CT scanning in patients with opsomyoclonus: importance of nonenhanced scan.

Children with neuroblastoma presenting with opsomyoclonus are a diagnostic dilemma; they may not have a palpable mass or elevated urine catecholamines and the neurologic manifestation often precedes the discovery of a primary tumor by several months. The delay in diagnosis probably reflects the difficulty in detecting small lesions. Even with high-resolution computed tomography (CT), difficulty was recently experienced in identifying small retroperitoneal lesions in three patients who presented with opsomyoclonus. Calcifications in these small neoplasms resembled contrast material within adjacent small-bowel loops that were not discernible until additional, unenhanced scans were obtained. It is recommended that the initial CT evaluation in patients presenting with opsomyoclonus be performed without bowel or intravenous contrast enhancement.