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Year : 2013  |  Volume : 61  |  Issue : 3  |  Page : 265--269

Parent artery occlusion with Onyx for distal aneurysms of posterior inferior cerebellar artery: A single-centre experience in a series of 15 patients

Qi Wu, Han-dong Wang, Qing-rong Zhang, Xin Zhang 
 Department of Neurosurgery, Jingling Hospital, School of Medicine, Nanjing University, Nanjing, 210002, China

Correspondence Address:
Xin Zhang
Department of Neurosurgery, Jinling Hospital, School of Medicine, Nanjing University, No. 305 East Zhongshan Road, Nanjing, 210002


Background: Aneurysms located at distal posterior inferior cerebellar artery (PICA) are rare. These aneurysms are difficult for surgical or endovascular treatment, especially for ruptured aneurysms. Aims: To investigate the clinical and radiologic efficacy of parent artery occlusion (PAO) with embolic agent Onyx in the treatment of distal PICA aneurysm. Materials and Methods: Case records of 15 consecutive patients with 15 ruptured distal PICA aneurysms treated with Onyx embolization were reviewed retrospectively. The follow-up ranged between 6 and 52 months. Cerebral angiography or cerebra computed tomography-angiogram (CTA) was performed for follow-up radiological study. Two aneurysms had origin from tonsillomedullary segment, nine from telovelotonsillar segments, and four from cortical segments. All patients were treated with Onyx to occlude aneurysm and proximal portion of vessel in front of aneurysm via endovascular approach. Results: Aneurysm was occluded completely in every patient. One patient died because of intra-procedure haemorrhage. Fourteen patients had good recovery and the last follow-up Glasgow outcome scale was 5. Head CT scan was performed in every survived patient before discharge. CT in 3 patients revealed cerebellar infarctions but without any neurological deficits. None of the 14 patients had rebleeding or fresh neurologic deficits during the follow-up period. Aneurysmal recanalization had not been observed in any of the survived patients. Conclusions: Onyx occlusion of proximal parent artery and aneurysm in the treatment of distal PICA aneurysm is safe and effective according to this study. Morphology and location of aneurysm are important to decide the therapeutic strategy.

How to cite this article:
Wu Q, Wang Hd, Zhang Qr, Zhang X. Parent artery occlusion with Onyx for distal aneurysms of posterior inferior cerebellar artery: A single-centre experience in a series of 15 patients.Neurol India 2013;61:265-269

How to cite this URL:
Wu Q, Wang Hd, Zhang Qr, Zhang X. Parent artery occlusion with Onyx for distal aneurysms of posterior inferior cerebellar artery: A single-centre experience in a series of 15 patients. Neurol India [serial online] 2013 [cited 2020 Feb 27 ];61:265-269
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Distal posterior inferior cerebellar artery (PICA) aneurysms arising at a peripheral segment are rare and account for 0.28-1.4% of all intracranial aneurysms. [1],[2] Clinical outcome in patients with these aneurysms after rupture is poor. Therapeutic options in patients with these aneurysms are unclear, endovascular treatment would be an alternative treatment option. [3] Onyx is recently used for chemoembolization for cerebral arteriovenous malformations (AVM) and aneurysms. [4],[5] The existing literature concerning parent artery occlusion (PAO) with Onyx for these aneurysms is limited and is controversial. Safety and efficacy of this treatment modality are unclear. This report presents the single centre experience of Onyx embolization of proximal parent artery and aneurysm in 15 patients with 15 distal PICA aneurysms.

 Materials and Methods

Case records of 15 consecutive patients with ruptured distal PICA aneurysms treated by endovascular treatment in Jinling Hospital from October 2007 to February 2012 were retrospectively reviewed. There were 13 women and the mean age was 47 ± 8 years (age range, 37-59 years). This study was conducted in accordance with the declaration of Helsinki. This study was conducted with approval from the Ethics Committee of Jingling Hospital, School of Medicine, Nanjing University. Written informed consent was obtained from all participants. Preoperative head computed tomography (CT) and/or magnetic resonance imaging (MRI) scans were performed to confirm diagnosis. One patient presented with intracerebellar haemorrhage (ICH), 3 patients presented with intraventricular haemorrhage (IVH), 2 patients presented with IVH and subarachnoid haemorrhage (SAH), the other 10 patients presented with SAH. Four-vessel cerebral angiography performed revealed 15 distal PICA aneurysms. According to the classification described by Lister et al., [6] 2 aneurysms had origin from tonsillomedullary segment, 9 from telovelotonsillar segments, and 4 from cortical segments. Morphology of aneurysm was analysed carefully from angiogram. Aneurysms were classified as dissecting or unknown aetiology according to the classification by Isokangas et al., [3] which defined dissecting aetiology as the lesion demonstrated a solitary or multiple irregular fusiform with or without associated narrowing of the PICA. Patients with aneurysms associated with AVM or Moyamoya disease were excluded. Preoperative clinical status was assessed according to the Hunt and Hess classification. Clinical characters of the 15 patients are showed in the [Table 1].{Table 1}

