Endovascular treatment of vertebral artery dissection using stents and coils: its pitfall and technical considerations.

OBJECTIVE: There are various options for the treatment of vertebral artery dissection aneurysms (VADA). Treatment with stents may be an effective method to treat VADA involving the posterior inferior cerebellar artery (PICA) and dissection of the dominant vertebral artery (VA). In this article, our personal experience of the treatment of VADAs by using stents and coils is reported. METHODS: Since 1998, 26 cases of VADA have been treated by endovascular surgery by the first author. Of these cases, 6 cases were treated using stents, 3 of which were treated using stent and coils, 2 patients were treated using double overlapping stents, and the remaining one patient was treated using a single stent. RESULTS: In all patients, dissection aneurysms were successfully covered by stents. There was one complication: an intraprocedural rupture during additional coil insertion without neurological deterioration. Follow-up angiography was performed in all 5 surviving patients except for one patient who died due to the severity of his original subarachnoid hemorrhage (mean duration of follow-up angiography 22.8 months, range 15-57 months). Total or subtotal disappearance of the VADA was achieved in all 5 cases. At one year after the treatment, all 5 surviving patients remained clinically stable without any neurological deficit. CONCLUSIONS: Treatment using stents is an effective alternative for the treatment of VA dissecting aneurysms, especially for lesions of the dominant VA or involving the PICA. However, additional coil insertion should be performed very carefully and may be avoided if stagnation of contrast material is achieved after overlapping stenting.

Non-adhesive cyanoacrylate as an embolic material for endovascular neurosurgery.

Endovascular neurosurgery is now becoming available as one of strategies for the treatment of cerebro-spinal arterio-venous malformations and aneurysms. For this treatment, a microcatheter is advanced into or close to a lesion and then an embolic material is administered through it to obliterate the lesion. N-butyl-2-cyanoacrylate (NBCA) has preferentially been used as an embolic material in Europe and America. However, its exceptionally strong adhesive force sometimes causes adhesion between the tip of the microcatheter and the artery. In this study, a new non-adhesive cyanoacrylate, isostearyl-2-cyanoacrylate (ISCA), was developed. It carries a long hydrophobic side isostearyl group with lower reactivity and adhesion than other cyanoacrylates. Its polymerization rate is, however, too low to obliterate a vascular lesion with a rapid blood flow. To increase the polymerization rate. ISCA was mixed with NBCA. As a result, the adhesive force of the mixture became extremely low, compared with that of NBCA. The viscosity of the mixture was low enough to allow its' use as an embolic material. Tissue reactions against the mixture was milder than those against NBCA. Radio-angiography became possible by mixing further with Lipiodol. The evaluation of this new embolic material with a rabbit renal artery showed that the obliteration effect of the mixture of ISCA and NBCA was excellent to use as an embolic material for clinical applications.

Treatment of a spontaneous carotid cavernous fistula using an electrodetachable microcoil.

The authors detail their use of a modified version of an electrolysis coil currently manufactured in the United States. They connect a platinum wire to a stainless steel wire via a copper segment, and apply low voltage current to induce thrombosis while electrolysis of the copper effects separation of the platinum coil. Their technique shows potential for treatment of complicated carotid cavernous fistulas.

Characteristics of ethylene vinyl alcohol copolymer (EVAL) mixtures.

PURPOSE: To determine physical characteristics of mixtures of ethylene vinyl alcohol copolymer (EVAL) and metrizamide dissolved in dimethyl sulfoxide, liquid materials developed for embolization of arteriovenous malformations. METHODS: EVAL and dimethyl sulfoxide were mixed in various proportions and sterilized. The viscosity and density of each mixture was measured. Precipitation times were determined by dropping the mixtures into saline or human blood. The mixtures were filtered and the filtrates weighed. RESULTS: Densities and viscosities of the various mixtures differed significantly, proportionally to the concentration of EVAL. Precipitation times also differed significantly, in inverse proportion to the concentration of EVAL. Temperature and aqueous solution did not affect precipitation times significantly. The weight of the filtrate significantly increased with time but was constant for each precipitation time. Temperature significantly affected filtrate weight; aqueous solution did not. CONCLUSIONS: Because of their different physical properties, the various EVAL mixtures are suited to embolizing different types of arteriovenous malformations.

