Tag: Cerebral blood flow

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Microcirculatory Impairment and Cerebral Injury in Hydrocephalus and the Effects of Cerebrospinal Fluid Diversion

Neurosurgery 95:469–479, 2024

Hydrocephalus is characterized by progressive enlargement of cerebral ventricles, resulting in impaired microvasculature and cerebral hypoperfusion. This study aimed to demonstrate the microvascular changes in hydrocephalic rats and the effects of cerebrospinal fluid (CSF) release on cerebral blood flow (CBF).

METHODS: On postnatal day 21 (P21), male Wistar rats were intracisternally injected with either a kaolin suspension or saline. On P47, Evan’s ratio (ER) was measured using MRI. On P49, the arteriolar diameter and vascular density of the pia were quantified using a capillary video microscope. The CBF was measured using laser Doppler flowmetry. The expressions of NeuN and glial fibrillary acidic protein determined by immunochemical staining were correlated with the ER. The CBF and rotarod test performance were recorded before and after CSF release. The expressions of 4-hydroxynonenal (4-HNE) and c-caspase-3 were studied on P56.

RESULTS: Ventriculomegaly was induced to varying degrees, resulting in the stretching and abnormal narrowing of pial arterioles, which regressed with increasing ER. Quantitative analysis revealed significant decreases in the arteriolar diameter and vascular density in the hydrocephalic group compared with those in the control group. In addition, the CBF in the hydrocephalic group decreased to 30%–50% of that in the control group. In hydrocephalus, the neurons appear distorted, and the expression of 4-HNE and reactive astrogliosis increase in the cortex. After CSF was released, improvements in the CBF and rotarod test performance were inversely associated with the ER. In addition, the levels of 4-HNE and c-caspase-3 were further elevated.

CONCLUSION: Rapid ventricular dilatation is associated with severe microvascular distortion, vascular regression, cortical hypoperfusion, and cellular changes that impair the recovery of CBF and motor function after CSF release. Moreover, CSF release may induce reperfusion injury. This pathophysiology should be taken into account when treating hydrocephalus.

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Persistent Metabolic Disturbance in the Perihemorrhagic Zone Despite a Normalized Cerebral Blood Flow Following Surgery for Intracerebral Hemorrhage

Neurosurgery 84:1269–1279, 2019

We hypothesized that reduced cerebral blood flow (CBF) and/or energy metabolic disturbances exist in the tissue surrounding a surgically evacuated intracerebral hemorrhage (ICH). If present, such CBF and/or metabolic impairments may contribute to ongoing tissue injury and the modest clinical efficacy of ICH surgery.

OBJECTIVE: To conduct an observational study of CBF and the energy metabolic state in the perihemorrhagic zone (PHZ) tissue and in seemingly normal cortex (SNX) by microdialysis (MD) following surgical ICH evacuation.

METHODS: We evaluated 12 patients (median age 64; range 26-71 yr) for changes in CBF and energy metabolism following surgical ICH evacuation using Xenon-enhanced computed tomography (n = 10) or computed tomography perfusion (n = 2) for CBF and dual MD catheters, placed in the PHZ and the SNX at ICH surgery.

RESULTS: CBF was evaluated at a mean of 21 and 58 h postsurgery. In the hemisphere ipsilateral to the ICH, CBF improved between the investigations (36.6 ± 20 vs 40.6 ±20 mL/100 g/min; P<.05). In total, 1026MD sampleswere analyzed for energymetabolic alterations including glucose and the lactate/pyruvate ratio (LPR). The LPR was persistently elevated in the PHZ compared to the SNX region (P < .05). LPR elevations in the PHZ were predominately type II (pyruvate normal-high; indicating mitochondrial dysfunction) as opposed to type I (pyruvate low; indicating ischemia) at 4 to 48 h (70% vs 30%) and at 49 to 84 h (79% vs 21%; P < .05) postsurgery.

CONCLUSION: Despite normalization of CBF following ICH evacuation, an energy metabolic disturbance suggestive of mitochondrial dysfunction persists in the perihemorrhagic zone.

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Effects of Cranioplasty on Cerebral Blood Flow Following Decompressive Craniectomy

Neurosurgery 81:204–216, 2017

Cranioplasty after decompressive craniectomy (DC) is routinely performed for reconstructive purposes and has been recently linked to improved cerebral blood flow (CBF) and neurological function.

OBJECTIVE: To systematically review all available literature to evaluate the effect of cranioplasty on CBF and neurocognitive recovery.

METHODS: A PubMed, Google Scholar, and MEDLINE search adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines included studies reporting patients who underwent DC and subsequent cranioplasty in whom cerebral hemodynamics were measured before and after cranioplasty.

RESULTS: The search yielded 21 articles with a total of 205 patients (range 3–76 years) who underwent DC and subsequent cranioplasty. Two studies enrolled 29 control subjects for a total of 234 subjects. Studies used different imaging modalities, including CT perfusion (n = 10), Xenon-CT (n = 3), single-photon emission CT (n = 2), transcranial Doppler (n = 6), MR perfusion (n = 1), and positron emission tomography (n = 2). Precranioplasty CBF evaluation ranged from 2 days to 6 months; postcranioplasty CBF evaluation ranged from 7 days to 6 months. All studies demonstrated an increase in CBF ipsilateral to the side of the cranioplasty. Nine of 21 studies also reported an increase in CBF on the contralateral side.Neurological function improved in an overwhelming majority of patients after cranioplasty.

CONCLUSION: This systematic review suggests that cranioplasty improves CBF following DC with a concurrent improvement in neurological function. The causative impact of CBF on neurological function, however, requires further study.

