[Intracerebral steal after acetazolamide administration]. / Intracerebralis steal jelenség acetazolamidterhelés alatt.

Occlusion or high grade stenosis of the internal carotid artery may be asymptomatic depending on the collateral patterns in the circle of Willis and the reserve capacity of the microvascular (arteriolar) system. The distensibility of the cerebral arterioles may be described quantitatively by the vasomotor reactivity. We present three patients with severe stenosis of an internal carotid artery associated with more severe stenosis or occlusion of the contralateral internal carotid artery. We continuously measured blood flow velocity in both middle cerebral arteries by transcranial Doppler ultrasound in rest and for 20 minutes after IV administration of 1 g acetazolamide. Arterial blood pressure was determined with tonometry, end-tidal CO2 was determined by a capnometer. In resting condition the anterior communicating artery, the posterior communicating artery and the ophthalmic artery supplied collateral blood flow towards the side of the more severe internal carotid artery disease. Blood flow velocity decreased after acetazolamide administration in all patients in the middle cerebral arteries on the side of the more severe occlusive carotid disease, while increased on the contralateral side. We assume that the exhausted arteriolar system on the more severely affected side was not able to further dilate and the open collateral system could have driven blood towards the other side with preserved reserve capacity. The reduced blood flow velocity in the middle cerebral arteries after acetazolamide may reflect this intracerebral steal phenomenon.

EEG correlates of subcortical optokinetic nystagmus.

OBJECTIVE: Our aim was to reveal the changes of concomitant scalp EEG activity during subcortical (stare-) optokinetic nystagmus (OKN). METHODS: Stare-OKN of 10 subjects was evoked and recorded simultaneously with the EEG. Frequency distribution of OKN-beats was determined in each subject. Power changes of alpha and beta frequency bands of the EEG during OKN stimulation were statistically analysed. RESULTS: During continuous subcortical OKN-the EEG alpha power decreased significantly while beta power increase was not significant. A significant transient alpha power enhancement around the onset of subcortical OKN-clusters was detected. CONCLUSIONS: We found significant changes in the parieto-occipital alpha EEG activity during subcortical OKN. The transient alpha synchronisation at the beginning of each OKN-cluster is a paradox phenomenon which might indicate increased visual attention. SIGNIFICANCE: The present study is the first report investigating EEG changes related to subcortical OKN. Our findings suggest the involvement of cortical mechanisms in the generation of stare-OKN. The results might help in the elucidation of cortico-genicular mechanisms of ocular movements under physiological and pathological conditions.

Delayed beta synchronization after movement of the more affected hand in essential tremor.

To investigate the pathomechanism of parkinsonian tremor (PT) and essential tremor (ET) by studying the correlation between tremor asymmetry and post-movement beta synchronization (PMBS) of the human EEG. We recorded the EEG of 10 patients with ET, 10 patients with Parkinson's disease and 10 controls. Subjects pressed an on-off switch in a self-paced manner with the thumb of their less (T+) and more (T++) tremulous hand. After digitalization of the EEG from the Cz, C3, C4 electrodes the movement reactive beta frequency, its maximum peak power value and its latency triggered to movement offset were determined. In ET tremor intensity did not influence the power of PMBS, however it was significantly delayed after the movement of the more tremulous hand. In Parkinson's disease after the movement of the more tremulous hand PMBS power was decreased, but it was not delayed. In controls the side of movement had no effect on the power and latency of the PMBS. The neuronal mechanisms underlying PMBS generation are differently affected in essential tremor and Parkinson's disease. The increase of PMBS latency after movement of the more affected hand in ET indicates possible cortical mechanisms in essential tremor generation.

[Complex tremor analysis for the differential diagnosis of essential tremor and Parkinson's disease]. / Komplex tremorometria az esszenciális tremor es a Parkinson-szindróma elkülönítésében.

OBJECTIVE: Tremor is the most common movement disorder which is most often either essential or caused by Parkinson's disease. The differentiation of these disorders at the initial stage may be difficult. Objective assessment of the efficacy of tremor medications is only possible by instrumental measurements. The aim of this study was to determine whether the computer assisted tremor analysis system CATSYS 2000 can help in the differentiation of parkinsonian from essential tremor. METHODS: The rhythmicity and maximal frequency of fast alternating hand and finger movements, simple reaction time and postural instability were recorded in healthy controls (n = 18), patients with Parkinson's disease (n = 39) and essential tremor (n = 37). Data were digitally converted and statistically analyzed. RESULTS: Tremor intensity, median frequency and frequency distribution showed characteristic differences in the three groups. Performance in fast alternating movements of hands and fingers were significantly worse in both tremor groups compared to the healthy controls. CONCLUSIONS: The data also indicated that quantitative measurements of tremor parameters must be performed on both sides, because the presence of significant side differences support the diagnosis of Parkinson's disease. The method presented can be used to objectively analyze tremor and performance in rhythmic movements. The results show that it helps to differentiate parkinsonian from essential tremor as well as to predict disease course and the effectiveness of therapy. Multivariate statistical analysis of tremor and movement performance also provides an opportunity to study the pathogenesis of human tremor.

