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Background
Parkinson-plus syndromes characterizes a group of different conditions that have similar features to Parkinson disease but are ineffective when treated with levodopa and have a more severe disease course. The most common entities included within Parkinson-plus syndrome include Lewy Body dementia (LBD), multiple system atrophy (MSA), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP). These conditions are often misdiagnosed as Parkinson’s Disease or Alzheimer’s Disease and, in fact, up to 24% of patients diagnosed with Parkinson’s Disease were shown to have atypical parkinsonian syndrome on autopsy. The purpose of this exhibit is to review the imaging features specific to Parkinson-plus syndromes to aid in timely and accurate diagnosis.

Educational Goals / Teaching Points
1. Review the pathologic basis and imaging features of each of the Parkinson-plus syndromes. 2. Case-based review of LBD, MSA, CBD, and PSP utilizing specific modalities.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
MR is generally the most useful imaging modality for characterization of each of the four syndromes highlighted in this exhibit. Imaging features associated with LBD include brain volume loss in the frontal and parietotemporal lobes, midbrain, and hypothalamus, and absent “swallow-tail” sign. On SPECT/PET, the characteristic ‘cingulate island sign’ may help to differentiate LBD from Alzheimer disease. MSA can be classified as MSA-C (olivopontocerebellar atrophy), characterized by the “hot cross bun” sign and disproportionate atrophy in the cerebellum and brainstem and MSA-P (striatonigral degeneration), characterized by predominantly putaminal abnormality. CBD is characterized by superior parietal lobule, perirolandic, basal ganglia, and corpus callosum atrophy, with corresponding hypometabolism on PET, with relatively preserved brainstem anatomy. Finally, PSP is characterized by predominantly midbrain atrophy, with reduced midbrain to pons ratio, and typical imaging signs including ”hummingbird” sign, “Mickey mouse” sign, and “morning glory” sign. There is loss of the normal crescentic uptake in the striatum on 123I-ioflupane SPECT.

Conclusion
The individual imaging characteristics of each of the Parkinson-plus syndromes is key in diagnosing patients in early stages of disease course. Familiarity with disease-specific imaging findings can aid the radiologist in successful diagnosis.