Immediately detachable coil for aneurysm treatment.

We developed an endovascular coil that is instantly detached by high-frequency electrical current. By applying the electrical current, a polyvinyl alcohol junction between the coil and the delivery wire is disrupted by heat within a second. This detachment system was shown to be reliable in the treatment of experimental aneurysms.

Effects of a mixture of a low concentration of n-butylcyanoacrylate and ethiodol on tissue reactions and the permanence of arterial occlusion after embolization.

OBJECTIVE: Cyanoacrylates are the most commonly used liquid embolic agents. For embolization of arteriovenous malformations, a mixture of a low concentration of n-butylcyanoacrylate (NBCA) and Ethiodol (Savage Laboratories, Melville, NY) has been recommended for deeper penetration of the nidus. Dilution of NBCA, however, might result in different degrees of tissue reaction and might influence the permanence of vessel occlusion, with an increased risk of vessel recanalization. We compared tissue reactions induced by different NBCA/Ethiodol mixtures and analyzed the permanence of their embolic effects. METHODS: NBCA was diluted with Ethiodol to prepare the following standard solutions: Mixture A, low concentration (NBCA/Ethiodol ratio of 20:80); Mixture B, high concentration (50:50). The study was designed in two parts, because tissue reactions after embolization are considered to be a combination of foreign body reactions to solidified material and reactions to the injured blood vessel. Foreign body reactions were studied by intramuscularly injecting both glue mixtures into the backs of 18 rats. Specimens were obtained at various times after implantation. Immunohistochemical analysis and esterase staining were used to detect macrophages and neutrophils, respectively. The densities of these inflammatory cells were calculated and statistically compared. To study the degree of vascular wall injury and the permanence of embolic effects, the renal arteries in 48 rabbits were embolized with NBCA Mixture A or B. Six specimens for each group were obtained at various times after embolization. RESULTS: There was no significant difference in foreign body reactions between groups treated with Mixtures A and B, at any time. However, the macrophage density was larger for both groups at 3 months versus 3 days and for the group treated with Mixture B at 3 months versus 2 weeks. There was no difference in the degree of vessel wall injury. None of the embolized vessels demonstrated evidence of recanalization. CONCLUSION: The low concentration of NBCA induced a tissue response similar to that of the high-concentration form. Embolized vessels exhibited no greater incidence of recanalization. Therefore, embolization of arteriovenous malformations with diluted NBCA may be safe.

Nonadhesive liquid embolic agent: role of its components in histologic changes in embolized arteries.

RATIONALE AND OBJECTIVES: The authors evaluated the safety and efficacy of a nonadhesive liquid embolic material and the role of its components in histologic changes in embolized arteries. MATERIALS AND METHODS: A Eudragit-E mixture (Rohm Chemische Fabrik, Darmstadt, Germany) was made of a cationic copolymer (Eudragit-E) dissolved in an equal volume of absolute ethanol and iopamidol. The Eudragit-E mixture, an ethanol-iopamidol mixture, and an iopamidol-saline mixture were injected into 12 rabbit renal arteries each. Three rabbits from each group were followed up for 1 day, 1 week, 1 month, and 3 months, at which time they were sacrificed. Kidneys were removed for histologic examination. RESULTS: The Eudragit-E mixture occluded all renal arteries without difficulty: the arteries did not recanalize. Histologically, acute vasculitis was caused by both the Eudragit-E and ethanol-iopamidol mixtures, but not by the iopamidol-saline mixture. Small infarctions were elicited with the ethanol-iopamidol mixture but not with the iopamidol-saline mixture. CONCLUSION: The Eudragit-E mixture is effective and easy to handle. Fifty percent ethanol may play a role in vessel occlusion with Eudragit-E mixture and in acute vasculitis.

