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Results for “Epilepsy, Complex Partial”

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At least 1,315 records · Page 73Linked to original sources
PubMed1996

Human brain GABA levels rise after initiation of vigabatrin therapy but fail to rise further with increasing dose.

Using 1H spectroscopy, we measured occipital lobe GABA levels serially in 18 patients enrolled in an ongoing open label trial of vigabatrin. Brain GABA levels were elevated twofold in patients taking vigabatrin (3 to 4 g/d) compared with nonepileptic subjects. Serial measurements suggested that brain GABA rose in proportion to vigabatrin dose up to 3 g/d. Doubling the dose from 3 to 6 g/d failed to increase brain GABA further. Serial measurements on three patients taking 6 g/d showed a gradual decrease in brain GABA in two patients over 1 to 2 years of treatment. These observations suggest that GABA synthesis may decrease at high GABA levels.

Adult↗
PubMed1999

Proper name anomia after left temporal lobectomy: a patient study.

A patient with a selective deficit in retrieving proper names after left temporal lobectomy is reported. He showed proper name anomia in conversation, in response to photographs, and in verbal descriptions, despite being able to provide semantic information about the people he was unable to name. This report provides evidence that the rostral part of the left temporal lobe plays a crucial role in processing proper names without involvement of other verbal functions.

Anomia↗
PubMed1999

Visual dysfunction in patients receiving vigabatrin: clinical and electrophysiologic findings.

BACKGROUND: Vigabatrin is an antiepileptic drug that, although relatively well tolerated, is associated with visual field constriction and other visual disturbances of unclear origin. METHODS: We performed a complete neuroophthalmologic examination and electrophysiologic studies on 39 patients receiving vigabatrin and on 11 control patients. RESULTS: Nearly 50% of patients receiving vigabatrin had constricted visual fields compared with control patients. Some of the vigabatrin patients also had reduced visual acuity and abnormal color vision. In addition, most vigabatrin patients had abnormal electroretinographic results, the severity of which correlated strongly with the degree of visual field constriction. CONCLUSIONS: Vigabatrin can cause electrophysiologic evidence of retinal dysfunction and clinically detectable disturbances of visual sensory function.

Adult↗
PubMed2001

Electrocorticographic gamma activity during word production in spoken and sign language.

OBJECTIVE: To investigate the functional-neuroanatomic substrates of word production using signed versus spoken language. METHODS: The authors studied single-word processing with varying input and output modalities in a 38-year-old woman with normal hearing and speech who had become proficient in sign language 8 years before developing intractable epilepsy. Subdural electrocorticography (ECoG) was performed during picture naming and word reading (visual inputs) and word repetition (auditory inputs); these tasks were repeated with speech and with sign language responses. Cortical activation was indexed by event-related power augmentation in the 80- to 100-Hz gamma band, and was compared with general principles of functional anatomy and with subject-specific maps of the same or similar tasks using electrical cortical stimulation (ECS). RESULTS: Speech outputs activated tongue regions of the sensorimotor cortex, and sign outputs activated hand regions. In addition, signed word production activated parietal regions that were not activated by spoken word production. Posterior superior temporal gyrus was activated earliest and to the greatest extent during auditory word repetition, and the basal temporal-occipital cortex was activated similarly during naming and reading, reflecting the different modalities of input processing. With few exceptions, topographic patterns of ECoG gamma were consistent with ECS maps of the same or similar language tasks. CONCLUSIONS: Spoken and signed word production activated many of the same cortical regions, particularly those processing auditory and visual inputs; however, they activated different regions of sensorimotor cortex, and signing activated parietal cortex more than did speech. This study illustrates the utility of electrocorticographic gamma for studying the neuroanatomy and processing dynamics of human language.

Brain Mapping↗
PubMed1995

Potential contribution of bilateral magnetic source imaging to the evaluation of epilepsy surgery candidates.