Movement-related beta responses in essential tremor and Parkinson's disease.

OBJECTIVE: To investigate the pathomechanism of essential (ET) and parkinsonian tremor (PT) by studying the correlation between tremor severity and movement-related beta rhythm changes of the human electroencephalogram. PATIENTS AND METHODS: We recorded the electroencephalogram of 10 patients with essential tremor, 10 with Parkinsonian tremor and 10 controls. In a preliminary session we determined the side with lower and higher tremor intensity (T+, T++ respectively), using accelerometry. Subjects pressed an on-off switch in a self-paced manner with left and right thumb. After digitalization of the EEG from Cz, C3, C4 electrodes, the movement reactive beta frequency (MRBF), its minimum/maximum peak power values and their latencies triggered to movement offset were determined. RESULTS: The time course and amplitude of movement related beta desynchronization (ERD) were similar in each group regardless of tremor intensity. In ET tremor severity did not influence post-movement beta synchronization (PMBS) amplitude (PMBS(ET+) = 100.98 +/- 48.874%, PMBS(ET++) = 135.1 +/- 92.87%; p = 0.231), however it was significantly delayed after the movement of the more tremulous hand (latPMBS(ET+) = 1.26 +/- 0.566 s, latPMBS(ET++) = 1.57 +/- 0.565 s, p = 0.003). In the PT group on the side of pronounced tremor the amplitude of PMBS decreased but it was not delayed, compared to the less affected hand (PMBS(PT+) = 115.19 +/- 72.131%, PMBS(PT++) = 77.84 +/- 53.101%, p = 0.0028; latPMBS(PT+) = 1.4 +/- 0.74 s, latPMBS(PT++) = 1.25 +/- 0.797 s, p = 0.191). In controls the power and latency of PMBS was similar on both sides. CONCLUSIONS: The results suggest that neuronal mechanisms underlying PMBS generation are differently affected by ET and PT. Investigation of PMBS might be used for the differential diagnosis of essential tremor and Parkinson's disease.

[Investigation of cerebral autoregulation in Parkinson's disease--a transcranial Doppler study]. / Az agyi autoreguláció vizsgálata Parkinson-betegségben.

BACKGROUND AND PURPOSE: The frequent orthostatic intolerance in Parkinson's disease could be the consequence of cardiovascular autonomic failure and/or a damaged cerebral autoregulation (AR). To clarify this question the regulation of cerebral circulation was investigated by polygraphic method. METHODS: On a tilt table simultaneous and continuous registrations were made of MCA velocity (V(MCA)) by transcranial Doppler, arterial blood pressure by non-invasive method, and end-tidal CO2, in supine and in tilted positions of 10 degrees, 30 degrees, 70 degrees grades. The cerebral autoregulation was characterized by the slope of the curve of the arterial blood pressure at the level of the Willis-circle (BP(W) as MCA perfusion pressure) plotted against the MCA velocity, achieved by linear regression (y = ax + b function, a=AR, or index of autoregulation). PATIENTS: The data of 17 parkinsonian patients (PP) and eight age-matched controls (C) were analyzed. RESULTS: The decrease of blood pressure in parkinsonian patients was significantly lower than in the controls when supine position was restored from 70 degrees (deltaABP 70 degrees - 0 degree pp = -3.1 +/- 7.5 Hgmm; deltaABP 70 degrees - 0(C) degrees = -11.1 +/- 7.3 Hgmm; p < 0.05), which suggests a damage to the sympathetic cardiovascular system. A disturbance of the cerebral autoregulation in patients was suggested by a 'progressively decreasing MCA average velocity (V(MCA)) during graded tilt, which was significant at 70 degrees (deltaV(ACM) = 9.8 +/- 8.82% cms(-1); p(C-PP) P 0.5), and by a higher slope of pressure-velocity curve (AR(C) = 0.143 +/- .125% cms(-1)/Hgmm; AR(PP) = 0.38 +/- 0.25% cms(-1)/Hgmm; p(C-PP) < 0.05). CONCLUSIONS: The results show that the cerebral blood flow of patients is more dependent on perfusion pressure compared to healthy controls. The disturbance of the sympathetic cardiovascular system and of cerebral autoregulation could be the consequence of a damage to the postganglionic structures in Parkinson's disease. These results could explain the frequent orthostatic intolerance of patients even with normal blood pressure.

