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V Babikian

Publications and source records attributed to V Babikian.

9 recordsLinked to original sources
PubMed1997

Intercenter agreement in reading Doppler embolic signals. A multicenter international study.

BACKGROUND AND PURPOSE: Different frequencies of asymptomatic Doppler embolic signals have been reported in studies. There has been concern that different criteria for identification may account for some of this variation. A previous reproducibility study between two centers found good agreement, but no studies among large numbers of centers have been performed. We performed an international reproducibility study among nine centers, each of which had published recent studies of embolic signal detection in peer-reviewed journals. METHODS: Each center performed blinded analysis of a taped audio Doppler signal composed of transcranial Doppler middle cerebral artery recordings from 6 patients with symptomatic carotid artery stenosis. The exact time of any embolic signal was recorded. Six centers also measured the intensity increase of any embolic signals detected. Interobserver agreement was determined by a method based on the proportion of specific agreement. RESULTS: Seven centers reported between 39 and 55 signals, but one center reported 142 embolic signals. The probability of agreement between observers was .678, which rose to .791 when the data from the highest reporting center were excluded. Introducing a decibel threshold resulted in a significant increase in the probability of agreement; a decibel threshold of > 7 dB resulted in a probability of agreement of .902. Intensity measurements made by different centers were usually highly correlated, but this was not always the case, and 3 of the 15 correlations were not significant. The absolute values of the intensities measured varied between centers by as much as 40%. CONCLUSIONS: Although most centers report similar numbers of embolic signals, some use less specific criteria and report more events. The use of a decibel threshold improves reproducibility. However, intensity thresholds developed by one center cannot be directly transferred without validation to another center; differing methods of measurement are being used, and this results in different intensity values for the same embolic signals, even when the same equipment is used.

Carotid Stenosis↗
PubMed1996

Cerebellar hemorrhagic infarction.

We investigated 17 patients with 26 cerebellar hemorrhagic infarcts for their vascular anatomy, stroke mechanisms, and clinical course. Sixteen infarcts involved the superior cerebellar artery, nine the posterior inferior cerebellar artery, and one the anterior inferior cerebellar artery territories. The infarcts involved the full territory of the supplying arteries in 19 of 26 infarcts (73%). Sixteen of 17 patients were stable or improving when the hemorrhagic infarction was detected. All but one patient had an imaging study at the time of presentation that was negative for blood; hemorrhagic infarction was detected on routine serial scans performed during the first 15 days. Nine of the 17 patients were on anticoagulants when the cerebellar hemorrhagic infarct was detected; anticoagulation was maintained in eight of them with no clinical worsening. The stroke mechanism in all patients was considered embolic from cardiac and intra-arterial sources. The causes, imaging findings, and consequences of hemorrhagic infarcts in the posterior circulation are similar to those in the anterior circulation.

Anticoagulants↗
PubMed1994

Recent developments in transcranial Doppler sonography.

Transcranial Doppler mapping, dual monitoring, color imaging, emboli detection, and insonation after administration of contrast media are recent technological advances that promise to bring new capabilities to transcranial Doppler ultrasonography, and are likely to change its applications in the near future. This article presents a critical review of these developments.

Cerebrovascular Disorders↗
PubMed1994

Longitudinal monitoring of intracranial arterial stenoses with transcranial Doppler ultrasonography.

The natural history of intracranial arterial stenoses remains relatively unknown. To monitor the progression of these lesions over time, the authors reviewed transcranial Doppler (TCD) laboratory reports at five hospitals for patients with angiographically documented intracranial arterial stenoses along the internal carotid artery distribution, and at least two TCD studies conducted more than 2 months apart. Twenty-two patients (19 men and 3 women; mean age, 64 years) with 29 stenoses were identified. The findings were compared to reproducibility data obtained from 11 age-matched control subjects with repeat TCD studies. During a mean follow-up period of 21 months, peak systolic flow velocities corresponding to the areas of stenosis increased in 9 arteries with lesions, and new collateral flow patterns, indicating further hemodynamic compromise distal to the lesions, developed in 2; one of the latter also had increased corresponding velocities. Thus, 10 (35%) arteries with lesions had TCD evidence of progression. Flow velocities remained the same in 13 (45%) stenotic vessels and dropped in 2 (7%). Findings were considered inconclusive for 4 lesions (14%). These findings suggest that intracranial arterial stenoses are dynamic lesions, and that they can evolve and cause further reductions of the arterial diameters after relatively short periods of time. TCD can noninvasively detect their hemodynamic effects.

Adult↗
PubMed1987

Evaluation of the 11CO2 positron emission tomographic method for measuring brain pH. I. pH changes measured in states of altered PCO2.

The 11CO2 method for measuring local brain pH with positron emission tomography (PET) has been experimentally evaluated, testing the adequacy of the kinetic model and the ability of the method to measure changes in brain pH. Plasma and tissue time/activity curves measured during and following continuous inhalation of 11CO2 were fit with a kinetic model that includes effects of tissue pH, blood flow, and fixation of CO2 into compounds other than dissolved gas and bicarbonate ions. For each of ten dogs, brain pH was measured with PET at two values of PaCO2 (range 21-67 mm Hg). The kinetic model fit the data well during both inhalation and washout of the label, with residual root mean square (RMS) deviations of the model from the measurements consistent with the statistical quality of the PET data. Brain pH calculated from the PET data shows a linear variation with log(PaCO2). These results were in good agreement with previously reported measurements of brain pH, both in absolute value and in variation with PCO2. The interpretation of these pH values in normal and pathological states is discussed.

Administration, Intranasal↗
PubMed1985

Occlusive disease of the middle cerebral artery.

We studied 20 patients with severe occlusive disease of the mainstem middle cerebral artery (MCA) or its major division branches, and 25 patients with internal carotid artery (ICA) disease. MCA disease patients were more often black, female, younger, and had fewer TIAs than the ICA disease patients. Neurologic signs in patients with MCA disease evolved progressively during days to weeks, whereas ICA disease patients more often had an acute onset of nonprogressive deficits. CT commonly showed restricted subcortical or wedge-shaped infarcts in MCA disease patients. All MCA disease patients had stroke, but 40% of ICA disease patients had no infarction. MCA lesions usually affected the mainstem MCA or its major superior division. Patients with MCA disease seldom had recurrent ischemia in the same vascular territory as the stroke and had a low incidence of subsequent cardiac death.

Adult↗
PubMed1984

Hypometric saccades and low-gain pursuit resulting from a thalamic hemorrhage.

Saccadic and pursuit eye movements were measured in a patient with a right thalamic hemorrhage using an infrared reflection technique. Saccades were hypometric when directed away from the side of the lesion, and pursuit was low in gain, with many interposed saccades, when directed toward the side of the lesion. This eye movement pattern is similar to that observed in hemidecorticate patients. We postulate that the ocular abnormalities observed in our patients were secondary to an interruption of the efferent pathways from the right cerebral areas mediating saccadic and smooth-pursuit eye movements.

Eye Movements↗