Coil embolization of a palatine artery pseudoaneurysm in a gelding

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Coil embolization of a palatine artery pseudoaneurysm in a gelding

  1. 1. Coil Embolization of a Palatine Artery Pseudoaneurysm in a Gelding Nathaniel R. McClellan1 , DVM, Margaret C. Mudge1 , VMD, Diplomate ACVS, ACVECC, Brian A. Scansen1 , DVM, MS, Diplomate ACVIM, Stephen S. Jung2 , MD, FACR, and Duncan Russell3 , BVMS (Hons), Diplomate ACVP 1 Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio ,2 Radiology Incorporated and Mount Carmel Health Care, The Ohio State University, Columbus, Ohio and 3 Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio Corresponding Author Margaret C. Mudge, VMD, Diplomate ACVS, ACVECC, Department of Veterinary Clinical Sciences, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, OH 43210. E‐mail: margaret.mudge@cvm.osu.edu Submitted November 2011 Accepted June 2012 DOI:10.1111/j.1532-950X.2014.12174.x Objective: To describe successful transarterial coil embolization of a palatine artery pseudoaneurysm that extended into the caudal maxillary sinus of a gelding. Study Design: Clinical report. Animal: A 24‐year‐old Morgan gelding with right‐sided epistaxis. Methods: The right maxillary sinus was imaged by radiography, computed tomography, and sinoscopy. Angiography was performed to locate the source of bleeding, and transarterial coil embolization of a right palatine artery pseudoaneurysm was performed. Results: There was some mucoid nasal discharge and an intermittent cough postoperatively. No epistaxis was seen after embolization. There was moderate swelling of the surgical incision over the mid‐cervical common carotid artery. The horse was discharged from the hospital 4 days after surgery, and had been doing well, with no signs of bleeding, for 2 months postoperatively. The horse had acute colic secondary to a strangulating lipoma at 2 months and was euthanatized after exploratory celiotomy. Placement of embolization coils in the right palatine artery was confirmed by CT and necropsy. Conclusions: Severe epistaxis in the horse may be caused by a ruptured major palatine artery pseudoaneurysm. Occlusion of this vessel can be successfully accomplished by transarterial coil embolization. Severe epistaxis in the horse has been reported secondary to guttural pouch mycosis, sinonasal trauma, and is occasion- ally associated with paranasal sinus neoplasia or ethmoid hematoma. Most commonly, rupture or erosion of the internal carotid, external carotid, and/or maxillary arteries have been reported to occur secondary to fungal infection of these vessels as they course through the guttural pouch.1–5 Transarterial coil embolization has been described in horses to control hemorrhage from the internal carotid, external carotid, and maxillary arteries individually or in combination with one another related to guttural pouch mycosis induced aneurysm.1,2 We are unaware of any reports describing transarterial coil embolization to control hemorrhage from other sites of aneurysm or pseudoaneurysm in the horse. Our objective was to report an unusual cause of life‐threatening hemorrhage in the horse and to describe the technique of transarterial coil embolization to successfully occlude the affected vessel. CLINICAL REPORT A 24‐year‐old Morgan gelding (482 kg) was admitted for evaluation of moderate to severe right‐sided epistaxis. Moderate to severe bleeding from the right nostril was noted 3 weeks before, and again 6 days before admission. Right‐ sided guttural pouch mycosis was suspected based on the severity of hemorrhage and endoscopic observation of clotted blood at the right salpingopharyngeal opening. The horse had been treated with sulfamethoxazole trimethoprim since the first episode of bleeding and was also being administered isoxsuprine, cyproheptadine, and levothyroxine (Thyro‐L, Usp, Lloyd, Inc., Shenandoah, IA) for management of equine pituitary pars intermedia dysfunction and chronic laminitis. On admission, the gelding was quiet, alert, responsive, and afebrile, with a heart rate of 52 beats/min and respiratory rate of 20 breaths/min. Mucous membranes were pale pink with a