Electroencephalography and clinical neurophysiology最新文献

Objectives: The purpose of this study was to research whether or not video games may induce paroxysmal discharges (PD) in different groups of patients.

Methods: One hundred and fifteen subjects from 5 different French laboratories were studied: 33 had seizures exclusively under visual stimuli, 42 had both photogenic seizures and spontaneous seizures occuring independently, and 40 had non-photogenic seizures. The same protocol which included one TV sequence, 3 sequences of video games selected on particular criteria (pattern, luminosity and nature of the scene), were presented at different distances from the TV screen at 50 and 100 Hz.

Results: Among the factors provoking paroxysmal discharges (PD) some seem crucial: the frequency of the TV screen (the 100 Hz screen was significantly safer than 50 Hz), the distance from the screen (1 m safer than 50 cm), and, particularly for the 50 Hz screen, the specific pattern of the images and the act of playing.

Conclusions: Video games are ineffective for subjects known as having a non-photosensitive epilepsy, but may induce PD on subjects known as photosensitive even when intermittent light stimulation (ILS) is not effective. These results based on a different approach than in other publications confirm data which were suggested by the literature, and suggest that 100 Hz TV screens should be recommended to patients with TV-induced attacks.

Objective: Periodic lateralized epileptiform discharges have been recognized for 33 years; however, little is known about the underlying mechanism causing periodic discharges. The following case provides an opportunity to study PLEDs in a patient with precisely localized subcortical grey matter lesions.

Methods: Routine EEGs and overnight polysomnography were performed on the study patient. Standard 10–20 electrode positions were used, as well as EOG and chin EMG for polysomnography.

Results: The study patient was a 39-year-old woman with severe left caudate nucleus atrophy and right hemi-dystonia. She had left ventral-lateral (VL) thalamotomies in 1989 and 1991, pallidotomy in 1992, and centromedian thalamic stimulator implantation in 1997. EEGs prior to surgical intervention demonstrated left hemisphere PLEDs during sleep. Following CM nucleus stimulatory implantation, the patient had overnight polsomnography. EEG during wakefulness and REM sleep was normal. With stages I–IV sleep left hemisphere PLEDs at 1–2 Hz were seen with fronto-temporal predominance. Sleep spindles were present bilaterally. There was no history of seizures, before or after surgery.

Conclusions: The finding of PLEDs confined to synchronized sleep which were not affected by surgical manipulation of the motor basal ganglia circuit suggests a role of the associative basal ganglia circuit in the generation of periodic phenomenon.

Objective: Recent studies indicate that people can learn to control the amplitude of mu or beta rhythms in the EEG recorded from the scalp over sensorimotor cortex and can use that control to move a cursor to targets on the computer screen. While subjects do not move during performance, it is possible that inapparent or unconscious muscle contractions contribute to the changes in the mu and beta rhythm activity responsible for cursor movement. We evaluated this possibility.

Methods: EMG was recorded from 10 distal limb muscle groups while five trained subjects used mu or beta rhythms to move a cursor to targets at the bottom or top edge of a computer screen.

Results: EMG activity was very low during performance, averaging 4.0±4.4% (SD) of maximum voluntary contraction. Most important, the correlation, measured as r², between target position and EMG activity averaged only 0.01±0.02, much lower than the correlation between target position and the EEG activity that controlled cursor movement, which averaged 0.39±0.18.

Conclusions: These results strongly support the conclusion that EEG-based cursor control does no depend on concurrent muscle activity. EEG-based communication and control might provide a new augmentative communication option for those with severe motor disabilities.

Objective: In the field of EOG correction, discrepancies have been found between the propagation rates for different types and frequencies of eye movement. This study attempted to determine whether these differences could be explained by the affect of EOG magnitude on the correction procedure.

Methods: Experiment 1 utilized simulated data to determine whether the combination of EOG magnitude and other forms of interference distorted the estimation of the propagation coefficients ($\text{B}$s). Experiment 2 used real data to determine if the patterns obtained in Expt. 1 were apparent in real data.

Results: Matched t tests found that simulated low power EOG produced inflated $\text{B}$s as a function of interference in Expt. 1. Experiment 2 found the same relationship between $\text{B}$ and EOG magnitude as with the simulations.

Conclusions: The findings are consistent with the thesis that eye movement related fields propagate similarly for a range of EOG types and frequencies, suggesting that the $\text{B}$ differences reported in the literature are artifactual, and indicating the need for a new correction procedure.

We demonstrate clinical data and findings of MRI, transcranial Doppler (TCD), single photon emission computed tomography (SPECT) and electroencephalography (EEG) in an 8 month follow-up study of a 15 year old girl who developed focal status epilepticus with sensory and visual illusions. EEG showed right temporal and occipital seizure activity and attenuation of the alpha activity with right predominance. MRI showed a right temporo-parietal hyper signal on the T2 weighted images involving the cortex with sulcal effacement. MRI-angiography suggested insufficient flow in the right transverse sinus. TCD detected an elevated flow velocity in the ipsilateral middle cerebral artery during status epilepticus, corresponding to an increased perfusion of the epileptic area revealed by SPECT. After normalization of the TCD finding, the MRI detected persistent cortical abnormality beyond the 70th day after admission. MRI normalized on the 103rd day of follow-up. Serial EEG frequency analysis demonstrated the recovery of alpha peak frequency on the left side, but the attenuation of rhythmic signals remained persistent on the right. In our case, the restitution of postictal EEG lag behind the consolidation of MRI signal abnormality.

