Presentation
Progressive right arm and leg weakness. Parkinsonism. Speech problems.
Patient Data
Bilateral low SWI signal along the lateral aspect of the putamen is present. Putaminal rim sign on 1.5 T T2 weighted images is also seen, better on the left, as a thin band of high signal.
The left putaminal SWI signal is arguably darker than globus pallidus and red nuclei.
Darker putaminal signal on T2 sequence, but subtle. Putaminal volume loss is difficult to judge.
SWI 1 year earlier showed asymmetry in the putaminal abnormality, left more than right. This could explain asymmetry in patient's symptoms - right side worse.
The patient eventually died and went on to have an autopsy.
Autopsy findings:
Within the putamen, there is subtotal loss of neurons, and gliosis and alpha-synuclein immunoreactive perinuclear inclusions.
Similar inclusions are seen in globus pallidus and midbrain white matter. Substantia nigra shows patchy neuronal loss and of the pigment. No evidence of Lewy body formation.
Pons shows minor neuronal loss from the pontine neurons. Unremarkable medulla and cerebellum.
Final diagnosis: multiple system atrophy (MSA-P) with striatonigral degeneration.
Case Discussion
The putaminal rim sign on 1.5 T MRI is useful if present but the sign is not reliable on 3 T as it can be observed in normal individuals.
Using the differential darkness of, and between, the putamina, globi pallidi, and red nuclei can be difficult - becoming familiar with one's own machine and GRE/SWI images in various age groups is a good start.