Microsurgical Strategies Following Failed Endovascular Treatment with the Pipeline Embolization Device: Case of a Giant Posterior Cerebral Artery Aneurysm
A 51 year-old male presented to an outside institution seven years prior with chronic headaches, which began following a motor vehicle accident. He had decreased visual acuity in the left eye from a previous gunshot wound to the face. The patient was diagnosed at initial presentation with a giant, fusiform left PCA aneurysm which was partially thrombosed. It was decided at the time of diagnosis that the risk of morbidity associated with either endovascular or microsurgical treatment of the aneurysm exceeded that of conservative management. Over time, the patient's headaches progressively worsened to an average visual analog scale (VAS) score of 7/10 despite maximal medical management, and the aneurysm gradually enlarged over serial angiographic imaging. The decision was made at this time to treat the lesion via an endovascular approach with the PED (). The aneurysm was successfully treated with two telescoping PEDs, 2.5×20 mm and 3.0×30 mm in size. The patient was discharged on standard oral dual antiplatelet therapy, clopidogrel 75 mg daily and aspirin 325 mg daily, without any change in neurological function. The severity of the patient's headache remained unchanged after PED treatment.\nThe patient presented three months post-PED with progressively worsening headaches to an average VAS score of 9/10, new gait ataxia, and new temporal hemianopsia of the right eye. While the stents remained patent at six weeks, by the follow-up angiography at three months, the diseased segment of the left PCA had progressed to complete occlusion at the origin of the proximal PED (). The patient's new temporal hemianopsia of the right eye was attributed to the left PCA occlusion. However, despite occlusion of the parent vessel, the aneurysm had continued to enlarge, resulting in local mass effect and cerebral edema as well as obstructive hydrocephalus. Therefore, the decision was made to surgically resect the aneurysm. The patient was taken to the operating room for an endoscopic third ventriculostomy, which was performed in a standard fashion through a right frontal burr hole without complications. An external ventricular drain was left in the frontal horn of the right lateral ventricle for subsequent cerebrospinal fluid drainage.\nThe patient was repositioned for aneurysm excision through an infratemporal, post-auricular, presigmoid skull base approach. Electrophysiological monitoring, including motor and somatosensory evoked potentials (motor evoked potential (MEP) and somatosensory evoked potential (SSEP), respectively), was utilized. A standard temporal craniotomy and partial mastoidectomy were performed. During the craniotomy, the sigmoid sinus was breached, requiring hemostatic control with gelfoam tamponade. After dural opening, 50 mL of cerebrospinal fluid was drained from the external ventricular drain to facilitate brain relaxation. After opening the arachnoid of the ambient cistern, the PCA and superior cerebellar artery were identified along with the fundus of the aneurysm dome posteriorly.\nDue to the high degree of thrombosis, the aneurysm was firm and immobile. Therefore the aneurysm dome was opened so that the intrasaccular thrombus could be debulked. Decompression of the fundus facilitated dissection of the aneurysm from the surrounding cortex and brainstem. The proximally placed PED was identified in the lumen of the diseased PCA without evidence of endothelialization and was removed cautiously. After PED extraction from the inflow segment of the parent artery, there was brisk bleeding from the proximal PCA which controlled by clipping the P2 segment. After further debulking of the thrombus, the distal PED placed in the aneurysm outflow was identified and a clip was placed on the outflow portion of the PCA, effectively trapping the aneurysm. The entirety of the aneurysm was then excised from the PCA (). During the final dissection, the right-sided arm and leg SSEPs were lost without change in MEPs. At the end of surgery, there was no recovery of SSEPs in the right arm or leg and MEPs remained stable.\nThe patient's postoperative course was complicated by an extradural hematoma requiring surgical evacuation and thrombosis of the left transverse and sigmoid sinuses, resulting in multiple large territory venous infarcts requiring decompressive craniectomy. The extent of the postoperative infarcts was neurologically devastating, and the patient expired two weeks following the initial surgical intervention.