Clinical Neuroscience

[CHANGES IN EEG-COMPLEXITY AFTER SUBCORTICAL ISCHEMIC BRAIN DAMAGE]

MOLNÁR Márk, CSUHAJ Roland, HORVÁTH Szabolcs, VASTAGH Ildikó, GAÁL Zsófia Anna, CZIGLER Balázs, BÁLINT Andrea, NAGY Zoltán

MAY 30, 2006

Clinical Neuroscience - 2006;59(05-06)

[Introduction - Complexity analysis of the EEG is a relatively new field in theoretical and cinical electrophysiology. The authors present results of EEG-analysis in a patient with stroke, utilizing the sensitivity of the new procedures with respect to linear and nonlinear synchronization. Participants and methods - The EEG (19 channels) was recorded in a patient with subcortical unilateral ischaemic completed stroke involving the frontoparietal white matter while leaving the cortex intact and in 12 healthy controls in eyes open and in eyes closed conditions. Results - In the patient, increased Omega-complexity was found in slow (delta, theta) and lower alpha frequencies in the side of the stroke and in high frequencies (beta2 in eyes closed, alpha2, beta1 and beta2 in eyes open conditions) in the intact side. Synchronization likelihood was higher in the ischaemic side in the beta2 (eyes closed) and both in the beta1 and beta2 (eyes open) frequencies. Increasing Omega-complexity caused by eyes opening was markedly reduced in the patient in the beta frequencies compared to that seen in the controls. The difference was more conspicuous in the side of the infarct and involved not only the beta but also the alpha frequencies as well. Opening the eyes decreased synchronization likelihood in all frequency bands in the controls and also in the patient except the alpha2, beta1 and beta2 bands in the side of the lesion. Conclusions - The increased Omega-complexity and decreased synchronization likelihood in the slow frequencies in the infarcted side is probably the result of lesioned interneuronal connections lowering the level of cooperation of neuronal systems involved in this type of activity. The increased Omega-complexity and decreased synchronization likelihood caused by eyes opening could not be observed in the beta and alpha frequencies in the side of the lesion, possibly caused by damaged thalamocortical connections.]

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[Out of an average total of 1400 autopsies per year, neuropathological examinations were performed in 477 cases between 1997 and 1999 to investigate the incidence of dementias. The majority of the studied subjects were over 50 years old. Bielschowsky's and/or Gallyas's silver methods and, in some cases, protein tau (MAP) immuncytochemistry and amyloid staining were performed beside routine examination. Pathological changes were found in 212 of the 364 cases studied by the above methods but histological changes associated with dementia were only detected in 167 cases. The various forms of Alzheimer's dementia were also classified by age. The "incipient" form of Alzheimer's disease was verified in 23 cases. Old infarcts of various extensions were found in 42 percent of Alzheimer's dementias. Very mild or age-related degenerative changes were observed in 82 cases among subjects over 50 years old. Of these, eight patients died in their 90s. In some cases (n=38) the number of neuritic plaques dominated over the number of neurofibrillary tangles but a reverse finding also occurred (n=13). Neuronal degeneration was variable and was not always proportional to the number of neurofibrillary tangles. "Simple type of senile atrophy" was defined by the presence of minor or age-related Alzheimer changes and was considered a separate entity. The "incipient" form of Alzheimer's dementia was diagnosed in relatively young individuals where mild Alzheimer changes were found at the neuropathological examination. "Preclinical" Alzheimer's dementia could only be suspected by clinical data and could very rarely be supported by the neuropathological finding of "incipient" form. The ratio of pure Alzheimer’s to vascular dementias cases proved to be 54:41 in this study. The results suggest that dementias are considerably underdiagnosed both in the clinical and pathological practice and that the recently defined "preclinical" and "incipient" forms are very hard to recognize both clinically and pathologically. The neuropathological study of the degenerative, mainly Alzheimer's type, findings in the randomly selected autopsies revealed great variations which raises many questions concerning the normal and pathologic aging of the brain as well as the "incipient" and senile forms of Alzheimer's dementia.]

