Journal of Clinical EEG & Neuroscience, July, 2006
Table of Contents
Alzheimer’s disease (AD) is associated with considerably decreased cerebral blood flow (CBF) thought to be secondary, since dead neurons do not need oxygen and glucose. This view, however, needs to be critically re-examined.
The role of CBF in AD was submitted to a thorough analysis, raising the question: “Is there really a lack of demand in the presence of undisturbed blood supply?”
CBF decline is present in AD while the number of affected CNS systems is still quite small. The step-by-step evolution of AD mirrors a brain that progressively becomes ischemic. Areas related to memory function (hippocampus, temporal lobe cortex and vicinity) are bound to suffer first because of their particularly vulnerable blood supply.
This is the scenario of a disorder caused by primary and not by secondary CBF deficiency — a deficiency perhaps attributable to the upright gait of homo sapiens. This new approach also opens new avenues for treatment and prevention, which will be briefly discussed.
Currently available digital EEG equipment provides considerably greater opportunities for clinical data analysis than is generally appreciated especially when appropriate software is used. Data from 7 different laboratories that had been obtained for routine diagnostic evaluations on 7 different EEG instruments and stored on compact disks were investigated. Since the instruments do not filter the data at input, ultra slow activity down to 0.01 Hz is currently being recorded but the attenuation factor is instrument dependent. Nevertheless, relevant clinical information is potentially available in these data and needs to be explored. Several examples in regard to epilepsy are presented. Determination of seizure onset may depend on the frequencies that are examined.
The use of appropriate filter settings and viewing windows for the clinical question to be answered is stressed. Differentiation between simple and complex spike wave discharges, as well as spread of spikes, can readily be achieved by expanding the time base to 1 or 2 seconds and placing a cursor on the peak of the negative spike. Latencies in the millisecond range can then become apparent.
EEGs co-registered with MEG should be evaluated with the same software in order to allow an adequate assessment of the similarities and differences between electrical and magnetic activity. An example of a comparison of EEG, planar gradiometers and magnetometers for an averaged spike is shown.
A recent study and report in which hyperventilation was used during electroencephalography (EEG) in 6 children with sickle cell disease (SCD) and seizures, without serious complication, prompted a cautionary response regarding the potential risks attending the practice of EEG hyperventilation in SCD patients. Earlier reports of neurological impairment and stroke precipitated by the routine use of hyperventilation in children with SCD are reviewed, the mechanism and management of vascular infarction following hyperventilation are discussed, and readers are reminded of the AEEGS guidelines and contraindications to routine hyperventilation, which include SCD and trait and cerebrovascular disorders. The frequent nonobservance of these guideline recommendations among neurologists, and the need to more widely inform practitioners of the risks of hyperventilation in SCD are discussed.
Benign Childhood Epilepsy With Centro-Temporal Spikes: Quantitative EEG and the Wechsler Intelligence Scale for Children (WISC-III)
Benign childhood epilepsy with centro-temporal spikes (BECTS) is a form of focal idiopathic epilepsy, with seizure remission by the age of 18. Recent studies have suggested that some children with BECTS can suffer from deficits of memory, attention and learning ability and in auditory-verbal and performance sub-tests. On the other hand, alterations in the baseline brain electrical activity determined by using the quantitative electroencephalogram (qEEG) have been described. The objective of this study was to evaluate the absolute and relative powers in the delta, theta, alpha and beta bands of the qEEG in children with BECTS, and their relation to IQ measurements (WISC-III).
Twenty-six 8 to 11-year-old children with BECTS were studied, paired with a control group of healthy children according to age and gender. It was shown that the absolute delta and theta powers were statistically greater in the children with BECTS than in the control group, at almost all the electrodes. In the children with BECTS, a negative correlation (Pearson’s correlation test) was observed at various electrodes between the absolute delta and theta powers and the performance IQ.
These data indicate a possible relationship between maturational disturbance in the brain electrical activity development and the tendency for inferior cognitive performance in children with BECTS.
This report is a 2-year follow-up to a previous study describing positive behavioral changes and a spurt of EEG maturation with theta/alpha neurofeedback (NFB) training in a group of Learning Disabled (LD) children. In a control paired group, treated with placebo, behavioral changes were not observed and the smaller maturational EEG changes observed were easily explained by increased age.
Two years later, the EEG maturational lag in Control Group children increased, reaching abnormally high theta Relative Power values; the absence of positive behavioral changes continued and the neurological diagnosis remained LD. In contrast, after 2 years EEG maturation did continue in children who belonged to the Experimental Group with previous neurofeedback training; this was accompanied by positive behavioral changes, which were reflected in remission of LD symptoms.
We report the first case of an autoimmune thyroid encephalopathy presenting with multifocal motor status epilepticus. A 37-year-old female patient was admitted with multifocal motor seizures intractable to intravenous status epilepticus treatments, asymmetrical quadriparesis, truncal ataxia and continuous semi-rhythmical jerks. Pathological signal alterations were detected in both precentral cortices in MRI examination. Autoimmune thyroiditis was diagnosed after radiological examinations of the thyroid gland and thyroid function tests. Seizures promptly ceased following intravenous steroid treatment. Immunohistochemistry studies showed mild to moderate neuronal staining with the plasma and CSF samples. Remarkably, autoimmune thyroiditis may present with migrating focal motor status epilepticus. We recommend anti-thyroid antibody screening for multifocal motor status epilepticus cases of unspecified cause.
