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Li M, He L, Zhang Z, Li Z, Zhu X, Jiao C, Hu D. The decoupling between hemodynamic parameters and neural activity implies a complex origin of spontaneous brain oscillations. Front Comput Neurosci 2023; 17:1214793. [PMID: 37583895 PMCID: PMC10423917 DOI: 10.3389/fncom.2023.1214793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 07/18/2023] [Indexed: 08/17/2023] Open
Abstract
Introduction Spontaneous low-frequency oscillations play a key role in brain activity. However, the underlying mechanism and origin of low-frequency oscillations remain under debate. Methods Optical imaging and an electrophysiological recording system were combined to investigate spontaneous oscillations in the hemodynamic parameters and neuronal activity of awake and anesthetized mice after Nω-nitro-L-arginine methyl ester (L-NAME) administration. Results The spectrum of local field potential (LFP) signals was significantly changed by L-NAME, which was further corroborated by the increase in energy and spatial synchronization. The important finding was that L-NAME triggered regular oscillations in both LFP signals and hemodynamic signals. Notably, the frequency peak of hemodynamic signals can be different from that of LFP oscillations in awake mice. Discussion A model of the neurovascular system was proposed to interpret this mismatch of peak frequencies, supporting the view that spontaneous low-frequency oscillations arise from multiple sources.
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Affiliation(s)
| | | | | | | | | | | | - Dewen Hu
- College of Intelligence Science and Technology, National University of Defense Technology, Changsha, China
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2
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Lele AV, Theard MA, Vavilala MS. Cerebrospinal fluid diversion devices and shunting procedures: a narrative review for the anesthesiologist. Int Anesthesiol Clin 2023; 61:29-36. [PMID: 37249174 DOI: 10.1097/aia.0000000000000399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Affiliation(s)
- Abhijit Vijay Lele
- Department of Anesthesiology and Pain Medicine, Harborview Medical Center, University of Washington, Seattle, Washington
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Lalou AD, Czosnyka M, Placek MM, Smielewski P, Nabbanja E, Czosnyka Z. CSF Dynamics for Shunt Prognostication and Revision in Normal Pressure Hydrocephalus. J Clin Med 2021; 10:jcm10081711. [PMID: 33921142 PMCID: PMC8071572 DOI: 10.3390/jcm10081711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Despite the quantitative information derived from testing of the CSF circulation, there is still no consensus on what the best approach could be in defining criteria for shunting and predicting response to CSF diversion in normal pressure hydrocephalus (NPH). OBJECTIVE We aimed to review the lessons learned from assessment of CSF dynamics in our center and summarize our findings to date. We have focused on reporting the objective perspective of CSF dynamics testing, without further inferences to individual patient management. DISCUSSION No single parameter from the CSF infusion study has so far been able to serve as an unquestionable outcome predictor. Resistance to CSF outflow (Rout) is an important biological marker of CSF circulation. It should not, however, be used as a single predictor for improvement after shunting. Testing of CSF dynamics provides information on hydrodynamic properties of the cerebrospinal compartment: the system which is being modified by a shunt. Our experience of nearly 30 years of studying CSF dynamics in patients requiring shunting and/or shunt revision, combined with all the recent progress made in producing evidence on the clinical utility of CSF dynamics, has led to reconsidering the relationship between CSF circulation testing and clinical improvement. CONCLUSIONS Despite many open questions and limitations, testing of CSF dynamics provides unique perspectives for the clinician. We have found value in understanding shunt function and potentially shunt response through shunt testing in vivo. In the absence of infusion tests, further methods that provide a clear description of the pre and post-shunting CSF circulation, and potentially cerebral blood flow, should be developed and adapted to the bed-space.
