Current Concepts of Cerebrovascular Disease Stroke. Use of Balloon Catheters in the Treatment of Cranial Arterial Abnormalities

Transcription

1 210 Current Concepts of Cerebrovascular Disease Stroke Use of Balloon Catheters in the Treatment of Cranial Arterial Abnormalities CHARLES KERBER, M.D. IMPORTANT and even dramatic, diagnostic and therapeutic advances can occur so rapidly that in this embarrassment of riches, some worth-while developments may be little noticed. In the last few years microsurgical techniques have changed the management of aneurysms, arterial malformations, and fistulas in the cranial circulatory tree. Nevertheless, there are situations in which the surgical approach appears inappropriate or hazardous, and, too often, it is assumed that no other reasonable treatment is available. Although this was once true, it is no longer. In 1904 Robert Dawbarn described his "starvation plan" for the treatment of some facial carcinomas and sarcomas. He exposed the external carotid artery, cannulated it, and injected a mixture of paraffin and vaseline into its branches, thus depriving the tumors of blood. He noted regression of many tumors, and he even claimed several cures. The technique was criticized by his colleagues, however, and was not heard of again until the 1960's when Luessenhop, 1 Newton, 2 and Boulous 8 and their associates introduced plastic and metallic emboli into the vessels of the central nervous system to obliterate arteriovenous malformations. Aided by good X-ray amplification, better contrast agents, and increasing angiographic skill, the technique gained support, and therapeutic embolization the deliberate embolic occlusion of the blood supply of vascular tumors and malformations became an accepted form of treatment. In the early application of the technique, the arterial flow was utilized to guide the emboli to their destination.. A catheter was introduced at a proximal point, such as the cervical internal carotid artery, and emboli were then injected through the catheter. The increased blood supply of the malformation carried the therapeutic embolus predominantly to the nidus. It quickly became apparent that while the technique was frequently successful, problems did occur. Reprinted from Current Concepts of Cerebrovascular Disease Stroke, July-August, 1979, edited by Oscar M. Reinmuth, M.D., published and copyrighted c by the American Heart Association. Dr. Kerber is from the Department of Radiology, University of Pittsburgh, Pittsburgh, PA. Reprints may be obtained from affiliates of the American Heart Association. In some patients the feeding vessels to the malformation exited from their parent arteries at a large angle. The emboli, having mass and more inertia than blood, tended to continue in a straight line and enter vessels supplying normal brain, producing ischemic infarction. This flow-guided technique also suffered from another more serious, fundamental defect. As sequential injections of occlusive material were made, more and more emboli blocked the vessels of the malformation, and eventually, the blood flow to the arteriovenous malformation became less than that to the surrounding normal tissues. Further emboli were likely to lodge in the vessels nourished by the flow to areas of normal brain. Unfortunately, this critical time of shift of flow from the abnormal tissue to the normal could not be reliably determined by angiographic evaluation during the execution of the embolization. The angiographers who pioneered this technique depended instead on the development of mild and usually reversible neurological deficits of function as a signal to stop. The deficits were not always transient, nor were they always mild. It may appear that flow-guided embolization has such theoretical disadvantages that it should not be used. That is not true however. Wolpert and Stein have now treated more than 50 patients with flowguided embolization, using silicone spheres as the therapeutic emboli. 4 " 6 Flow-guided embolization is very useful for treating vascular abnormalities located outside the central nervous system. It is accepted that surgical ligation of arteriovenous malformation feeders offers only short-term palliation. Other unseen feeding arteries often open up, some within hours, and the patient's symptoms may recur. Particulate flow-guided embolization provided significant improvement in the success of the treatment by delivering many small emboli close to and within the nidus. The recurrence of vascularization of the malformation was not prevented however. An important new approach, was proposed by Sano et al. 7 and later Doppman et al.' These investigators attempted to fill the smallest vessels of the arteriovenous malformation with plastic material which could then be hardened in place. If other potential feeding arteries were present, they would have no runoff, and revascularization would be prevented. This last refinement has been called "the formation of an intravascular cast." In the design of a system to create an intravascular cast, three problems must be solved:

