Brain metastases associated with vascular malformations are described in literature and typically called ‘collision metastases’. In this case, an 18 year-old male with a history of choriocarcinoma-seminoma mixed germ cell tumor status-post orchiectomy and systemic chemotherapy presented to the hospital with left-sided hemiparesis one month after treatment completion. The patient had known metastases to the brain, spleen, and lung. Brain computed tomography (CT) and magnetic resonance imaging revealed a right frontoparietal intracerebral hemorrhage (ICH) attributed to his intracranial metastases (figure 1a). The patient was treated non-operatively and continued his systemic chemotherapy. One month later, the patient presented with headaches and seizures. Brain CT angiogram (CTA) demonstrated a possible abnormal peritumoral vessel. The vessel was considered a normal vessel displaced by mass effect from the hemorrhage. The patient was managed conservatively until he presented again the following month with worsening left-sided hemiparesis. On brain CT, the patient was found to have progression of perilesional edema and ICH of variable chronicity. Brain CTA revealed more conspicuous abnormal vessels at the site of the right frontoparietal metastasis, particularly at the midline near the superior sagittal sinus (SSS). Digital subtraction angiogram revealed a complex pial arteriovenous fistula (AVF) with arterial supply from bilateral middle meningeal arteries and right middle cerebral artery (figure 1b). The fistula drained through multiple cortical veins into the SSS and venous ectasia was present. Based on these anatomic features, the AVF is classified as Borden III and Cognard IV indicating a high risk for future rupture. Therefore, the AVF was partially embolized with ethylene-vinyl alcohol copolymer. The patient then underwent craniotomy for tumor removal and complete AVF occlusion. Post-operative imaging showed complete resolution of both lesions. The patient’s left hemiparesis improved in the post-operative period and the patient was discharged from the hospital. Subsequently, the patient presented in a delayed fashion with a remote, large spontaneous right cerebellar ICH. The patient had a progressive decline in his neurological status and the patient’s family elected to withdraw care. Numerous reports have described collision metastases associated with arteriovenous malformations, however to our knowledge, this is the first described collision metastasis associated with a pial arteriovenous fistula.

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Abstract E-066 Figure 1

Disclosures J. Fisher: None. D. Klinger: None. R. Morton: None.