Hideo Takizawa

Changes in the Cerebrospinal Fluid Pulse Wave Spectrum Associated with Raised Intracranial Pressure

The frequency spectrum of the cerebrospinal fluid (CSF) pulse and the amplitude transfer function between arterial and CSF pressures were measured from the cisterna magna of anesthetized, artificially ventilated cats when the intracranial pressure (ICP) was raised by saline infusion. The spectrum of CSF pulsation was composed of a fundamental and three higher harmonic waves. The amplitude and the amplitude transfer function of each spectral component revealed significant positive correlation with ICP and negative correlation with cerebral perfusion pressure (CPP). Both the amplitude and the transfer function of the fundamental CSF pulse wave showed an exponential correlation with ICP and CPP. A distortion factor of the CSF pulse wave, a measure of its difference from a simple sine wave, was calculated from the spectral components. This showed that distortion of the CSF pulse wave was rapidly and progressively reduced as the ICP rose to 50 mm Hg and then was reduced less thereafter.

Analysis of changes in intracranial pressure and pressure-volume index at different locations in the craniospinal axis during supratentorial epidural balloon inflation.

During experimental supratentorial epidural compression of the brain, cerebrospinal fluid (CSF) pressure and pressure-volume index (PVI) were measured in the supra- and infratentorial compartments of the craniospinal axis in anesthetized ventilated cats. A transtentorial gradient of CSF pressure developed when CSF pressure in the lateral ventricle exceeded 20 mm Hg at balloon volumes of 0.4 to 1.2 ml. The shapes of both the pressure vs. volume and the pressure gradient vs. volume curves were exponential. PVI in the supratentorial compartment was lowered more rapidly as brain compression advanced than PVI in the infratentorial compartment. An index was calculated to represent the relative resistance to the flow of CSF across the tentorial hiatus during supratentorial brain compression. This revealed different resistances to the flow of CSF in the cephalic and caudal directions. A hypothesis concerning the hydrodynamic aspects of the development of tentorial herniation is presented.

Structural mechanics of the blowout fracture: numerical computer simulation of orbital deformation by the finite element method.

Blowout fractures most frequently involve the orbital floor. The contour of the orbit has been postulated as one of the factors responsible for this phenomenon, but only a few studies have been carried out. The present study was planned to determine the effect of the contour of the orbit when intraorbital pressure is raised to simulate the hydraulic mechanism of blowout fracture. The profile of the orbit was estimated from five dry human skulls, and the measurements were approximated to frame models. The deformation of these models by raised intraorbital pressure was calculated by computer simulation using the finite element method. In all of the orbital models, the deformation of the orbital floor was significantly greater than that of the roof. These findings verified that the orbital roof has a higher resistance than the floor against raised intraorbital pressure. We suspect that this resistance is due to the arched shape of the orbital roof, whereas the floor is rather flat.

Parasellar chondroma: A case report

A case of a 19-year-old man with a right parasellar chondroma examined with computed tomography (CT) and nuclear magnetic resonance (NMR) scan is reported. The literature about CT and NMR scan findings of intracranial chondroma is reviewed. Typical CT findings are a round, high density mass with calcification, that is only slightly enhanced by contrast medium.

Intracranial pressure monitoring by a subdurally placed silicone catheter: technical note.

A silicone catheter manufactured originally for ventricular fluid drainage was used for continuous monitoring of intracranial pressure. It can be placed under the dura mater immediately before replacing the craniotomy flap or by introduction through an ordinary burr hole. Pressure is monitored isovolumetrically by connecting the catheter to a pressure transducer mounted at the bedside. This technique has been used in 34 neurosurgical patients for periods of up to 12 days without any untoward effects. This monitoring system by a subdurally placed silicone catheter is simple, safe, inexpensive, and acceptably reliable. It has a place in clinical practice, particularly when the lateral ventricle cannot be tapped because of its deviation or collapse.

Validity of Measurements of Cerebrospinal Fluid Outflow Resistance Estimated by the Bolus Injection Method

Estimation of cerebrospinal fluid (CSF) outflow resistance (Ro) using a bolus injection method was carried out under normal conditions and in a state of artificially increased elastance produced by saline loading into the CSF space. These values of Ro were compared with Ro estimated by the steady state infusion method. Saline loading into the subarachnoid space decreased the buffering capacity significantly, as represented by the pressure-volume index (PVI), which was lowered from 0.72 ml under normal conditions of 0.56 ml during saline loading. The estimated values of Ro under normal conditions and during saline loading were 90.6 and 133.6 mm Hg/ml/minute, respectively. The steady state infusion method yielded an Ro value of 166.3 mm Hg/ml/minute. Ro was therefore considerably underestimated by the bolus method when used under normal conditions of resting intracranial pressure. Moreover, its error was bigger when Ro was higher. On the other hand, during the course of saline loading, the estimated value of Ro using the bolus method was not significantly different from that estimated by the steady state infusion method, even in the higher range of Ro. Estimation of Ro by the bolus injection method was more reliable when the buffering capacity of the craniospinal space was reduced.

Postoperative Morphological Recovery of Deformed Brain in Cases with Chronic Subdural Hematoma: The Difference Between a Burr Hole Closed Drainage and a Burr Hole Irrigation

This study was planned to evaluate morphologically whether a burr hole closed drainage (BD) is superior to a burr hole irrigation (BI) for a smoother re-expansion in cases with chronic subdural hematoma (CSDH). 107 cases with CSDH were treated either by BI or BD. The post-operative changes in clinical symptoms and CT findings in both groups were compared. Post-operative changes in clinical symptoms were not different significantly between the two surgical methods. The re-expansion of brain took a biphasic pattern in the BI group. In contrast, in the BD group, the course of re-expansion was not biphasic but more straight. We consider that BD is superior to BI by allowing steadier and slower re-expansion of the compressed brain.