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Abstract
Objective Cerebral arteriovenous malformations (AVMs) are vascular lesions that are amenable to various treatment modalities including stereotactic radiosurgery, fractionated radiotherapy, endovascular embolization, microsurgical obliteration or combined modality treatment. A potential complication of endovascular therapy with embolization material is microcatheter entrapment. We report on a patient for whom surgery was combined with endovascular embolization to obliterate an AVM and retrieve an entrapped endovascular microcatheter.
Participant A 52-year-old woman suffered a left parietal hemorrhage from an AVM. She underwent staged endovascular embolization of the lesion using Onyx material. During the second stage of the embolization, the microcatheter (Marathon Flow Directed Microcatheter; eV3 Neurovascular, Inc., Irvine, CA, USA) was retained in the Onyx plug. It was decided to section the microcatheter at the groin and proceed with microsurgical obliteration of the AVM, with removal of the entrapped microcatheter remnant.
Intervention The AVM was dissected circumferentially allowing the meticulous obliteration of the feeding vessels. A single remaining feeding vessel originating from the distal anterior cerebral artery was identified and suspected to contain the entrapped microcatheter. The location was confirmed using stereotactic guidance (BrainLab, Munich, Germany) and the vessel was then sectioned allowing complete removal of the AVM. The microcatheter (102 cm) was then extracted cranially using gentle traction.
Conclusion This demonstrates the first incidence of microcatheter removal after procedural entrapment in Onyx embolization material.
- Arteriovenous malformation
- artery
- brain
- catheter
- complication
- hemorrhage
- microcatheter
- onyx
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Introduction
Arteriovenous malformations (AVMs) of the cerebrum are treated with many different modalities.1–3 Typically, lesions with a low Spetzler–Martin grade are considered good candidates for microsurgical extirpation.4 Other treatment options include stereotactic radiosurgery and endovascular embolization.1 5 6 For complex lesions, combined modality approaches can be used to improve outcome.7 8 An embolization material, Onyx (eV3 Neurovascular, Inc., Irvine, CA, USA), is increasingly being used to treat AVMs.9–12 Onyx can also be used as part of staged, multimodal treatment in conjunction with surgery and radiosurgery.13–15
Onyx represents an alternative over previous embolization materials, such as N-butyl cyanoacrylate, as it is hydrophilic and non-adhesive. However, entrapment of a microcatheter in Onyx can still occur and the management of this occurrence is not standardized.
Case description
The patient is a 52-year-old previously healthy woman who in July 2008 presented in extremis with a 6 cm parietal hemorrhage that dissected into her ventricular system. She underwent emergent craniotomy for clot evacuation. At the time of her postoperative angiogram, she was found to have a left parietal 3.4 cm AVM with feeding vessels from the left pericallosal and callosomarginal arteries and drainage into two major cortical veins (figure 1). She was discharged to inpatient rehabilitation where her neurological function continued to improve over a period of several months. At the time of her follow-up angiogram in January of 2009 her neurological exam was notable for contralateral hemiparesis and aphasia (expressive component greater than receptive).
Cerebral angiogram demonstrating a left parietal arteriovenous malformation (arrow) with feeding vessels from the pericallosal and callosomarginal arteries.
In August 2009, the patient underwent the second stage of her embolization procedure. The dead space of the microcatheter (Marathon Flow Directed Microcatheter; eV3 Neurovascular, Inc., Irvine, CA, USA) was filled with 0.25 ml of dimethyl sulfoxide. Onyx was then slowly hand injected, so that the dimethyl sulfoxide in the dead space of the catheter would be displaced over the course of 90 s. Under fluoroscopic guidance, ∼0.6 ml of Onyx was pulse injected into the AVM, not exceeding a rate of 0.16 ml/min. Intermittent angiogram through the 6 Fr guide was performed during the embolization to assess the progress of obliteration. An attempt to slowly extract the catheter from the Onyx plug was made without success (figure 2). Follow-up angiogram of the left common carotid artery demonstrated a residual arteriovenous shunt. At the conclusion of the procedure, it was felt that the remaining shunt would be difficult to obliterate endovascularly and it was decided to remove the AVM with microsurgery. Given this decision, it was thought that the catheter could be left in place and removed surgically to avoid the potential risk of hemorrhage with catheter removal. The microcatheter was sectioned at the level of the femoral artery at the conclusion of the embolization procedure. A fine-cut CT scan (non-contrast) was then obtained and uploaded into neuronavigation software for stereotactic guidance (BrainLab, Munich, Germany).