capillary refill time of 1–2 seconds. A moderate amount of blood was observed on the muzzle, chest, and forelimbs. No other abnormalities were identifies on physical examination. On hematologic examination, there was anemia (PCV, 16%), mild hypoproteinemia (5.4 g/dL) and a blood lactate of 2.1 mmol/L. Endoscopic examination of the upper airway revealed a region of swollen red tissue interpreted as hematoma in the pharynx, immediately rostral to the right salpingopharyngeal opening (Fig 1A). A small amount of fresh blood was seen at the right nasomaxillary opening. Both guttural pouches were Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons 487
  2. 2. free of blood and exudate. Skull radiographs revealed homogenous soft tissue opacity within the right rostral and caudal maxillary sinuses as well as the dorsal and ventral conchal sinuses, consistent with sinusitis and/or hemorrhage. There was no evidence of distortion of bony structures or fluid line present in the paranasal sinuses. Widening of the periodontal space along the left upper PM3, PM4, M1 (Triadan 207, 208, 209) and mild remodeling of the tooth roots of the right upper PM3 and rostral root of PM4 (Triadan 107 and 108) were seen, indicating periodontal disease (Fig 1B–D). Oral examination revealed good alignment of all premolar and molar teeth with mild points on the lingual surfaces of both mandibular cheek teeth arcades and the buccal surfaces of both maxillary cheek teeth arcades. There was no evidence of any fractures, fistula, masses, or foreign bodies. Considering the signalment and history top differential diagnoses were neoplasia or ethmoid hematoma with unusual hemorrhage. Because of a lack of a definitive radiographic diagnosis, computed tomography (CT) was recommended to diagnose the problem and determine if surgical intervention would be an option. The day after admission, cross‐matching was performed in preparation for blood transfusion before general anesthesia and if indicated during/after any potential surgical intervention. Based on the gelding’s anemia and continued mild epistaxis, 4 L whole blood was administered before anesthesia. Immediately after the horse was anesthetized and positioned in dorsal recumbency for the CTscan, there was profuse hemorrhage from the right nostril. Additional whole blood was transfused and the right nasal cavity was packed to help reduce hemorrhage during CT. On the CT scan, there was diffuse soft tissue attenuating material that filled the entire right paranasal sinuses as well as the nasopharynx (interpreted as hemorrhage). The areas of attenuating material were later analyzed using Hounsfield units (HU) and were determined to have a CT density of $60 HU. This value of Hounsfield unit falls within the range of fresh blood, early hematoma, and some soft tissue structures.6 Unfortunately, because of the severity of hemorrhage that started before CT evaluation, the entire right paranasal sinuses were completely filled with blood which may have masked an accurate diagnosis of any potential difference in CT density of an abnormal soft tissue structures versus fresh hemorrhage. CT images demonstrated the presence of both expansion and lysis of the right wing of the basisphenoid bone and right maxillary Figure 1 (A) Endoscopic image showing hematoma (white arrows) on the right pharyngeal wall immediately rostral to the right salpingopharyngeal opening (black arrow). (B) Dorsoventral radiograph of the skull demonstrating increased radiopacity in the right paranasal sinuses (outlined by black arrows). (C) Right lateral oblique radiograph of the skull demonstrating increased radiopacity within the right paranasal sinuses compared to the left (Fig 1D). Mild widening of the periodontal space and remodeling of the tooth roots of the right upper PM3 and rostral root of PM4 (black arrows). (D) Left lateral oblique radiograph of the skull demonstrating mild widening of the periodontal space along the left upper PM3, PM4, M1 (black arrows). The left paranasal sinuses appear clear (radiolucent) in this image. 488 Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons Coil Embolization of a Palatine Artery Pseudoaneurysm McClellan et al.
