The Shy-Drager syndrome (SDS) is a form of progressive autonomic nervous system failure (PAF) with orthostatic hypotension and associated extrapyramidal involvement that is often mistaken for Parkinson disease. SDS includes olivopontocerebellar atrophy and striatonigral degeneration which is attended by PAF. Eight patients with SDS were studied on a 0.5-T superconducting system utilizing T1-weighted inversion recovery (IR) and T2-weighted spin-echo pulse sequences and also on a 1.5-T system using spin-echo sequences. With IR sequences, atrophy of the putamina was demonstrated in patients with SDS that is consistent with findings of neuronal loss in these nuclei reported on postmortem examinations. An abnormal decrease in signal intensity of the putamina, particularly along their lateral and posterior portions, was also detected, predominantly on T2-weighted sequences, and in three cases on T1-weighted spin-echo sequences. Abnormalities were detected on both imagers but were shown with greater clarity on the 1.5-T device. SDS is the first disease in which convincing basal ganglia changes have been shown in vivo exclusively by MR imaging.

SUMMARY A significant rank correlation between rigidity and putaminal signal dropout on magnetic resonance imaging (MRI) in patients with multiple system atrophy suggests that putaminal degeneration may cause this clinical finding. Absence of putaminal abnormalities on MRI in patients with pure autonomic failure may prove useful in differentiating these two autonomic disorders.Autonomic failure may occur alone (pure autonomic failure) or in association with central neurological disorders, including Parkinsonism, ataxia and pyramidal findings (multiple system atrophy).' Multiple system atrophy includes both striatonigral degeneration and olivopontocerebellar atrophy, since there is frequently overlap of patients in these two categories, and the clinical and pathological findings in multiple system atrophy encompass those described for both striatonigral degeneration and olivopontocerebellar atrophy.2 The pathology of pure autonomic failure, however, has not yet been clearly defined.Biochemical and pharmacological differences between multiple system atrophy and pure autonomic failure have increased our understanding of these diseases.1 Unfortunately, these differences cannot be exploited as diagnostic tests in individual cases. The development of magnetic resonance imaging (MRI) has made it possible to examine structural details within the brain not visualised by computed tomography (CT) scans. We recently described putaminal atrophy on T1 weighted axial scans of three of eight multiple system atrophy patients, and decreased signal intensity in the posterolateral putamen on T2 weighted scans of seven of these patients by MRI,3 in

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