Journal of Clinical Neuroscience (2000) 7(Supplement 1), 86–87 © 2000 Harcourt Publishers Ltd doi: 10.1054/ jocn.2000.0719, available online at http://www.idealibrary.com on
Strategic embolisation for successful resection of a large cerebral arteriovenous malformation Hisashi Nagashima MD, Hiroshi Okudera MD, Shinsuke Muraoka MD, Kazuhiro Hongo MD, Shigeaki Kobayashi MD Department of Neurosurgery, Shinshu University School of Medicine, Matsumoto, Japan
Summary The risks accompanied by the treatment of cerebral arteriovenous malformation (AVM) are still cumulative despite recent progress in available treatment options. Pre-operative embolisation is one such option, however, it seldom makes the surgical resection difficult. The excessive embolised nidus makes the surgical resection difficult because it cannot be compressed during the resection surgery and embolised nidus as a ‘glue ball’ with marginal hypervascular territory is most difficult to remove. The aim of pre-operative embolisation for successful surgical resection is to put glue into the marginal part of the nidus so as to make a cleavage between the surrounding normal tissues. Remaining feedings via the dilatated leptomeningeal anastomoses from surrounding normal cortical arteries do not interfere with the resection and can be eliminated easily by coagulating the pia matter around the nidus. Strategic planning with regard to the systemic course of treatment, including the manner of resection, is important for effective pre-operative embolisation. © 2000 Harcourt Publishers Ltd Keywords: arteriovenous malformation, embolisation, surgery, initerventional neuroradiology
INTRODUCTION
CASE STUDY
Despite current progress in available treatment options for cerebral arteriovenous malformations (AVM), the risks accompanied by the treatment are still cumulative and the treatment of AVMs is still controversial – especially in cases of large, high-flow AVMs. Currently available treatment options include surgical excision, stereotactic radiosurgery, embolisation and combinations of these methods. As one-stage resection of a large AVM has a high risk of breakthrough, pre-operative staged embolisations are utilised to decrease the risk.1,2 However, pre-operatively embolised nidus seldom makes the surgical resection difficult and strategic planning with regard to the systemic course of treatment, including the manner of resection (‘strategic embolisation’), is important for effective pre-operative embolisation.
A 20-year-old man with convulsion attacks was found to have a left frontal AVM. Magnetic resonance imaging (MRI) showed a left frontal large AVM adjacent to the motor cortex and an angiogram showed that the nidus was fed by the branches of the left anterior cerebral artery (ACA) and middle cerebral artery (MCA) (Fig. 1). Embolisation was performed preoperatively three times, including most of the small feeders via the pericallosal artery and the deeper branches of the internal frontal artery. The callosomarginal artery, the main feeder of the AVM which fed the middle part of this nidus, was obliterated at the proximal part with N-butylcyanoacryl (NBCA). The nidus pacified via the dilatated leptomeningeal arteries (‘transitional feeders’) from ACA and MCA was kept intact. The AVM was then totally resected, without neurological complications.
MATERIALS AND METHODS Between April 1993 and August 1998, 26 cases were treated with 48 sessions of embolisation. Of the 26 cases, 21 were pre-operatively embolised, 3 were treated with radiosurgery and 2 were treated with embolisation alone. All the AVMs in the pre-operatively embolised cases were removed totally. Of the 21 cases, 20 AVMs were removed by a one-stage operation and one was removed with two operations. As for the pre-operative embolisation, no clinical and angiographical complication was experienced, except two cases of predicted visual field deficit. Postoperatively, another three cases showed predicted visual field deficit and one case presented with hemiparesis. The authors mainly utilised polyvinyl acetate as an embolic material, because it is soft enough for the clinician to cut an embolised nidus with microsurgical scissors during the resection surgery.3,4
Correspondence to: K Hongo, Department of Neurosurgery, Shinshu University School of Medicine, 3–1–1 Asahi, Matsumoto 390-8621, Japan. Tel: +(81) 263 37 2690; Fax: +(81) 263 37 0480
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DISCUSSION Surgical excision is the most definitive measure for treating an AVM, but breakthrough phenomenon has been a problem and several treatment options were developed to deal with AVM.1,2,5 Stereotactic radiosurgery is a less invasive measure with short hospitalisation; however, it is only applicable for an AVM with a nidus up to 25 cm3 in size. With endovascular embolisation alone, the complete cure rate is as low as 13–40%.6,7 Size reduction embolisation followed by stereotactic radiosurgery is one of the most popular measures used to treat a large AVM, but the longterm safety of embolic materials is unknown as yet.8 Therefore, the authors regard surgical resection of a nidus with the embolic material inside as a safer measure for treating a large AVM. In pre-operative embolisation of an AVM, different concepts are required from those employed in pre-radiosurgery embolisation. In surgical dissection of the AVM nidus, superficial feeders are easy to detect and control, however, confirmation of the eloquent area is difficult. Direct compression of the nidus is important and too much embolised nidus becomes hard as a ‘glue ball’ which interferes with the surgical resection. In contrast, the deep-seated feeders are easy to embolise and it is possible to embolise the nidus adjacent to the eloquent area after a functional test. Therefore, the aims of strategic embolisation are to obliterate the angiographically fragile points such as peri- or intra-nidal aneurysm first, to isolate the nidus margin from the adjacent eloquent area with glue and to reduce the haemodynamic shunt
Strategic embolization and resection of large AVM 87
Fig. 2 Schematic drawing of angio-architicture of AVM nidus and strategic embolisation. Small double arrows indicate the feeding arteries which penetrate into the nidus, open arrow indicates the ‘terminal’ feeder which terminates in the middle part of the nidus, arrow heads show the nidus opacification via pial anastomosis and the black arrow indicates the passingthrough artery. In strategic embolisation of AVM, the marginal part of the nidus is obliterated through such penetrating feeding arteries, the terminal feeder is obliterated at the entrance of the nidus and the main part of the nidus is kept opacified via the pial anastomosis.
REFERENCES 1.
2. Fig. 1 Lateral view of the left carotid angiogram (upper, arterial phase; lower, capillary phase) of a 20-year-old man showing a large AVM in the left frontal lobe. 3.
flow by obliterating direct A-V shunt in the nidus. In obliterating deep feeders, it is important to keep the nidus compressive by embolising the feeders with nidus which penetrate into the nidus and obliterating the feeders which terminate in the middle part of the nidus at the proximal part (Fig. 2). CONCLUSIONS Pre-operative embolisation should be planned carefully, to make surgical resection safer and easier. The important points for strategic embolisation are endovascular dissection by isolating the nidus margin and keeping the nidus specified.
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Journal of Clinical Neuroscience (2000) 7(Supplement 1), 86–87