Callosal changes in obstructive hydrocephalus: observations with FLAIR imaging, and diffusion MRI

Sagittal and transverse fluid attenuated inversion recovery (FLAIR) images were obtained in age-matched 16 normal individuals, and 24 patients with obstructive hydrocephalus. The inner (inferior) callosal surface, which is covered by ependyma, was electronically measured ranging from 0.15 to 0.25 cm (mean=0.20±0.02 cm) in normal individuals. This region was thicker in hydrocephalus cases due to transcallosal accumulation of water, ranging from 0.29 to 1.10 cm (mean=0.65±0.30 cm). Furthermore, there was a prominent difference between mild hydrocephalus and moderate-to-severe hydrocephalus cases that in mild hydrocephalus the ranges were 0.29–0.40 cm (mean=0.34±0.03 cm), and in moderate-to-severe hydrocephalus the ranges were 0.50–1.10 cm (mean=0.80±0.22 cm). It is concluded that especially sagittal FLAIR images could be useful for identifying especially milder forms of hydrocephalus by evaluation of the appearance and thickness of the inner callosal layer. Twelve patients with moderate-to-severe obstructive hydrocephalus, and eight of the controls were studied with diffusion MRI, using the echo-planar trace imaging. In moderate-to-severe hydrocephalus patients apparent diffusion coefficient (ADC) values from the inner callosal surface were high, similar to that of transependymal resorption of water, ranging from 1.30 to 2.20×10 −3 mm 2/s (mean: 1.78±0.27×10 −3 mm 2/s), compared to the normal ADC values of the splenium in controls: 0.78±0.12×10 −3 mm 2/s.