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    ABSTRACT: Cerebral autoregulation (CA) is not universally impaired in acute intracerebral hemorrhage (ICH); however, the dynamic components of CA are probably more vulnerable. This study, therefore, evaluates the time course of dynamic CA in acute ICH and its relationship to clinical outcome. Twenty-six patients with ICH were studied on days 1, 3, and 5 after ictus. Dynamic CA was measured from spontaneous fluctuations in blood pressure and middle cerebral artery flow velocity by transfer function phase (reflecting rapidity of CA) and gain (reflecting damping characteristics of CA) in the low frequency range. Results were compared with those from 55 controls and related with clinical factors and 90-day outcome (modified Rankin scale). Phase did not fluctuate significantly over time, nor did it differ between sides or differ from controls. Gain was always higher in patients than in controls but showed no significant association with outcome or other clinical factors. At day 1, poorer ipsilateral phase was associated with lower blood pressure and higher ICH volume. Poorer phase always coincided with lower Glasgow Coma Scale values. Poorer ipsilateral phase on day 5 was related with poorer clinical outcome according to multivariate analysis (P=0.013). Dynamic temporal characteristics of CA (phase) are not generally altered in acute ICH. Poorer individual phase values are, however, associated with larger ICH volume, lower blood pressure, and worsened outcome. Dampening characteristics of CA (gain) are generally impaired in acute ICH but not related to clinical factors or outcome.
    Stroke 08/2013; 44(10). DOI:10.1161/STROKEAHA.113.001913
  • BMJ (online) 02/2013; 346:f1000. DOI:10.1136/bmj.f1000
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    ABSTRACT: The authors report a case of an isolated schwannoma of left hypoglossal nerve in a 9-year-old girl. To the authors' knowledge, this is the first case report of hypoglossal nerve schwannoma in the pediatric population in the absence of neurofibromatosis Type 2. The patient presented with a 2-month history of morning nausea and vomiting with occasional daytime headaches. Magnetic resonance imaging and subsequent CT scanning revealed a dumbbell tumor with a belly in the lower third of the posterior fossa and head underneath the left jugular foramen. Its neck protruded through an expanded hypoglossal canal. Although the lesion bore radiological characteristics of a hypoglossal schwannoma, the absence of hypoglossal palsy and the apparent lack of such tumors in the pediatric population the preoperative diagnosis was not certain. The tumor was approached via a midline suboccipital craniotomy, and gross-total resection was achieved. Pathological examination confirmed the diagnosis of schwannoma. Blood and tumor tests for mutations in the NF2 gene were negative. Postoperative mild hypoglossal palsy recovered by the 3-month follow-up, and an MRI study obtained at 1 year did not show recurrence.
    Journal of Neurosurgery Pediatrics 06/2012; 10(2):130-3. DOI:10.3171/2012.3.PEDS11555
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    ABSTRACT: Local anesthesia is widely used, in isolation or in conjunction with general anesthesia. The authors describe 2 adolescent patients presenting with absent brainstem reflexes and delayed awakening following elective foramen magnum decompression for Chiari Type I malformation. In both cases, neurological deficits were closely associated with the administration of a levobupivacaine field block following wound closure. In the absence of any structural or biochemical abnormalities, and with spontaneous recovery approximating the anesthetic half-life, the authors' observations are consistent with transient brainstem paralysis caused by perioperative local anesthetic infiltration.
    Journal of Neurosurgery Pediatrics 06/2012; 10(1):60-1. DOI:10.3171/2012.3.PEDS11394
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    European Journal of Intensive Care Medicine 04/2012; 38(6):925-7. DOI:10.1007/s00134-012-2572-6
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    ABSTRACT: The Monro-Kellie doctrine describes the principle of homeostatic intracerebral volume regulation, which stipulates that the total volume of the parenchyma, cerebrospinal fluid, and blood remains constant. Hypothetically, a slow shift (e.g., brain edema development) in the irregular vasomotion-driven exchanges of these compartmental volumes may lead to increased intracranial hypertension. To evaluate this paradigm in a clinical setting and measure the processes involved in the regulation of systemic intracranial volume, we quantified cerebral blood flow velocity (CBFv) in the middle cerebral artery, arterial blood pressure (ABP), and intracranial pressure (ICP), in 238 brain-injured subjects. Relative changes in compartmental compliances C(a) (arterial) and C(i) (combined venous and CSF compartments) were mathematically estimated using these raw signals through time series analysis; C(a) and C(i) were used to compute an index of cerebral compliance (ICC) as a moving correlation coefficient between C(a) and C(i). Conceptually, a negative ICC would represent a functional Monro-Kellie doctrine by illustrating volumetric compensations between C(a) and C(i). Clinical observations show that Lundberg A-waves and arterial hypertension were associated with negative ICC, whereas in refractory intracranial hypertension, a positive ICC was observed. In subjects who died, ICC was significantly greater than in survivors (0.46 ± 0.027 versus 0.22 ± 0.017; p<0.01) over the first 5 days of intensive care. The mortality rate is 5% when ICC is less than 0, and 43% when above 0.7. ICC above 0.7 was associated with terminally elevated ICP (chi-square p=0.026). We propose that the Monro-Kellie doctrine can be monitored in real time to illustrate the state of intracranial volume regulation.