Interactive Effects of Hypertension and Alcohol Dependence on the P300 Event-Related Potential in African-Americans
Although hypertension and alcohol dependence have been linked by epidemiological surveys and clinical observations, their interactive effects on brain function have rarely been tested. The present study involved the recording of P300 event related potentials (ERP) from 106 middle-aged African-American adults assigned to one of four groups: normotensive/nondependent (n = 56), hypertensive/nondependent (n = 11), normotensive/dependent (n = 27), and hypertensive/dependent (n = 12). The numbers of Nicotine Dependence, Major Depressive Disorder, and Conduct Disorder symptoms were specified as covariates within a 2 by 2 factorial design. ERPs were recorded during separate visual and auditory oddball tasks.
The major result was a synergistic effect of hypertension and alcohol dependence on auditory P300 latency: the combination of both factors was associated with greater slowing than the sum of their independent effects. Future studies should continue to examine the potential synergistic effects of alcohol dependence and hypertension with a view toward identifying and reducing neurophysiological decrements and stroke risk among middle-aged patients.
Subacute encephalopathy with seizures in alcoholics (SESA syndrome) is a rare neurologic disorder complicating the chronic abuse of alcohol. This acute or subacute condition is characterized by transient neurologic deficits, seizures and severe lateralized abnormalities on the electroencephalogram (EEG). Our case demonstrates that in SESA syndrome, convulsive (generalized tonic-clonic) and nonconvulsive (complex partial) seizures may coexist.
We describe the case of a 13-year-old boy, in good health, with transient occipital MRI abnormalities just after one generalized seizure and the appearance of macropsia. The EEG showed a 3-5 Hz sub-continuous left occipital activity, with sporadic sharp waves. Macropsia disappeared in 2 years. This case may suggest that the presence of transient MRI abnormalities does not exclude a favorable prognosis.
The mismatch negativity (MMN) component of the event-related potentials reflects the automatic detection mechanism of sound change. MMN is elicited by a neuronal mismatch process between deviant (infrequent) auditory input and the sensory memory trace of the standard (frequent) stimuli. Although many previous studies have investigated MMN to reveal the sensory memory mechanism, the development of memory representation still remains unclear, in particular, the topographical aspect of the trace-development in sensory memory has not been clarified.
We measured the frontal and the temporal MMN components, respectively, when the sound trace was developed as the number of standard stimuli was changed to 1, 3, 5 or 7. In this experiment, the inter-train interval was 15 sec. The stimulus train with the different frequency of 800Hz, 900Hz, or 1000Hz was repeatedly presented. Thus, we reduced the influence of the previous train. For the first time, we found not only the enhanced amplitude but also the shortened latency for both MMN components when the number of standard stimuli was increased. These findings indicate that both frontal and temporal MMN components reflect the development of memory trace depending on the number of standard stimuli.
EEG Correlates of Startle Reflex With Reactivity to Eye Opening in Psychiatric Disorders: Preliminary Results
Previous studies have shown alterations of eyeblink reflex in patients with various psychiatric disorders. It has previously been demonstrated by our group that EEG measures of the reactivity to eye opening could effectively predict patient-reported startle response in patients with acute stress reaction.
In our present study, EEG spectral power analysis and eyeblink electrical startle responses were acquired from a total of 39 patients diagnosed with various psychiatric disorders: 7 patients with schizophrenia, 10 patients with major depressive disorder (MDD), 10 patients with panic disorder, 5 patients with posttraumatic stress disorder (PTSD) and 7 patients with generalized anxiety disorder (GAD). EEG percent power data of each frequency band (delta, theta, alpha, beta) obtained from the 19 leads under open or closed eyelid conditions were used to calculate the arithmetical difference between eyes-open and eyes-closed states as representative of “EEG reactivity to eye opening.” Data was analyzed separately for each diagnostic group.
For all of the disorders, right-sided R2c (contralateral secondary component) latency was the single eyeblink startle measure that was found to be significantly correlated with EEG reactivity to eye opening. The correlation was most significant for right temporal theta frequency in schizophrenia, right temporal theta frequency in MDD, left central beta frequency in panic disorder, left parietotemporal delta frequency in PTSD and right occipital alpha frequency in GAD. Findings showed a newly identified pattern that has potential scientific and clinical value with respect to psychiatric medicine.
Similar or Disparate Brain Patterns? The Intra-Personal EEG Variability of Three Women With Multiple Personality Disorder
Quantitative EEG was used to assess the intra-personal variability of brain electrical activity for 3 women diagnosed with Multiple Personality Disorder (MPD). Two separate control groups (within-subject and between-subject) were used to test the hypothesis that the intra-personal EEG variability between 2 alters would be less than the interpersonal EEG variability between 2 controls, and similar to the intra-personal EEG variability of a single personality. This hypothesis was partially supported. In general, the 2 EEG records of a MPD subject (alter 1 vs. alter 2) were more different from one another than the 2 EEG records of a single control, but less different from one another than the EEG records of 2 separate controls. Most of the EEG variability between alters involved beta activity in the frontal and temporal lobes.
Somatosensory evoked potentials elicited by trigeminal nerve stimulation (TSEPs) allow the study of the trigeminal system, its peripheral to its central portion. As a routine clinical testing procedure, however, this method has not yet received greater attention and still has to wait to become a part of the diagnostic workup in multiple sclerosis (MS).
The motor threshold is an important parameter in selecting the treatment intensity of patients undergoing transcranial magnetic stimulation. The large variance in magnitude of motor evoked responses has forced clinicians to perform many trials and average the results to find a repeatable value for motor threshold. Our objective is to investigate the source of the variance in amplitude.