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Schmidt B.,Chemnitz Medical Center | Czosnyka M.,Academic Neurosurgical Unit | Klingelhofer J.,Chemnitz Medical Center
Perspectives in Medicine | Year: 2012

Background: Small cerebral vessels respond to variations of cerebral perfusion pressure (CPP) by changes of vessel diameter inducing changes of blood flow resistance and keeping cerebral blood flow constant. This mechanism is called cerebral autoregulation (CA). Recently stronger reactions of CA during pressure increase than during decrease were reported. Aim of this study was to assess the symmetry behavior of CA during spontaneous CPP changes and compare it to cerebrovascular pressure reactivity (CVR). Methods: In 238 patients with traumatic brain injury or stroke, correlation indices between CPP and cerebral blood flow velocity (CBFV) were calculated during periods of increasing (upMx) and decreasing CPP (downMx). The indices range from -1 to +1, values ≤0 indicating intact, values >0 indicating impaired autoregulation. Similar correlation between arterial blood pressure (ABP) and ICP was calculated during increasing (upPRx) and decreasing ABP (downPRx), negative values indicating intact, positive values indicating impaired CVR. Only recordings with strong pressure changes (CPP/ABP > 10 mmHg) were evaluated. Results: CA was assessed in 62 patients. On average (mean±SD) upMx was 0.06±0.52, downMx was 0.15±0.55 (P > 0.005). CVR was assessed in 47 patients. On average upPRx was 0.45±0.43, downPRx was 0.38±0.48 (P < 0.05). In 40 patients both Mx and PRx were calculated. On average upMx was 0.21±0.55 and downMx was 0.27±0.56 (P = 0.05), upPRx was 0.35±0.43 and downPRx was 0.27±0.47 (P < 0.05). Conclusions: During pressure increase the autoregulatory response was significantly stronger than during decrease, while in contrast the cerebrovascular reactivity was significantly weaker. The reason for this opposed behavior remains unclear and needs further exploration. © 2012 Elsevier GmbH.

Higgins J.N.P.,Addenbrookes Hospital | Kirkpatrick P.J.,Academic Neurosurgical Unit
British Journal of Neurosurgery | Year: 2013

The extent to which arterial steal or venous hypertension contributes to symptoms in patients with high flow brain arteriovenous malformations (AVMs) is not always clear. We describe a patient with an inoperable AVM of the pons, presenting with headache and neurological deficit where improving venous outflow by stenting produced substantial clinical benefit. © 2013 The Neurosurgical Foundation.

Higgins J.N.P.,Addenbrookes Hospital | Pickard J.D.,Academic Neurosurgical Unit
British Journal of Neurosurgery | Year: 2013

A 47 year old man developed severe headaches after resection of an acoustic neuroma ipsilateral to non dominant venous drainage. CSF pressures were normal but imaging studies showed acquired, severe narrowing of the sigmoid sinus where it traversed the surgical defect. Stenting the sinus gave a lasting clinical improvement. © 2013 The Neurosurgical Foundation.

Kasprowicz M.,University of California at Los Angeles | Kasprowicz M.,Wroclaw University of Technology | Kasprowicz M.,Academic Neurosurgical Unit | Asgari S.,University of California at Los Angeles | And 4 more authors.
Journal of Neuroscience Methods | Year: 2010

This study aimed to develop a new approach to detect intracranial pressure (ICP) slow waves based on morphological changes of ICP pulse waveforms. A recently proposed Morphological Clustering and Analysis of ICP Pulse (MOCAIP) algorithm was utilized to calculate a set of metrics that characterize ICP pulse morphology. A regularized linear quadratic classifier was used to test the hypothesis that classification between ICP slow wave and flat ICP could be achieved using features composed of mean values and dispersion of 24 MOCAIP metrics. To optimize the classification performance, three feature selection techniques (differential evolution, discriminant analysis and analysis of variance) were applied to find an optimal set of MOCAIP metrics under different criteria. In addition, we selected three sets of metrics common to those found by combination of two selection methods, to be used as classification features (differential evolution and analysis of variance, discriminant analysis and analysis of variance, and combination of differential evolution and discriminant analysis). To test the approach, a total of 276 selections of ICP recordings corresponding to two patterns without waves and containing slow waves were obtained from overnight ICP studies of 44 hydrocephalus patients performed at the UCLA Adult Hydrocephalus Center. Our results showed that the best classification performance of differentiation of slow waves from the ICP recording without slow waves was obtained using the combination of metrics common to both differential evolution and analysis of variance methods; achieving an accuracy of 89%, specificity 96%, and sensitivity 83%. © 2010.

Kasprowicz M.,Academic Neurosurgical Unit | Kasprowicz M.,Wroclaw University of Technology | Diedler J.,Academic Neurosurgical Unit | Diedler J.,University of Heidelberg | And 10 more authors.
Acta Neurochirurgica, Supplementum | Year: 2012

We have defined a novel cerebral hemodynamic index, a time constant of the cerebral arterial bed (τ), the product of arterial compliance (C a) and cerebrovascular resistance (CVR). C a and CVR were calculated based on the relationship between pulsatile arterial blood pressure (ABP) and transcranial Doppler cerebral blood flow velocity. This new parameter theoretically estimates how fast the cerebral arterial bed is filled by blood volume after a sudden change in ABP during one cardiac cycle. We have explored this concept in 11 volunteers and in 25 patients with severe stenosis of the internal carotid artery (ICA). An additional group of 15 subjects with non-vascular dementia was studied to assess potential age dependency of τ. The τ was shorter (p = 0.011) in ICA stenosis, both unilateral (τ = 0.18 ± 0.04 s) and bilateral (τ = 0.16 ± 0.03 s), than in controls (τ = 0.22 ± 0.0 s). The τ correlated with the degree of stenosis (R =-0.62, p = 0.001). In controls, τ was independent of age. Further study during cerebrovascular reactivity tests is needed to establish the usefulness of τ for quantitative estimation of haemodynamics in cerebrovascular disease. © 2012 Springer-Verlag/Wien.

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