2 CURRENT CONCEPTS OF CBVD STROKE/Kerber 211 (1) a suitable polymer must be found, (2) an experimental model must be designed to test the polymer, and (3) a catheter system must be developed to allow placement of embolic material precisely. The Polymer Food and Drug Administration (FDA) regulations make the search for appropriate intrayascular plastics extremely difficult. Manufacturers are unwilling to bear the high cost of development of these materials because of the small market expected for their use. As a result there are only a few plastics with which to experiment. All require FDA approval. The silicone rubbers are the most readily available, and an extensive literature has accumulated on their use in humans. Liquid silicones require the addition of a catalyst to initiate polymerization, which then occurs simultaneously within both the malformation and the catheter. Silicones are viscous, making their introduction through microcatheters difficult. They are also inert and cause almost no inflammatory reaction. As a result there is no subsequent clot propagation and no later ingrowth of fibrous tissue. The other available polymers, the cyanoacrylates, are powerful tissue adhesives. They have low viscosity and will pass readily through microcatheters. They do not require the external addition of catalyst and polymerize within one to two seconds on contact with blood and endothelium where excess electrons are available. The isobutyl-2 homologue is used in humans because it causes a mild inflammatory response. Concern about the possible carcinogenic potential of this class of drugs is not justified on the basis of the present evidence. Because it is a powerful adhesive and polymerizes rapidly, care must be taken not to glue the catheter to the tissue during treatment. It is possible to render both materials radiopaque by the addition of tantalum dust. The cyanoacrylate polymerization time may be modified by the addition of iophendylate.9 FIGURE 1. Carotid-external jugular vein fistula, canine. Angiography has been performed with magnification and subtraction techniques. (A) Contrast outlines the carotid artery (c), the short segment shunt (sj and the external jugular vein. Arrows show the direction of blood and contrast agent movement. (B) After deposition of cyanoacrylate, a large filling defect is present within the shunt. (C) Seven days later, repeat angiography shows complete occlusion of the shunt segments with preservation of carotid artery flow. No steal is present; note the increased perfusion of the muscular branches of the carotid artery. (Reprinted from Investigative Radiology, by permission.) Refinement of the Technique After practice with the various catheters, adapters, and stopcocks and with their assembly, adjustment, and manipulation, proficiency in use developed to the degree that all catheter manipulations could be made while maintaining the system clot-free. Next, a shortsegment, high-flow arteriovenous shunt was created in a series of dogs. Such an experimental fistula is often more difficult to treat than the slower flow abnormalities found in man. Skill in the successful treatment of the animal model led to easier and more confident manipulation of the human disease. The dog possesses a large external jugular vein which bifurcates high in the neck. One limb of this vein can be mobilized and sutured into the commdn carotid artery (fig. 1). After a suitable healing period a No. 5 French catheter was introduced into the common femoral artery and its tip directed into the orifice of the fistula under fluoroscopic observation. A second coaxial microcatheter was then directed into the proximal portion of the fistula. Simply allowing the cyanoacrylate to flow slowly into the fistula caused its closure (fig. IB, C). The fistulas remained closed, but autopsy demonstrated unacceptable quantities of the cyanoacrylate in the dogs' lungs. It became evident that a balloon-tipped catheter would be necessary to slow the rapid flow through the fistula during deposition of the polymer to prevent progression of slowly polymerizing material through the venous tree and into the right heart and lungs.10' Design of the Microcatheter Development of a microcatheter small enough to enter cerebral arterial branches of 1-mm diameter was undertaken. Since the arteries feeding an arteriovenous malformation are tortuous and thin-walled, the catheter must be soft and flexible to avoid causing spasm. A balloon tip introduced to control blood flow

