Clinical utility of EEG in diagnosing and monitoring epilepsy in adults.

Electroencephalography (EEG) remains an essential diagnostic tool for people with epilepsy (PWE). The International Federation of Clinical Neurophysiology produces new guidelines as an educational service for clinicians to address gaps in knowledge in clinical neurophysiology. The current guideline was prepared in response to gaps present in epilepsy-related neurophysiological assessment and is not intended to replace sound clinical judgement in the care of PWE. Furthermore, addressing specific pathophysiological conditions of the brain that produce epilepsy is of primary importance though is beyond the scope of this guideline. Instead, our goal is to summarize the scientific evidence for the utility of EEG when diagnosing and monitoring PWE.

The value of multichannel MEG and EEG in the presurgical evaluation of 70 epilepsy patients.

OBJECTIVE: To evaluate the sensitivity of a simultaneous whole-head 306-channel magnetoencephalography (MEG)/70-electrode EEG recording to detect interictal epileptiform activity (IED) in a prospective, consecutive cohort of patients with medically refractory epilepsy that were considered candidates for epilepsy surgery. METHODS: Seventy patients were prospectively evaluated by simultaneously recorded MEG/EEG. All patients were surgical candidates or were considered for invasive EEG monitoring and had undergone an extensive presurgical evaluation at a tertiary epilepsy center. MEG and EEG raw traces were analysed individually by two independent reviewers. RESULTS: MEG data could not be evaluated due to excessive magnetic artefacts in three patients (4%). In the remaining 67 patients, the overall sensitivity to detect IED was 72% (48/67 patients) for MEG and 61% for EEG (41/67 patients) analysing the raw data. In 13% (9/67 patients), MEG-only IED were recorded, whereas in 3% (2/67 patients) EEG-only IED were recorded. The combined sensitivity was 75% (50/67 patients). CONCLUSION: Three hundred and six-channel MEG has a similarly high sensitivity to record IED as EEG and appears to be complementary. In one-third of the EEG-negative patients, MEG can be expected to record IED, especially in the case of lateral neocortical epilepsy and/or cortical dysplasia.

Sleep-inducing effects of low doses of melatonin ingested in the evening.

We previously observed tht low oral doses of melatonin given at noon increase blood melatonin concentrations to those normally occurring nocturnally and facilitate sleep onset, as assessed using and involuntary muscle relaxation test. In this study we examined the induction of polysomnographically recorded sleep by similar doses given later in the evening, close to the times of endogenous melatonin release and habitual sleep onset. Volunteers received the hormone (oral doses of 0.3 or 1.0 mg) or placebo at 6, 8, or 9 PM. Latencies to sleep onset, to stage 2 sleep, and to rapid eye movement (REM) sleep were measured polysomnographically. Either dose given at any of the three time points decreased sleep onset latency and latency to stage 2 sleep. Melatonin did not suppress REM sleep or delay its onset. Most volunteers could clearly distinguish between the effects of melatonin and those of placebo when the hormone was tested at 6 or 8 PM. Neither melatonin dose induced "hangover" effects, as assessed with mood and performance tests administered on the morning after treatment. These data provide new evidence that nocturnal melatonin secretion may be involved in physiologic sleep onset and that exogenous melatonin may be useful in treating insomnia.

Aspartame: neuropsychologic and neurophysiologic evaluation of acute and chronic effects.

BACKGROUND: Neurobehavioral symptoms have been reported anecdotally with aspartame. OBJECTIVE: This study sought to determine whether aspartame can disrupt cognitive, neurophysiologic, or behavioral functioning in normal individuals. DESIGN: Forty-eight healthy volunteers completed a randomized, double-blind, placebo-controlled, crossover study. The first month was aspartame free. Subjects then consumed sodas and capsules with placebo, aspartame, or sucrose for 20 d each. Order was randomized and subjects were assigned to either a high- (45 mg x kg body wt(-1) x d(-1)) or low- (15 mg x kg body wt(-1) x d(-1)) dose aspartame group. Neuropsychologic and laboratory testing was done on day 10 of each treatment period to determine possible acute effects and on day 20 for possible chronic effects. RESULTS: Plasma phenylalanine concentrations increased significantly during aspartame treatment. Neuropsychologic results; adverse experiences; amino acid, insulin, and glucose values; and electroencephalograms were compared by sex and by treatment. No significant differences were found for any dependent measure. CONCLUSION: Large daily doses of aspartame had no effect on neuropsychologic, neurophysiologic, or behavioral functioning in healthy young adults.

