Keywords
brain AVM - endovascular embolization - hydrocephalus - Onyx
Introduction
Brain arteriovenous malformation (AVM) is a rare congenital disorder of intracranial vasculature supplying the brain parenchyma. Its incidence is 0.94 per 100,000 population. They are the potential source of intracranial hemorrhage especially in young adult. So, their site and size should be identified and treated on an early basis because they can get ruptured at any time and cause bleeding. Preoperatively, AVM size is estimated with magnetic resonance imaging (MRI) brain angiography, and all AVMs are classified according to the Spetzler-Martin scale. Brain AVM can be treated by many modalities such as open surgery, endovascular embolization, and stereotactic radiosurgery.
In general, AVMs of size larger than 3 cm are embolized to reduce size, to enhance the safety of surgery, and to make them amenable to radiosurgery. Nowadays, the endovascular approach to brain AVMs using different embolizing agents is a well-established treatment option. The procedure allows complete obliteration of the AVM in most of cases reported in different literature series. The incidence of major complications also varies widely, probably because successful treatment is highly operator-dependent. Nowadays, a new embolizing agent, Onyx has been marketed and is a preferred treatment of choice for endovascular embolization by most of the endovascular neurosurgeons in a case of deeply located large high flow AVM.
We report a case of left-side basal ganglia, moderate-size high-flow AVM treated by endovascular embolization using Onyx.
Case Report
We report a case of 40-year-old male who came to us with complaints of headache on and off and diminution of vision in his right eye for the last 4 months. The symptoms of diminution of vision had increased for the last 1 month.
On examination, he was fully conscious, oriented to time place and person and obeying verbal commands.
Vision examination was as follows: left eye—vision 6/6, right eye—only perception of light present. Bilateral pupil was normal size and equally reacting to light. Bilateral extraocular movement was normal and there were clinical findings of raised intracranial pressure in the form of headache and blurring of vision.
Fundoscopy examination showed bilateral optic disc edema, which was suggestive of papilledema.
We proceeded to do MRI of brain with intracranial angiography ([Figs. 1] and [2]) which showed the large AVM involving the left basal ganglia measuring approximately 31 × 21 × 27 mm (AP × TR × CC) (anterior-posterior x transverse x craniocaudal) with feeder from perforators of left middle cerebral artery and drainage into straight sinus via left thalamostriate vein ([Fig. 3]). The ventricles were also dilated on MRI suggestive of hydrocephalus. So, the diagnosis was made for AVM of left basal ganglia with hydrocephalus.
We planned further to proceed with digital subtraction cerebral angiography of the brain which ([Fig. 4]) showed that there was moderate-size flow AVM involving left basal ganglia that is supplied by perforators from left middle cerebral artery. It was draining into left caudate vein → left thalamostriate vein → left internal cerebral vein to the vein of Galen. So, the final diagnosis was made to be moderate-size high flow AVM (Spetzler-Martin scale grade 3) involving left basal ganglia with hydrocephalus.
After necessary preoperative workup, we planned to do endovascular embolization of AVM as early as possible because patient was symptomatic and the hydrocephalus was also present.
Embolization Procedure
Under general anesthesia, skin overlying right femoral artery was painted and draped with all aseptic precautions. Femoral artery puncture was done with appropriate catheter (5F sheath). On angiography, left common carotid artery with carotid bifurcation was identified. Left internal carotid artery angiogram showed moderate flow left caudate—basal ganglia AVM. Guiding catheter was navigated over guidewire into left internal carotid artery. The guiding catheter was flushed with saline containing heparin. After that microcatheter was passed into one of the big perforators. Once the microcatheter tip was in the desired position, the Onyx was injected as follows: (1) the microcatheter was flushed with normal saline; (2) Dimethyl Sulfoxide (DMSO) was injected into the microcatheter; (3) Onyx was taken into a 2 mL syringe, and 1 mL was injected slowly for 1 minute; and (4) confirmation of Onyx in vessel was done using fluoroscopy.
After Onyx injections, we also did an angiogram to check nidus occlusion and the blood flow within draining veins ([Fig. 5]).
After embolization check, angiogram showed approximately 70 to 75% AVM embolization. Other vessels like middle cerebral artery, anterior cerebral artery, and their branches were normal. Venous sinuses were normal. After procedure completed, patient was extubated and shifted to neurosurgery intensive care unit. Computed tomography (CT) brain was done that ([Fig. 6]) showed reducing hydrocephalus and patient was discharged after 72 hours without any neurological deficit. During follow-up visit after 60 days, CT brain was done and ([Fig. 7]) it showed significant reduction in hydrocephalus and the patient's vision was improved and papilloedema was regressing. Patient was totally symptom free.
Discussion
In today's era, treatment of brain AVM includes open surgery, stereotactic radiosurgery, embolization, and combinations of these. Embolization is mainly used to reduce the size of large high-flow deep-seated AVMs, to increase the safety of surgery, or to make the AVM amenable to radiosurgery and to reduce chances of complications of open surgery.1–4 Previously, the commonly used embolic agent was rapidly polymerizing liquid agent such as n-butyl cyanoacrylate (nBCA). The use of nBCA in brain AVMs requires experience and expertise, because intranidal flow and polymerization of nBCA are rapid and highly unpredictable. Nowadays, a new Onyx liquid embolic agent is available that is less adhesive and polymerizes slowly, which has advantage over nBCA.5,6 In this article, we report our experience with Onyx in the embolization of brain AVMs.
Result
In this article, we present a case of left basal ganglia AVM in a 40-year-old male who came to us with headache and diminution of vision. In our opinion, diminution of vision in right eye was due to steal phenomenon in right eye and papilloedema, which was due to increase in caliber of thalamostriate vein that was occluding the foramen of Monro. Our experience with the use of Onyx for embolization of brain AVMs is encouraging, with an average size reduction of 75%. Patient was having complete relief from headache and vision was improved in his right eye to hand movement. During follow-up fundoscopy examination showed that papilloedema was regressing. Follow-up CT brain was done that showed there was reducing hydrocephalus and the patient was totally symptoms free.
