SAT-325 Unveiling a Rare Complication: Transverse Myelitis Arising After Osseous Trans Arterial Chemoembolization (TACE) for Follicular Thyroid Carcinoma Metastases

Abstract Disclosure: B. Jennings: None. A. Riaz: None. Introduction: Follicular thyroid carcinoma, the second most prevalent type of thyroid cancer, encompasses a spectrum from minimally invasive to aggressive forms, necessitating tailored treatment strategies. For metastatic disease, therapeutic options may include radiotherapy, chemotherapy, or both, following total thyroidectomy. Transarterial chemoembolization (TACE) involves injecting chemotherapy into the feeding arteries of a tumor in combination with particles designed to slow or stop the arterial supply to the tumor. Here, we present a case of a patient with metastatic follicular thyroid carcinoma who underwent intercostal chemoembolization with the aim of enhancing subsequent radioactive iodine therapy and local disease control, yet experienced a rare and debilitating complication of transverse myelitis. Case Presentation: A 54-year-old male with metastatic follicular thyroid carcinoma with osseous metastasis, with remote history of testicular choriocarcinoma and melanoma over 20 years prior, presented for outpatient procedure with interventional radiology for focal area metastatic disease management through chemoembolization of osseous metastasis of iliac wing, left fifth and ninth ribs, and left pubic ramus, to be followed by cryoablation. Prior to this, patient did undergo thyroidectomy and radioactive iodine therapy. During the embolization, a balloon microcatheter was used to minimize the potential for retrograde reflux. The diagnostic injection of the left fourth intercostal artery demonstrated the presence of an anterior spinal artery, which was not radiographically evident on initial contrast injection of the T9 intercostal artery. Doxorubicin and mitomycin C were administered in an emulsion with endothelialized oil and Embozene microspheres. Following intercostal chemoembolization, the patient developed acute onset numbness below the umbilicus and motor weakness in bilateral lower extremities. The patient was diagnosed with transverse myelitis, approximately T9 level on left and L1 on right, secondary to chemotherapeutic toxicity exposure. Patient started on IV dexamethasone. Patient had minor improvement of symptoms with this including sensation improvement in right leg and mild strength improvement with adduction. He was discharged to the inpatient rehab team on a prolonged steroid taper. The patient has had gradual clinical improvement over the coming months with steroids and physical therapy. Discussion: To our knowledge, this represents the first reported case of transverse myelitis following TACE for follicular thyroid cancer metastases. This complication underscores the importance of managing rare adverse events after chemoembolization, in patients presenting with acute neurological deficits post-procedure. Despite incremental symptomatic improvement, our patient continues to have significant residual symptoms. Presentation: Saturday, July 12, 2025