The current procedures that are used to evaluate candidates for epilepsy surgery are time-consuming, costly, and often invasive. Magnetic source imaging (MSI), the combination of magnetoencephalography and anatomic imaging modalities, has shown promise as an efficient noninvasive means of localizing and characterizing seizure sources for possible resection. However, MSI has been limited by the inability to conduct simultaneous bilateral monitoring. In this study, a newly developed dual-magnetometer system was employed to record bilaterally the interictal activity in 30 candidates for epilepsy surgery. A standard monitoring protocol that included concurrent electroencephalographic recording and required a 2- to 3-hour examination period for each patient was developed. As a first step in a series of studies, the resultant MSI indications were compared with the information available from standard magnetic resonance imaging and concurrent electroencephalographic results. In 83% of the cases, this MSI protocol provided new information about the location of interictal epileptic activity that could be directive for subsequent patient care. Based on these results, it seems that MSI may become a cost-effective early step in epilepsy surgery evaluation. To continue the development on this basis, a study intended to validate the accuracy of MSI indicated by comparison with invasive electroencephalography has been initiated.

Adolescent↗
PubMed2005

Cortical sites critical for speech discrimination in normal and impaired listeners.

We used statistical modeling to investigate variability in the cortical auditory representations of 24 normal-hearing epilepsy patients undergoing electrocortical stimulation mapping (ESM). Patients were identified as normal or impaired listeners based on recognition accuracy for acoustically filtered words used to simulate everyday listening conditions. The experimental ESM task was a binary (same-different) auditory syllable discrimination paradigm that both listener groups performed accurately at baseline. Template mixture modeling of speech discrimination deficits during ESM showed larger and more variable cortical distributions for impaired listeners than normal listeners, despite comparable behavioral performances. These results demonstrate that individual differences in speech recognition abilities are reflected in the underlying cortical representations.

Adolescent↗
PubMed2005

Responses of human anterior cingulate cortex microdomains to error detection, conflict monitoring, stimulus-response mapping, familiarity, and orienting.

Human anterior cingulate cortex (ACC) activity modulation has been observed in numerous tasks, consistent with a wide variety of functions. However, previous recordings have not had sufficient spatial resolution to determine whether microdomains (approximately one to two columns) are involved in multiple tasks, how activity is distributed across cortical layers, or indeed whether modulation reflected neuronal excitation, inhibition, or both. In this study, linear arrays of 24 microelectrodes were used to estimate population synaptic currents and neuronal firing in different layers of ACC during simple/choice reaction time, delayed word recognition, rhyming, auditory oddball, and cued conditional letter-discrimination tasks. Responses to all tasks, with differential responses to errors, familiarity, difficulty, and orienting, were recorded in single microdomains. The strongest responses occurred approximately 300-800 ms after stimulus onset and were usually a current source with inhibited firing, strongly suggesting active inhibition in superficial layers during the behavioral response period. This was usually followed by a sink from approximately 800 to 1400 ms, consistent with postresponse rebound activation. Transient phase locking of task-related theta activity in superficial cingulate layers suggested extended interactions with medial and lateral frontal and temporal sites. These data suggest that each anterior cingulate microdomain participates in a multilobar cortical network after behavioral responses in a variety of tasks.

Acoustic Stimulation↗
PubMed2004

Material-specific recognition memory deficits elicited by unilateral hippocampal electrical stimulation.

Although the medial temporal lobe is thought to be critical for recognition memory (RM), the specific role of the hippocampus in RM remains uncertain. We investigated the effects of transient unilateral hippocampal electrical stimulation (ES), subthreshold for afterdischarge, on delayed item RM in epilepsy patients implanted with bilateral hippocampal depth electrodes. RM was assessed using a novel computer-controlled test paradigm in which ES to left or right hippocampus was either absent (baseline) or synchronized with item presentation. Subsequent yes-no RM performance revealed a double dissociation between material-specific RM and the lateralization of ES. Left hippocampal ES produced word RM deficits, whereas right hippocampal ES produced face RM deficits. Our findings provide the first demonstration in humans that selective unilateral stimulation-induced hippocampal disruption is sufficient to produce impairments on delayed RM tasks and provide support for the material-specific laterality of hippocampal function with respect to RM.

Adult↗