Treatment of unclippable giant posterior cerebral artery aneurysms with detachable balloons--report of three cases.

Three patients presented with rare giant posterior cerebral artery aneurysms, clinically manifesting as cerebral ischemia, mass effect, and subarachnoid hemorrhage. All aneurysms were partially thrombosed, originated at the P2 segment, and possessed broad necks. Surgical neck clipping was difficult but proximal occlusion of the parent artery was feasible. Aneurysm occlusion sparing the parent artery was attempted in all cases, but failed because the detachable balloon did not successfully block the aneurysmal neck. All patients tolerated test occlusion at the P2 segment, so the parent artery was occluded proximally with detachable balloons, leaving the important perforating arteries unaffected. Two transient ischemic attacks were associated with the procedure. Where surgical treatment is unusually difficult, and proximal ligation or trapping just feasible, embolization with detachable balloons is an acceptable substitute.

Improved provocative test for the embolization of arteriovenous malformations--technical note.

A modified provocative test to assess the safety of embolization of cerebral and spinal arteriovenous malformations is described. The modified test uses successive amobarbital and lidocaine injections to elicit any possible neurological deficit, both mixed with radiopaque material to visualize the distribution of the anesthetic in the vessels. The modified provocative test caused no false negative results in 11 patients tested, compared to six of 27 patients with the unmodified method.

[Basilar artery occlusion after STA-SCA anastomosis; case report].

A case of basilar artery occlusion after STA-SCA bypass surgery is reported. The patient was a 56 year old male and presented a TIA of vertigo and speech disturbance. The preoperative angiogram revealed severe stenosis of the basilar artery in its midportion between the bifurcation of AICA and that of SCA. After surgery, the patient's clinical course was uneventful, but the angiogram showed that the previous stenotic segment of the basilar artery had been occluded and the distal portion of the basilar artery and its branches were perfused through the widely-patent STA-SCA bypass. About 6 months after the operation, the patient developed a pontine infarction in the right paramedian region, which was confirmed on MRI. The angiogram revealed that the occlusion of the basilar artery extended further proximally to a point just distal to the bifurcation of AICA. So it was suspected that the perforating branches of the basilar artery to the pons were occluded with the extension of the thrombosis of the basilar artery. The hemodynamic changes associated with the EC-IC bypass was thought to be responsible for the occlusion of the previous stenotic lesion.

[Percutaneous transluminal angioplasty (PTA) for stenosis at the subclavian artery and at the origin of the vertebral artery: therapeutic indication and some adjunctive safe methods during PTA].

Percutaneous transluminal angioplasty (PTA) for brachiocephalic occlusive lesions has progressed. In this paper our experiences and results of PTA in dealing with those lesions are described with emphasis on adjunctive procedures during PTA. Recently, twenty-four patients with stenosis of the subclavian artery (SA) and/or stenosis at the origin of the vertebral artery (VA) were included in this study. Among the 24, there were 16 cases with SA stenosis, 6 cases with stenosis at the origin of VA and 3 cases with both SA and stenosis at the origin of VA. The stenosis was due to atherosclerosis in 21 cases and aortitis in 3 cases. Most of the patients presented ischemic symptoms of vertebrobasilar circulation and affected upper extremities. In PTA of brachiocephalic lesions, one of the most formidable complications is an embolism distal to the central nervous system. To prevent this complication, a vascular endoscope was used for visualization of the luminal surface of the stenotic lesions in 7 cases, and a protective balloon was used in 4 recent cases. The protective balloon was used for transient occlusion of the artery to alter the flow direction so that the possible emboli might be forced to flow away to a less critical distal artery. In the distal protective balloon technique, the protective balloon was set so as to occlude the stenotic artery distally. Debris caused by PTA was aspirated and/or washed out to an extracranial artery with heparinized saline. In the proximal protective balloon technique, the protective balloon was set so as to occlude the stenotic artery proximally. Debris was washed out with blood flow caused by the induced steal phenomenon to an extracranial artery.(ABSTRACT TRUNCATED AT 250 WORDS)

[A large vertebrobasilar junction aneurysm grown at the proximal end of basilar artery fenestration--usefulness of balloon occlusion test with 99mTc-HMPAO SPECT under induced hypotension and consideration in therapeutic strategies].