Broca's aphasia following damage to Wernicke's area. For or against traditional aphasiology?

Classic aphasiology has been challenged by studies that have employed cranial computed tomography to test predicted anatomic-behavioral correlations. We treated a patient who developed a classic Broca's aphasia but whose computed tomographic scan revealed damage to Wernicke's area, thus seeming to contradict the principles of traditional aphasiology. However, subsequent information obtained by magnetic resonance imaging, intracarotid amobarbital (Amytal) testing, and electrophysiologic studies, including cortical stimulation, demonstrated that the brain-behavior correlations in this patient can be understood in terms of the formulations of traditional aphasiology.

Reproductive endocrine disorders in men with partial seizures of temporal lobe origin.

Twenty consecutive men with partial seizures of temporal lobe origin were evaluated for sexual or reproductive dysfunction. Eleven (55%) had diminished sexual interest or reduced potency. Nine of them had reproductive endocrine disorders, with features of hypogonadotropic hypogonadism in five, hyperprolactinemia in two, and hypergonadotropic hypogonadism in two. Among these nine were cases in which the reproductive endocrine abnormalities could not readily be attributed to antiseizure medication use. Other possible interpretations are as follows: epileptic discharges in medial temporal lobe structures may disrupt hypothalamic regulation of pituitary secretion, hypogonadism may promote the development of epileptic discharges, and temporal lobe epilepsy and associated reproductive endocrine disorders may represent the parallel effects of prenatal factors common to the development of both the brain and the reproductive system.

Reproductive endocrine disorders in women with partial seizures of temporal lobe origin.

Of 50 consecutive women with partial seizures of temporal lobe origin (temporal lobe epilepsy [TLE]) evaluated for reproductive dysfunction, 28 had menstrual problems. Of those, 19 had reproductive endocrine disorders. Polycystic ovarian syndrome and hypogonadotropic hypogonadism occurred significantly more often in women with TLE than in the general female population. Polycystic ovarian syndrome was associated with predominantly left-sided lateralization of interictal epileptic discharges; hypogonadotropic hypogonadism was more commonly found with right-sided discharges. Hyposexuality occurred more often in women with predominantly right-sided interictal epileptic discharges and was associated with low serum luteinizing hormone levels. There are several possible interpretations: epileptic discharges in medial temporal limbic structures may disrupt hypothalamic regulation of pituitary gonadotropin secretion; anovulatory cycles of reproductive endocrine disorders may promote the development of epileptic discharges; and TLE and some associated reproductive endocrine disorders may represent the parallel effects of prenatal factors common to the development of the brain and the reproductive system.

Neurophysiologic correlates of implicit face memory in intracranial visual evoked potentials.

Visual evoked potentials were recorded in the amygdala, hippocampus, mid- and inferotemporal cortex, orbitofrontal cortex, and lateral frontal cortex of seven epileptic patients while they were engaged in a difficult task requiring the discrimination between repeated and nonrepeated faces. The explicit recognition of previously seen faces was at chance levels, as measured by the accuracy of push-button responses. Nevertheless, all subjects showed clear-cut differential evoked responses to repeated versus nonrepeated faces, indicating implicit encoding of the distinction between the two types of stimuli. Differential responses were more frequent in neocortical recording sites (especially in the mid- and inferotemporal leads) than in limbic recording sites such as the amygdala and hippocampus. The authors conclude that implicit encoding processes are modulated by neocortical visual association areas of the temporal lobes.

Abnormal pulsatile secretion of luteinizing hormone in men with epilepsy: relationship to laterality and nature of paroxysmal discharges.