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Affiliation(s)
- Afroditi Despina Lalou
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
- Correspondence: ; Tel.: +44-774-3567-585
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
- Institute of Electronic Systems, Faculty of Electronics and Information Sciences, Warsaw University of Technology, 00-661 Warsaw, Poland
| | - Michal M. Placek
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Peter Smielewski
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Eva Nabbanja
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Zofia Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
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Papaioannou VE, Budohoski KP, Placek MM, Czosnyka Z, Smielewski P, Czosnyka M. Association of transcranial Doppler blood flow velocity slow waves with delayed cerebral ischemia in patients suffering from subarachnoid hemorrhage: a retrospective study. Intensive Care Med Exp 2021; 9:11. [PMID: 33768351 PMCID: PMC7994457 DOI: 10.1186/s40635-021-00378-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 02/17/2021] [Indexed: 11/25/2022] Open
Abstract
Background Cerebral vasospasm (VS) and delayed cerebral ischemia (DCI) constitute major complications following subarachnoid hemorrhage (SAH). A few studies have examined the relationship between different indices of cerebrovascular dynamics with the occurrence of VS. However, their potential association with the development of DCI remains elusive. In this study, we investigated the pattern of changes of different transcranial Doppler (TCD)-derived indices of cerebrovascular dynamics during vasospasm in patients suffering from subarachnoid hemorrhage, dichotomized by the presence of delayed cerebral ischemia. Methods A retrospective analysis was performed using recordings from 32 SAH patients, diagnosed with VS. Patients were divided in two groups, depending on development of DCI. Magnitude of slow waves (SWs) of cerebral blood flow velocity (CBFV) was measured. Cerebral autoregulation was estimated using the moving correlation coefficient Mxa. Cerebral arterial time constant (tau) was expressed as the product of resistance and compliance. Complexity of CBFV was estimated through measurement of sample entropy (SampEn). Results In the whole population (N = 32), magnitude of SWs of ipsilateral to VS side CBFV was higher during vasospasm (4.15 ± 1.55 vs before: 2.86 ± 1.21 cm/s, p < 0.001). Ipsilateral SWs of CBFV before VS had higher magnitude in DCI group (N = 19, p < 0.001) and were strongly predictive of DCI, with area under the curve (AUC) = 0.745 (p = 0.02). Vasospasm caused a non-significant shortening of ipsilateral values of tau and increase in SampEn in all patients related to pre-VS measurements, as well as an insignificant increase of Mxa in DCI related to non-DCI group (N = 13). Conclusions In patients suffering from subarachnoid hemorrhage, TCD-detected VS was associated with higher ipsilateral CBFV SWs, related to pre-VS measurements. Higher CBFV SWs before VS were significantly predictive of delayed cerebral ischemia.
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Affiliation(s)
- Vasilios E Papaioannou
- Department of Intensive Care Medicine, Alexandroupolis Hospital, Democritus University of Thrace, 68100, Alexandoupolis, Greece. .,Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.
| | - Karol P Budohoski
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.,Department of Neurosurgery, Cambridge University Hospitals, Cambridge, CB20QQ, UK
| | - Michal M Placek
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.,Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, 50-370, Wrocław, Poland
| | - Zofia Czosnyka
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
| | - Peter Smielewski
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
| | - Marek Czosnyka
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
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Lalou AD, Levrini V, Czosnyka M, Gergelé L, Garnett M, Kolias A, Hutchinson PJ, Czosnyka Z. Cerebrospinal fluid dynamics in non-acute post-traumatic ventriculomegaly. Fluids Barriers CNS 2020; 17:24. [PMID: 32228689 PMCID: PMC7106631 DOI: 10.1186/s12987-020-00184-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 03/06/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Post-traumatic hydrocephalus (PTH) is potentially under-diagnosed and under-treated, generating the need for a more efficient diagnostic tool. We aim to report CSF dynamics of patients with post-traumatic ventriculomegaly. MATERIALS AND METHODS We retrospectively analysed post-traumatic brain injury (TBI) patients with ventriculomegaly who had undergone a CSF infusion test. We