“LASS WITH EAR MASS”: EXTRA-CRANIAL AVM DIAGNOSIS & TREATMENT.

Fig.1 Posterior aspect of Left Ear. Shortly after embolization, the AVM area can be appreciated with the reaction to the NBCA.

The swollen area, upon physical examination, proved to be a pulsatile mass, with some reddish discoloration. (Fig.1) The results of MRI/MRA imaging were consistent with an extra-cranial AVM, with feeders anterior and posterior auricular branches. Suggestion of feeders from branches of the middle meningeal artery.

Fig. 2A PA view of Left External Carotid Angiogram showing posterior and anterior Auricular Arteries, a ear helix, and scapha feeding with a dominate fistula.

Fig. 2B Total angiographic obliteration of AMC and fistula with sparing of the Helix cascade (as seen on late films).

Selective angiogram revealed feeders from the anterior and posterior auricular arteries. (Fig. 2A) Super selective embolization of feeders involved in the auricular cascade with penetration into the draining veins, nidus, and distal dedicated feeding arteries while the ear was packed in ice to stop flow to the normal tissue lead to total obliteration One-tenth of a cc of non-opacitied NBCA was used to minimize the mass of embolic material and discoloration. (Fig. 2B).

Fig. 3 Two weeks after embolization the inflammation of the NNCA is gone and the shunt gone by Doppler.

In follow-up, shows obliteration of the AV shunting. Additional angiography is indicated in 6-12 months to confirm obliteration.

Key Points:

1. Extra-cranial AVMs can become quite active, and apparently grow with trauma, puberty, or pregnancy.
2. Normal tissue blood flow is controlled by tissue temperature, whereas pathological shunts seen in AVM’s are fixed. At temperatures below 20°C, there is virtually no flow to normal tissue.It is possible to take advantage of this to spare the normal tissue and target the shunts as in this case.
3. Angiographic follow-up is needed in all AVM treated cases by all methods when the non-invasive imaging has been negative for 6-12 months as it is the only way to confirm cure.

Discussion:

AVMs are less common than venous malformations, and rare compared to more common hemangiomata (a.k.a. birthmarks). Clinical examination and history can usually tell them apart. Skin hemangiomata are almost always self-limiting, present in infancy, and regress with time. Venous malformations, local dilated venous structures, grow in proportion to the patient, and symptoms develop due to local mass effect. AVMs have a saltatory course. They can be quiet for years, then expand rapidly which can be related to growth, trauma, or childbirth. Particularly treacherous is growth of AVMs related to pregnancy. Although thought to be “malformations’ lacking capillaries, it is likely they are a remodeling disease. Long-term surveillance is needed. Effective treatment requires obliteration of the feeding artery, “nidus” and proximal vein. This can be done by embolization and surgical en-block resection1,2. Recurrence is possible due to ongoing remodeling or tiny residual areas that where initially angiographically occult. The extensive blood supply of the face with a rich connection between the cutaneous, muscular, osseus, and nervous systems can make treatment difficult. Thankfully, the deep structure of the temporal bone was not directly involved in this lass. This area is usually rich with anastomoses from arteries of the brain stem. In addition, all cranial nerves have an associated artery that runs the course of the nerve and picks up collaterals along its course.

Penetration of embolic material into normal tissues can lead to ischemic damage and reflux into anastomoses can lead to nerve damage. Strategies used to avoid this “off target” embolization include super-selective catheter placement and temporal vascular blockade of normal tissue. Packing the normal tissue in ice was used in this case. Tissue blood-flow is tightly controlled by tissue temperature, whereas pathological shunts as seen in AVMs are decoupled from this physiological thermal control. At temperatures below 20°C, there is only minimal flow to normal tissue3. Therefore, it is possible to take advantage of this to spare the normal tissue and selectively target the high-flow shunts. Trans-venous embolization with ethanol can be effective, if there is a single draining vein but offers its own set of risks.

Acknowledgments: We appreciate the care and help of Dr. Charles Corwin and Dr. Susanne Kowel-Connelly.

References:

1. Dabus G, Linfante I, Benenati J, Perlyn CA, Martínez-Galdámez M. Interventional management of high-flow craniofacial vascular malformations: a database analysis and review of the literature. J Neurointerv Surg. 2017 Jan;9(1):92-96. doi: 10.1136/neurintsurg-2016-012315. Epub 2016 Mar 30. PMID: 27029395. https://pubmed.ncbi.nlm.nih.gov/27029395/
2. Griauzde J, Wilseck ZM, Chaudhary N, Pandey AS, Vercler CJ, Kasten SJ, Gemmete JJ. Endovascular Treatment of Arteriovenous Malformations of the Head and Neck: Focus on the Yakes Classification and Outcomes. J Vasc Interv Radiol. 2020 Nov;31(11):1810-1816. doi: 10.1016/j.jvir.2020.01.036. Epub 2020 Sep 18. PMID: 32958379. https://pubmed.ncbi.nlm.nih.gov/32958379/
3. Walter B, Bauer R, Kuhnen G, Fritz H, Zwiener U. Coupling of cerebral blood flow and oxygen metabolism in infant pigs during selective brain hypothermia. JCBFM 2000; 20: 1215-24. https://journals.sagepub.com/doi/full/10.1038/jcbfm.2013.214