Letter: Hemorrhage Following Complete Arteriovenous Malformation Resection With No Detectable Recurrence: Insights From a 27-Year Registry (2021)

To the Editor: We are very interested in the article of Rapaport et al1 regarding hemorrhage after complete resection of intracranial arteriovenous malformations (AVMs) and congratulate the authors on the extensive work evaluating this 27-yr registry. They hypothesize that possible residual nidus (not seen on postoperative angiogram) and/or inflammation could explain these hemorrhagic complications after complete resection. Our team recently encountered a hemorrhage shortly after complete resection of an intracranial arteriovenous malformation for which we have a confirmed etiology different than the hypotheses discussed by Rapaport et al.1 We present the case of a 54-yr-old female who presented with 2 episodes of seizures and was found to have a right frontal AVM upon workup (Figure 1). After discussion about the potential risks and benefits of the different treatment strategies (conservative, surgical removal, embolization, and radiosurgery), the patient opted to have her AVM surgically removed. Except for the presence of numerous prominent deep arterial feeders requiring AVM clip ligation, the surgery was uneventful, as was the early postoperative period. A postoperative cerebral angiogram done the day after the surgery confirmed the absence of residual AVM nidus and failed to show an early draining vein (Figure 2).FIGURE 1.: Preoperative MRI of our patient. Axial T2 A, coronal T2 B, and coronal T1 gadolinium-enhanced C cuts showing a right frontal AVM. AVM, arteriovenous malformation; MRI, magnetic resonance imaging.FIGURE 2.: Postoperative cerebral angiogram. Injection of the right ICA (AP A and lateral B views) showing no residual nidus and no early draining vein. AP, antero-posterior; ICA, internal carotid artery.The patient was discharged home neurologically intact on postoperative day 2. She returned to our emergency department (ED) 2 h after her discharge complaining of a headache. A head computed tomography (CT) done at this time was read as normal with postoperative changes, but on close inspection, there was subtle increased hypodensity surrounding the surgical bed consistent with edema (Figure 3). The patient was discharged home by the ED team with instructions to follow-up with the neurosurgical team within the next 2 d. Instead, she returned to our ED 3 d later, complaining of a severe headache again. A head CT again showed an increased area of hypodensity and a new hemorrhage within the surgical bed with a serpiginous hyperdensity on the cortical surface (Figure 4). This raised the suspicion of hemorrhage secondary to venous thrombosis, which was confirmed by head CT angiography/CT venography (Figure 5). Because the patient was only on postoperative day 5, we opted to start her on aspirin 325 mg Per os (PO) daily and enoxaparin 40 mg s/c daily to be replaced by rivaroxaban 15 mg PO daily on postoperative day 11. The rationale behind this approach was to try to treat the venous thrombosis, which was felt to be the etiology of this new hemorrhage and to prevent further clot propagation while also avoiding a new hemorrhage secondary to anticoagulation too soon after surgery. The patient's headache completely resolved the day after she started taking rivaroxaban, and she did not suffer from any neurological deficit or further hemorrhage thereafter.FIGURE 3.: Head CT done on postoperative day 2 showing edema around the surgical cavity.FIGURE 4.: Head CT done on postoperative day 5 showing increased edema around the surgical cavity, hemorrhage within the surgical cavity A, and a serpiginous hyperdense structure in the subarachnoid space (white arrows) B.FIGURE 5.: Sagittal cut of a head CTA done on postoperative day 5 showing thrombosis within one of the draining veins of the resected AVM. AVM, arteriovenous malformation; CTA, CT angiogram.Our case demonstrates that venous thrombosis is a possible etiology for postoperative hemorrhage following confirmed complete resection of an intracranial AVM. Other cases supporting this finding have been published.2-4 In all cases, the hemorrhage occurred within 2 d of surgical resection. Edema surrounding the hematoma is usually present. This complication seems to be associated with extensive and redundant venous networks.3 The presence of these networks may increase the risk of flow stasis after AVM removal, which in turn may result in venous thrombosis. Hemorrhagic complications after stereotactic radiosurgery (SRS) treatment of AVMs have been reported.5-9 Some cases were secondary to residual AVM not seen on follow-up imaging, but confirmed on histologic examination,8-11 and others attributed to venous thrombosis.5-7 This shows that venous thrombosis can also occur after SRS and could be the reason for post-AVM treatment hemorrhage. Venous thrombosis also has a possible role in rupture of untreated AVMs12,13 The 5 cases presented by Rapaport et al1 had a postoperative hemorrhage at least 3 mo after resection, which is later than in the surgical cases previously reported,2-4 including ours. It is unclear if venous thrombosis is likely to be a cause of hemorrhage late after AVM removal. We suggest that hemorrhage after complete removal of intracranial AVMs should warrant a workup to rule out venous thrombosis as well as residual nidus. Further research is warranted to understand the reason for hemorrhagic complications after complete AVM removal because the purpose of surgical intervention is usually to reduce or eliminate the hemorrhagic risk. A more comprehensive national or international registry of these cases could help us understand this phenomenon. Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.