All patients were treated with Onyx to occlude proximal parent arteries and aneurysms by three neurosurgeons. Under general anaesthesia, the procedures were performed via transfemoral route with 6-Fr arterial sheath (Terumo, TYO, JPN). Six-Fr Envoy guiding catheter (Cordis Neurovascular, FL, USA) was placed into the corresponding vertebral artery. Marathon catheter (ev3, Irvine, CA, USA) under X-Pedion-10 microguidewire (ev3, Irvine, CA, USA) guiding was advanced to access the aneurysm as close as possible. Onyx-18 (ev3, Irvine, CA, USA) was injected to a short proximal segment of parent artery and aneurysm using real-time digital subtraction fluoroscopic mapping after microcatheter lumen was flushed with 0.3 ml-dimethyl sulphoxide (DMSO, ev3, Irvine, CA, USA). "Reflux-hold-reinjection" technique for Onyx was performed during the procedure. Angiography was performed immediately after injection to verify the occlusion of aneurysm. Intravenous heparin was given before guiding catheter was advanced to keep activated clotting time from 200 to 300 seconds.


Two patients were in Hunt and Hess grade 1, 10 patients in grade 2 and 3 patients in grade 3. The aneurysm was occluded completely in all 15 patients. Proximal segments of PICA were preserved, which was verified from postoperative angiography. Intra-procedure haemorrhage occurred in two patients, when the parent artery was catheterized with microcatheter causing parent artery angiorrhexis because of the tortuous vessel. Onyx was injected immediately to occlude proximal parent artery and aneurysm, however, one patient died after the procedure because of the bleeding [Case 11; [Figure 1]. Hydrocephalus occurred in one patient after embolization for which ventriculoperitoneal shunt was performed [Case 3; [Figure 2]. Only 1 patient had dizziness and vomiting 1 day after embolization [Case 2]. Low-molecular-weight heparin (LMWH), aspirin and clopidogrel were administrated for this case. LMWH 4100U twice daily was administrated for 3 days and aspirin 100 mg and clopidogrel 75 mg once daily for 1 month. Patient had symptomatic relief in relieved 3 days. Head CT scan was performed before discharge in 14 patients. CT in three patients revealed cerebellar infarcts with no neurological deficits [Cases 7, 14, 15; [Figure 3]]. Follow-up period in the survived patients ranged from 6 months to 52 months. Glasgow outcome scale (GOS) was used to assess clinical outcome. Seven patients had check angiograms at 6 months after embolization, 3 had at 6 and 24 months. The other 4 patients were followed-up by CTA at 6 months after embolization as they refused permission for angiogram. In none of the patients the aneurysms had recanalization and none had rebleeding or fresh neurological deficits in the follow-up period. All the survived patients had good recovery, GOS of 5. Results of 15 patients are summarized in [Table 1].{Figure 1}{Figure 2}{Figure 3}


The aetiology of distal PICA aneurysm is unclear and the proposed mechanisms include trauma, infection (mycotic) and haemodynamic. [2],[7] Haemodynamic stress was considered to play an important role in the evolution of these aneurysms from the recent study. [2] PICA is divided to five segments: Anterior-medullary, lateral-medullary, tonsillomedullary, telovelotonsillar and cortical. [6] Most PICA aneurysms arise from the origin or anterior-medullary segment. Aneurysms arising from more distal segments are less common, and they account for about a fifth of PICA aneurysms. [3],[8] The treatment options are clipping, or endovascular treatment with coiling. However, management of distal PICA aneurysm remains controversial. Because most distal PICA aneurysms involve the circumference of the small parent vessels, it would be hard to clip sparing of the parent artery. Moreover, clinical features of distally located PICA aneurysms are significantly different from that located proximally. Most distal cerebellar artery aneurysms are supposed to be secondary to arterial dissection, [7] as high as 58.3% of the aneurysms. [3] Clipping would lead to postoperative recanalization. In addition, distal PICA aneurysms are uncommon and PICA shows many varied morphology. [9] Because of these facts, endovascular treatment is suggested as an alternative treatment option. Strategies of endovascular treatment for distal PICA aneurysm include embolization with parent artery preservation and PAO. Because the morphology of distal PICA aneurysm could be fusiform or relatively wide-necked, selective embolization of aneurysmal sac preserving parent artery would be difficult. PAO with coiling could be a substitute for selective embolization in these cases.

The therapeutic strategy with selective or PAO embolization is still controversial. However, PAO has been reported for treatment of distal intracranial aneurysms, [8],[10],[11] including some distal PICA aneurysms. Contralateral PICAs, ipsilateral anterior inferior cerebellar artery (AICA) and superior cerebellar artery (SCA) are often interconnected to PICA by anastomotic arteries. [2] PICA would be filled retrogradely from the pial collateral circulation if peripheral segments were occluded. [8],[10],[11] Therefore, the risk of infarction is limited. Cases of cerebellar ischaemia after distal occlusion of PICA have been described, but the infarcts were limited and well tolerated. [3],[10] Brainstem perforators arise from first 3 segments of PICA, which are important and are preserved. [12] Nevertheless, some reports hypothesized the risk of brainstem ischaemia in cases of occlusion at the first three segments of PICA would be also limited because of the numerous anastomoses of the perforating arteries forming a plexiform network on the medullary surface and absence of normal perforating branches due to aneurysmal dilations of the dissected arterial segments. [7],[13] We performed PAO for two dissecting aneurysm located at tonsillomedullary segment. However, PAO is not recommended for the treatment of the aneurysm arising from first three segments in most cases. Because normal perforating branches usually are not visible on angiogram because of their small diameter. PAO at first three segments would be associated with the risk of lateral medullary syndrome secondary to brainstem ischaemia. Amobarbital test or balloon occlusion test (BOT) were suggested before PAO. [8],[14],[15] But in our early patients with ruptured aneurysms in acute stage could not cooperate for amobarbital test and selective PICA BOT could not be achieved because of small calibre of the vessel. In our opinion collateral supply cannot be assessed accurately by these two methods. We no longer use them routinely.