We compared the pulsatile secretion of luteinizing hormone (LH) between 13 men with clinically and electrographically documented temporal lobe seizures and 8 age-matched controls. Serum for LH measurement was drawn every 15 minutes during 8 hours of EEG telemetry in both groups. The 2 groups did not differ significantly in average mean baseline LH secretion, total LH secretion, or average pulse amplitude. The group with seizures, however, showed a significantly greater (p less than 0.05) variability of baseline LH secretion and pulse frequency. Among the men with unilateral paroxysmal EEG findings, pulse frequency was significantly greater (p = 0.05) with right epileptiform discharges or left slowing (6.4 +/- 0.4) than with left epileptiform discharges or right slowing (3.0 +/- 1.3). The relationship of pulse frequency to the nature and laterality of paroxysmal discharges makes it unlikely that endocrine abnormalities can be attributed to medication alone and strengthens the notion that temporal lobe epileptiform discharges may disrupt hypothalamic regulation of pituitary secretion.

Paraneoplastic temporal lobe epilepsy with testicular neoplasm and atypical amnesia.

We report a patient who, at age 38, presented with temporal lobe seizures and an atypical memory disorder 3 years before the discovery of a testicular tumor. Detailed neuropsychological testing revealed a relatively isolated amnestic syndrome. The amnesia was atypical as the patient could retain information for hour-long periods, only to lose it later. Serologic studies revealed the presence of a circulating autoantibody that demonstrated an unusual affinity for the nucleolus of cerebral cortical neurons. Western blot analysis of cortical neurons revealed that this antibody reacted with proteins different from other previously identified paraneoplastic neurologic antigens (Hu, Yo, Ri). We believe this to be a case of paraneoplastic limbic encephalitis secondary to the testicular tumor. This patient presents unique characteristics with respect to the mode of presentation, features of the amnesia, and the presence of a circulating antibody with an unusual reactivity pattern.

Visual neglect during intracarotid amobarbital testing.

The unilateral suppression of hemispheric function by sodium amobarbital may result in hemispatial visual neglect, as measured by performance on a random letter cancellation task. Our study not only investigates this hypothesis but also attempts to identify more precisely the anatomic locus of control for directed attention to extrapersonal space by correlating scanning performance with EEG activity. Forty-eight consecutive patients with epilepsy underwent preoperative intracarotid amobarbital tests. The results indicated that disruption of scanning and contralateral neglect occurred only after right-hemisphere suppression and seemed specifically related to changes in right frontal lobe EEG activity. This pattern of performance held not only for right-handed subjects, but also for those who were left-handed, and even for those who had right-hemisphere language dominance.

Ictal agraphia: a patient study.

We present a case of "pure" or "apraxic" agraphia, a recognized writing disturbance, caused by intermittent focal seizures from the left posterior parasagittal parieto-occipital region. Pure agraphia has been described in focal lesions or as part of a generalized confusional syndrome. The posterior cerebral vascular territory is the characteristic site for the transient neurologic syndromes associated with cyclosporine toxicity. Our patient was at risk for this complication while recovering from a lung transplant, with elevated cyclosporine levels.

Altered pulsatile secretion of luteinizing hormone in women with epilepsy.

Menstrual disorders and infertility are common among women with epilepsy of temporal lobe origin (TLE). Reproductive endocrine disorders may be the cause. Polycystic ovarian syndrome (PCO) and hypothalamic amenorrhea (hypogonadotropic hypogonadism, HH), in particular, are significantly overrepresented and attributable to hypothalamic dysfunction. We therefore compared the hypothalamic function of 14 women with clinically and electrographically documented TLE with that of eight age-matched normal controls by determining the interictal pulse frequency and amplitude of luteinizing hormone (LH) secretion. Serum for LH measurement was drawn every 15 minutes from 8 AM to 4 PM in both groups. LH pulse frequency values were significantly more variable (p < 0.05) and lower (p < 0.05) among women with TLE than among controls. Women with left temporal EEG foci showed a trend toward higher pulse frequencies compared to women with right foci (p = 0.05 to 0.10). Among five women with reproductive endocrine disorders, the three with PCO had left-sided foci and average LH pulse frequency two times higher than that of the two women with HH, who had right-sided foci. Eight reproductively normal, medically treated women with TLE had significantly lower LH pulse frequencies than did the one reproductively normal, untreated woman with TLE (p < 0.05) and the eight normal controls (p < 0.001). These findings suggest that LH pulse frequencies in women with TLE may be influenced by the laterality of the epileptic focus, the reproductive endocrine status, and the use of antiseizure medications.

