Masahiro Furuse

Brain Tissue Pressure Gradients

The problem of the existence, propagation and meaning of intracranial tissue pressure gradients has attracted an increasing interest since the initial application of the wick-catheter method to the brain (1). In the present study, the development of brain tissue pressure gradients, as well as their influence on cerebral blood flow distribution, and on intracranial volume buffering capacity were examined in mechanically ventilated normocapnic cats under Nembutal anesthesia (35 mg/kg body-weight). The following expanding lesions were studied: (1) unilateral cryogenic damage (by application of liquid nitrogen through the intact calvarium) in 33 animals and (2) traumatic intracerebral hemorrhage (in 13 animals). Brain tissue pressure was continuously recorded from both internal capsules and one cerebellar peduncle by means of wick-catheters. Further parameters measured included: systemic arterial and central venous pressures, blood gases, and EEG. At the end of each experiment cerebral blood flow distribution was studied by the “single dye passage” technique as developed in our laboratory (2,3).

Assessment of T1 time course changes and tissue-blood ratios after Gd-DTPA administration in brain tumors

Sequential T1 changes in brain tumor tissue after Gd-DTPA administration were investigated in 10 patients, including 4 meningiomas, 2 gliomas, 3 metastatic cerebral tumors and 1 brain abscess. T1 values were measured serially for 60 minutes following Gd-DTPA injection using a magnetic focusing technique. In vitro T1 of the whole blood samples was also comparatively examined. Time processes in the tissue-blood ratio (TBR) were calculated from two-point relaxation rates at 5 and 30 minutes. The obtained ratios of TBR were ranged from 1.0 to 3.0, probably depending on histological types of brain tumor (the value of 1.0 to 1.5 for meningioma and 1.5 to 3.0 for glioma and metastatic tumor). No significant changes in the T1 value were observed in the examined normal tissue and peritumoral edema. These results indicate that Gd-DTPA plays an important role not only as an image enhancer for tumor tissue but also as an indicator for estimating the blood-brain barrier function.

Spin-lattice relaxation times of bound water—Its determination and implications for tissue discrimination

Measurements were made of T1 of bound water (T1b) and bound water fraction (alpha) for gelatin solutions and human tissues (sera, brain tumor, cerebral white matter). Bound water fraction in each sample was measured by means of thermal analysis (differential scanning calorimetry: DSC). T1 values were measured by FONAR QED 80-alpha. T1b values were calculated by an equation derived from the fast-exchange two-state model. In the study of gelatin solutions, the relationship between T1 and water content differed depending on the sort of solutions. This was considered to be due to differences in T1b values. In each biological tissue the values of T1b and alpha had different distributions. These results indicate that values of T1b and alpha for biological tissues may be altered in correspondence to the changes in pathophysiological states in those tissues.

Thermal Analysis on the State of Free and Bound Water in Normal and Edematous Brains

Analysis of the state of tissue water in brain parenchyma is essential for studying the pathogenesis of brain edema. However, due to technological problems the state of water in tissue remains difficult to assess. Ambo1 attempted in 1951 to measure bound water by the cobalt chloride method applied to formalin-fixed brain. Utilizing NMR, Go and Edzes5 studied in 1975 the state of protons of fresh brain tissue and found an increase in relaxation time of edematous brain tissue compared to controls. An increase of relaxation time is considered to result from an increase of free water. However, absolute values of free and bound water have not been determined yet.

Magnetic Resonance Imaging quantitation of superior sagittal sinus flow: Correlation to cerebral blood flow measured by xenon-enhanced computed tomography