  3. 3. bone of the ventral aspect of the caudal maxillary sinus, including the bone surrounding the right maxillary third molar and right ventral aspect of the infraorbital canal (Fig 2A–C). These CT findings did not definitively diagnose the problem, but with the bony lysis and expansile nature of the lesion, neoplasia or large sinus ethmoid hematoma was considered highly likely. During the CT scan, mean arterial blood pressure decreased to 52 mmHg. The previously placed nasal cavity packing was producing an inadequate level of hemostasis, so the decision was made to stop the CT scan and proceed to emergency temporary ligation of the right common carotid artery. The right neck was clipped and scrubbed with chlohexidine and alcohol. A 7 cm skin incision was made immediately dorsal to the jugular vein in the right mid‐cervical region. The incision was then extended through the brachio- cephalicus and omohyoid muscles using a combination of blunt and sharp dissection. Once located, the right carotid sheath was carefully incised so that the right carotid artery could be isolated from both the vagosympathetic trunk and recurrent laryngeal nerve. Once isolated, the right common carotid was ligated using sterile umbilical tape. The hemor- rhage appeared to decrease after carotid artery ligation, but did not stop completely. Therefore, the decision was made to proceed directly to surgery for an emergency right frontonasal sinusotomy in an attempt to achieve both a definitive diagnosis and stop the hemorrhage by application of direct pressure with gauze packing. The right frontonasal sinus region was prepared for a frontonasal sinusotomy, which was performed using an oscillating bone saw.7 Hemorrhage from the sinus continued once the flap was elevated, and bleeding was reduced with manual pressure and gauze packing. One soft friable red/black mass $6 cm diameter was discovered in the right frontal sinus and another firm fibrous tan mass $4 cm diameter was observed in the right caudal maxillary sinus. Portions of both masses were removed using sponge forceps which significantly increased the severity of hemorrhage. Gauze packing was used to apply pressure within the sinuses, and this stopped the hemorrhage. The end of the packing was exited through the right nostril by attaching it to a Chamber’s catheter passed retrograde through the nostril with 3 polymerized caprolactum suture (Braunamid; Jorgensen Laboratories, Loveland, CO) and then removing the catheter from the nostril. The packing was then tacked to the external surface of the right nares using 0 polypropylene suture in a simple interrupted pattern. The frontonasal bone flap was repositioned and secured. After being in place for $45 minutes, the umbilical tape was removed from the right common carotid artery and the approach incision was closed in 2 layers. Total anesthetic time was 105 minutes and total surgical time was 60 minutes. Anesthetic recovery time was $30 minutes and the quality of recovery was subjectively graded as smooth and uneventful. Intraoperatively, the PCV and total solids were 11% and 3.8 g/dL. Whole blood transfusion (12 L) was initiated during surgery and continued after recovery, for a total transfusion volume of 16 L. Potassium penicillin (22,000 U/kg intrave- nously [IV] every 6 hours), gentamicin (6.6 mg/kg IV every 24 hours), flunixin meglumine (1.1 mg/kg IV every 12 hours), and aminocaproic acid (40 mg/kg IV once) were administered postoperatively. Biopsies obtained during surgery were evaluated by cytology (impression smears made with fresh tissue) and histopathology (formalin fixed tissue). Cytologic evaluations were made the same day as surgery and revealed mild to moderate neutrophilic inflammation with a large amount of red blood cells; however, no definitive causative agents or neoplastic cells were observed. By Day 5, the histopathology Figure 2 (A) Transverse CT image of the skull at the level the third maxillary molars demonstrating bony lysis and remodeling surrounding the right maxillary third molar (black arrow). The right paranasal sinuses and nasopharynx are diffusely filled with a soft tissue attenuating material (60 Hounsfield units [HU]). (B)Transverse CT image of the skull at the level of the caudal maxillary sinus demonstrating bony lysis/remodeling of the ventral aspect of the caudal maxillary sinus (black arrows) and the ventral aspect of the right infraorbital canal (white arrow). The right paranasal sinuses and nasopharynx are diffusely filled with a soft tissue attenuating material (60 HU). (C) Transverse CT image of the skull at the level of the caudal aspect of the caudal maxillary sinus, demonstrating bony lysis in the right caudal maxillary sinus (black arrows). The right paranasal sinuses and nasopharynx are diffusely filled with a soft tissue attenuating material (60 HU). Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons 489 McClellan et al. Coil Embolization of a Palatine Artery Pseudoaneurysm
