A case of atherothrombotic embolization developing with slowly progressive symptoms and requiring differential diagnosis from metastatic tumor recurrence

We report a case of atherothrombotic embolization that developed with slowly progressive symptoms and required differential diagnosis from metastatic tumor recurrence. A 64-year-old man with a history of lung cancer and metastatic brain tumor was carefully followed at our outpatient department for tumor recurrence. Five years after surgery for brain metastasis and whole brain radiation therapy, he had no recurrence and systemic disease was well controlled. At a routine follow up in October 2013, he complained of slight right arm dysesthesia. Follow up brain magnetic resonance (MR) imaging revealed no lesion. Two months later, he developed right hemiparesthesia and gait disturbance. Spinal MR imaging was unremarkable. However, at a routine follow up in January 2014, multiple enhancements were detected near the resection cavity and regions delineating the sulci. At first, this was diagnosed as tumor recurrence. However, 3 days later, additional MR imaging detected new multiple small infarctions after worsening right hemiparesis and dysarthria. With the diagnosis of embolic stroke, we searched for an embolic source. Cardiogenic embolization and carotid bifurcation stenosis studies were negative, but severe stenosis and thrombosis were detected near the left common carotid artery origin. This site was in the field of radiation the patient received as treatment for primary lung cancer.