Feeding and Draining Vessel Ligation with Sclerotherapy of High Flow Arteriovenous Malformations in the Head and Neck

High flow arteriovenous malformations (AVMs) are infiltrative, invading tissue planes and structures and may be life threatening when they bleed.1 They have a feeding artery and an anomalous capillary bed shunting blood from the arterial system to the venous system.1 The present trend of management of small AVMs is surgical excision with a high success rate. The problematic cases are diffuse AVMs infiltrating structures that render them impossible to totally extirpate surgically without causing much blood loss and tissue damage. The mainstay of management is embolization, surgical resection and reconstruction.2 Ligation or proximal embolization (alone) of feeding vessels should never be done because such maneuvers result in rapid recruitment of new vessels from adjacent arteries to supply the AVM nidus.2 Incomplete surgical excision definitely leads to recurrences, making this type of AVM very difficult to manage. What is the point of this paper? The complete destruction of the “nidus” of the AVM, from the artery to the capillary to the venous component, is the only potential cure.3 Well and good if there could be a way of doing this by sclerosing the entire vascular malformation. But since sclerosis only works well in low flow vascular malformations and tumors like hemangiomas, and poorly or not at all in high flow lesions,4 we have to convert this high flow AVM into a “no-flow” or “low flow” AVM by ligating the feeding and draining vessel and injecting the sclerosant intra-arterially thereafter at a dose sufficient enough to blanch out the AVM even up to its peripheral branches. This paper aims to demonstrate how we do this. Definition of Terms Vascular malformation: They are a result of abnormal development of vascular elements during embryonic or fetal stages of life.2 They originate from mesenchymal cells at an early stage of embryogenesis.3 and most are present at birth but there are several case reports of these lesions presenting after trauma in adults.1 Some AVMs appear as part of a familial genetic disorder called angiomatous syndrome i.e. Rendu-Osler-Weber Syndrome presenting with telangiectasia of the skin and mucous membranes.3 Some propose that a defect in vascular stabilization like TGF-beta signaling could be a cause of AVM development.5,6 Still, progesterone receptors have been isolated in AVMs explaining their expansion during puberty.7 Hemangioma: These are vascular tumors that exhibit endothelial proliferation.2 A hemangioma of infancy usually undergoes 3 stages: a proliferative phase of rapid growth up to 10 to 12 months of age; an involuting phase where growth slows down and signs of regression appear usually at 1 to 7 years; and an involuted phase.2 Sclerosants: Agents used in sclerotherapy that induce a toxic effect on the vascular endothelium and results in fibrosis. There are 3 types: Detergents that disrupt cell membranes by protein theft desaturation ie: ethanolamine oleate, sodium morrhuate, polidocanol, sodium tetradecyl sulfate; Osmotic agents ie: sclerodex; and Chemical irritants that damage cell walls by direct contact ie: chromatin glycerine, polyiodinated iodine.8 Sclerodex: an osmotic sclerosant that is a combination of dextrose monohydrate 250mg/ml and sodium chloride 100mg/ml. It shifts water balance through cellular gradient (osmotic) dehydration that leads to endothelial destruction. Since component materials are naturally occurring bodily, it has no molecular toxicity in calibrated dosages. If extravasated, it could cause tissue necrosis.8 It is manufactured by OMEGA Laboratories, Ltd. Montreal, QC, Canada. REVIEW OF PRESENT PRACTICE AND LITERATURE The first task of the physician is to establish a diagnosis, whether the lesion is a vascular malformation or a vascular tumor. Taking the history of the patient could point to a diagnosis as vascular tumors like hemangiomas usually proliferate and involute from the time of infancy to about the age of 10. Vascular malformations grow as the child grows and do not involute. Vascular malformations have an arterial supply and a venous drainage and are classified into high or low flow. Capillary, venous and lymphatic types are low flow while arteriovenous malformations are usually high flow. A high flow AVM has an arterial blood supply and a venous drainage. In rare instances, a vascular malformation could co-exist with a hemangioma forming a mass effect.2 On physical examination, a bruit and a strong pulsation (thrill) is appreciated. The head and neck is the most common location of AVMs at 70%. When fully developed, they are deeper in color with increasing erythema, local warmth, palpable mass and a bruit.9 These malformations are composed of vascular channels lined by flat mature epithelium and are not hypercellular and not proliferative.10 Schobinger proposed a staging system for Head and Neck AVM. Stage 