[Leptomeningeal carcinomatosis from duodenal papillary carcinoma].

A woman in her 50s presented with ataxia and repeated falls during 2nd line S-1 therapy for duodenal papillary carcinoma with metastasis. She was diagnosed with leptomeningeal carcinomatosis based on gadolinium contrast-enhanced magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) examination, although plain computed tomography (CT) and MRI of the head showed no intracranial occupying lesions. This is a rare leptomeningeal carcinomatosis case with duodenal papillary carcinoma as the primary lesion, although aggressive treatment was not possible due to the decreased consciousness level.