Onyx has been an option in the treatment for cerebral AVM and aneurysms. [4],[5] Onyx embolization of intracranial aneurysm has been reported as a safe and effective treatment option. [16],[17] This liquid agent is easier to handle compared to N-butyl cyanoacrylate (NBCA). NBCA is an adhesive liquid embolic agent that polymerizes rapidly when it contacts blood. It is used for the treatment of AVM, dural arteriovenous fistula or distal aneurysm, which can be obliterated completely and permanently, if NBCA was mixed with Ethiodol (Codman, FL, USA) in a proper mixture ratio. It can result in lesser recanalization rates in the treatment of distal aneurysm than Onyx. Nonetheless, NBCA embolization must be performed quickly and continuously, that demands skills. On the other hand, risk of gluing catheter, inadvertent reflux and excessive penetration are less frequent with Onyx embolization when compared with NBCA in the treatment for distal aneurysms. Gao et al.[14] reported 10 cases of distal cerebellar aneurysms treated with intra-aneurysmal Onyx embolization, 2 in AICA, 3 in SCA and 5 in PICA, with excellent clinical outcome. However, we still prefer PAO with Onyx for distal PICA aneurysms to intra-aneurysmal embolization, because intra-aneurysmal Onyx embolization for these aneurysms requires fairly skilled technique, occluding aneurysm with sparing of the parent artery would be almost impossible in our experience. In the series by Gao et al., of the five patients with PICA aneurysms treated, two patients developed silent cerebellar infarcts and of them had vessel occlusion. Post-procedure aneurysmal recanalization is an issue with preserving parent artery, because of residual dissected arterial segments in many distal aneurysms.

Reports of PAO with Onyx for distal PICA aneurysms have been limited to a few case reports, [18] but the outcomes are unclear. This report describes the outcomes in 15 patients treated with this treatment option. One patient died during the procedure due to intracerebral haemorrhage, 14 patients had good recovery, long-term GOS of 5. Silent cerebellar infarcts were noted in 3 patients before discharge. None of the patients had rebleeding or fresh neurologic deficits during the follow-up. The outcomes in this study are similar to the previous reports. [10],[11],[14] Onyx migration to proximal or distal trunk and perforators, even inadequate collateral blood flow may account for the cerebellar infarcts observed in the three patients. Repeat follow-up angiogram did not show reconalization of the aneurysms in all the 14 patients. PAO with coils is safer than Onyx in most cases, however, Onyx embolization may be an appropriate choice for distal PICA aneurysms. PICA is often tortuous and it would be difficult to super-select the parent artery and distal aneurysms with the microcatheters thus predisposing to the risk of stretching force. Marathon catheter, which is compatible with Onyx and flow-directed, would be an alternative option for superselective catheterization. Compared to PAO with coiling, this technique is simple to perform and allows Marathon catheter to catheterize more distal vessels easily. Even with this procedure intra-procedure haemorrhage had occurred in two patients due to tortuous parent arteries. Excessive reflux and distal migration can be controlled to the minimum possible with "reflux-hold-reinjection" technique. Rate of aneurysmal recanalization is low theoretically due to characteristics of Onyx. [19] On the other hand, it is less costly than coiling.

PAO with Onyx for the treatment of distal PICA aneurysms should be performed with due consideration of the following points: (1) Morphology and location of aneurysm should be analysed carefully before Onyx PAO emobilization. The risk would be relatively less when aneurysm is located at the last 2 segments of PICA. Dissecting aneurysm would be an indication of PAO; (2) Marathon catheter, rather than Echelon (ev3, Irvine, CA, USA) or Rebar (ev3, Irvine, CA, USA) catheter should be used for selective catheterization to access the aneurysm as close as possible, as it is more soft with better flow-directed ability than other microcatheters. If microcatheter is superselected into aneurysm, it would be optimal selective catheterization. (3) Onyx-18 should be injected with "reflux-hold-reinjection" technique to block a short proximal segment of parent artery, avoid reflux to proximal trunk and perforators. Injection has to be held about 20 seconds to 2 minutes to solidify the Onyx and then restart to occlude aneurysm. Excessive flow of Onyx to distal arteries could be limited accordingly under this flow control technique. (4) Injection should be under real-time digital subtraction fluoroscopic mapping to monitor the whole procedure of Onyx embolization.


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