Clinical-pathology review: Supratentorial cerebral arteriovenous fistula

European Journal of Radiology Extra 72 (2009) e97–e102

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Clinical-pathology review: Supratentorial cerebral arteriovenous fistula Chuhan Jiang, Xianli Lv, Zhongxue Wu ∗ Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, No. 6, Tiantan Xili, Chongwen, Beijing 100050, China

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Article history: Received 14 November 2008 Accepted 25 May 2009 Keywords: Cerebral arteriovenous fistula Endovascular embolization Blindness

a b s t r a c t Objective: We present the first report in the literature on the bilateral tentorial herniation after the endovascular embolization of a large brain arteriovenous fistula. Clinical presentation: A 7-year-old boy who had chronic headaches underwent computed tomography (CT), which disclosed an abnormal intracranial mass in the right cerebral hemisphere. Magnetic resonance imaging (MRI) scan shows multiple tortuous signal void lesions suggesting vascular lesions. Cerebral angiography revealed a cerebral arteriovenous fistula with a very large venous pouch. The patient was referred to Beijing Tiantan Hospital for further treatment. Intervention: Partial embolization of the AVF from the arterial side was initially attempted successfully resulting in a reduction of the shunt flow. The patient developed swelling of his right hemisphere and caused bilateral tentorial herniation. Although the decision was made to attempt resection of the thrombosed varix, there was yet any recovery of blindness caused by herniation. Conclusion: Our study suggests that tentorial herniation can cause compression of optic tracts leading to complete blindness with conscious clarity. Clinicopathologic considerations of the complete bilateral blindness produced from the above events are discussed in detail. Prevention is the only therapeutic approach to this type of visual catastrophe. The outcome of radical surgical intervention for this kind of patients is still unclear and further investigation should be given. © 2009 Elsevier Ireland Ltd. All rights reserved.

Compression of the PCA during tentorial herniation as a cause of homonymous hemianopsia with central vision sparing has been described in great detail [2,3,5,6,9]. However, our patient was the first complete bilateral blindness without sparing of central vision caused by bilateral tentorial herniation due to severe head edema with clear CT and MRI evidence. 1. Case report A 7-year-old boy who had chronic headaches underwent computed tomography (CT), which disclosed an abnormal intracranial mass in the right cerebral hemisphere (Fig. 1A). Magnetic resonance imaging (MRI) scan shows multiple tortuous signal void lesions suggesting vascular lesions (Fig. 1B). Cerebral angiography revealed a cerebral arteriovenous fistula with a very large venous pouch (Fig. 2A and B). The patient was referred to Beijing Tiantan Hospital for further treatment. Partial embolization of the AVF from the arterial side was initially attempted successfully resulting in a reduction of the shunt flow (Fig. 2C). The venous outflow was left intact. The patient developed swelling of his right hemisphere without midline shift after embolization. By the sixth postem-

∗ Corresponding author. Tel.: +86 10 67098850; fax: +86 10 95105105. E-mail address: [email protected] (Z. Wu). 1571-4675/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrex.2009.05.007

bolization day, the patient presented with a sudden onset of seizure, and emergency CT scanning demonstrated thrombosis of the venous pouch and intraventricular hemorrhage (Fig. 2E). On the seventh day, the residual fistula was obliterated completely with Onyx-34 injection (Fig. 3A and B) and heparination was administered to alleviate the acute thrombosis of the venous drainage. The patient developed bilateral oculomotor nerve pareses gradually after the second embolization, and pupils were 5 mm in size and fixed to light with conscious clarity and normal movement of four limbs. Bilateral ptosis was found without papilledema. He was sufficiently alert by the seventh day after the second embolization to complain of sudden onset of bilateral blindness. The bilateral pupils were 4.5 mm in size and both were fixed to light. No evidence of visual perception could be elicited. Bilateral ptosis was present and bilateral ophthamoplasia. CT scanning demonstrated thrombosis of venous pouch, parietotemporal brain edema, and disappearance of basal cistern (Fig. 3C), suggesting tentorial herniation. However, his consciousness and movement function were normal. We then began to administer anticonsultant agent in combination with the hypertonic hypotensive drug. Two weeks after the second embolization he remained completely blind, pupils were not reactive, and his ptosis impairment had slowly resolved. MR imaging was obtained and demonstrated a massive thrombosis of the venous pouch, brain edema and bilateral tentorial herniation causing bilateral optic tract displacement (Fig. 4). Mild disc pallor