We compared measurements of venous blood flow velocity in the superior sagittal sinus (SSS) obtained by magnetic resonance imaging (MRI) and quantitative measurements of cerebral blood flow (CBF) obtained by xenon-enhanced CT, in neurosurgical patients and normal volunteers, to assess the clinical usefulness of MRI for determination of CBF. Flow measurements were obtained in 15 neurosurgical patients and 3 normal volunteers. SSS velocimetry was performed using the direct bolus imaging technique with a 1.5-tesla MRI system near the point of lambda on a sagittal MR image. Quantitative CBF was measured by xenon-enhanced CT and correlated with SSS flow velocity. We also examined the effect of surgical evacuation of a hematoma or cranioplasty in 3 patients, mannitol in 5 patients and acetazolamide in 4 patients by performing SSS velocimetry. The peak SSS flow velocity during the entire cardiac cycle was 27.2 +/- 6.3 cm sec-1 (mean +/- SD) in normal volunteers and 23.5 +/- 8.9 cm sec-1 in patients. The SSS flow velocity increased after surgery. Mean SSS peak flow velocity increased by 24% and 48% at 10 min after administration of mannitol and acetazolamide, respectively. SSS peak flow velocity showed significant linear correlations with both cerebral cortical (r = 0.74) and hemispheric flows (r = 0.73). Our results suggest that SSS flow velocity reflects CBF and that MRI assessment of SSS flow provides a simple method for assessing and monitoring global changes in cerebral hemodynamics.

Fastigial Pressor Response Observed during an Operation on a Patient with Cerebellar Bleeding–An Anatomical Review and Clinical Significance

The fastigial pressor response (FPR) consists of an abrupt rise in blood pressure and tachycardia with hyperpneic response. The FPR is an important sign in posterior fossa surgery for respiration in postoperative patients. The authors experienced a distinct pressor, tachycardiac, and hyperpneic response elicited when controlling bleeding using a bipolar coagulator forceps at the subfastigial white matter in a 72-year-old man with cerebellar hemorrhage. This response was confirmed by bipolar electrodes, which produced a weak current under deeper anesthesia by increasing the concentration of enflurane. The postoperative course of this patient was uneventful. A FPR was suggested to be mediated by axons passing between the nucleus fastigii and the fourth ventricle. These commissural fibers mediating the FPR were suggested to be countercurrent efferent pathways from both sides of the nucleus parabrachialis lateralis, located at the dorsolateral corner of the rostral pons. The authors conclude that the partial destruction of the subfastigial commissural fiber bundle did not result in permanent respiratory deficit. Fatal respiratory disturbance might be anatomically suggested by completely cutting off this fiber bundle.

Pressure wave with apnoea evaluated by sleep level in patient with ventricular dilation.

Seventeen patients who were suspected of having hydrocephalus, because of ventricular dilation from various causes, were included in this study of the pathophysiologic basis of the appearance of pressure waves (PWs). Pressure waves accompanied by apnoeas originated in arousal responses in the resting state of these patients. Frequent fits of apnoea were included in the entire sleep apnoea syndrome. Most pressure waves characteristically appeared in the state of non-REM sleep. During the appearance of such pressure oscillations, intracranial pressure was elevated transiently. This coincidence in the appearance of pressure oscillations with sleep apnoea was the most characteristic pathophysiologic result from this polygraphic study of the patients.

Mutual Relations Between Shifting of Focal Brain Structures and Intracranial Pressure

During expansion of an intracranial mass, variation in focal structural shiftings are possibly caused from tissue pressure gradients and local tissue plastic properties, convincingly playing an essential role in functional dynamics in the cranium and the formation of hernia. This study is designed to examine the mode of shifting in various Parts of the brain and its correlations to ICP change during the process of the gradual expansion of an intracerebral balloon.

Effect of internal jugular vein ligation on resorption of cerebrospinal fluid

The influence of jugular vein ligation on CSF resorption was examined experimentally by means of a manometric ventricular infusion test in dogs. Capacity of CSF absorption was decreased in a stepwise manner according to whether unilateral or bilateral ligation of jugular veins was performed. Interestingly, in addition to rises in ICP, dural sinus pressure was predominantly elevated after bilateral jugular ligation, often exceeding the ICP level. The CSF malresorption observed was considered to be closely related to the lowered pressure gradients between ICP and intracranial sinus pressure.

Intracranial Pressure/Volume Relationship in Acute Experimental Water Intoxication

The steep slope of the intracranial pressure/volume (P/V) curve at higher intracranial pressures is attributed to a decrease in volumetric buffering capacity within the cranium, and is believed to play an important role in cerebral hemodynamics. The experiments herein reported were designed to study the relations between the development of brain edema, the increase in brain tissue pressures, and the changes in cerebral blood flow distribution in acute water intoxication.