3 212 STROKE FIGURE 2. Balloon and silicone microcatheter (4X magnification). (A) Uninflated. The black catheter measures 0.86 mm (0.034 inch) in diameter. Uninflated balloon diameter is 1.1 mm (0.045 inch). (B) Inflated. (C) Further pressure causes liquid, either contrast agent or cyanoacrylate, to squirt from the tip. (Reprinted from Radiology, by permission.) during plastic deposition had the additional advantage that it could be partially inflated to act as a kind of parachute and thereby provide a flow-guided system. Poisseuille's equation indicates that resistance to flow varies inversely to the 4th power of the catheter radius. Reducing the diameter by half increases resistance 16-fold. In microcatheters of the small luminal diameter required for the present application, the resistance to flow is a very important factor in catheter design. In other catheter applications such as the Swan-Gantz catheter, two lumens are provided: one to inflate or deflate the balloon, the other to sample or deliver fluid distal to the balloon. Such a double-lumen system is impossible in microcatheters because of the flow resistance factor. To provide for balloon control, fluid delivery, and a reasonable lumen size, it was necessary to design a single-lumen system. A reinforcement on the tip of the balloon allowed the creation of a calibrated leak. The first increment of pressure expanded the balloon; then, with more pressure, the fluid, either contrast agent for catheter localization or polymer for treatment, was delivered distally (fig. 2)."-12 With these tools a cautious exploration of the VOL 11, No 2, MARCH-APRIL 1980 human vascular tree began. Before attempting intracranial treatment, renal arteries were occluded, and 2 patients were given satisfactory palliation chemotherapy for renal carcinoma. The microcatheter was next placed intracranially (fig. 3). Vessels as small as 1 mm were catheterized. The silicone microcatheter appeared to be well tolerated, and after introduction of microcatheters more than 100 times into the intracranial circulation, no visible vascular spasm or vessel rupture was found.12 Temporary neurological deficits did occur at times. The deficits would usually appear 30 seconds after balloon inflation and, with one exception, disappeared completely within 30 seconds after balloon deflation. The deficits did not always seem precisely appropriate for the anatomical distribution of the vessels being catheterized and occluded. Occasionally, there were surprises. After balloon occlusion of one patient's right internal carotid artery, a profound right hemiparesis and severe aphasia developed. Further angiographic evaluation showed that the left internal carotid artery was completely occluded by arteriosclerotic plaque. The collateral pathways could not always be predicted correctly and probably account for some of the inappropriate neurological signs. Sometimes the deficits occurred within a few seconds of balloon inflation. Apparently, this represented an area of no collateral reserve. For example, one young patient had a sudden tonic movement of the head to the left and violent left nystagmus when the catheter was inadvertently placed in her posterior inferior cerebellar artery. Injection into the riuukt 3. Lateral SKUII raaiograpn oj a b-year-oid girt. Catheterization of the posterior portion of the thalamus via the vertebral artery shows the flexibility of the catheter. The catheter tip lies within one of the thalamo perforate arteries and a small amount of contrast agent can be seen outlining the thalamic arterioles. (Reprinted from Radiology, by permission.)

4 CURRENT CONCEPTS OF CBVD STROKE/Kerber 213 FIGURE 4. Recurrent anterior intramedullary spinal cord arteriovenous malformation. Fron^ lal view, subtraction films except for C. (A) No. 5.8 French catheter (c), is in the supreme thoracic artery. Multiple small feeders and an enlarged anterior spinal artery (open arrows) supply the malformation (closed arrows) at about the T4 level. (B) The balloon microcatheter (open arrows) injected through the 5.8 French catheter perfuses the malformation (closed arrows) with contrast agent during a provocative test occlusion; (b) balloon. (C) Cyanoacrylate impregnated with tantalum has been deposited and the microcatheter withdrawn. (D) Followup angiogram. Selective injection into the supreme thoracic artery now shows better filling of soft tissue radicals and no filling of the malformation. (Reprinted from American Journal of Roentgenology, by permission.)

5 214 STROKE posterior inferior cerebellar artery of another patient produced an immediate feeling of impending death, which resolved when the catheter was removed. As a general rule, however, the brain has tolerated well the catheterization of its vessels and the selective infusion of contrast agents. The deficits produced, even though alarming, have usually resolved promptly. Results It is possible to group the central nervous system abnormalities treated into 3 general categories: spinal cord and brain arteriovenous malformations and carotid cavernous fistulas. Of more than 200 patients seen for possible treatment, only 22 were selected. Our indications are 1) a clearly deteriorating clinical course; 2) subjective feelings incompatible with con- VOL 11, No 2, MARCH-APRIL 1980 tinued life (uncontrollable headaches or suicidal feelings caused by the symptoms); 3) intractable seizures; 4) presurgical reduction of blood flow. We have now treated 4 spinal cord arteriovenous malformations. One of these was an anterior intramedullary lesion which had recurred following surgery (fig. 4). After a second hemorrhage we were able to obliterate the lesion with marked improvement in clinical function. Three carotid cavernous fistulas have been treated with improvement in vision and resolution of associated cranial nerve palsies. All three patients suffered significant but temporary neurological deficit either during or after the treatment but are now nearly asymptomatic (fig. 5). In all 3 patients flow through the internal carotid artery was preserved. Fifteen patients with intracranial malformations FIGURE 5. Lateral view of the skull. The patient's nose is to the right. (Upper left) Internal carotid arteriogram shows immediate filling of the cavernous sinus (closed arrows) and a dilated superior ophthalmic vein (open arrows). (Lower left) The balloon microcatheter has been flowguided into the fistula orifice. (Upper right) Fluoroscopic controlled deposition of the tantalumimpregnated cyanoacrylate. (Lower right) Lateral carotid arteriogram, subtraction technique. A follow-up examination shows complete obliteration of the fistula with preservation of the flow through the carotid artery. The ophthalmic artery is patent, and there is now better filling of the intracranial branches.