A 48-year-old lady suffered a transient loss of consciousness. CT and MRI revealed a large vascular lesion compressing the left lower pons. Angiography revealed a large aneurysm at vertebro-basilar junction, dome of which projected anteriorly and left to midline. Her previous vertebral angiogram taken 10 years ago when she suffered a subarachnoid hemorrhage from the left MCA aneurysm, had showed a fenestration of lower basilar artery without apparent aneurysm. Bilateral super-selective vertebral angiograms revealed that the aneurysm arose at the proximal end of the fenestration, and vertebrobasilar junction was incorporated into the aneurysm indicating broad neck aneurysm. The left posterior communicating artery was well developed. Balloon test occlusion (BTO) of bilateral vertebral artery was performed under normotension and induced hypotension. 99mHM-PAO SPECT was used to examine cerebral blood flow (CBF) during hypotensive BTO. The patient tolerated the test and CBF imaging showed insignificant sight decrease in bilateral cerebellar hemispheres. Exploration of the aneurysm was carried out by the right far lateral suboccipital approach. Bilateral vertebral arteries and the right segment of the basilar artery fenestration were identified. Neck clipping of the aneurysm with reconstruction of the parent vessels were tried with fenestrate clip. However, narrow operative field and large dome of the aneurysm made it hard to identify the left segment of the fenestration. Neck clipping was given up and clipping of bilateral vertebral arteries were performed distal to posterior inferior cerebellar artery with three body clippings. The patient showed moderate postoperative left lower nerve palsy, which was gradually improved in several weeks. Follow-up angiography revealed no opacification of the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of pulsation in unruptured cerebral aneurysms by ECG-gated 3D-CT angiography (4D-CTA) with 320-row area detector CT (ADCT) and follow-up evaluation results: assessment based on heart rate at the time of scanning.

PURPOSE: Many epidemiological studies on unruptured cerebral aneurysms have reported that the larger the aneurysm, the higher the risk of rupture. However, many ruptured aneurysms are not large. Electrocardiography (ECG)-gated 3D-computed tomography angiography (4D-CTA) was used to detect pulsation in unruptured cerebral aneurysms. The differences in the clinical course of patients in whom pulsation was or was not detected were then evaluated. METHODS: Forty-two patients with 62 unruptured cystiform cerebral aneurysms who underwent 4D-CTA and follow-up 3D-CTA more than 120 days later were studied. The tube voltage, tube current, and rotation speed were 120 kV, 270 mA, and 0.35 s/rot., respectively. ECG-gated reconstruction was performed, with the cardiac cycle divided into 20 phases. Patients with heart rates higher than 80 bpm were excluded, so 37 patients with 56 aneurysms were analyzed. RESULTS: Pulsation was detected in 20 of the 56 unruptured aneurysms. Of these 20 aneurysms, 6 showed a change in shape at the time of follow-up. Of the 36 aneurysms in which pulsation was not detected, 2 showed a change in shape at follow-up. There was no significant difference in the follow-up interval between the two groups. The aneurysms in which pulsation was detected were significantly more likely to show a change in shape (P = 0.04), with a higher odds ratio of 7.286. CONCLUSION: Unruptured aneurysms in which pulsation was detected by 4D-CTA were more likely to show a change in shape at follow-up, suggesting that 4D-CTA may be useful for identifying aneurysms with a higher risk of rupture.