Cerebral angiogram demonstrating the tip of the microcatheter (arrow) retained at the proximal portion of the Onyx cast.
The patient was taken to the operating room the next morning where the AVM was dissected circumferentially. Near the conclusion of the resection, attention was turned to the final remaining feeding artery suspected to contain the retained microcatheter based on neuronavigation coordinates. This was partially transected and the microcatheter became visible. The artery was then sharply transected and the AVM was removed en bloc. The microcatheter was then grasped gently with forceps and gentle traction was applied over an interval of 30 min (figure 3). Once sufficiently free, a small hemostat was used to remove the remainder of the microcatheter. The length of both segments was measured to ensure complete removal. Postoperatively, the patient's neurological exam was unchanged.
Intraoperative view of the microcatheter retrieval. Forceps are being used to gently apply traction to the microcatheter (arrow).
Discussion
Entrapment of a microcatheter in embolic material is a known potential problem with AVM embolization. Entrapment of the microcatheter has been reported with the use of N-butyl cyanoacrylate, occurring in four of 52 patients in one series.16 The entrapment rates for Onyx are more elusive. This may be due to the non-adhesive and hydrophilic nature of the substance. The technique of Onyx embolization often involves forming a plug of material around the distal catheter, allowing reduced inflow and slow embolization of the actual AVM nidus. Certain factors are likely to be associated with an increased risk of catheter entrapment: prolonged injection times, a large amount of reflux along the microcatheter tip, close proximity of the microcatheter tip to a curve in the selected artery and steam-shaping of the catheter tip.14 We suspect that tortuous angioarchitecture may have led to catheter entrapment in this case.
In the event of entrapment (refractory to both the tincture of time and spasmolytics), several options exist. The microcatheter can be sectioned at the groin sheath and pushed into the common femoral artery. This allows the microcatheter to endothelialize against the vessel wall. As with all intravascular foreign bodies, microcatheter retention poses a thromboembolic risk that is particularly concerning in the cerebrovascular system. Strategies to manage these retained catheters have included anticoagulation, antiplatelet regimens and surgical removal.17 ‘Glued in’ microcatheters have also been retrieved using the endovascular snare technique; however, only in the external carotid circulation.18 Another technique, using a triaxial catheter system can be used where a distal access catheter is used as a guide for the microcatheter. The distal access catheter can then be advanced intracranially to allow a more stable construct to withdraw the microcatheter against. Most recently, new technology is reflected in device modification to potentially avoid this complication. Detachable microcatheter tips have been used successfully outside of the USA and may prove effective in preventing entrapment.19 20
There have been no reported clinical sequelae attributed to microcatheter entrapment in cases in which Onyx was used.6 21–23 However, there remains a potential for significant vascular injury during prolonged traction and with vigorous attempts to remove a microcatheter that has become trapped in the distal cerebral vasculature.6 14 22 This case highlights a unique situation in which obliteration of the AVM required sectioning of the vessel in which the microcatheter was retained. Additionally, anticoagulation and antiplatelet therapy in the setting of residual AVM presents an increased risk for catastrophe in the occurrence of re-hemorrhage and would therefore be relatively contraindicated. These factors effectively precluded the endothelialization technique as a possible solution. An alternative technique would have been to leave the groin sheath and catheter in place and once the catheter was released surgically, withdraw the catheter from the groin. In theory, cranial traction of the catheter limits the potential of an embolic event. Should the catheter have been removed caudally, Onyx material and thrombus may have become dislodged and posed a significant embolic risk. The most effective solution in this case was microsurgical obliteration of the remaining AVM and extraction of the microcatheter cranially.
Conclusion
Microcatheter entrapment in Onyx embolization material used for AVM obliteration is a rare occurrence. This case highlights the first successful cranial retrieval of an entrapped microcatheter at the time of subsequent microsurgical obliteration.
Key messages
Cerebral arteriovenous malformations are vascular lesions that are amenable to various treatment modalities including stereotactic radiosurgery, fractionated radiotherapy, endovascular embolization, microsurgical obliteration or combined modality treatment.
A potential complication of endovascular therapy with embolization material is microcatheter entrapment.
Microcatheter removal after procedural entrapment in Onyx embolization material is possible and can be performed at the time of microsurgical resection.
Acknowledgments
The authors would like to thank Dr Anoop Patel for his helpful review and comments in the preparation of this manuscript.
References
Footnotes
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.