Type I Dural Arteriovenous Fistula Mimicking Dural Venous Thrombosis-Related Intracranial Hypertension

Letters to the Editor Myofibroma as a cause of Horner syndrome has been reported once previously, in a neonate with a left apical lung lesion and atrophy of the muscles of the ipsilateral arm (8). The treatment and prognosis of this disease is highly dependent on the extent of organ involvement, particularly of the viscera. Outcomes are generally excellent for patients who have solitary or multicentric disease confined to soft tissue and bone without visceral involvement and treatment primarily consists of observation (6,9,10). Because of the high mortality associated with multicentric myofibromatosis with visceral involvement, various medical treatments have been used including corticosteroids, interferon alpha, radiation and chemotherapy with a favorable outcome in some patients (11). Seyed Ali Nabavizadeh, MD Robert A. Zimmerman, MD Department of Radiology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania Peter Mattei, MD Department of General, Thoracic and Fetal Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania Grant T. Liu, MD Neuro-ophthalmology Service, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania Type I Dural Arteriovenous Fistula Mimicking Dural Venous Thrombosis- Related Intracranial Hypertension W e read with interest the recent editorial by Davies and Hopkins (1) on "Neuro-endovascular intervention: Evolving at the intersection of Neurosurgery and Neuro-ophthalmology." We share our experience of a patient in which neurointervention helped in the management of intracranial hypertension (ICH) caused by a Type I dural arteriovenous fistula (DAVF) that is otherwise considered benign and only rarely associated with ICH. A 30-year-old man with a body mass index of 54.52 kg/m2 experienced visual blurring and new-onset headache. He also reported tinnitus in his right ear. Visual acuity was 20/50, right eye and 20/70, left eye. The pupil examination was normal, and extraocular movements were full. He had bilateral hemorrhagic papilledema (Frisen Grade 5) with exudates extending into the macula (Fig. 1). Blood 460 The authors report no conflicts of interest. REFERENCES 1. Sadaka A, Schockman S, Golnik K. Evaluation of Horner Syndrome in the MRI Era. J Neuroophthalmol. 2017;37: 268-272. 2. Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone. Geneva, Switzerland: World Health Organization, 2002. 3. Beck JC, Devaney KO, Weatherly RA, Koopman CF Jr, Lesperance MM. Pediatric myofibromatosis of the head and neck. Arch Otolaryngol Head Neck Surg. 1999;125:39-44. 4. Gopal M, Chahal G, Al-Rafai Z, Eradi B, Ninan G, Nour S. Infantile myofibromatosis. Pediatr Surg Int. 2008;24:287-291. 5. Loundon N, Dedieuleveult T, Ayache D, Roger G, Josset P, Garabedian EN. Head and neck infantile myofibromatosisa report of three cases. Int J Pediatr Otorhinolaryngol. 1999;15:181-186. 6. Chung EB, Enzinger FM. Infantile myofibromatosis. Cancer. 1981;48:1807-1818. 7. Wiswell TE, Davis J, Cunningham BE, Solenberger R, Thomas PJ. Infantile myofibromatosis: the most common fibrous tumor of infancy. J Pediatr Surg. 1988;23:315-318. 8. Tierney TS, Tierney BJ, Rosenberg AE, Krishnamoorthy KS, Butler WE. Infantile myofibromatosis: a nontraumatic cause of neonatal brachial plexus palsy. Pediatr Neurol. 2008;39:276-278. 9. Wiswell TE, Davis J, Cunningham BE, Solenberger R, Thomas PJ. Infantile myofibromatosis: the most common fibrous tumor of infancy. J Pediatr Surg. 1988;23:314-318. 10. Coffin CM, Dehner LP, O'Shea PA. Fibroblasticmyofibroblastictumors: fibromatosis: juvenile fibromatoses: infantile myofibromatosis. In: Mitchell CW, ed. Pediatric Soft Tissue Tumors: A Clinical, Pathological, and Therapeutic Approach. Baltimore, MD: Williams & Wilkins, 1997. 11. Azzam R, Abbound M, Muwakkit S, Khoury N, Saab R. Firstline therapy of generalized infantile myofibromatosis with lowdose vinblastine and methotrexate. Pediatr Blood Cancer. 2009;52:308. pressure in the clinic was 158/70. The patient was immediately sent to the emergency department for further workup. Brain computed tomography was unremarkable. Opening pressure on lumbar puncture was 36 cm H2O, and cerebrospinal fluid composition was normal. Magnetic resonance imaging and magnetic resonance venography (MRV) of the brain were concerning for venous sinus thrombosis of the right sigmoid sinus and proximal internal jugular vein. However, a second review of the time-resolved angiography with interleaved stochastic trajectories (TWIST) sequence indicated early opacification of the right sigmoid sinus and internal jugular vein indicating an underlying DAVF (Fig. 2). A nonocclusive thrombus extended from the right transverse/sigmoid sinus junction to the right internal jugular vein. Cerebral angiography revealed a Type I DAVF involving the right sigmoid and transverse sinuses with antegrade flow and without alteration of cortical venous drainage. This study also confirmed the small, nonocclusive nature of the venous thrombus found on the MRV. Venous Letters to the Editor: J Neuro-Ophthalmol 2017; 37: 458-465 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Letters to the Editor FIG. 1. There is bilateral, severe (Frisen Grade 5) papilledema. blood flow was spontaneous with preserved antegrade flow around the thrombus. The patient underwent successful Onyx embolization of the DAVF with 90% occlusion (Fig. 3). He was treated with acetazolamide, topiramate, and anticoagulants and, 4 weeks later, he underwent left optic nerve sheath fenestration for persistent papilledema. The papilledema slowly resolved over 3 months and visual acuity improved to 20/30 FIG. 2. Coronal magnetic resonance venography (TWIST sequence) shows opacification in the arterial phase of the right sigmoid sinus and internal jugular vein (arrows) indicative of the presence of a DAVF. DAVF, dural arteriovenous fistula; TWIST, time-resolved angiography