Objective: There has been considerable discussion regarding the accuracy of topographic electroencephalographic (EEG) maps for assessing local cerebral function. We performed this study to test the accuracy of EEG mapping by examining the association between electrical activity and the perfusion under each electrode as another measure of local cerebral function.

Methods: EEG mapping was performed simultaneously with H₂¹⁵O positron emission tomography (PET) scanning in 6 normal adult subjects, both at rest and during a simple motor task. EEG data were processed using 3 different montages; two EEG power measures (absolute and relative power) were examined.

Results: Relative power had much stronger associations with perfusion than did absolute power. In addition, calculating power for bipolar electrode pairs and averaging power over electrode pairs sharing a common electrode yielded stronger associations with perfusion than data from referential or single source montages.

Conclusions: These findings indicate (1) that topographic EEG mapping can accurately reflect local brain function in a way that is comparable to other methods, and (2) that the choice of EEG measure and montage have a significant influence on the degree with which maps reflect this local activity and function.

Objectives: The present study aimed at offering a standardized database for cyclic alternating pattern (CAP) parameters across representative ages of life.

Methods: CAP parameters were quantified in 40 healthy sleepers and polygraphically investigated in a partially sound-proof recording chamber under a standard laboratory setting. Four age groups were investigated (teenagers: 10–19 years; young adults: 20–39 years; middle-aged: 40–59 years; elderly: 60 years). Each group included 10 subjects (5 males and 5 females). Nocturnal recordings were accomplished after adaptation to the sleep laboratory that also served to rule out the presence of sleep-related disorders. The study indicated that CAP is a natural phenomenon of NREM sleep, with specific age-related characteristics across the life cycle.

Results: CAP rate in NREM sleep, defined as the percentage ratio of total CAP time to total NREM sleep time, showed a U-shape profile with minimum in young adults (31.9%), maximum in the elderly group (55.3%), and intermediate values in teenagers (43.4%) and in middle-aged subjects (37.5%). The longest duration of CAP cycles was found among the older subjects (31 s). The highest amounts of subtypes A1 were identified in teenagers (n=261), while the highest amounts of A2 and A3 subtypes occurred in the elderly group (n=183). Across the ages, the level of arousal mostly fluctuated in stages 1 and 3, whereas stage 4 emerged as the most stable NREM stage. Overall, stage 2 better reflected the CAP values referred to as total NREM sleep.

Conclusions: The periodic arousal fluctuations reflected by CAP are a natural phenomenon of NREM sleep with specific age-related variations across the life cycle.

Nasal continuous positive airway pressure (CPAP) therapy is usually effective in the treatment of obstructive sleep apnea (OSA), reversing the excessive daytime sleepiness associated with OSA. We investigated how polysomnography and maintenance of wakefulness test (MWT) predicted response to CPAP therapy in 10 patients with obstructive sleep apnea and 10 healthy controls. After a full polysomnography and MWT the patients were started on CPAP. MWT was repeated to quantify the treatment effect. Oxygen desaturation index and the percentage of slow wave sleep were the best predictors for baseline S1 latency in MWT. Baseline S1 latency in the MWT was the most important determinant of improvement in MWT S1 latency after CPAP, followed by the latency to 10 min of continuous nocturnal sleep, arousal index and CPAP use. We suggest that in mild sleep apnea, knowledge of sleep architecture is not necessary before deciding whether or not to initiate CPAP treatment.

Objective: In the field of EOG correction, discrepancies have been found between the propagation rates for different types and frequencies of eye movement. However, Croft and Barry demonstrated that these differences can be explained by the affect of EOG magnitude on the correction procedure (Croft, R.J. and Barry, R.J. EOG correction: a new perspective. Electroenceph. clin. Neurophysiol., 1998, 107: 387–394). This study utilized a new `aligned-artifact average' technique (AAA) to examine whether propagation is constant across eye movement types and frequencies, and tested the AAA as an EOG correction tool.

Methods: Two experiments manipulated interference levels in real data sets to determine if interference affected propagation coefficients ($\text{B}$s). The third tested real data for the effect of forward propagation of eye movement related neural potentials on $\text{B}$s, and the fourth utilized computer simulations to assess the effectiveness of the new AAA correction procedure.

Results: Interference was found to inflate $\text{B}$ at low EOG amplitude, and its removal removed $\text{B}$ variation and inflation. The forward propagation of eye movement related neural potentials had very little effect on $\text{B}$. The AAA procedure produced near perfect corrections of the simulated data, superior to a comparison method.

Conclusions: EOG propagation is constant across eye movement types and frequencies, and thus only one correction coefficient should be calculated and applied to data. The AAA method provides a more accurate correction and makes possible, for the first time, the adequate correction of posterior sites.