Postictal heart rate oscillations in partial epilepsy.

We report postictal heart rate oscillations in a heterogeneous group of patients with partial epilepsy. This pattern is marked by the appearance of transient but prominent low-frequency heart rate oscillations (0.01 to 0.1 Hz) immediately after 5 of 11 seizures recorded in 5 patients. This finding may be a marker of neuroautonomic instability and, therefore, may have implications for understanding perturbations of heart rate control associated with partial seizures.

EEG-triggered echo-planar functional MRI in epilepsy.

We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.

EEG abnormalities in patients with atypical panic attacks.

BACKGROUND: Panic attacks and certain partial seizures have phenomenologic similarities which suggest that they may somehow be related. No evidence of such a relationship, however, was found when the routine EEGs of patients with panic attacks were examined. METHOD: Fifteen subjects with atypical panic attacks who met DSM-III-R criteria for panic disorder agreed to have routine followed by prolonged ambulatory EEG monitoring with sphenoidal electrodes. Fourteen subjects actually underwent monitoring; 1 had a panic attack during premonitoring routine EEG. RESULTS: Focal paroxysmal EEG changes consistent with partial seizure activity occurred during panic attacks in 33% (N = 5) of the 15 subjects; 2 (40%) of the 5 subjects with panic-related EEG changes had normal routine EEGs. Multiple attacks were recorded before panic-related EEG changes were demonstrated in several subjects. CONCLUSION: It may be necessary to monitor the EEG during multiple panic attacks to reveal an association between atypical panic attacks and epileptiform EEG changes.

Seizures in rats treated with kainic acid induce Fos-like immunoreactivity in locus coeruleus.

Kainic acid-triggered seizures (KATS) induce Fos-like immunoreactivity (FLI) in limbic structures, which send efferents to the locus coeruleus (LC). Following KATS, brain stem sections were stained for Fos immunocytochemistry and double immunostained for Fos and dopamine beta-hydroxylase (DBH). KA-treated animals showed significantly greater numbers of FLI neurons in the LC than control animals (p < 0.05). Co-localization of DBH/Fos was observed in 89.7% of the LC neurons in KA-treated animals and in 1.4% of LC neurons in control animals. Thus, KATS heavily induce Fos in DBH-containing neurons in the LC, which are known to project to the hippocampus. However, the role of activation of the LC noradrenergic neurons during KATS is not well understood at this present time.

Evidence for rapid face recognition from human scalp and intracranial electrodes.

It is still generally believed that complex visual analysis is not carried out within the first 100 ms. Here we show that intra- and extracranial visual evoked potentials (VEPs) differentiate previously seen faces from novel faces as early as 50 ms after stimulus onset. EEG was recorded from scalp electrodes in 12 male healthy volunteers (group I) and intracranially from implanted depth electrodes in the temporal and frontal cortex of seven epilepsy patients (group II). Both groups were engaged in a face recognition task. All subjects showed significant differential responses which occurred very early (50-90 ms) and later (190-600 ms). In group II, the early responses were recorded more frequently in the right hemisphere, whereas the late differential VEPs were found in both hemispheres. Both types of VEPs were more frequent in the temporal neocortex, underlining its role as a major contributor to these fast recognition processes.

Increased susceptibility to generalized seizures after immunolesions of the basal forebrain cholinergic neurons in rats.

We investigated whether basal forebrain cholinergic neurons influence the expression of generalized seizures. Animals received intracerebroventricular injections of saporin (lesioned) or saline (controls) and were tested for susceptibility to flurothyl- or pentylenetetrazole-induced seizures. Lesioned rats had significantly shorter latencies to onset of generalized tonic-clonic seizures than controls. Our findings suggest that basal forebrain cholinergic neurons may participate in the modulation of generalized seizures.