calculated the resistance to CSF outflow (Rout), AMP (pulse amplitude of intracranial pressure, ICP), dAMP (AMPplateau-AMPbaseline) and compensatory reserve index correlation coefficient between ICP and AMP (RAP). To avoid confounding factors, included patients had to be non-decompressed or with cranioplasty > 1 month previously and Rout > 6 mmHg/min/ml. Compliance was assessed using the elasticity coefficient. We also compared infusion-tested TBI patients selected for shunting versus those not selected for shunting (consultant decision based on clinical and radiological assessment and the infusion results). Finally, we used data from a group of shunted idiopathic Normal Pressure Hydrocephalus (iNPH) patients for comparison. RESULTS Group A consisted of 36 patients with post-traumatic ventriculomegaly and Group B of 45 iNPH shunt responders. AMP and dAMP were significantly lower in Group A than B (0.55 ± 0.39 vs 1.02 ± 0.72; p < 0.01 and 1.58 ± 1.21 vs 2.76 ± 1.5; p < 0.01. RAP baseline was not significantly different between the two. Elasticity was higher than the normal limit in all groups (average 0.18 1/ml). Significantly higher Rout was present in those with probable PTH selected for shunting compared with unshunted. Mild/moderate hydrocephalus, ex-vacuo ventriculomegaly/encephalomalacia were inconsistently reported in PTH patients. CONCLUSIONS Rout and AMP were significantly lower in PTH compared to iNPH and did not always reflect the degree of hydrocephalus or atrophy reported on CT/MRI. Compliance appears reduced in PTH.
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Affiliation(s)
- Afroditi D Lalou
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK.
| | - Virginia Levrini
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
| | - Laurent Gergelé
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
- Department of Intensive Care, Hôpital privé de la Loire, Saint Etienne, France
| | - Matthew Garnett
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
| | - Angelos Kolias
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
| | - Peter J Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
| | - Zofia Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge and Cambridge University Hospital NHS Foundation Trust, Cambridge, UK
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Influence of mild-moderate hypocapnia on intracranial pressure slow waves activity in TBI. Acta Neurochir (Wien) 2020; 162:345-356. [PMID: 31844989 PMCID: PMC6982632 DOI: 10.1007/s00701-019-04118-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 10/23/2019] [Indexed: 12/30/2022]
Abstract
BACKGROUND In traumatic brain injury (TBI) the patterns of intracranial pressure (ICP) waveforms may reflect pathological processes that ultimately lead to unfavorable outcome. In particular, ICP slow waves (sw) (0.005-0.05 Hz) magnitude and complexity have been shown to have positive association with favorable outcome. Mild-moderate hypocapnia is currently used for short periods to treat critical elevations in ICP. Our goals were to assess changes in the ICP sw activity occurring following sudden onset of mild-moderate hypocapnia and to examine the relationship between changes in ICP sw activity and other physiological variables during the hypocapnic challenge. METHODS ICP, arterial blood pressure (ABP), and bilateral middle cerebral artery blood flow velocity (FV), were prospectively collected in 29 adult severe TBI patients requiring ICP monitoring and mechanical ventilation in whom a minute volume ventilation increase (15-20% increase in respiratory minute volume) was performed as part of a clinical CO2-reactivity test. The time series were first treated using FFT filter (pass-band set to 0.005-0.05 Hz). Power spectral density analysis was performed. We calculated the following: mean value, standard deviation, variance and coefficient of variation in the time domain; total power and frequency centroid in the frequency domain; cerebrospinal compliance (Ci) and compensatory reserve index (RAP). RESULTS Hypocapnia led to a decrease in power and increase in frequency centroid and entropy of slow waves in ICP and FV (not ABP). In a multiple linear regression model, RAP at the baseline was the strongest predictor for the decrease in the power of ICP slow waves (p < 0.001). CONCLUSION In severe TBI patients, a sudden mild-moderate hypocapnia induces a decrease in mean ICP and FV, but also in slow waves power of both signals. At the same time, it increases their higher frequency content and their morphological complexity. The difference in power of the ICP slow waves between the baseline and the hypocapnia period depends on the baseline cerebrospinal compensatory reserve as measured by RAP.
