Complete Obliteration of Intracranial Arteriovenous Malformation with Endovascular Cyanoacrylate Embolization: Initial Success and Rate of Permanent Cure

Methods

Our institutional review board approved this prospective study. Forty-two consecutive patients with intracranial AVMs were included between August 1995 and April 1998. Tables 1 and 2 list patient demographic data and characteristics of their AVMs.

Results

No procedure-related complications occurred in the 10 patients in whom curative embolization was attempted. Complete nidus occlusion was achieved in six patients. Five patients required one treatment session, and one patient required two sessions. In two of these six patients, the AVM was located in the deep supratentorial region, three were in the supratentorial convexity region, and one was in the cerebellum. The number of arterial feeders for these lesions ranged from one to three, with a median of one and an average of 1.5.

In these six patients, follow-up angiography was performed 17–32 months after embolization (average, 23 months). Images showed that the AVM lesions remained completely obliterated without evidence of recurrence. These patients remained clinically asymptomatic 5–7 years after embolization.

On the basis of these results, we conclude that the permanent or long-term cure rate after initial complete occlusion of the nidus was 100% (six of six). The success rate of endovascular cure for patients treated with curative intent was 60% (six of 10). The overall cure rate was 22% (six of 27).

Twenty-one patients had a residual AVM after embolization. Seven were subsequently treated with surgical excision, 11 were treated with radiosurgery between April 1998 and June 2002, and two were treated with a combination of excision and radiosurgery. Table 1 shows the clinical and angiographic outcomes of all 27 patients treated with embolization. Table 2 provides the clinical outcomes of the 15 patients initially treated with surgical excision.

Discussion

In many intracranial AVMs, lesions are not amenable to surgery or radiosurgery. Surgery is usually limited to relatively small lesions located in noneloquent regions without complex deep venous drainage, such as Spetzler Martin grade 1 or 2 lesions (7). In contrast, radiosurgery is restricted to lesions smaller than 3 cm. Endovascular embolization provides a treatment option.

Small AVM lesions that fulfill the selection criteria for curative embolization are likely to be suitable for surgical excision or radiosurgery as well. In fact, the treatment outcome of these two other options is extremely good. The risk of major complications from surgical excision is close to zero for AVM lesions smaller than 3 cm (7). For radiosurgery, the risk of major complications for AVM lesions in the cerebral cortex and smaller than 2 cm is also close to zero (8), and the risk is less than 5% in lesions smaller than 3 cm diameter (9–11). Nevertheless, endovascular embolization remains a less invasive alternative for patients who are reluctant to undergo open surgery or too anxious to wait for the therapeutic effects of radiosurgery. Although embolization poses a risk of intracranial hemorrhage and stroke, the complication rate is minimal and comparable to that of surgery and radiosurgery in patients selected according to the criteria for curative embolization; this observation is exemplified by the zero complication rate in the present series of patients treated with curative intent. The only treatment-related mortality was due to massive brain infarction after surgery, which was performed to remove a glued catheter complicating an embolization procedure. It is now understood that the surgical removal of such glued catheters is not necessary.

The goal of endovascular embolization is the permanent and complete obliteration of the AVM nidus and the restoration of normal cerebral blood flow (12). Despite that cyanoacrylate embolization is the most effective technique for endovascular embolization (1, 13), endovascular cure of an AVM is considered unusual if not rare (13). Only about 40% of practitioners who routinely perform cyanoacrylate embolizations of intracranial AVMs claim to have achieved a true cure of any AVM (8). The most widely reported endovascular cure rates for AVMs are in the range of 5–10% (2–5, 13).

An initially high degree of obliteration of the AVM nidus may be followed by its recurrence shortly after embolization. The extent to which the collateral supply develops and the time required for its development may depend on the degree of nidus obliteration and the material used for the obliteration. Permanent, complete endovascular cure is considered possible with the use of cyanoacrylate. The degree of permanent obliteration is probably high but remains unknown (13).

In the present study, we found that the permanent cure rate of initially complete endovascular cure was 100%, as evaluated by use of follow-up angiography performed 17–32 months after treatment. We believe that complete AVM obliteration at such delayed follow-up is a reliable indication of permanent cure, as an AVM is unlikely to recur after such a long time. A similar finding at 4-month follow-up also suggests permanent cure (13).

The size of the AVM nidus was one of the selection criteria we adopted for attempted curative embolization in this study. About 34% of the AVM lesions in our series were 3 cm or smaller; this percentage concurs with the 30% reported in another larger series (14). Of 10 patients who had received attempted curative embolization, six had successful complete embolization, resulting in an initial success rate of 60%. Our overall initial success rate of 22% was higher than that reported in most series in the literature.

The criteria we adopted for attempted curative embolization were based on radiologic observation of the features of AVM lesions regarding the technical feasibility and likelihood of complete embolization. We had not considered a comprehensive analysis of the angioarchitecture of the AVM and the intrinsic vascular composition of the AVM nidus, as is possible with superselective angiography; although Valavanis and Christoforidis (1) recommend this approach. In that consecutive series of 387 patients, the overall success rate of complete embolization was 40%. This was an exceptionally high rate not yet reproduced; perhaps it was related to a detailed analysis of the angioarchitecture and vascular composition before the procedure. However, the authors did not report the long-term success rate or the permanency of the initial success. Another limitation of our current study was that the assessment of success was based on the assumption that complete nidus obliteration at 17–32 months was equivalent to permanent cure.

Conclusion

The overall initial cure rate for intracranial AVMs treated with cyanoacrylate embolization was 22%. In select patients treated with curative intent, the initial cure rate was 60%. The rate of permanency cure was 100%. Initial angiographic evidence of complete embolization indicated a permanent cure.