  4. 4. results were available and were inconclusive for the cause of hemorrhage. Histopathology was consistent with subacute hemorrhage and organizing hematoma. At this point the PCV had stabilized at 25% and without a definitive diagnosis, the decision was made to reopen the sinus flap for further evaluation of the soft tissue mass noted in the right maxillary sinus during the previous surgery. The sinus flap was reopened with the horse standing and sedated (0.1 mg/kg morphine IV; 18 mg/kg detomidine IV) and local anesthesia to avoid the hemorrhage experienced during general anesthesia. The gauze packing material was removed from the sinuses, the sinuses were lavaged with sterile saline solution, and several blood clots were removed. A 4 cm diameter round firm, white to tan mass was present in the right caudal maxillary sinus. Sinoscopy was performed through the previous right frontonasal sinus flap to aid viewing of the right caudal maxillary mass. After closer examination with sino- scopy, the mass was observed to be pulsating leading to suspicion that the mass was an aberrant arterial structure (Fig 3A). Gauze packing material was placed in the right frontal and maxillary sinuses to prevent further bleeding. Transarterial Surgical Technique Angiography was performed 2 days later, with the gelding anesthetized and positioned in left lateral recumbency. The right common carotid artery (CCA) was accessed through the previous mid‐cervical incision, and elevated after ensuring that it was separated from the vagosympathetic trunk and recurrent laryngeal nerve. The CCAwas isolated with umbilical tape. An 18 g, 7 cm arterial access needle (Argon Medical Devices, Inc.; Athens, TX) was placed into the CCA, and a 0.889 mm, 150 cm angled hydrophilic guidewire (Weasel Wire; Infiniti Medical, LLC; Menlo Park, CA) was advanced through the needle. The arterial needle was exchanged over the wire for a 7 Fr 55 cm long sheath (Flexor Check‐Flo Introducer, RAABE; Cook, Inc.; Bloomington, IN). Angiograms were performed through the sheath and with a 5 Fr 100 cm straight marker catheter (Royal Flush II Angiographic Catheter with Beacon‐Tip; Cook, Inc.) to delineate the anatomy. After entering the right external carotid artery, the right maxillary artery was selected, and angiography revealed a focal dilation (interpreted as a pseudoaneurysm) in the proximal to mid aspect of the greater palatine artery (Fig 3B). The frontonasal bone flap was reopened to ensure that the abnormality seen on angiography correlated with the aberrant arterial structure in the maxillary sinus. Metallic hemostats were placed into the caudal maxillary sinus to the level of the mass through the previous frontonasal sinus flap site, and confirmed by fluoroscopy to precisely overlie the pseudoaneurysm diagnosed with angiography. The pseudoaneurysm was not readily accessible through the sinusotomy, as the full extent could not be seen, even with an endoscope. A maxillary sinusotomy was considered to gain more direct access to the area of the pseudoaneurysm; however, it was decided that a transarterial approach would be less invasive and would be more likely to ensure complete occlusion of the abnormal vasculature. A 5 Fr 100 cm multipurpose end‐hole (MPA Beacon‐Tip Torcon NB Advantage Catheter; Cook, Inc.) catheter was used to place a 10 mm to 5 mm tapered platinum embolization coil (Tornado Embolization Coil; Cook, Inc.) in the greater palatine artery beginning distal to and extending into the pseudoaneur- ysm. Two more tapered platinum embolization coils were deployed within the pseudoaneurysm and extended into the proximal greater palatine artery. A final 5 mm  3 cm coil (Embolization Coil; Cook, Inc.) was placed at the entrance to the pseudoaneurysm. Digital subtraction angiography (DSA) performed immediately after coil embolization showed a small amount of flow into the pseudoaneurysm, which ruptured under pressure. Complete hemostasis was achieved within seconds as the pseudoaneurysm thrombosed and there was no longer flow through the right greater palatine artery (Fig 3C,D). The catheter was withdrawn to the maxillary artery and further DSA in both the maxillary artery and right ECA failed to identify any other vascular abnormalities or tumor blush. Exit angiography in the right ECA and CCA showed normal flow with profound vasospasm. All catheters were withdrawn and the carotid access was closed with a single cruciate suture of 3‐0 polydioxanone. The brachiocephalicus and omohyoid muscles and skin were closed and a Penrose drain placed. Total anesthesia time was 185 minutes and total surgical/procedure time was 140 minutes. Recovery time from anesthesia was $35 minutes and the quality of recovery was subjectively assessed as good. Figure 3 (A) Sinoscopy image showing a portion of the palatine artery pseudoaneurysm in the caudal maxillary sinus (white arrow) via right frontonasal sinus flap approach. (B) Pseudoaneurysm pre coil emboliza- tion observed under digital subtraction angiography (à ) in the proximal to mid aspect of the greater palatine artery, infraorbital artery (black arrow), and maxillary artery (white arrow). (C) Pseudoaneurysm post coil embolization observed under digital subtraction angiography (à ). (D) Embolization coils observed within the palatine artery pseudoaneurysm on fluoroscopy (à ). 490 Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons Coil Embolization of a Palatine Artery Pseudoaneurysm McClellan et al.