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Cerebrospinal fluid dynamics in pediatric pseudotumor cerebri syndrome. Childs Nerv Syst 2020; 36:73-86. [PMID: 31325030 DOI: 10.1007/s00381-019-04263-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 06/17/2019] [Indexed: 12/18/2022]
Abstract
PURPOSE There is a growing body of evidence highlighting the importance of comprehensive intracranial pressure (ICP) values in pseudotumor cerebri syndrome (PTCS). Due to the highly dynamic nature of ICP, several methods of ICP monitoring have been established, including the CSF infusion study. We have performed a retrospective review of the CSF dynamics measurements for all pediatric patients investigated for PTCS in our center and examined their diagnostic value compared with clinical classification. METHODS We retrospectively recruited 31 patients under 16 years of age investigated for PTCS by CSF infusion test. We used the clinically provided Friedman classification 13/31 patients with definite PTCS (group A), 13/31 with probable PTCS (group B), and 5/31 not PTCS (group C), to compare CSF dynamics in the 3 groups. RESULTS CSF pressure (CSFp) was significantly increased in group A (29.18 ± 7.72 mmHg) compared with B (15.31 ± 3.47 mmHg; p = 1.644e-05) and C (17.51 ± 5.87; p = 0.01368). The amplitude (AMP) was higher in the definite (2.18 ± 2.06 mmHg) than in group B (0.68 ± 0.37; p = 0.01382). There was no in either CSFp or AMP between groups B and C. No lower breakpoint of the AMP-P line was observed in group A but was present in 2/13 and 2/5 patients in groups B and C. In group A, sagittal sinus pressure (SSp) and elasticity were the only parameters above threshold (p = 4.2e-06 and p = 0.001953, respectively), In group B, only the elasticity was significantly higher than the threshold (p = 004257). Group C did not have any of the parameters raised. The AUC of CSFp, elasticity, and SSp for the 3 groups was 93.8% (84.8-100% CI). CONCLUSIONS Monitoring of CSFp and its dynamics, besides providing a more precise methodology for measuring CSFp, could yield information on the dynamic parameters of CSFp that cannot be derived from CSFp as a number, accurately differentiating between the clinically and radiologically derived entities of PTCS.
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Martinez-Tejada I, Arum A, Wilhjelm JE, Juhler M, Andresen M. B waves: a systematic review of terminology, characteristics, and analysis methods. Fluids Barriers CNS 2019; 16:33. [PMID: 31610775 PMCID: PMC6792201 DOI: 10.1186/s12987-019-0153-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/15/2019] [Indexed: 11/18/2022] Open
Abstract
Background Although B waves were introduced as a concept in the analysis of intracranial pressure (ICP) recordings nearly 60 years ago, there is still a lack consensus on precise definitions, terminology, amplitude, frequency or origin. Several competing terms exist, addressing either their probable physiological origin or their physical characteristics. To better understand B wave characteristics and ease their detection, a literature review was carried out. Methods A systematic review protocol including search strategy and eligibility criteria was prepared in advance. A literature search was carried out using PubMed/MEDLINE, with the following search terms: B waves + review filter, slow waves + review filter, ICP B waves, slow ICP waves, slow vasogenic waves, Lundberg B waves, MOCAIP. Results In total, 19 different terms were found, B waves being the most common. These terminologies appear to be interchangeable and seem to be used indiscriminately, with some papers using more than five different terms. Definitions and etiologies are still unclear, which makes systematic and standardized detection difficult. Conclusions Two future lines of action are available for automating macro-pattern identification in ICP signals: achieving strict agreement on morphological characteristics of “traditional” B waveforms, or starting a new with a fresh computerized approach for recognition of new clinically relevant patterns.
