The "cross" signs in patients with multiple system atrophy: a quantitative study.

Patients with multiple system atrophy (MSA) may show the "cross" sign in the pontine base that has been considered as an expression of the degeneration of pontine neurons and transverse pontocerebellar fibers. However, correlations between pontine base atrophy and existence of "cross" sign have not been fully investigated. The authors studied 68 patients with MSA (47 MSA-C [predominantly cerebellar ataxia], 21 MSA-P [predominantly parkinsonism], mean [+/-SD ] 58.7 +/- 10.9 years). T1-weighted (T1W) sagittal and axial images and T2-weighted (T2W) axial images were obtained for all patients and controls. To measure the areas of pontine basis and cerebellar vermis, the authors used midsagittal T1W images and analyzed a bit map transformed on a computer. They classified atrophy in the pontine base into 3 grades. There is significant correlation between atrophies of pontine base and existence of the cross sign. All patients with a smaller area of pontine base 2 standard deviations below those of normal controls had the cross sign. This supports that existence of the cross sign depends only on the extent of pontine base atrophies.