with interleaved stochastic trajectories. Letters to the Editor: J Neuro-Ophthalmol 2017; 37: 458-465 bilaterally. The patient remained stable over the ensuing 8 months. Our patient highlights 3 important points regarding DAVF. First, the clinical presentation of DAVFs is variable and depends on the venous drainage pattern and the location. Type I DAVF drains directly into the dural venous sinuses with antegrade flow and has minimal to low risk of intracranial hemorrhage and nonhemorrhagic neurologic deficits, unlike other types (2,3). DAVFs located in the transverse-sigmoid sinus typically present with symptoms of raised intracranial pressure including headache, bruit and pulsatile tinnitus, and visual symptoms mimicking the clinical presentation of idiopathic intracranial hypertension often leading to a diagnostic dilemma (4-6). Although ICH due to DAVFs previously has been described, reports of association with Type I DAVFs are limited (4). Second, venous sinus thrombosis is often associated with DAVFs as in our case, but the cause-effect relationship is not clear. One hypothesis is that the thrombosis causes opening of congenital channels leading to a fistula. Another mechanism postulated is that the venous hypertension from the fistula causes sluggish blood flow leading to thrombus formation. In patients being evaluated for pseudotumor cerebri syndrome, if MRV shows venous sinus thrombosis, it is important to look for a DAVF. Third, as our case highlights, endovascular intervention plays a critical role in managing ICH secondary to a DAVF. Hang Pham, MD Sangeeta Khanna, MD Department of Ophthalmology, Saint Louis University, St. Louis, Missouri The authors report no conflicts of interest. 461 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Letters to the Editor FIG. 3. A. Preoperative cerebral angiogram shows a Type I DAVF (arrow) involving the right sigmoid and transverse sinuses. B. The postoperative cerebral angiogram reveals decreased flow through the DAVF after Onyx embolization. DAVF, dural arteriovenous fistula. REFERENCES 1. Davies JM, Hopkins LN. Neuroendovascular intervention: evolving at the intersection of neurosurgery and neuroophthalmology. J Neuroophthalmol. 2017;37:111-112. 2. Borden JA, Wu JK, Shucart WA. A proposed classification for spinal and cranial dural arteriovenous fistulous malformations and implications for treatment. J Neurosurg. 1995;82:166-179. 3. Cognard C, Gobin YP, Pierot L, Bailly AL, Houdart E, Casasco A, et al. Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revised classification of venous drainage. Radiology. 1995;194:671-680. Why a One-Way Ticket to Mars May Result in a One-Way Directional Glymphatic Flow to the Eye W e read with great interest the article by Mader et al (1) entitled "Persistent asymmetric optic disc swelling after long-duration space flight: implications for pathogenesis." Mader et al point out that ophthalmic abnormalities including optic disc swelling, optic nerve sheath distention, globe flattening, and choroidal folds have been reported in astronauts after long-duration space flight. They emphasize 2 potential mechanisms to explain optic disc edema observed in astronauts. The first explanation is that optic disc swelling results from elevated intracranial pressure (ICP) secondary to cephalad fluid shifts. The second is compartmentation of cerebrospinal fluid (CSF) in the orbital subarachnoid space (SAS). We provide a possible additional explanation of how microgravity, at least in part, may cause optic disc edema due to an imbalance between ocular glymphatic inflow and outflow. In 2012, the glymphatic system was discovered in mice by Iliff et al (2). Their findings suggested that a brain-wide network of paravascular pathways along which a large proportion of subarachnoid CSF recirculates through brain parenchyma, 462 4. Cognard C, Casasco A, Toevi M, Houdart E, Chiras J, Merland JJ. Dural arteriovenous fistulas as a cause of intracranial hypertension due to impairment of cranial venous outflow. J Neurol Neurosurg Psychiatry. 1198;65:308-316. 5. Gelwan MJ, Choi IS, Berenstein A, Pile-Spellman JM, Kupersmith MJ. Dural arteriovenous malformations and papilledema. Neurosurgery. 1988;22:1079-1084. 6. Lamas E, Lobato RD, Esperarza J, Escudero L. Dural posterior fossa AVM producing raised sagittal sinus pressure: case report. J Neurosurg. 1977;46:804-810. facilitating the clearance of interstitial solutes, including amyloid-b, from the brain. CSF enters the brain along para-arterial channels to exchange with interstitial fluid which is, in turn, cleared from the brain along paravenous pathways. Intriguingly, other reports (3) together with preliminary data from our own postmortem study (4) suggest that a similar paravascular transport system is present in the human optic nerve and retina. We examined cross-sections of human optic nerves by light microscopy after injecting India ink into the SAS of the optic nerve. Our results showed a striking accumulation of India ink in paravascular spaces around the central retinal artery and vein, whereas the lumens of these vessels and the surrounding axons remained unlabeled. We speculated that a "paravascular communication" may exist between the surroundings of the retinal vascular system and the surroundings of the central retinal vessels in the optic nerve. Such a para-arterial "retino-orbital" pathway would include a paraarterial CSF influx route around the central retinal artery to enter the paravascular spaces of the retina, followed by a paravenous efflux route around the central retinal vein. Normally, intraocular pressure exceeds ICP, and, on average, there is a small force (mean 4 mm Hg) directed posteriorly across the lamina cribrosa (5). This trans-lamina cribrosa pressure difference (TLCPD) would ensure effective paravenous outflow from Letters to the Editor: J Neuro-Ophthalmol 2017; 37: 458-465 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.