  5. 5. Postoperative Care The gelding was hospitalized for 4 days after the coil embolization procedure. Trimethoprim‐sulfa tablets (25mg/kg orally every 12 hours) and phenylbutazone (2.2 mg/kg orally every 12 hours) were administered for another 5 days after discharge. Levothyroxine and cyproheptadine were administered throughout hospitalization. The skin staples and sutures were removed from the sinus flap and neck incision, respectively, at 14 days postoperatively. Exercise was restricted to a small paddock for 30 days followed by a return to normal turnout and exercise. Outcome There was no active bleeding seen after the coil embolization procedure. The gelding developed mild mucoid nasal discharge and had an intermittent cough while in the hospital. There was moderate swelling and drainage associated with the carotid access incision, and some incisional discharge from the sinus flap site was noted $5 days after hospital discharge. All complications were self‐limiting and resolved within 30 days after discharge. Two months after surgery, the gelding had acute abdominal pain. On exploratory celiotomy, ischemic necrosis of the jejunum secondary to a strangulating lipoma was identified and resection and jejunocecostomy performed. The gelding was euthanatized 1 day after surgery because of his poor prognosis following severe postoperative abdominal pain and endotoxemia. Necropsy Findings CTwas performed on the head before and after infusion of a 1:4 barium/latex mixture infused into the right external carotid artery. Barium was used to add contrast to the vasculature to aid identification of any vascular anomalies on CT. Figure 4A–C demonstrates the location of the coils in the right greater palatine artery along with the unaffected left side for anatomic comparison. Gross dissection of the head revealed bony proliferation in the caudal and rostral maxillary sinuses with disruption of the septum dividing the maxillary sinuses. There was also severe thickening of the infraorbital canal as it coursed through the affected area. A small 7–8 mm segmentally distended vessel was noticeable in the right caudal maxillary sinus at the level of the nasomaxillary opening with the coils present within its lumen (Fig 5A,B). Histopathology performed on the palatine artery at the site of coil embolization showed a luminal obstruction by fibrovascular connective tissue interpreted as a recanalized thrombus. The arterial wall had severe myointimal hyperplasia (remodeling), with chronic intramural hemorrhage, and moderate lymphoplasmacytic arteritis (Fig 5C). Elastic fibers within the tunica media were disrupted, coiled, and fragmented (degeneration) and the wall contained multiple, small caliber vascular profiles (neovascularization). Both the tunica intima and tunica media contained a moderate amount of myxomatous material and foci of mineralization. Special stains for fungal elements (periodic acid‐Schiff [PAS] and Grocott’s methena- mine silver [GMS]) were unremarkable; however, previous fungal disease could not be excluded. In the associated sinus mucosa there were reactive, non‐specific changes consistent with chronic hemorrhage and granulation tissue. Other findings included moderate lymphoplasmacytic and neutrophilic sinus- itis, periosteal reaction, and mild Wallerian degeneration of peripheral nerves. DISCUSSION We are unaware of reports of pseudoaneurysm of the palatine artery in horses. Arterial pseudoaneurysms are rare in people, but have been reported after orthognathic surgery, gunshot wounds, penetrating knife injuries, facial fractures, placement of circummandibular wires, visceral transplantation, obstetric and gynecological procedures, and vascular and endovascular interventions.8–10 Pseudoaneurysms are believed to form after trauma to an arterial vessel wall that allows the flow of blood to be maintained through the