Intracranial electroencephalographic and evoked-potential recording from intravascular guide wires.

We describe a technique for recording electroencephalographic and evoked-potential information directly from the cerebral hemispheres and brain stem, via an endovascular approach. Recordings were performed with polytef-insulated guide wires in the course of interventional angiographies in 23 patients. All registrations were compared with simultaneous recordings from extracranial electrodes. This preliminary study raises the possibility that this technique may help to explore the electric activity of deep cerebral structures otherwise accessible only by stereotactic puncture or electrode insertion.

[The basis for ultrasonic phenomena during the injection of x-ray contrast media]. / Zur Grundlage der Ultraschallphänomene während der Injektion von Röntgenkontrastmitteln.

During the injection of contrast media for cerebral angiography, high-intensity ultrasound reflections can be recorded by Doppler sonography and B-mode scanning. This phenomenon was examined during carotid angiography and by in vitro experiments in tube models. Our results show that these high-intensity reflections are caused by: (1) transient interfaces of impedance between small compartments of contrast medium and blood and (2) small gas bubbles, which are always present in freshly aspirated contrast medium. Therefore, intraarterially injected contrast medium acts as an ultrasound contrast medium as well.

[Synchronous pulse changes in contrast density during carotid angiography]. / Pulssynchrone Anderungen der Kontrastdichte bei der Karotisangiographie.

The relationship between maximal contrast density in DSA and blood flow in doppler sonography was examined in tube model studies and in carotid angiography. During pulsatile flow, pulse-synchronous changes of contrast density can be registered. The maxima of opacification coincide with the doppler-sonographic phase of re-increasing blood flow after a preceding depression. This is caused by the accumulation of contrast medium at the tip of the catheter during diastole and the subsequent dilution of contrast medium by the increasing blood flow during systole. In model studies as well as in angiography, the time interval between the doppler-sonographic maximum of flow and the maximum of contrast density is very constant and is prolonged with increasing distance from the tip of the catheter. This latency between 2 maxima which are registered at the same region of interest, is caused by the higher speed of propagation of the flow wave compared to the actual movement of the blood corpuscles and contrast medium. The understanding of the relationship between cardiac action, blood flow, and contrast density may improve the functional interpretation of angiograms.

Transcranial Doppler monitoring of blood flow in the middle cerebral artery during angiography and drug perfusion.

With the new technique of transcranial Doppler sonography it is possible to record transient changes of blood flow within the major basal cerebral arteries. The injection of saline and contrast medium into the internal carotid artery is followed immediately by a marked turbulence of flow within the middle cerebral artery depending on the amount and pressure of the injected material. In addition, the flow in the middle cerebral artery is increased by the injection of saline, but reduced by the injection of contrast medium for 3 to 4 seconds and finally increased for 8 to 10 seconds. No changes are seen on the contralateral side. The recordings of blood flow within the middle cerebral artery during 1.3-bis(2-chlorethyl)nitrosurea (BCNU) perfusion of glioblastoma recurrences via a flow-directed balloon catheter showed no obvious alterations during injections into the upper part of the carotid siphon, but a marked reduction of diastolic flow during injections into the middle cerebral artery. The reduction of flow may explain some of the complications of angiography.

Doppler-sonographic examination of the arterial flow in the carotid and supratrochlear arteries during carotid angiography.

In 55 patients, the blood flow in the carotid and supratrochlear arteries was examined by Doppler sonography during cerebral angiography. In general, a threefold response was observed: an initial phase of turbulence during the injection was followed by a phase of depressed and then of increased arterial flow. The second phase of reduced perfusion which probably is caused by the increased viscosity of the mixture of contrast medium and blood, is more pronounced in the internal carotid artery, whereas the third phase of accelerated flow is more marked in the external carotid artery. In patients with an occlusion of the internal carotid artery, the cerebral blood supply often depends on the collateral pathway via the ophthalmic artery. In these cases, the reduction of the blood flow is specially marked and long-lasting, as we could show. This may contribute to a higher angiographic risk of those cases with an important ophthalmic collateral flow.