    Journal of neurotrauma 09/2011; 29(7):1354-63. DOI:10.1089/neu.2011.2018
  • Journal of the Royal Society of Medicine 07/2011; 104(7):299-301. DOI:10.1258/jrsm.2011.100398
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    ABSTRACT: Bedside monitoring of cerebral metabolism in traumatic brain injury (TBI) with microdialysis is gaining wider clinical acceptance. The objective of this study was to examine the relationship between the fundamental physiological neuromonitoring modalities intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygen (P(bt)O(2)), and cerebrovascular pressure reactivity index (PRx), and cerebral chemistry assessed with microdialysis, with particular focus on the lactate/pyruvate (LP) ratio as a marker of energy metabolism. Prospectively collected observational neuromonitoring data from 97 patients with TBI, requiring neurointensive care management and invasive cerebral monitoring, were analyzed. A linear mixed model analysis was used to account for individual patient differences. Perilesional tissue chemistry exhibited a significant independent relationship with ICP, P(bt)O(2) and CPP thresholds, with increasing LP ratio in response to decrease in P(bt)O(2) and CPP, and increase in ICP. The relationship between CPP and chemistry depended upon the state of PRx. Within the studied physiological range, tissue chemistry only changed in response to increasing ICP or drop in P(bt)O(2)<1.33 kPa (10 mmHg). In agreement with previous studies, significantly higher levels of cerebral lactate (p<0.001), glycerol (p=0.013), LP ratio (p<0.001) and lactate/glucose (LG) ratio (p=0.003) were found in perilesional tissue, compared to "normal" brain tissue (Mann-Whitney test). These differences remained significant following adjustment for the influences of other important physiological parameters (ICP, CPP, P(bt)O(2), P(bt)CO(2), PRx, and brain temperature; mixed linear model), suggesting that they may reflect inherent tissue properties related to the initial injury. Despite inherent biochemical differences between less-injured brain and "perilesional" cerebral tissue, both tissue types exhibited relationships between established physiological variables and biochemistry. Decreases in perfusion and oxygenation were associated with deteriorating neurochemistry and these effects were more pronounced in perilesional tissue and when cerebrovascular reactivity was impaired.
    Journal of neurotrauma 06/2011; 28(6):849-60. DOI:10.1089/neu.2010.1656
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    ABSTRACT: Cerebrovascular pressure reactivity depends on cerebral perfusion pressure (CPP), with the optimal CPP (CPPopt) defined as pressure at which cerebrovascular reactivity is functioning optimally, reaching minimal value of pressure reactivity index (PRx). The study investigates the association between vasospasm, PRx, and CPPopt in poor grade patients (WFNS 4&5) after subarachnoid hemorrhage (SAH). Data of intracranial pressure (ICP), arterial blood pressure (ABP), and flow velocities (FV) in the Middle Cerebral Artery (MCA) on transcranial Doppler from 42 SAH patients were analyzed retrospectively. PRx was calculated as a correlation coefficient between 10 s mean values of ABP and ICP calculated over a moving 3 min window. Data recorded during the first 48 h were available in 25 cases and during the first 3 days in 29 patients. Recordings obtained from day 4 to day 24 were available in 23 patients. PRx at optimal CPP measured during the first 48 h showed better cerebrovascular reactivity in patients who were alive at 3 months after ictus than in those who died (PRx value -0.17 +/- 0.05 vs. 0.1 +/- 0.09; P < 0.01). PRx below zero at CPPopt during the first 48 h had 87.5% positive predictive value for survival. CPPopt was lower before than during vasospasm (78 +/- 3 mmHg, N = 29 vs. 98 +/- 4 mmHg; N = 17, P < 0.0001). The overall correlation between CPPopt and Lindegaard ratio was positive (R = 0.39; P < 0.01; N = 45). Most WFNS 4&5 grade SAH patients with PRx below zero at optimal CPP during the first 48 h after ictus survived. Optimal CPP increases during vasospasm.
    Neurocritical Care 08/2010; 13(1):17-23. DOI:10.1007/s12028-010-9362-1
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    ABSTRACT: Background: During the last decade, with the development of on-line monitoring and waveform analysis, inte-gration of brain signals has increasingly been used in patients with traumatic brain injury (TBI) to guide clinical manage-ment and predict outcome. Objective: The goal of this review is to describe current methodology for brain signal integration in TBI patients focusing on 'reactivity indices'. Methods: We reviewed selected techniques to monitor patients in the acute phase of TBI using the comparison and inte-gration of different physiological signals. The autoregulation indices, Mx and Mxa were defined as the moving correla-tion between cerebral blood flow velocities (CBFV) and cerebral perfusion pressure (CPP) or arterial blood pressure (ABP), respectively. The cerebrovascular pressure reactivity index PRx was defined as the moving correlation coefficient between ABP and intracranial pressure (ICP). The oxygen reactivity index, Orx, was defined as the moving correlation co-efficient between brain tissue oxygenation and CPP. Finally, Tox was defined as the moving correlation coefficient be-tween brain tissue oxygenation measured by Near Infrared Spectroscopy (NIRS) and ABP. Results: Both Mx > 0.3 and Mxa > 0.45 as well as an asymmetry of Mx between both hemispheres of the brain in the acute phase were associated with poor outcome. PRx may be used to determine the individual optimal CPP and is also a powerful and independent predictor of outcome. Orx showed conflicting results and more studies are need to determine its role in the acute setting of TBI. Studies concerning the role of NIRS in the acute phase of TBI are ongoing.
    The Open Neurosurgery Journal 07/2010; 3(1):17-27. DOI:10.2174/1876529701003010017
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