6 CURRENT CONCEPTS OF CBVD STROKE/Kerber 215 have been treated. Although complete obliteration of all abnormal vascular channels has not been achieved in any, there has been gratifying alleviation of major symptoms or signs, and in several the partial treatment has permitted a much less difficult definitive surgical excision (fig. 6). Areas of brain surrounding arteriovenous malformations are often deprived of blood and frequently lose their homeostatic mechanisms. Total occlusion of the blood supply to a malformation suddenly produces a perfusion pressure in these vessels which, although relatively normal, is much higher than before. Spetzler et al. 13 noted the development of fatal cerebral edema following the removal of a large arteriovenous malformation in one of his patients because of this phenomenon. To avoid such irreversible edema, the FIGURE 6. Lateral views of the skull. Treatment for deep parieto-occipital arteriovenous malformation. (Upper left) One subtracted view, left vertebral angiogram. The malformation is fed by posterior temporal, calcarine, and parieto-occipital branches of the posterior cerebral artery. (Lower left) Microcatheter in place. (Upper right) Tantalum-impregnated isobutyl-2 cyanoacrylate has been deposited and the catheter withdrawn. (Lower right) Angiogram performed two weeks later shows some residual filling of the malformation. Follow up angiogram one year later shows no change.

7 216 STROKE VOL 11, No 2, MARCH-APRIL 1980 patients are premedicated with dexamethasone before the treatment, and the occlusions are staged over several weeks. Complications One man developed a severe parietal lobe infarction during catheter manipulation in the middle cerebral artery, probably caused by a clot from the coaxial catheter system. In 3 patients the catheters became glued in the vascular tree, trapped by the rapid polymerization of the plastic. One was removed percutaneously; one was removed during subsequent surgery for his malformation, and the third remains in place. None of the 3 patients had symptoms referable to the trapped catheters. Treatment of carotid cavernous fistula has been difficult. With our first patient we caused an infarct with hemiparesis and aphasia which lasted 24 hours. The third carotid cavernous fistula treatment appeared uncomplicated, but approximately 2 weeks after the treatment the patient had a transient ischemic attack. Follow up study showed some cyanoacrylate present in middle cerebral branches. She remains asymptomatic. There has been no instance of vascular spasm or rupture associated with the use of the microcatheter. The Future Catheterization and treatment of the intracranial vessels is an exciting undertaking. Our efforts are still primitive, relatively few patients have been treated, and no long-term results are available. Nonetheless, the results until now have encouraged us to continue this undertaking. Although we feel the technique is already a valuable treatment tool, we anticipate that new uses will develop, such as regional cerebral perfusion or the delivery of specific therapeutic agents. References 1. Luessenhop AJ, Spence WT: Artificial embolization of cerebral arteries: Report of use in a case of arteriovenous malformation. JAMA 172: 1153, Newton TH, Adams JE: Angiographic demonstration and nonsurgical embolization of spinal cord angioma. Radiology 91: 873, Boulous R, Kricheff II, Chase NE: Value of cerebral angiography in the embolization treatment of cerebral arteriovenous malformation. Radiology 97: 65-70, Wolpert SM, Stein BM: Catheter embolization of intracranial arteriovenous malformations as an aid to surgical excision. Neuroradiology 10: 73-88, Stein BM, Wolpert SM: Surgical and embolization treatment of cerebral arteriovenous malformations. Surg Neurol 6: , Wolpert SM, Stein BM: Factors governing the course of emboli in the therapeutic embolization of cerebral arteriovenous malformations. Radiology (in press) 7. Sano K, Jimbo M, Sarto I, et al: Artificial embolization with liquid plastic. Neurol Medicochir (Tokyo) 8: 198, Doppman JL, Zapol W, Pierce J: Transcatheter embolization with a silicone rubber preparation: Experimental observations. Invest Radiol 6: 304, Cromwell LD, Kerber CW: Modification of cyanoacrylate for therapeutic embolization: Preliminary experience. Am J Roentgen (in press) 10. Kerber CW: Experimental arteriovenous fistula: Creation and percutaneous catheter obstruction with cyanoacrylate. Invest Radiol 10: 10-17, Kerber CW: Balloon catheter with a calibrated leak. Radiology 120: , Kerber CW, Bank WO, Cromwell LD: Calibrated leak balloon microcatheter: Device for arterial exploration and occlusive therapy. Am J Roentgen 132: , Spetzler RF, Wilson CB, Weinstein P, et al: Normal perfusion pressure breakthrough theory. Clin Neurosurg 25: , 1977