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Fig. 1. (A) Preoperative CT scan shows a large mass in the right cerebral hemisphere (arrow). (B) Axial MRI scan, T2-weighted, shows multiple tortuous signal void lesions.

was present on fundus examination, more evident on the right side (Fig. 5). Two weeks after the onset of blindness, there was not any recovery of his blindness. The decision was made to attempt resection of the thrombosed varix. Mobilization of the varix, and removal of the fistula were successful without much blood loss. One week after surgery, there was yet not any recovery of blindness. 2. Discussion A case of chronic headaches from a congenital cerebral AVF is presented. Because of a high risk of bleeding in cerebral AVFs, expeditious definitive treatment should be performed [14,15,18–20]. The goal of treatment in cerebral AVFs in young children, even when asymptomatic, is the rapid control of the AV shunt [20]. Surgery was reported to be successful in the small number of cases of neonates and infants presenting with symptomatic cerebral AVFs [15]. However, endovascular intervention has gained an important role in the treatment of intracranial arteriovenous fistula so far [1,18–20]. This approach has demonstrated its efficacy in treating patients with arteriovenous fistula and to alleviate their symptoms and signs. The preferred treatment of arteriovenous fistula is obliteration of the fistula or interruption of all feeding vessels at the fistulous point

while preserving the cerebral venous drainage. Endovascular treatment by transarterial approach was the first therapeutic choice. Usually, the endovascular approach is performed by percutaneous femoral puncture under general anesthesia. Although endovascular techniques involving the use of different agents (balloons, coils, NBCA, and Onyx) have been reported as being successful in treating high flow fistulas, it can be technically difficult to deliver embolic materials precisely to the site of fistula. The most common embolic agents employed for the treatment of high-flow AVFs are balloons and coils although liquid embolic material (NBCA) has also been used occasionally [1,4]. Onyx is usually used as a combination with coils. The disadvantage of balloons is that they cannot be guided through tortuous vessels into the position where the fistula is occluded. We have encountered the detachable balloon migrated into a varix, into the lung or, most dangerous, into a draining vein. Detachable coils are useful because they can be repositioned until a stable and safe position is obtained and, therefore, distal embolization can be eliminated or minimized. In addition, they can act as a template for the deposition of other embolic materials, such as glue. NBCA has the advantage of being relatively easy to deliver, having good penetration and producing immediate thrombosis and permanent occlusion of the fistula. The drawback is the difficulty in

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Fig. 2. Multiple views of cerebral angiography. Right internal carotid artery injection in the lateral-early arterial (A), and lateral-late arterial (B) phases. A fistula with a very large venous pouch was revealed. (C) Right internal carotid artery angiogram after initial partial embolization. (D) CT scanning on the next day after the first embolization. (E) CT scanning on the sixth day after the first embolization.

controlling the flow and polymerization of glue and its cast formation. Andreou et al. reported their technique of transarterial balloon-assisted NBCA embolization and the clinical results of using this approach in two patients with pial AVFs [4]. But in this case, the feeder is short and blood flow was high and fast, injection of NBCA

will be with the risk of reflux into normal arterial trunk and venous occlusion so coils should be used, Onyx-34 can also be used as a combination. Hemodynamic rearrangements of the cerebral circulation predispose to edema, infarction, and hemorrhage in the brain after occlusion or resection of the lesions [15]. Stepwise reduction

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Fig. 3. Right internal carotid angiogram, anteroposterior view (A) and lateral view (B) reveals complete obliteration of the fistula and distal antegrade filling of the MCA branches. (C) CT scanning at the onset of blindness.

of flow in AVFs is thought to reduce these complications. And we will obliterate this shunt in two sessions. Compression of the PCA during tentorial herniation as a cause of homonymous hemianopsia with central vision sparing has been described in great detail [2,3,5,6,9]. However, our patient was the first complete bilateral blindness without sparing of central vision caused by bilateral tentorial herniation due to severe head edema with clear CT and MRI evidence. Other evidence that brain herniation has occurred would be bilateral oculomotor nerve pareses and ptosis. The visual field examination and visual evoked potential were not performed because there was no evidence of visual perception. It would be difficult to explain the sparing of the posterior pole of the occipital lobe by a tentorial herniation, whereas it caused bilateral blindness with normal consciousness. The manifestations of tentorial herniation vary considerably. Some degree of herniation, particularly when it develops slowly, may be asymptomatic; rapid herniation, however, may seriously influence the outcome [10]. Our patient developed optic atrophy on the eighth day after blindness onset, indicating a pregeniculate site of optic pathway damage. The association of optic atrophy with tentorial herniation is not well appreciated. In addition to occipital infarction, tentorial herniation may result in unilateral or bilateral optic pathway damage at the level of optic nerves, chiasm, optic