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Affiliation(s)
- Isabel Martinez-Tejada
- Clinic of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. .,Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark.
| | - Alexander Arum
- Clinic of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Jens E Wilhjelm
- Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Marianne Juhler
- Clinic of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Morten Andresen
- Clinic of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
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Lalou AD, Czosnyka M, Donnelly J, Pickard JD, Nabbanja E, Keong NC, Garnett M, Czosnyka ZH. Cerebral autoregulation, cerebrospinal fluid outflow resistance, and outcome following cerebrospinal fluid diversion in normal pressure hydrocephalus. J Neurosurg 2019; 130:154-162. [PMID: 29547089 DOI: 10.3171/2017.7.jns17216] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 07/24/2017] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Normal pressure hydrocephalus is not simply the result of a disturbance in CSF circulation, but often includes cardiovascular comorbidity and abnormalities within the cerebral mantle. In this study, the authors have examined the relationship between the global autoregulation pressure reactivity index (PRx), the profile of disturbed CSF circulation and pressure-volume compensation, and their possible effects on outcome after surgery. METHODS The authors studied a cohort of 131 patients in whom a clinical suspicion of normal pressure hydrocephalus was investigated. Parameters describing CSF compensation and circulation were calculated during the CSF infusion test, and PRx was calculated from CSF pressure and mean arterial blood pressure (MAP) recordings. A simple scale was used to mark the patients’ outcome 6 months after surgery (improvement, temporary improvement, and no improvement). RESULTS The PRx was negatively correlated with resistance to CSF outflow (R = -0.18; p = 0.044); patients with normal CSF circulation tended to have worse autoregulation. The correlation for patients who were surgically treated (n = 83) was R = -0.28; p = 0.01, and it was stronger in patients who experienced sustained improvement after surgery (n = 48, R = -0.43; p = 0.002). In patients who did not improve, the correlation was not significantly different from zero (n = 19, R = -0.07; p = 0.97). There was a trend toward higher values for PRx in nonresponders than in responders (0.16 ± 0.04 vs 0.09 ± 0.02, respectively; p = 0.061), associated with higher MAP values (107.2 ± 8.2 in nonresponders vs 89.5 ± 3.5 in responders; p = 0.195). The product of MAP × (1 + PRx), which was proposed as a measure of combined arterial hypertension and deranged autoregulation, showed a significant association with outcome (greater value in nonresponders; p = 0.013). CONCLUSION Autoregulation proves to associate with CSF circulation and appears strongest in shunt responders. Outcome following CSF diversion is possibly most favorable when CSF outflow resistance is increased and global cerebral autoregulation is intact, in combination with arterial normotension.
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Affiliation(s)
- Afroditi Despina Lalou
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
| | - Marek Czosnyka
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
| | - Joseph Donnelly
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
| | | | - Eva Nabbanja
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
| | - Nicole C Keong
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
- 2Department of Neurosurgery, National Neuroscience Institute and Duke-NUS Medical School, Singapore
| | - Matthew Garnett
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
| | - Zofia H Czosnyka
- 1Division of Neurosurgery, University of Cambridge Department of Clinical Neuroscience, Addenbrooke's Hospital, Cambridge, United Kingdom; and
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Abstract
OBJECTIVES Slow waves of intracranial pressure (ICP) are spontaneous oscillations with a frequency of 0.3-4 cycles/min. They are often associated with pathological conditions, following vasomotor activity in the cranial enclosure. This study quantifies the effects of general anaesthesia (GA) on the magnitude of B-waves compared with natural sleep and the conscious state. MATERIALS AND METHODS Four groups of 30 patients each were formed to assess the magnitude of slow waves. Group A and group B consisted of normal pressure hydrocephalus (NPH) patients, each undergoing cerebrospinal fluid (CSF) infusion studies, conscious and under GA respectively. Group C comprised conscious, naturally asleep hydrocephalic patients undergoing overnight ICP monitoring; group D, which included deeply sedated head injury patients monitored in the intensive care unit (ICU), was compared with group C. RESULTS The average amplitude for group A patients was higher (0.23 ± 0.10 mmHg) than that of group B (0.15 ± 0.10 mmHg; p = 0.01). Overnight magnitude of slow waves was higher in group C (0.20 ± 0.13 mmHg) than in group D (0.11 ± 0.09 mmHg; p = 0.002). CONCLUSION Slow waves of ICP are suppressed by GA and deep sedation. When using slow waves in clinical decision-making, it is important to consider the patients' level of consciousness to avoid incorrect therapeutic and management decisions.
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