Case presentation
A 45-year-old female was referred to our hospital with headache, nausea, and vomiting, followed by mental changes in the morning. She was diagnosed with MMD ten years previously. Initially, non-contrast computed tomography (CT) of the brain revealed a left dominant intraventricular hemorrhage (IVH) with hydrocephalus, scant subarachnoid hemorrhage along both frontal sulci and diffuse brain parenchymal swelling (Figure 1a). For emergency cerebrospinal fluid (CSF) diversion, the patient was referred to the neurosurgery department, and her consciousness recovered immediately after extraventricular drainage. Digital subtraction angiography (DSA) revealed bilateral MMD and the prominent development of a choroidal anastomosis (ChA) originating from the left lateral posterior choroidal artery (LPChA). The ChA involved a small pseudoaneurysm, which was considered the culprit lesion for the bleeding (Figure 1b-c). The postcontrast high-resolution vessel wall image (HR-VWI) demonstrated strong wall enhancement of the pseudoaneurysm, indicating the rupture point of the aneurysm.
A superficial temporal artery-middle cerebral artery (STA-MCA) bypass was performed to reduce the ChA and banish the pseudoaneurysm (Figure 1d). Immediate post-bypass indocyanine green angiography confirmed the patency of the anastomosis; however, extensive brain swelling was observed in the surgical field 20 min after the bypass. The surgical procedure for the bony defect was completed. Postoperative magnetic resonance imaging (MRI) revealed multiple microbleeds, T2 white matter changes in the left frontotemporal area, and external brain herniation via the craniectomy site (Figure 2a). A neurological examination revealed motor aphasia and paresis of the right hand. Post-bypass brain single photon emission computed tomography (SPECT) revealed hyperperfusion in the left MCA territory (Figure 2b). Intensive blood pressure control was achieved with the administration of a hyperosmolar agent to prevent hemorrhage expansion and progression of hyperperfusion syndrome.
The patient complained of severe headache, nausea, and vomiting postoperatively. Brain CT revealed a left dominant IVH, suggesting rebleeding from the pseudoaneurysm. The second DSA revealed significant growth of the pseudoaneurysm and non-patent flow of the bypass (Figure 3a-d). The patient underwent emergency coil embolization for a ruptured pseudoaneurysm under general anesthesia. A 6Fr guiding catheter (DA-XB Envoy, CERENOVUS, Le Locle, Switzerland) was placed into the distal cervical left vertebral artery (V3), and a microcatheter (Excelsior® SL-10® pre-shaped 45, Stryker, Cork, Ireland), advanced over an 0.010 inch microguidewire (Synchro®, Stryker, Salt lake city, USA) into the distal left LPChA. The resulting super selective angiogram revealed a 13 mm pseudoaneurysm in the distal choroidal portion of the left LPChA and the medullary tributaries distal to the aneurysm (Figure 3e). Coil embolization was then carefully conducted under fluoroscopic observation with five coils (Axium™ Prime 8 mm x 20 cm, ev3™, Irvine, USA / Target® 360 ULTRA 5 mm x 10 cm, 4.5 mm x 10 cm, 4 mm x 10 cm, Stryker, Cork, Ireland / Target® HELICAL NANO™ 2.5 mm x 4 cm, Stryker, Cork, Ireland). During coil embolization, we attempted to preserve the flow of the medullary tributaries distal to the aneurysm due to the risk of LPChA territory infarction (Figure 3f). The patient’s immediate postoperative period was uneventful. The patient underwent a second STA-MCA bypass to minimize the medullary tributaries of the ChA (Figure 2c-d), and the postoperative course was uneventful. Follow-up DSA revealed no recanalization of the pseudoaneurysm, the disappearance of the ChA, or patent bypass (Figure 3g-h). Strict blood pressure control was achieved, and the clinical symptoms gradually improved within a week. The patient was discharged after an additional two-week course of conservative management. The right hand paresis had fully resolved by the three-month follow-up, but mild aphasia persisted. At the four-month follow-up, MRI showed signal intensity normalization of the T2 white matter high-signal lesion (Figure 2e). At the six-month follow-up, patent flow of the bypass was confirmed by cerebral angiography (Figure 3h).