinuation of treatment for epilepsy (unless comorbid PNES and epilepsy is present), acceptance of the diagnosis, and a multidisciplinary treatment plan with clinical psychologists, neurologist, and psychiatrist improve patient and healthcare outcomes.

Sudden Unexpected Death in Epilepsy (SUDEP) is the most common cause of epilepsy related mortality in treatment resistant epilepsy. Most SUDEPs occur after one or more seizure(s) during sleep. Nocturnal seizures may go unrecognized. Respiratory depression in the peri-ictal period is one of the primary potential causes of SUDEP. Ictal and postictal apnea is often overlooked because it is not routinely assessed, but appears common and has been a recent focus of SUDEP research. We report a 37 year-old man who had central apnea as the initial manifestation of partial complex seizures associated with oxygen desaturation. This important pathophysiological consequence of a nocturnal complex seizure was identified by respiratory monitoring during a combined video EEG and sleep study. Diagnostic and therapeutic implications are discussed.

Intracranial electrode arrays are routinely used in the pre-surgical evaluation of patients with medically refractory epilepsy, and recordings from these electrodes have been increasingly employed in human cognitive neurophysiology due to their high spatial and temporal resolution. For both researchers and clinicians, it is critical to localize electrode positions relative to the subject-specific neuroanatomy. In many centers, a post-implantation MRI is utilized for electrode detection because of its higher sensitivity for surgical complications and the absence of radiation. However, magnetic susceptibility artifacts surrounding each electrode prohibit unambiguous detection of individual electrodes, especially those that are embedded within dense grid arrays. Here, we present an efficient method to accurately localize intracranial electrode arrays based on pre- and post-implantation MR images that incorporates array geometry and the individual's cortical surface. Electrodes are directly visualized relative to the underlying gyral anatomy of the reconstructed cortical surface of individual patients. Validation of this approach shows high spatial accuracy of the localized electrode positions (mean of 0.96mm+/-0.81mm for 271 electrodes across 8 patients). Minimal user input, short processing time, and utilization of radiation-free imaging are strong incentives to incorporate quantitatively accurate localization of intracranial electrode arrays with MRI for research and clinical purposes. Co-registration to a standard brain atlas further allows inter-subject comparisons and relation of intracranial EEG findings to the larger body of neuroimaging literature.

Object The authors evaluated the extent to which the Subdural Pharmacotherapy Device (SPD), chronically implanted over the frontal cortex to perform periodic, localized muscimol-delivery/CSF removal cycles, affects overall behavior, motor performance, electroencephalography (EEG) activity, and blood and CSF neurochemistry in macaque monkeys. Methods Two monkeys were used to adjust methodology and 4 monkeys were subjected to comprehensive testing. Prior to surgery, the animals' behavior in a large test chamber was monitored, and the motor skills required to remove food pellets from food ports located on the walls of the chamber were determined. The monkeys underwent implantation of the subdural and extracranial SPD units. The subdural unit, a silicone strip integrating EEG electrodes and fluid-exchange ports, was positioned over the right frontal cortex. The control unit included a battery-powered, microprocessor-regulated dual minipump and radiofrequency module secured to the cranium. After implantation, the SPD automatically performed periodic saline or muscimol (1.0 mM) deliveries at 12-hour intervals, alternating with local CSF removals at 6-hour intervals. The antiepileptic efficacy of this muscimol concentration was verified by demonstrating its ability to prevent focal acetylcholine-induced seizures. During SPD treatment, the monkeys' behavior and motor performance were again monitored, and the power spectrum of their radiofrequency-transmitted EEG recordings was analyzed. Serum and CSF muscimol levels were measured with high-performance liquid chromatography electrochemical detection, and CSF protein levels were measured with turbidimetry. Results The SPD was well tolerated in all monkeys for up to 11 months. The behavioral study revealed that during both saline and muscimol SPD treatment, the monkeys could achieve the maximum motor performance of 40 food-pellet removals per session, as before surgery. The EEG study showed that local EEG power spectra were not affected by muscimol treatment with SPD. The neurochemical study demonstrated that the administration of 1.0 mM muscimol into the neocortical subarachnoid space led to no detectable levels of this compound in the blood and cisternal CSF, as measured 1-125 minutes after delivery. Total protein levels were within the normal range in the cisternal CSF, but protein levels in the cortical-site CSF were significantly higher than normal: 361 +/- 81.6 mg/dl. Abrupt discontinuation of 3-month, periodic, subdural muscimol treatments induced withdrawal seizures, which could be completely prevented by gradually tapering off the subdural muscimol concentration from 1.0 mM to 0.12-0.03 mM over a period of 2 weeks. The monkeys' general health and weight were maintained. Infection occurred only in one monkey 9 months after surgery. Conclusions Long-term, periodic, transmeningeal muscimol delivery with the SPD is essentially a safe procedure. If further improved and successfully adapted for use in humans, the SPD can be used for the treatment of intractable focal neocortical epilepsy affecting approximately 150,000 patients in the US.