vessel. Arterial trauma may be caused by infection/inflammation, vasculitis, iatrogenic causes, and tumor invasion.10 As a result of arterial damage, a hematoma can be formed when hemorrhage occurs into the soft tissues surrounding the vessel. The hematoma will continue to increase in size until the periarterial pressure becomes greater than the mean arterial pressure. After pressure equilibration, the hematoma and perivascular connective tissue becomes more organized to form a fibrous “sac” like structure around the injured artery. The “sac” is contained by the media or adventitia or simply by soft‐tissue structures surrounding the injured vessel.11 As the hematoma resolves, the mass or “sac” expands with arterial pressure producing pulsations. Once formed, a pseudoaneurysm can either progressively enlarge or rupture.9 This can be distinguished from a true aneurysm which has all 3 layers of the arterial wall ‐ intima, media, and adventitia.10 Angiography in this gelding was supportive of pseudo- aneurysm, though the histopathology was not confirmatory, likely because of distortion of the vessel secondary to the coil deployment and associated thrombosis. Histopathology re- vealed sections that contained evidence of chronic arterial thrombosis and recanalization. Products of blood breakdown were identified in the vessel wall and surrounding connective tissue, indicating long‐standing hemorrhage. Because of the chronicity and extensive vascular remodeling from coil embolization it was difficult to make the distinction between aneurysm and pseudoaneurysm. Although an inciting cause was not apparent, possible explanations for the vascular pathology might include primary intramural degeneration, vascular trauma or previous inflam- matory disease (vasculitis), external or foreign body related trauma, or severe dental disease. The level of dental disease affecting the right upper PM3 and rostral root of PM4 was diagnosed on radiographs and CTas mild disease; therefore we did not suspect that the inciting cause was secondary to dental disease. In fact the overall alignment and condition of all 4 dental arcades were considered excellent given the gelding’s Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons 491 McClellan et al. Coil Embolization of a Palatine Artery Pseudoaneurysm
  6. 6. Figure 4 (A) Postmortem CT 3D reconstructions with barium:latex (1:4) vascular contrast, right sagittal view; embolization coils in the palatine artery (Ã ), external carotid artery (1), linguofacial trunk (2), maxillary artery (3), lingual artery (4), and facial artery (5) infraorbital artery (6). B) Postmortem CT 3D reconstructions with barium:latex (1:4) vascular contrast, left sagittal view; external carotid artery (1), linguofacial trunk (2), maxillary artery (3), infraorbital artery (6), uncoiled palatine artery (7). (C) Postmortem CT 3D reconstructions with barium:latex (1:4) vascular contrast, dorsoventral view; embolization coils in the palatine artery (asterix), maxillary artery (3), uncoiled palatine artery (7). Figure 5 (A) Dorsal view of the right nasomaxillary opening with the remnant of the palatine artery pseudoaneurysm (Ã ) observed by sectioning of the skull in a dorsal to ventral direction. (B) Close up view of the right nasomaxillary opening with the remnant of the palatine artery pseudoaneurysm. (C) Equine, longitudinal section through palatine artery. There is severe thickening of the tunica intima, with occlusion of the arterial lumen (black arrow). The tunica intima contains loosely arranged mesenchymal cells with intramural hemorrhage and recanalization (Ã ); multiple deposits of hematoidin are also present, indicating chronic hemorrhage (white arrow). Hematoxylin and eosin. Bar ¼ 500 mm. 492 Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons Coil Embolization of a Palatine Artery Pseudoaneurysm McClellan et al.