tract, or lateral geniculate bodies [10–13]. Sunderland summarized the possible causes of visual involvements (homonymous hemianopsias) secondary to increased intracranial pressure. In addition to compression of the PCA, he points out that on rare occasions the anterior choroidal artery may be compressed between the cerebral peduncle and the hippocampal gyrus, and that the optic tract may be pressed directly against the tentorial edge [10]. As early as 1904 Collier described the occurrence of homonymous hemianopsia as a false localizing sign of frontal lobe brain tumors in two patients [11]. He postulated pressure on the optic tracts as the cause of the hemianopsia. Learmoth et al. described two patients with supratentorial tumors in whom homonymous hemianopsia was present as a false localizing sign. Again pressure on the optic tracts was the suspected etiology. Most reports concern with false localizing hemianopsias have ascribed the hemianopsia to optic tract compression, with as a consequence of mechanical compression against the tentorial edge or secondary to the dilation of the third ventricle seen in the posterior fossa tumors. (Bitemporal field defects in the latter case are more common.) [13,14] Pregeniculate visual damage was not evident by CT scanning, and the location of the damage leading to optic atrophy in our patient revealed by MRI images. The timing of optic fundus changes was similar to the known evaluation of nerve fiber layer atrophy and optic disc pallor following intracranial optic

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Fig. 4. MR images. (A) Axial MRI scan (T1-weighted). (B) Saggital MRI scan (T1-weighted). (C) Axial MRI scan (T2-weighted) at the inferior colliculus level. (D) Axial MRI scan (T2-weighted) at the superior colliculus level. To demonstrate venous thrombosis and brain edema leading to bilateral tentorial herniation without damage in the posterior pole of the occipital lobe was very clearly visualized. Note the bilateral optic tracts (arrowheads) are unsymmetrical, because the right optic tract is compressed medially and inferiorly and the left optic tract is compressed laterally. Dilated the III ventricle compressed bilateral optic tracts medially (arrows).

nerve destruction, and this delay in the appearance of optic atrophy appears to be independent of the location of pregeniculate injury [6]. Sometimes, patients with papilledema have been left blind following intracranial procedures. A likely explanation in many of these instances is the precipitation of ischemic optic neuropathy in discs in which perfusion is compromised by severe papilledema. Again, the absence of severe disc edema makes this possibility remote in the present cases. Damage to the visual cortex or radiation can result in transsynatic degeneration with subsequent optic atrophy [6]. This phenomenon occurs only with congenital or peri-

natal injury and can be excluded as a cause of optic atrophy in our patients. Decompressive craniectomy in the setting of acute brain swelling from cerebral infarction is a life-saving procedure, which is established for younger patients who have a rapidly deteriorating neurologic status [7,8,16,17]. However, the value of such radical surgical intervention has yet to be established for tentorial herniation with conscious clarity and visual involvements. It is unknown whether evacuation of the venous pouch would have resulted in a more satisfactory outcome. So we initially treated our patient conservatively.

Fig. 5. Optic fundi examination demonstrated optic nerve fiber layer begins to atropy.

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In the present case, despite the staged reduction of flow through the AVF was performed, brain edema still developed because of hemodynamic rearrangements of cerebral circulation. However, it allowed the fistula to be manipulated with greater ease so that the thrombosed venous varix could be evacuated. Although whether surgical evacuation of the venous pouch will result in a more satisfactorily or not, a surgery was performed 3 weeks after the onset of blindness because of no recovery and optic fundus atrophy. The patient was followed and we anticipate his visual recovery. 3. Conclusion Our study suggests that tentorial herniation can cause compression of optic tracts leading to complete blindness with conscious clarity. Clinicopathologic considerations of the complete bilateral blindness produced from the above events are discussed in detail. Prevention is the only therapeutic approach to this type of visual catastrophe. The outcome of radical surgical intervention for this kind of patients is still unclear and further investigation should be given. Conflict of interest The authors declare that there are no conflicts of interest. References [1] Lv X, Li Y, Lv M, Liu A, Wu Z. Successful endovascular treatment of a deep cerebral arteriovenous fistula with unusual venous drainage. Eur J Radiol Extra 2008. [2] Sato M, Tanaka S, Kohama A, Fujii C. Occipital lobe infarction caused by tentorial herniation. Neurosurgery 1986;18(March (3)):300–5.

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