Cushing’s adenoma invading the cavernous sinus requires aggressive resection to be cured. MRI is frequently inconclusive for identifying microadenomas, and visualizing the involvement of the medial cavernous sinus is even more challenging. In this video, the authors present a patient with an adrenocorticotropic hormone (ACTH)–producing microadenoma with doubtful left medial cavernous sinus involvement on MRI. She underwent an endoscopic endonasal exploration of the medial compartment of the cavernous sinus. The abnormally thickened wall, confirmed by intraoperative endoscopic endonasal ultrasound, was safely excised using the "interdural peeling" technique. Complete resection of the tumor resulted in normalization of her postoperative cortisol levels and disease remission with no complications.The video can be found here:https://stream.cadmore.media/r10.3171/2023.4.FOCVID22150