Comparison of cerebral aneurysm volumes as determined by digitally measured 3D rotational angiography and approximation from three diameters.

This study compared digital measurement of aneurysm volume by 3D rotational angiography (3D-RA) with an approximation technique using three diameters of an aneurysm to re-interpret previously reported optimal packing densities (volume embolization ratio, VER) in coil embolization of intracranial aneurysms. Estimation of the volume of saccular aneurysms is important for calculation of the VER, which is in turn reported to be useful for prediction of coil compaction. The conventional formula for the volume estimation is V=4/3 π(A/2) (B/2) (C/2), where A, B, and C are the aneurysmal height, length, and width measured on 3D-RA image respectively. Using 3D rotational angiography data from 74 aneurysms, the approximated volume generated using the conventional formula was directly compared with the digitally measured volume. The digitally measured volume varied from 0.003 ml to 7.935 ml, and the dome-to-neck ratio (D/N) from 0.79 up to 4.62. We found that the conventional formula almost systematically underestimated the volume by up to 50 %, particularly when the neck was large relative to the dome (D/N<2). On average, digitally measured volume was 1.26~1.29 times larger than the approximated volume obtained using the conventional formula.Conventional 2D angiography based aneurysm volume calculation tends to underestimate an aneurysm volume, so the so-called VER (volume embolization ratio) could be overestimated.

Endovascular occlusion of intracranial aneurysms with Guglielmi detachable coils: correlation between coil packing density and coil compaction.

This retrospective analysis was undertaken to evaluate a possible relationship between coil packing density and coil compaction on intracranial aneurysms embolized using Guglielmi detachable coils (GDCs). Of the patients who underwent endovascular surgery using GDC in our hospital between 1994 and 1998, 33 patients had endovascular treatment with GDC and were examined by follow-up angiography at least 12 months after surgery. They had coil embolization to the extent where aneurysms were no longer filled or only faintly filled as shown by cerebral angiography immediately after surgery. At follow-up angiography, coil compaction was observed in 3 aneurysms. In all patients with coil compaction, the coil packing density was below 20% (14.5 +/- 4.0%). On the other hand, it was over 20% (25.7 +/- 4.7%) in all patients without coil compaction. In the 11 patients with a basilar bifurcation aneurysm, the coil packing density was over 24% and no coil compaction was observed. The coil packing density seems to be one of the critical factors, particularly for predicting whether or not coil compaction will occur. Endovascular surgery should be performed to obtain coil packing density higher than 20%.

Transvenous embolization of dural caroticocavernous fistulae: technical considerations.

Sixteen patients with symptomatic dural caroticocavernous fistulae were treated by transvenous embolization, via the jugular vein and inferior petrosal sinus. The fistula was occluded by thrombogenic coils. Complete resolution of symptoms and signs was achieved in 14 patients, and complete angiographic resolution was also obtained in 14 patients. Failures to achieve angiographic cure were attributed to failure to reach the fistula within the cavernous sinus precisely. Factors which make placement of the catheter at the fistula difficult are trabeculae within the cavernous sinus, a specific configuration of the superior ophthalmic vein and venous thrombosis. To improve the efficacy of transvenous embolization, every possible venous route to the cavernous sinus therefore should be tried, to facilitate reaching the fistula and the possibility of transvenous embolization should not be thwarted by venous thrombosis.

Initial experiences of carotid stenting with palmaz stent.

Results of cervical carotid stenting are reported. Twenty-nine lesions in 25 cases were treated by percutaneous transluminal balloon angioplasty combined with stent placement. All the lesions were successfully dilated. There was one embolic complication during the operation that caused deterioration of preoperative symptoms. Stent deformation causing more than 30% luminal narrowing occurred in one case. Instent restenosis with more than 50% luminal narrowing was seen in bilateral lesions in one case. These were satisfactory results as an initial experience, but further improvement in this technique is considered essential especially to avoid embolic complications.