Neuroimaging Spectrum of Erdheim-Chester Disease: An Image-based Review.

Erdheim-Chester Disease (ECD) is a rare, multisystem histiocytic disorder characterized by its variable clinical presentations. Central Nervous System (CNS) involvement is observed in approximately half of ECD patients (up to 76% in some series), and often carries a poorer prognosis. While CNS involvement may remain asymptomatic, others may experience a range of neurological symptoms, including cognitive decline, neuropsychiatric disturbances, motor deficits, cranial or peripheral neuropathies, and endocrine abnormalities.Neuroimaging findings in CNS-ECD are diverse, including neurodegeneration manifesting as cerebral or cerebellar volume loss, solitary or multifocal variably enhancing intraparenchymal lesions along the neuroaxis, meningeal infiltration, involvement of the Hypothalamo-pituitary axis, perivascular sheathing or basal ganglia lesions. Other well documented sites of involvement include the craniofacial region, orbits and spine. Awareness of these findings is relevant, not only because of the non-specific nature of these findings, but also given the high proportion of CNS involvement in ECD as well as the higher mortality associated with CNS involvement.This review provides an in-depth overview of the various manifestations of CNS involvement in ECD and their imaging features, along with a brief overview of the differential considerations which include other histiocytic and non-histiocytic processes.ABBREVIATIONS: ECD＝Erdheim-Chester Disease; RDD＝Rosai-Dorfman Disease; LCH= Langerhans cell histiocytosis.