The EEG Split Alpha Peak: Phenomenological Origins and Methodological Aspects of Detection and Evaluation.

Electroencephalographic (EEG) patterns were analyzed in a group of ambulatory patients who ranged in age and sex using spectral analysis as well as Directed Transfer Function, a method used to evaluate functional brain connectivity. We tested the impact of window size and choice of reference electrode on the identification of two or more peaks with close frequencies in the spectral power distribution, so called "split alpha." Together with the connectivity analysis, examination of spatiotemporal maps showing the distribution of amplitudes of EEG patterns allowed for better explanation of the mechanisms underlying the generation of split alpha peaks. It was demonstrated that the split alpha spectrum can be generated by two or more independent and interconnected alpha wave generators located in different regions of the cerebral cortex, but not necessarily in the occipital cortex. We also demonstrated the importance of appropriate reference electrode choice during signal recording. In addition, results obtained using the original data were compared with results obtained using re-referenced data, using average reference electrode and reference electrode standardization techniques.

Differentiating Stroke and Seizure in Acute Setting-Perfusion Computed Tomography?

BACKGROUND: Perfusion computed tomography (PCT) is part of acute stroke protocol in many hospitals; however, its clinical utility is still being disputed. Beyond its use in core and penumbra estimation, there is also a question about PCT role in stroke mimics diagnosis. Case series or small, retrospective studies showed equivocal results. This is the first published prospective, comparative study on PCT in differentiating stroke and seizure in acute setting. METHODS: Patients with acute focal neurologic deficits and without acute ischemic lesions on routine CT underwent PCT and electroencephalography (EEG) within 12 hours after symptom onset. Perfusion parameters were set up as asymmetry indices for corresponding regions of brain hemispheres. EEG findings were assigned to 1 of 5 classes. Neurologic examination was performed using the National Institutes of Health Stroke Scale (NIHSS). Follow-up noncontrast computed tomography was performed on the third day after symptom onset. If no CT changes appeared, magnetic resonance diffusion-weighted imaging was conducted. RESULTS: Final diagnosis was hemispheric ischemic stroke in 17 patients and focal neurologic deficits in the course of seizures (post- and intraictally) in 12 patients. Those groups were significantly different only in one single PCT parameter-time to peak (TTP)-in the lateral part of the middle cerebral artery territory. Analyzed groups were not significantly different in the NIHSS scores and the EEG evaluation. CONCLUSIONS: TTP may stay relatively when seizure is a cause of focal neurologic deficits, but not stroke. Further, large, prospective studies are necessary to verify the results.

[ln search of the sharp wave of epileptic nature]. / W poszukiwaniu fali ostrej o charakterze padaczkowym.

INTRODUCTION: Proper identification of the EEG patterns is the basic stage of objective evaluation of EEG records. AIM: This paper is concentrated on the usefulness of contemporary analytical methods in rational evaluation of the distribution of brain electrical potentials recorded in routine, 10-20 system of electrode placement. MATERIAL AND METHODS: The paper illustrates results of analysis of the EEG records in a person with suspicion of existence of the state of nonconvulsive status epilepticus. The EEG was recorded using sampling frequency 250 Hz, with time constant 0.3 s, low pass filter 70 Hz and notch filter on. RESULTS AND CONCLUSIONS: The results illustrate advantages of the methods of imaging distribution of the brain electrical potentials during evaluation of EEG records as well as possible limitations resulting from the difficulties in obtaining reasonable basic set of data representing true spatial distribution of EEG patterns in basic montage.

Automatic detection and analysis of the EEG sharp wave-slow wave patterns evoked by fluorinated inhalation anesthetics.

OBJECTIVE: The aim of this study was to develop a method for the automatic detection of sharp wave-slow wave (SWSW) patterns evoked in EEG by volatile anesthetics and to identify the patterns' characteristics. METHODS: The proposed method consisted in the k-NN classification with a reference set obtained using expert knowledge, the morphology of the EEG patterns and the condition for their synchronization. The decision rules were constructed and evaluated using 24h EEG records in ten patients. RESULTS: The sensitivity, specificity and selectivity of the method were 0.88 ± 0.10, 0.81 ± 0.13 and 0.42 ± 0.16, respectively. SWSW patterns' recruitment was strictly dependent on anesthetic concentration. SWSW patterns evoked by different types of anesthetics expressed different characteristics. CONCLUSIONS: Synchronization criterion and adequately selected morphological features of "slow wave" were sufficient to achieve the high sensitivity and specificity of the method. SIGNIFICANCE: The monitoring of SWSW patterns is important in view of possible side effects of volatile anesthetics. The analysis of SWSW patterns' recruitment and morphology could be helpful in the diagnosis of the anesthesia effects on the CNS.

[EEG paroxysmal patterns: problems of identification and interpretation]. / Problemy identyfikacji i kwalifikacji zjawisk o charakterze napadowym wystepujacych we wzorze czynnosci bioelektrycznej osrodkowego ukladu nerwowego.

This paper is a review of theoretical and methodological problems encountered in the process of evaluation of EEG records displaying patterns of paroxysmal activity. Results of EEG analysis are presented, including results of application of a new computer program enabling transformation of the original EEG record into color spatio-temporal maps of selected EEG samples, presenting information basic for defining final conclusions and of particular importance in case of documenting existence of epileptiform discharges.

[Analysis of causes for falls in people with Parkinson's disease]. / Analiza przyczyn upadków u osób z choroba Parkinsona.

Falls in Parkinson's disease may pose a significant threat for patients. This is not only a clinical problem, but also an economic one. The effects of falls may cause deterioration of the quality of life for both patients and their caretakers. The causes of falls are not clinically uniform: the falls are caused by various factors and require a differential diagnosis. The purpose of this paper is to analyse the above mentioned causes, as well as to draw clinicians' attention to the possibility of effective therapy for certain disorders that cause such falls in patients with Parkinson's disease. 51 patients with recognized Parkinson's disease were examined, including 25 persons who reported falls that had occurred within the past 6 months and 26 persons who had no falls. In both groups there were patients with different types of the disease (tremulous, akinetic-hipertonic and mixed). The clinical status of the patients was assessed using the Hoehn and Yahr scale. In each patient Schellong test and EEG examinations were performed. It has been established that the occurrence of falls is related to the duration of the disease (on average 9.6 years in the group with falls versus 6.2 years in the group without falls) and the daily levodopa dosage (on average 806.0 mg in the group with falls versus 499.0 mg in the group without falls). The proportion of patients with abnormalities in the EEG (revealed mainly as slowing of EEG background activity) was notably higher in the group with falls. The comparison of such groups from the point of view of sex, age, stage of the disease and the occurrence of asymptomatic orthostatic hypotension did not reveal any statistically significant differences. The analysis of the causes of falls in the examined patients revealed that in 8 cases they fell due to unstable posture, 4--due to freezing or festination, 1--due to symptomatic orthostatic hypotension, 1--due to co-existing neurological disorders, 2--due to the heart arrhythmia (requiring implantation of pacemaker), in 8 persons--due to toppling falls and in 1 patients the falls could not be classified.