The Combination of Hypointense and Hyperintense Signal Changes on T2-Weighted Magnetic Resonance Imaging Sequences

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Abstract
THE DIFFERENTIAL diagnosis of patients with parkinsonism very often remains a challenging task for neurologists and may require additional investigations. The most important alternative diagnoses of Parkinson disease (PD) are progressive supranuclear palsy (PSP) and multiple system atrophy (MSA).1 In the early course of the disease, both PSP and MSA may be clinically difficult to distinguish from PD, but this distinction has important prognostic and therapeutic implications. In contrast to PD, in which degeneration does not involve striatal or pallidal neurons, cell degeneration is found in those areas in PSP and MSA.2,3 Most cases of MSA of the striatonigral degeneration (SND) type reveal a prominent degeneration of the putamen.4 Thus, magnetic resonance imaging (MRI) may be helpful in differentiating PD from MSA or PSP by identifying putaminal involvement. Nevertheless, the specific role of MRI in the differential diagnosis of parkinsonism has yet not been established, for several reasons. First, hypointense signal changes on T2-weighted MRI sequences in the putamen, which have been proposed as an indicator of nonidiopathic parkinsonism,5 have been shown to be clearly age dependent and therefore misleading or nonspecific.6,7 Second, the amount of pathological MRI findings in patients with MSA varies in the literature from 35% to 100%.8-16 Recently, we described a pattern consisting of hypointense and hyperintense signal changes within the putamen in 2 patients with MSA of the SND type, as well as the corresponding neuropathological findings.17 Other authors have also reported similar findings.14,18 One of the studies, however, was conducted on lower-field strength, which is known to influence the pathological signal changes within the basal ganglia.14 None of the prior studies compared the frequency of hypointense areas in the putamen with the combination of hyperintense and hypointense changes in patients with PD, MSA, and PSP. Therefore, the aim of this study was to compare the frequency and specificity of hypointense signal changes alone with those of the combination of hypointense and hyperintense signal changes in the putamen in a large population of patients with parkinsonism of various origins.

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