Correlation between blood flow velocity in the middle cerebral artery and EEG during cognitive effort.

Cognitive effort modifies blood flow velocity (BFV) in the middle cerebral artery (MCA) which can be recorded by transcranial Doppler sonography (TCD). EEG parameters can be used as indicators of cortical activation. To find temporal and spatial relation between circulatory and bioelectric phenomena, we used combined EEG and TCD measurements during cognitive experiments. Bilateral BFV in the MCAs and 16-channel scalp EEG were recorded during mental arithmetic (MA) and verbal fluency (VF) tests in 12 healthy volunteers. Temporal profile of BFV, heart rate (HR), EEG central frequency (CF), relative alpha power (ralphap), and laterality index (Li) for BFV and CF were statistically analysed. During mental effort, BFV changes showed a reproducible pattern, which was different in MA and VF tests. The Li(BFV) correlated with handedness in 9/12 subjects (75%) in the VF, and in 6/12 subjects (50%) in the MA test. Significant correlation was found between Li(BFV) and Li(CF) during VF (r(2) = 0.69). Li was more indicative for the hemispheric dominance in the VF than in the MA test. During VF test, correlation between HR and BFV was significant in 7/12 subjects. CF and ralphap provide real time assessment of the functional state of the brain tissue during cognition. The correlation between CF and BFV during mental activity suggests a short latency neurogenic and a long latency, supposedly chemical regulation of regional blood flow. Parallel analysis of EEG and flow parameters increases the confidence of determining hemispheric dominance and provides an alternative to study physiological consequences of cognitive processes.

[Differentiation of parkinsonian and essential tremor using electrophysiological methods]. / A Parkinson-tremor és az esszenciális tremor elkülönítése elektrofiziológiai módszerrel.

OBJECTIVE: Tremor is one of the most common movement disorders. Different tremors are induced by central and/or peripheral oscillators. The motor cortex plays a significant role in the generation of parkinsonian tremor but its function in essential tremor is not clear. We examined the effect of motor cortex activation on parkinsonian and essential tremor during movement of the contralateral hand. Our aim was to study the role of interhemispheric motor connections in genesis of different tremors. PATIENTS AND METHODS: We recorded the tremor of nine Parkinson patients and seven patients suffering from essential tremor using accelerometry. After Fast Fourier-transformation of digitized tremor signal we measured the power changes at the peak frequency after flash triggered movement (FM) and self-paced movement (SPM). For control we used flash signal without movement. RESULTS: Peak frequency of parkinsonian and essential tremor was not different. The power decrease of parkinsonian tremor was significant during flash triggered and self-paced movement compared to the effect of flash (p(Flash-FM)=0.0008; p(Flash-SPM)=0.002), changes during the different movement protocols were not different (p(FM-SPM)=0.33). During self-paced movement parkinsonian tremor became significantly smaller than essential tremor (p<0.05). The effect of movement was not significant on the power of essential tremor (p=0.42), probably due to high standard deviation of individual data. CONCLUSIONS: Voluntary movement of the contralateral hand decreases parkinsonian tremor suggesting that its generator can be inhibited via the activation of the motor cortex. The diverse reaction of essential tremor may reflect various connections between its generator system and the motor areas, therefore it is not a separate disease entity.

[Effect of mental arithmetic and verbal fluency on blood flow velocity in the middle cerebral arteries]. / A fejszámolás és a szóalkotás hatása az arteria cerebri mediákban mért véráramlás-sebességre.

INTRODUCTION: Using transcranial Doppler sonography (TCD), changes in blood flow velocity (BFV) can be measured in the Medial Cerebral Artery (MCA) during cognitive effort. Our goal was to define the time-course and laterality of BFV in healthy volunteers during arithmetic and verbal fluency tasks according to handedness. METHODS: Twelve subjects (8 right-handed, 4 left-handed) were assessed. The TCD registered BFV in both MCA simultaneously. Heart rate was also recorded using TCD. Finally we included a 16-channel EEG. BFV laterality index (LI) was calculated. Participants were asked to count silently and generate words beginning with a specified letter. To estimate hemispheric differences in BFV, two-tailed Wilcoxon tests were utilized along with correlational analyses. RESULTS: During cognitive effort the BFV changed in a tri-phasic manner in all participants. A 6-8% elevation of BFV was observed in MCAs without latency at the time of the evoking signal. Laterality of BFV developed after 5-13 seconds during cognitive effort in right-, and several seconds later in left-handed subjects. During tasks the BFV increased in the dominant hemisphere up to 2.6-4.7% compared to the subdominant one. We also calculated the LI. During the verbal task the LI agreed with the handedness in 9 out of 12 subjects. During the mental arithmetic task, agreement was found in 6 out of 12 subjects. According to LI results we found a discrepancy between verbal and arithmetic tests in 3 out of 12 subjects. CONCLUSION: Cognitive effort elicites significant bilateral BFV increases in the MCAs, which suggests fast neurogenic regulation. The course of BFV during mental arithmetic proved to be different from course BFV assessed during the word fluency task. Based on the laterality of the BFV, the word-generation task was more sensitive in determining the dominant hemisphere when compared to the mental arithmetic task. The use of LI may help to estimate hemispheric functions even in pathologic circumstances.