  7. 7. age. The owner was unable to recall any specific incidences, but did inform us that the gelding shared a pasture with another gelding and they would sometime play roughly. There was no obvious sign of trauma on physical examination or skull radiographs that would indicate that the vascular anomaly occurred secondary to external trauma. Although a foreign body penetration sometime before admission could not be ruled out we were unable to identify a foreign body presence with any of our diagnostic modalities performed. Potentially a stick or other organic foreign body may have caused trauma to the palatine artery several months before admission. We feel that the client would have noticed some bleeding associated with such trauma, but we cannot rule out the possibility. Another striking, yet puzzling aspect of this lesion was the amount of bony lysis and remodeling associated with the right maxillary sinus and infraorbital canal. One potential explana- tion is that the remodeling is simply a response to the chronic expansile and inflammatory nature of the lesion as it relates to the pressure placed on the surrounding bony and soft tissue structures during the formation of the pseudoaneurysm. Or perhaps there was initial damage to the bony structures during some unidentified event that caused the formation of a palatine artery pseudoaneurysm. Unfortunately, we were unable to find a primary cause for the bony lysis in this gelding, instead we believe it is all a result of the chronic inflammatory nature of the lesion. Diagnosis of pseudoaneurysms may be extremely difficult because they are often clinically silent until weeks or months after the initial trauma to the artery. In people, pseudoaneurysm is most commonly associated with a severe bleed $2 weeks after orthognathic surgery, however as late as 11 weeks post surgery has been reported.9 A pseudoaneurysm may be diagnosed with CT or DSA as a rounded structure arising from the side of the artery.10 Advances in CT technology including contrast‐enhanced multidetector CT angiography, have facilitated fast, non‐invasive, accurate diagnosis of aneurysm/pseudoaneurysm in people. However, for ruptured pseudoaneurysm, DSA is the “gold standard” because of the ability to diagnose and treat concurrently.10 In this gelding, we chose DSA because of the availability at our hospital, limitations of CT angiography in an adult horse, and the high potential for another life threatening bleed that would require immediate intervention. In retrospect, standing CT angiography might have avoided the bleeding complications encountered during the initial anesthetic episode. However, standing CT is not available in our hospital and since we initially suspected neoplasia or ethmoid hematoma we did not anticipate the marked hemorrhage that occurred.12 To address the severe bleeding, the decision to ligate the ipsilateral common carotid artery was made when simple nasal packing failed to reduce the amount of hemorrhage. Clinically, we observed a decrease in the amount of hemorrhage after ligation which is consistent with previous reports of a reduction to 30% of normal blood flow with ipsilateral common carotid artery ligation.13 However the reduction in hemorrhage could also have been the result of a decrease in blood pressure which prompted the decision for an emergency right frontonasal sinusotomy with direct pressure applied to the location of the hemorrhage. Palatine artery occlusion was considered necessary because of previous life‐threatening hemorrhage; however, we had to consider the potential complications of transarterial embolization or ligation of the palatine artery such as local ischemic tissue necrosis and inciting the “steal phenomenon.” In people, ligation of the descending palatine artery during Le Fort I osteotomy produces no change in the maxillary gingival blood flow between groups with and without arterial ligation.14 This is most likely a result of the large amount of collateral circulation that exists in the head region of most species. The “steal phenomenon” is proposed to cause blindness after arterial occlusion for the treatment of guttural pouch mycosis in the horse. The phenomenon occurs when the major blood flow to the horse’s eye (external ophthalmic artery) is reduced indirectly through ligation of the external carotid artery in addition to simultaneous ligation of the major palatine artery which is the largest terminal branch of the maxillary artery and another potential path for blood to reach the external ophthalmic artery by retrograde flow.15,16 We felt that this was unlikely to occur if we could occlude only the palatine artery without the need