In 2016, when we first launched the BrainWaves podcast, cryptogenic stroke was a poorly understood concept. 3 years later, it remains poorly understood. But we are making progress. In this week's update of episode 10, we review the progress that has been made in the pathogenesis, diagnosis, and management of these patients. Produced by James E. Siegler. The original 2016 version of this show was also produced by Dr. Noah Levinson. Music courtesy of Josh Woodward, Julie Maxwell, Dan Lebowitz, and this group called E’s Jammy Jams. Sound effects by Mike Koenig and Daniel Simion. BrainWaves' podcasts and online content are intended for medical education only and should not be used for clinical decision making. Be sure to follow us on Twitter @brainwavesaudio for the latest updates to the podcast. REFERENCES Siegler JE, Swaminathan B, Giruparajah M, Bosch J, Perera KS, Hart RG, Kasner SE and Investigators EGR. Age disparity in diagnostic evaluation of stroke patients: Embolic Stroke of Undetermined Source Global Registry Project. Eur Stroke J. 2016;1:130-138. Jacobs BS, Boden-Albala B, Lin IF and Sacco RL. Stroke in the young in the northern Manhattan stroke study. Stroke; a journal of cerebral circulation. 2002;33:2789-93. Hart RG, Sharma M, Mundl H, Kasner SE, Bangdiwala SI, Berkowitz SD, Swaminathan B, Lavados P, Wang Y, Wang Y, Davalos A, Shamalov N, Mikulik R, Cunha L, Lindgren A, Arauz A, Lang W, Czlonkowska A, Eckstein J, Gagliardi RJ, Amarenco P, Ameriso SF, Tatlisumak T, Veltkamp R, Hankey GJ, Toni D, Bereczki D, Uchiyama S, Ntaios G, Yoon BW, Brouns R, Endres M, Muir KW, Bornstein N, Ozturk S, O'Donnell MJ, De Vries Basson MM, Pare G, Pater C, Kirsch B, Sheridan P, Peters G, Weitz JI, Peacock WF, Shoamanesh A, Benavente OR, Joyner C, Themeles E, Connolly SJ and Investigators NE. Rivaroxaban for Stroke Prevention after Embolic Stroke of Undetermined Source. The New England journal of medicine. 2018;378:2191-2201. Diener HC, Sacco RL, Easton JD, Granger CB, Bernstein RA, Uchiyama S, Kreuzer J, Cronin L, Cotton D, Grauer C, Brueckmann M, Chernyatina M, Donnan G, Ferro JM, Grond M, Kallmunzer B, Krupinski J, Lee BC, Lemmens R, Masjuan J, Odinak M, Saver JL, Schellinger PD, Toni D, Toyoda K, Committee R-SES and Investigators. Dabigatran for Prevention of Stroke after Embolic Stroke of Undetermined Source. The New England journal of medicine. 2019;380:1906-1917. Di Tullio M, Sacco RL, Gopal A, Mohr JP and Homma S. Patent foramen ovale as a risk factor for cryptogenic stroke. Annals of internal medicine. 1992;117:461-5. Overell JR, Bone I and Lees KR. Interatrial septal abnormalities and stroke: a meta-analysis of case-control studies. Neurology. 2000;55:1172-9. Li J, Liu J, Liu M, Zhang S, Hao Z, Zhang J and Zhang C. Closure versus medical therapy for preventing recurrent stroke in patients with patent foramen ovale and a history of cryptogenic stroke or transient ischemic attack. The Cochrane database of systematic reviews. 2015;9:CD009938. Mas JL, Derumeaux G, Guillon B, Massardier E, Hosseini H, Mechtouff L, Arquizan C, Bejot Y, Vuillier F, Detante O, Guidoux C, Canaple S, Vaduva C, Dequatre-Ponchelle N, Sibon I, Garnier P, Ferrier A, Timsit S, Robinet-Borgomano E, Sablot D, Lacour JC, Zuber M, Favrole P, Pinel JF, Apoil M, Reiner P, Lefebvre C, Guerin P, Piot C, Rossi R, Dubois-Rande JL, Eicher JC, Meneveau N, Lusson JR, Bertrand B, Schleich JM, Godart F, Thambo JB, Leborgne L, Michel P, Pierard L, Turc G, Barthelet M, Charles-Nelson A, Weimar C, Moulin T, Juliard JM, Chatellier G and Investigators C. Patent Foramen Ovale Closure or Anticoagulation vs. Antiplatelets after Stroke. The New England journal of medicine. 2017;377:1011-1021. Saver JL, Carroll JD, Thaler DE, Smalling RW, MacDonald LA, Marks DS, Tirschwell DL and Investigators R. Long-Term Outcomes of Patent Foramen Ovale Closure or Medical Therapy after Str