1 are AVMs that are quiescent and remain stable for long periods of time. Stage 2 is a time for expansion followed by pain and bleeding. Stage 3 is heralded by destruction of adjacent tissues and ulceration. Stage 4 is presented by decompensation where symptoms of cardiac failure are present.11 Ultrasound with color Doppler imaging, Magnetic Resonance Imaging and Phlebography (arteriography/venography) contribute to diagnosis, classification and management.3 In our setting were we do not have the facilities, we use CT- angiography. These imaging modalities should be used to evaluate the characteristics of the lesion, such as size, flow velocity, flow direction, relation to surrounding structures and lesion content.3 Ultrasound demonstrates flow rates, contrast-enhanced magnetic resonance imaging (MRI) shows presence or absence of a mass, and CT angiography reveals the arborization (the blood supply and drainage) of the vascular anomaly. Vascular tumors like hemangioma, if located in non-strategic areas where function is not impaired can be observed over its developmental phases until involution at about 10 years old.2 For hemangiomas that impair function or are possibly life threatening because of potential hemorrhage, these tumors are treated with the following modalities: 1. Intralesional corticosteroids ie: triamcinolone; 2.Systemic corticosteroids in a tapered dose like prednisolone and some second choice pharmacotherapeutics like interferon, vincristine; and 3. Propranolol. Surgery is indicated in ulcerating, bleeding, and life threatening lesions like airway obstruction.2 Over 90% demonstrate dramatic reduction in size of hemangioma in one to two weeks from the above medical therapeutic modalities. Propranolol has been successfully used as hemangioma treatment since 2008 and is believed to have an antiproliferative effect on the vascular endothelium. The mechanism of action may involve the regulation of growth factors.1 Low flow vascular malformations are treated with sclerotherapy or surgical excision for accessible tumors. These malformations do not regress like hemangioma but grow in time. High flow AVMs are treated with surgical excision if they have limited extent and are surgically accessible. Embolization before surgery decreases bleeding and is the standard. Embolization followed by repeated sclerotherapy is recommended for surgically inaccessible areas.4 There is a 64 to 96% response rate , defined as improvement in symptoms or a reduction in the lesion size after ethanol sclerotherapy of venous low flow malformations.3 Partial surgical excision leads to only temporary improvement followed by re-expansion of tumor overtime.9 Sometimes, complete resection is not possible in diffuse or infiltrating AVMs and surgery can result in severe disfigurement and impairment of function of involved structures.9 METHODS After establishing the diagnosis of a high flow AVM with identification of an arterial feeding vessel and a venous draining vessel, surgery is commenced away from the malformation to expose the arterial and venous supplies. The procedure is done under general anesthesia because sclerotherapy of large malformations and vascular tumors is very painful. We do this because we have no interventional radiology services in our hospital. We ligate the feeding artery and if possible, the draining vein to convert the AVM into a “ low or no flow” and to allow ample contact time between the sclerosant (sclerogen) and the vessel endothelium. The sclerosant is then injected intravascularly distal to the ligation until all visible malformation blanches out. Aspirating the blood content of the ligated (arterial supply and venous drainage) malformation before introduction of the sclerosant will further potentiate the action of the sclerosant. While injecting the sclerosant slowly, the patient’s vital signs are monitored. A drop in the pulse rate is a signal to stop or slow down the injection of the sclerosant because it may be a sign that some sclerosant is escaping the venous drainage and reaching the general circulation in a concentration picked up by the sensors of the vascular system. Injections resume in a slower manner as the vital signs revert to normal. Our sclerosing agent sclerogen is an osmotic agent composed of sodium chloride and dextrose which are naturally present in our body so they are not toxic in manageable concentrations. Other sclerosants can be nephrotoxic so we must be very careful in injecting not to overload the vascular system. The objective is to push the sclerosant to all branches of the malformation to eliminate all possible nidus. The end point of injection is when all cutaneous or mucosal components of the malformation blanch out. Injection of the sclerosant intravascularly is done under direct visualization to prevent extravascular introduction. A review of literature has this to say about sclerotherapy. Extravascular i

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