OBSERVATIONS ON THE TOLERANCE OF THE INTRACRANIAL ARTERIES TO CATHETERIZATION.

EVERSIBLE segmental or diffuse narrowing of the larger cerebral arteries has been documented in the following circumstances: 1) direct mechanical, chemical or electrical stimulation, 4,~~ ~) traction during surgery, 9 3) subarachnoid hemorrhage from saccular aneurysms, 1,~ and 4) secondary to angiographic contrast media when the arteries are in a state of hyperirritability. 11 Further we have observed, anglographically, segmental narrowing persisting for weeks at the sites of applications of clips in postoperative patients with saccular aneurysms. In conditions with more generalized cerebral arterial involvement and slowing of the cerebral-circulation time, such as acute increased intracranial pressure, 2 cerebral trauma, s systemic hypertension and inhalation of hyperbaric oxygen, 3 the importance of arterial spasm is less certain. In a recent communication relating to the effects of other forms of arterial trauma, the responses of the larger cerebral arteries to the direct and saltatory passage of spherical plastic emboli were described. 6 This technique of artificial embolization has been useful in the treatment of certain inoperable arteriovenous malformations and the associated intraluminal trauma, similar to pathological embolization, does not induce spasm. Moreover, evidence indicates delayed proximal and distal dilatation may be a characteristic response. However, extension of this technique to include manipulation of delicate catheters or emboli within the intracranial arteries, as conceivably useful for the urgent