Torcular pseudomass: a potential diagnostic pitfall in infants and young children.

Abstract

Incidental findings on brain MRI may constitute a diagnostic pitfall. We observed an incidental extra-axial midline rounded pseudomass between the torcular Herophili and the occipital squama, with spontaneous resolution, which we called "torcular pseudomass." We investigated the frequency, imaging features, natural history and developmental background of this finding in a large group of infants and young children. We conducted a single-center retrospective study by reviewing all brain MRIs performed in children younger than 3years between 2007 and 2013 in a specialized pediatric hospital. We looked for soft tissue (minimum 2mm thick) interposed between the torcula and the occipital squama on midsagittal T1 and T2 images; we recorded the maximal diameters and outcome. Of 2,283 the children who had brain MRIs during the study period, 291 (12.7%, 95% confidence interval [CI] 0.11, 0.14) presented with a torcular pseudomass (median age 4months, range 0days to 35months, 56% male). MRI features were the same in all of these children: T1 isointensity and T2 hyperintensity to the cerebral cortex, facilitated diffusion on diffusion-weighted imaging and apparent diffusion coefficient maps, and contrast enhancement. The median diameters were: anteroposterior, 5.8mm; transverse, 10.5mm; cranio-caudal, 20.6mm. Follow-up MRI was available in 34.7% (95% CI: 0.20, 0.40) of the children; median follow-up time was 18months. Among these children, 35.6% (95% CI: 0.26, 0.45) had total involution, 52.5% (95% CI: 0.26, 0.62) had partial involution and 4.1% (95% CI: 0.05, 0.18) showed stability. Redundant soft tissue in the torcular region, or torcular pseudomass, is not an infrequent finding in infants and young children. It should be considered a physiological tissue, reflecting the postnatal developmental process of the brain and cranial vault, without the need for further investigation or follow-up imaging studies.