to affect the external carotid artery which would preserve blood flow to the eye via the external ophthalmic artery. Another decision we had to make was whether or not to attempt open surgical repair using ligatures, vascular clips, or other means of vascular hemostasis. In people, options for treatment include open surgical repair, direct percutaneous thrombin injection, transarterial embolization with coils, glue, or Gelfoam, and deployment of covered stents or detachable balloons.8–10 We choose transarterial emboliza- tion with coils because of anatomic inaccessibility of the pseudoaneurysm, availability of equipment, and expertise of the surgeons/interventional radiologists. We could not completely see or access the entire extent of the lesion through the frontonasal sinusotomy, and complete occlusion of the vessel could be easily performed and confirmed by transarterial approach. It is possible that an additional maxillary sinusotomy would have provided better access to the lesion, allowing occlusion by ligatures or vascular clips. Overall we found that the approach through the right common carotid artery was uncomplicated and the pseu- doaneurysm was effectively treated with transarterial coil embolization. ACKNOWLEDGMENT The authors are indebted to Elizabeth M. Santschi, Diplomate ACVS of The Ohio State University Veterinary Medical Center for her surgical assistance/expertise, and Melissa A Milligan, DVM, MS, Diplomate ACVS of Equine Specialty Hospital, Burton, OH. REFERENCES 1. Lepage OM, Piccot‐Crézollet C: Transarterial coil embolization in 31 horses (1999–2002) with guttural pouch mycosis: a 2‐year follow‐up. Equine Vet J 2005;37:430–434 2. Lévéille R, Hardy J, Robertson JT, et al.: Transarterial coil embolization of the internal and external carotid arteries for Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons 493 McClellan et al. Coil Embolization of a Palatine Artery Pseudoaneurysm
  8. 8. prevention of hemorrhage from guttural pouch mycosis in horses. Vet Surg 2000;29:389–397 3. Delfs KC, Hawkins JF, Hogan DF: Treatment of acute epistaxis secondary to guttural pouch mycosis with transarterial nitinol vascular occlusion plugs in three equids. J Am Vet Med Assoc 2009;235:189–193 4. Baptiste KE: The mystery of guttural pouch mycosis: the paradox of advancing knowledge of a rare disease. Vet J 2004;168:1–2 5. Parizel PM, Makkat S, Van Miert E, et al.: Intracranial hemorrhage: principles of CT and MRI interpretation. Eur Radiol 2001;11:1770–1783 6. Lepage OM, Perron MF, Cadore JL: The mystery of fungal infection in the guttural pouches. Vet J 2004;168:60–64 7. McIlwraith CW, Robertson JT: Paranasal sinus exploration. in McIlwraith CW, Robertson JT (eds): McIlwraith and Turner’s equine surgery. (ed 2). Baltimore, MD, Williams & Wilkins, 1998, pp 270–275 8. Fernández‐Prieto A, Garcia‐Raya P, Burgueño M, et al.: Endovascular treatment of a pseudoaneurysm of the descending palatine artery after orthognathic surgery: technical note. Int J Oral Maxillofac Surg 2005;34:321–323 9. Krempl GA, Noorily AD: Pseudoaneurysm of the descending palatine artery presenting as epistaxis. Otolaryngology Head Neck Surg 1996;114:453–456 10. Keeling AN, McGrath FP, Lee MJ: Interventional radiology in the diagnosis, management, and follow‐up of pseudoaneurysms. Cardiovasc Intervent Radiol 2009;32:2–18 11. Saad NEA, Saad WEA, Davies MG, et al.: Pseudoaneurysm and the role of minimally invasive techniques in their management. Radiographics 2005;25:S173–S189 12. Benredouane K, Lepage O: Trans‐arterial coil embolization of the internal carotid artery in standing horses. Vet Surg 2012;41:404–409 13. Woodie JB, Ducharme NG, Gleed RD, et al.: In horses with guttural pouch mycosis or after stylohyoid bone resection, what arterial ligation(s) could be effective in emergency treatment of a hemorrhagic crisis? Vet Surg 2002;31:498(abstr) 14. Dodson TB, Bays RA, Neuenschwander MC: Maxillary perfusion during Le Fort I osteotomy after ligation of the descending palatine artery. J Oral Maxillofac Surg 1997;55:51–55 15. Hardy J, Robertson JT, Wikie DA: Ischemic optic neuropathy and blindness after arterial occlusion for treatment of guttural pouch mycosis in two horses. J Am Vet Med Assoc 1990;196:1631–1634 16. Freeman DE, Ross MW, Donawick WJ: “Steal phenomenon” proposed as the cause of blindness after arterial occlusion for treatment of guttural pouch mycosis in horses. J Am Vet Med Assoc 1990;197:811–812 494 Veterinary Surgery 43 (2014) 487–494 © Copyright 2014 by The American College of Veterinary Surgeons Coil Embolization of a Palatine Artery Pseudoaneurysm McClellan et al.

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