Intracranial Leptomeningeal Carcinomatosis: A Diagnostic Study with 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

Leptomeningeal carcinomatosis (LC) diagnosis is based on cerebrospinal fluid (CSF) cytological analysis and contrast-enhanced magnetic resonance imaging (MRI); however, low sensitivity was evidenced in some cases delaying prompt and adequate treatments. Brain 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) was also employed in doubtful cases. We retrospectively described 4 suspected LC cases with uncertain or undetectable MRI and initially negative CSF cytology. Whole-body (WB) and brain 18F-FDG PET/computed tomography (CT) were used, the latter showing intracranial tracer uptakes suspected for LC in 3/4 cases. In 2 of these 3 cases, WB scan also evidenced spinal cord lesion and pulmonary tumor, respectively, while both procedures were true negative in the fourth case. CSF cytology became positive after repeated exams in the 3 PET/CT-positive cases. In 1 of these 3 patients, it was also confirmed at MRI, while it stayed negative in the remaining PET/CT-negative case with uncertain MRI. 18F-FDG PET/CT could be a useful supportive diagnostic tool in doubtful intracranial and spinal LC.