Idiopathic SIADH: 4 years of diagnostic wandering

Excerpt

A 39-years-old woman was initially admitted for psychomotor slowing. Hyponatremia was the lone abnormal finding, without any lesion on conventional imaging (i.e., brain, thoraco-abdominal contrast-enhanced CT, and cerebral MRI), biologic infectious sign, or cerebrospinal fluid abnormality. Three consecutive whole-body ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography (PET)/computed tomography (CT) were performed on the following years and interpreted as normal. Considering the possibility of neuroendocrine tumor-related syndrome of inappropriate secretion of antidiuretic hormone (SIADH), [⁶⁸ Ga-DOTA,1-Nal³]-octreotide ([⁶⁸ Ga]Ga-DOTA-NOC) PET/CT was realized and showed a left ethmoidal thickening with intense overexpression of somatostatin receptors (Figure A). …