Clinical Neuroscience

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Clinical Neuroscience

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[SPECTRAL EEG-CHARACTERISTICS OF SUBCORTICAL ISCHEMIC BRAIN LESION - A CASE STUDY]

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[Introduction - Although the EEG-changes caused by ischemic stroke are well known, data of the literature are rather ambiguous. The EEGfindings recorded in a patient with a unilateral subcortical ischemic lesion are evaluated with special emphasis related to the effect of the dynamics caused by eyes opening. Participants and methods - Data recorded from a patient (54 years old male with a completed stroke involving the frontal and parietal subcortical region in the left side) were compared to those of a control group (12 healthy age matched subjects). Absolute and relative frequency spectra, theta/beta quotients, the interaction index characterizing the effect of eyes opening and the symmetry index were calculated from the EEG recorded in eyes closed and eyes open conditions. Data of the patient were compared to those recorded in the control group on the basis of 95% confidance intervals. Results - Irrespective of the recording conditions the predominance of slow activity and the increase of theta/beta quotients were found in the absolute frequency spectra. The increase of beta1 and beta2 frequency bands following eyes opening on the side of the lesion were found to be less obvious than that seen on the intact side and that observed in the control group. With respect to the interaction index related to the side differences caused by eyes opening the change of the beta2 frequency band was found to be the most conspicuous. The symmetry index underscored the predominance of slow (delta, theta, alpha1) frequencies on the lesion side, and that of the fast (beta1, beta2) frequencies on the intact side in both recording conditions. Conclusions - Localized lesion of the white matter without cortical damage can cause the predominance of slow activity and decrease of the fast frequency bands on the side of the lesion which can be shown by the absolute frequency spectra and is revealed by the symmetry index. The lack of functional reactivity of the fast frequencies in the side of the lesion can clearly be seen in the change of relative spectra following eyes opening and on the basis of the calculation of the interaction index reflecting the dynamics of side differences.]

Clinical Neuroscience

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[During mental arithmetic operations working memory playsan important role, but there are only few studies in which anattempt was made to separate this effect from the process ofarithmetics per se. In this study the effects of arithmetic onthe EEG of young adults (14 participants, six of themwomen, mean age 21.57 years, SD: 2.62) was investigatedduring a subtraction task in the θ(4-8 Hz) frequency band.Besides the power density spectrum analysis phasesynchrony based on recently developed graph theoreticalmethods were used and strength of local connections (clustercoefficient; C) and global interconnectedness of network(characteristic path length; L) were determined. Before thearithmetic task passive viewing (control situation) and anumber recognition paradigms were used. During the arith-metic task compared to the control situation significantlyincreasing phase synchrony and C values were found. L wassignificantly shorter (F(2, 26)=818.77, p<0.0001) only dur-ing the arithmetic task: this fact and the former two resultsimply that the network topology shifted towards the “smallworld” direction. Our findings concerning regionaldifferences confirm those reported earlier in the literature:compared to the control condition significant task-relatedincrease was found in C values in the parietal areas [moreexplicitly in the left side, (F(1, 13)=7.2020, p=0.0188)],which probably corresponds to stronger local connectionsand more synchronized (sub)networks. During the task con-dition significantly increased θband power; (F(1,13)=7.9708, p=0.0144) and decreased L values werefound in the left frontal region compared to the right side(F(1, 13)=6.0734, p=0.0284), which can also be interpret-ed as an indicator of optimized network topology ofinformation processing.]

Clinical Neuroscience

Creutzfeldt-Jakob Disease: A single center experience and systemic analysis of cases in Turkey

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We aimed to analyze the clinical, laboratory and neuroimaging findings in patients with sporadic Creutzfeldt-Jakob disease (CJD) in a single center as well as to review other published cases in Turkey. Between January 1st, 2014 and June 31st, 2017, all CJD cases were evaluated based on clinical findings, differential diagnosis, the previous misdiagnosis, electroencephalography (EEG), cerebrospinal fluid and cranial magnetic resonance imaging (MRI) findings in our center. All published cases in Turkey between 2005-2018 were also reviewed. In a total of 13 patients, progressive cognitive decline was the most common presenting symptom. Two patients had a diagnosis of Heidenhain variant, 1 patient had a diagnosis of Oppenheimer-Brownell variant. Seven patients (53.3%) had been misdiagnosed with depression, vascular dementia, normal pressure hydrocephalus or encephalitis. Eleven patients (87%) had typical MRI findings but only 5 of these were present at baseline. Asymmetrical high signal abnormalities on MRI were observed in 4 patients. Five patients (45.4%) had periodic spike wave complexes on EEG, all appeared during the follow-up. There were 74 published cases in Turkey bet­ween 2005 and 2018, with various clinical presentations. CJD has a variety of clinical features in our patient series as well as in cases reported in Turkey. Although progressive cognitive decline is the most common presenting symptom, unusual manifestations in early stages of the disease might cause misdiagnosis. Variant forms should be kept in mind in patients with isolated visual or cerebellar symptoms. MRI and EEG should be repeated during follow-up period if the clinical suspicion still exists.