Angiographic and Isotope Pool Circulation Study of the Cerebral Hemispheres After Internal Carotid Artery Occlusion

¹ Indianapolis, Indiana

Fifty-eight patients with known occlusive disease of the internal carotid artery were examined by arteriograms and radio-iso

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tope flow studies. The arteriograms offered an excellent demonstration of collateral pathways, particularly via the ophthalmic, pterygopalatine and midmeningeal branches of the external system. The patency and presence of anterior or posteriorly communicator arteries are likewise readily assessed by this method. Radio-isotope flow studies were particularly useful for finite assessment of blood flow per unit time to the affected hemisphere. The angle of the ascending slope of the isotope curve, the width of the base, and the angle of the descending slope give a reliable picture of the overall flow rate per unit time to the affected hemisphere. The width of the slope more or less corresponding to the brain pool transit time is the most sensitive indicator. A mean normal brain pool transit time is five to nine seconds. With significant occlusive disease, the transit time may be prolonged 14 to 26 seconds. The angle and steepness of the ascending slope are likewise a sensitive indicator for the intactness of the isotope bolus and rapidity of delivery of blood to the affected area. The overall volume entering the affected hemisphere reflected by the area below the entire curve is the least sensitive and appropriate measurement. The height of the peak of the curve is likewise of secondary clinical significance since sluggishness of the circulation and increased brain pool transit time may actually result in increased height of the peak. An excellent correlation between the clinical picture and the appearance of the isotope curve, as well as the arteriogram was noted in this series. The change in the width of the curve and the width of the base of the curve appeared to bear a most significant correlation to the clinical improvement of the patient and his potential for ultimate recovery.