Contralateral voluntary hand movement inhibits human parkinsonian tremor and variably influences essential tremor.

While voluntary movement blocks Parkinsonian rest tremor (PT), essential tremor (ET) is enforced by postural and/or kinetic action. We studied the effect of contralateral externally- and internally triggered hand movement on PT and ET to investigate the transhemispheric influences on tremor genesis. We measured the changes of tremor peak frequency power after flash signal (F), flash triggered (FM) and self-paced (SPM) movement of the contralateral hand in nine PT and seven ET patients using accelerometer. PT significantly decreased both during FM and SPM tasks, suggesting that it is generated by a constant subcortico-cortical network, which includes higher order motor areas. Intensity of ET showed a remarkable intra- and interindividual variability both during FM and SPM reflecting a different generator circuitry with variable functional connections.

Impairment of post-movement beta synchronisation in parkinson's disease is related to laterality of tremor.

OBJECTIVE: Post-movement beta synchronisation (PMBS) is a physiological indicator of the activity of movement related neural networks. To investigate the pathophysiology of this phenomenon, we examined its characteristics in patients with unilateral tremor-dominant Parkinson's disease (PD). METHODS: Movement duration and PMBS was measured after self-paced movement of the thumb at movement-reactive beta frequencies, over the supplementary motor area in 10 PD patients and 8 control subjects. RESULTS: Movement duration in PD patients was longer than in controls. In left hand tremor patients, movement of the left hand was significantly longer compared to the right hand. When PD patients moved their non-affected hand, similarly to the controls, PMBS was higher contralateral to the movement. After movement of the tremulous hand, the contralateral PMBS decreased significantly and the contralateral preponderance disappeared. In the same hemisphere, PMBS was higher after contralateral to the non-affected hand movement, than after ipsilateral to the tremulous hand after movement. CONCLUSIONS: PMBS in PD is affected by the activity of tremor related neural networks, suggesting that both cortical and subcortical sources are responsible for its generation. Examination of PMBS in various neurological diseases might provide further data on its physiological significance.

[Electrophysiologic investigation of cerebral cortex in the subtypes of Parkinson disease]. / Az agykéreg múködésének elektrofiziológiai vizsgálata a Parkinson-kór klinikai altípusaiban.

OBJECTIVE: Post-movement beta synchronization is an increase in EEG beta power after movement termination. Its characteristics in movement disorders are not well described. Tremor dominant Parkinson's disease shows unique clinical, anatomical and biochemical features. In our study we examined the relation between the laterality of tremor and size of post-movement beta synchronisation in tremor dominant Parkinson's disease. METHODS: In a self-paced movement paradigm we measured movement duration and analyzed EEG power changes at movement-reactive beta frequencies. RESULTS: Movement duration was significantly longer in Parkinson-patients than in controls (0.49 +/- 0.170 s, 0.35 +/- 0.087 s, p = 0.013, Mann-Whitney test). There was no difference between the two hands in the control group (0.36 +/- 0.078 s, 0.34 +/- 0.099 s, p = 0.207, Wilcoxon-test), while Parkinson patients performed longer movement with their left hand (0.52 +/- 0.195 s, 0.46 +/- 0.148 s, p = 0.049, Wilcoxon), unrelated to the side of tremor. In controls, post-movement beta synchronisation contralateral to the movement was not significantly different after right and left hand movement (108.1 +/- 68.21% and 92.1 +/- 23.43%, p = 0.78 Wilcoxon). In Parkinson patients post-movement beta synchronisation was significantly smaller contralateral to the tremulous hand movement (36.9 +/- 47.79%, 104.7 +/- 91.42%, p = 0.012, Wilcoxon-test). The post-movement beta synchronisation showed anterior shifting in Parkinson-patients. CONCLUSIONS: In tremor dominant Parkinson's disease the asymmetric decrease of post-move beta synchronisation is related to the laterality of tremor rather than bradykinesia. Analysis of this phenomena might provide further insight to the pathophysiology of Parkinson's disease.