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Novel method for dynamic control of intracranial pressure

J Neurosurg 126:1629–1640, 2017

Intracranial pressure (ICP) pulsations are generally considered a passive result of the pulsatility of blood flow. Active experimental modification of ICP pulsations would allow investigation of potential active effects on blood and CSF flow and potentially create a new platform for the treatment of acute and chronic low blood flow states as well as a method of CSF substance clearance and delivery. This study presents a novel method and device for altering the ICP waveform via cardiac-gated volume changes.

METHODS The novel device used in this experiment (named Cadence) consists of a small air-filled inelastic balloon (approximately 1.0 ml) implanted into the intracranial space and connected to an external programmable pump, triggered by an R-wave detector. Balloons were implanted into the epidural space above 1 of the hemispheres of 19 canines for up to 10 hours. When activated, the balloons were programed to cyclically inflate with the cardiac cycle with variable delay, phase, and volume. The ICP response was measured in both hemispheres. Additionally, cerebral blood flow (heat diffusion and laser Doppler) was studied in 16 canines.

RESULTS This system, depending on the inflation pattern of the balloon, allowed a flattening of the ICP waveform, increase in the ICP waveform amplitude, or phase shift of the wave. This occurred with small mean ICP changes, typically around ± 2 mm Hg (15%). Bilateral ICP effects were observed with activation of the device: balloon inflation at each systole increased the systolic ICP pulse (up to 16 mm Hg, 1200%) and deflation at systole decreased or even inverted the systolic ICP pulse (-0.5 to -19 mm Hg, -5% to -1600%) in a dose-(balloon volume) dependent fashion. No aphysiological or deleterious effects on systemic pressure (≤ ±10 mm Hg; 13% change in mean pressure) or cardiac rate (≤ ± 17 beats per minute; 16% change) were observed during up to 4 hours of balloon activity.

CONCLUSIONS The results of these initial studies using an intracranially implanted, cardiac-gated, volume-oscillating balloon suggest the Cadence device can be used to modify ICP pulsations, without physiologically deleterious effects on mean ICP, systemic vascular effects, or brain injury. This device and technique may be used to study the role of ICP pulsatility in intracranial hemo- and hydrodynamic processes and introduces the creation of a potential platform of a cardiac-gated system for treatment of acute and chronic low blood flow states, and diseases requiring augmentation of CSF substance clearance or delivery.

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Comparison of Indocyanine Green Angiography and Laser Speckle Contrast Imaging for the Assessment of Vasculature Perfusion

Neurosurgery 71:1023–1031, 2012

Assessment of the vasculature is critical for overall success in cranial vascular neurological surgery procedures. Although several methods of monitoring cortical perfusion intraoperatively are available, not all are appropriate or convenient in a surgical environment. Recently, 2 optical methods of care have emerged that are able to obtain high spatial resolution images with easily implemented instrumentation: indocyanine green (ICG) angiography and laser speckle contrast imaging (LSCI).

OBJECTIVE: To evaluate the usefulness of ICG and LSCI in measuring vessel perfusion.

METHODS: An experimental setup was developed that simultaneously collects measurements of ICG fluorescence and LSCI in a rodent model. A 785-nm laser diode was used for both excitation of the ICG dye and the LSCI illumination. A photothrombotic clot model was used to occlude specific vessels within the field of view to enable comparison of the 2 methods for monitoring vessel perfusion.

RESULTS: The induced blood flow change demonstrated that ICG is an excellent method for visualizing the volume and type of vessel at a single point in time; however, it is not always an accurate representation of blood flow. In contrast, LSCI provides a continuous and accurate measurement of blood flow changes without the need of an external contrast agent.

CONCLUSION: These 2 methods should be used together to obtain a complete understanding of tissue perfusion.

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Microscope-Integrated Quantitative Analysis of Intraoperative Indocyanine Green Fluorescence Angiography for Blood Flow Assessment

Neurosurgery 70[ONS Suppl 1]:ons65–ons74, 2012 DOI: 10.1227/NEU.0b013e31822f7d7c

Intraoperative measurements of cerebral blood flow are of interest during vascular neurosurgery. Near-infrared indocyanine green (ICG) fluorescence angiography was introduced for visualizing vessel patency intraoperatively. However, quantitative information has not been available.

OBJECTIVE: To report our experience with a microscope with an integrated dynamic ICG fluorescence analysis system supplying semiquantitative information on blood flow.

METHODS: We recorded ICG fluorescence curves of cortex and cerebral vessels using software integrated into the surgical microscope (Flow 800 software; Zeiss Pentero) in 30 patients undergoing surgery for different pathologies. The following hemodynamic parameters were assessed: maximum intensity, rise time, time to peak, time to halfmaximal fluorescence, cerebral blood flow index, and transit times from arteries to cortex.

RESULTS: For patients without obvious perfusion deficit, maximum fluorescence intensity was 177.7 arbitrary intensity units (AIs; 5-mg ICG bolus), mean rise time was 5.2 seconds (range, 2.9-8.2 seconds; SD, 1.3 seconds), mean time to peak was 9.4 seconds (range, 4.9-15.2 seconds; SD, 2.5 seconds), mean cerebral blood flow index was 38.6 AI/s (range, 13.5-180.6 AI/s; SD, 36.9 seconds), and mean transit time was 1.5 seconds (range, 360 milliseconds-3 seconds; SD, 0.73 seconds). For 3 patients with impaired cerebral perfusion, time to peak, rise time, and transit time between arteries and cortex were markedly prolonged (.20, .9 , and .5 seconds). In single patients, the degree of perfusion impairment could be quantified by the cerebral blood flow index ratios between normal and ischemic tissue. Transit times also reflected blood flow perturbations in arteriovenous fistulas.

CONCLUSION: Quantification of ICG-based fluorescence angiography appears to be useful for intraoperative monitoring of arterial patency and regional cerebral blood flow.

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