Segmental Artery Mediolysis Involving the Internal Carotid Artery

Segmental Artery Mediolysis Involving the Internal Carotid Artery: An Uncommon Diagnosis Electronic Excerpta Poster #: EE-06 Control #: 1350 Daniel A. Adamo, MD Jonathan M. Morris, MD Department of Radiology, Mayo Clinic - Rochester American Society of Neuroradiology Washington, DC 5/23/2016

Disclosures • No financial or other conflicts of interest to disclose

Purpose • To review the clinical and imaging features of segmental arterial mediolysis (SAM). • Identify the complications of SAM • Understand the radiologists role in diagnosis and therapy of SAM

Case Report • 53 year old female presented to her local emergency department for severe epigastric and left upper quadrant pain • CT of the abdomen showed a splenic infarction • Further workup with CTA of the abdomen ordered

Imaging Findings • CTA of the abdomen: Irregular beaded dilatation of the renal arteries, right gastroepiploic, left gastric and left gastroepiploic arteries.

Case Report • Additional consultation with Vascular Medicine and Rheumatology • ANCA – negative • ANA – negative • RF – negative • ESR – 12 mm/hr (normal 0 -29) • CRP – 3 mg/d. L (normal <3)

Case Report • The patient subsequently experienced multiple episodes of tingling and twitching of her right forehead, nose, cheek and eyelid. • An MRI/MRA of the head and neck was obtained to evaluate her neurologic symptoms.

Imaging Findings – MRA of the neck 5 mm pseudo aneurysm in the left ICA Long segment dilation of the right ICA

Imaging Findings – MRA of the neck Focal dissection of the left ICA © 2015 MFMER | slide-9

Imaging Findings – MRA of the head 3 mm supraclinoid pseudoaneurysm of the left ICA

Segmental Artery Mediolysis (SAM) • First described by Slavin and Gonzalez-Vitale in 19761 • Idiopathic non-atherosclerotic, non-inflammatory arteriopathy • Characterized by lysis of the medial layer of arterial wall • leads to the imaging features of focal dissection, aneurysm, stenosis or occlusion • Male > Females, 1. 5 : 1 • Typically middle aged to elderly • Almost always over age of 40 2 • Most often involves abdominal vessels, but cranial involvement can be seen

Angiographic Presentation 3 • Arterial Dilatation • Single Aneurysm • Multiple Aneurysms – “string of beads” • Dissecting hematomas • Arterial stenosis • Arterial Occlusion 3. Slavin, R. E. , Segmental arterial mediolysis: course, sequelae, prognosis, and pathologic-radiologic correlation. Cardiovasc Pathol, 2009. 18(6): p. 352 -60.

Histology/Pathology • Injurious Phase –mediolysis/disruption of smooth muscle • Starts in the outer media layer • Can involve the entire medial muscle • Can eventually lead to damage of the internal elsatica and intima • Causes “arterial gaps” which can lead to aneurysms • Large gaps fusiform aneurysms • Smaller gaps saccular aneurysms • Reparative Phase – the medial defects are rapidly repaired by granulation tissue • The healing process can cause stenosis • If the injury involved the intima, reparative granulation tissue fills the intimal injury forming a plaque • This is thrombogenic – can lead to occlusion or embolism 3. Slavin, R. E. , Segmental arterial mediolysis: course, sequelae, prognosis, and pathologic-radiologic correlation. Cardiovasc Pathol, 2009. 18(6): p. 352 -60.

Vascular Distribution A review of the literature by Shenouda et al decribed 85 cases of SAM 4 Territories Involved Celiac axis and branches SMA and branches IMA and branches n = 85 47 (55%) 32 (38%) 11 (13%) Cranial/Cerebral arteries 15 (18%) • • • 9 (11%) 7 (8%) 2 (2%) 1 (1%) Internal Carotid Vertebral Basilar Anterior Cerebral Anterior Communicating Superficial Temporal 4. Shenouda, M. , et al. , Segmental arterial mediolysis: a systematic review of 85 cases. Ann Vasc Surg, 2014. 28(1): p. 269 -77.

Differential Diagnosis Medium vessel vasculitis • Unlike vasculitis, SAM does not have elevated inflammatory and immune markers such as ESR, CRP, ANA, ANCA Cystic Medial Necrosis • typically involves larger arteries, often seen in Marfan’s Cystic Adventitial Artery Disease • involves extremities of younger adults Fibromuscular Dyplasia 5. Chao, C. P. , Segmental arterial mediolysis. Semin Intervent Radiol, 2009. 26(3): p. 224 -32.

SAM vs FMD • Significant histologic overlap • However clinical presentations are distinct • Chicken or egg? • SAM may be an evolutionary precursor to FMD 6 • Some authors argue visa versa 7 6. Slavin RE, Saeki K, Bhagavan B, Maas AE. Segmental arterial mediolysis: a precursor to fibromuscular dysplasia? Mod Pathol 1995; 8(3): 287– 294 7. Hall, E. T. , et al. , Segmental arterial mediolysis and fibromuscular dysplasia: what comes first, the chicken or the egg? Cardiovasc Pathol, 2016. 25(2): p. 113 -5.

SAM vs FMD SAM FMD • Typically older • Patients typically younger • More common in men • More common in women • More often involves abdominal splanchnic arteries • More often involves renal and carotid arteries • Often presents with aneurysmal hemorrhage • Rarely ruptures © 2015 MFMER | slide-17

Treatment of SAM • No definitive treatment • Therapies are targeted at prevention of hemorrhage and other complications • Medical therapy • Antihypertensives help to prevent complications(Steroids and immunosuppressants are ineffective and may have adverse outcomes 8 • Coiling of aneurysms is effective to prevent hemorrhage 9, 10 • Surgical options have been reported involving the internal carotid 11 8. Lie, J. T. , Systemic, cerebral, and pulmonary segmental mediolytc arteriopathy: Villainous masqueraders of vasculitis. Cardiovasc Pathol, 1996. 5(6): p. 305 -14. 9. Shimohira, M. , et al. , Transcatheter arterial embolization for segmental arterial mediolysis. J Endovasc Ther, 2008. 15(4): p. 493 -7. 10. Ryan, J. M. , P. V. Suhocki, and T. P. Smith, Coil embolization of segmental arterial mediolysis of the hepatic artery. J Vasc Interv Radiol, 2000. 11(7): p. 865 -8. 11. Obara, H. , et al. , Reconstructive surgery for segmental arterial mediolysis involving both the internal carotid artery and visceral arteries. J Vasc Surg, 2006. 43(3): p. 623 -6.

Summary • SAM is a non-immune, non-atherosclerotic arteriopathy characterized by lysis of the tunica media in medium sized vessels • Commonly affects abdominal vasculature, but can affect cranial vessels • Characteristic findings on angiography include aneurysm, dissection, stenosis and occlusion • Significant overlap with FMD, but distinct clinical presentations • Typically presents as hemorrhage in older adults • Coil embolization is a mainstay of therapy to prevent hemorrhage