A Retrospective Imaging Evaluation of Presynaptic Dopaminergic Degeneration in Multiple System Atrophy with Levodopa Induced Dyskinesia

Background: Multiple system atrophy (MSA) may develop levodopa-induced dyskinesia, which is dystonic and predominant in the orofacial region. We aimed to characterize the patterns of presynaptic dopaminergic degeneration in patients with MSA and dyskinesia using 123I-N-x-fluoropropyl-2b-carbo-methoxy-3b-(4-iodophenyl) nortropan single-photon emission computed tomography (123I-FP-CIT SPECT).

Methods: A single center cross-sectional retrospective study was conducted using consecutive chart review of patients with probable MSA who underwent 123I-FP-CIT SPECT. The degeneration patterns were compared between the groups with and without dyskinesia via visual assessment of 123I-FP-CIT SPECT images.

Results: Twenty-five patients with probable MSA who had undergone dopamine transporter imaging were identified (age [mean ± standard error], 62.5 ± 1.7 years; disease duration, 48.8 ± 7.0 months). Four of them presented dyskinesia and 21 of patients did not. Twenty-five patients with MSA were visually classified into five grades: one Grade 1 (normal), two Grade 2 (eagle wing), three Grade 3 (mixed), nine Grade 4 (egg shape), and ten Grade 5 (burst striatum). All patients with MSA and dyskinesia were classified into Grade 5. Visual grading significantly correlated with disease duration and levodopa responsiveness.

Conclusions: Severe presynaptic dopaminergic dysfunction in 123I-FP-CIT SPECT images, higher doses of dopaminergic medication, and longer disease durations were associated with occurrence of levodopa-induced dyskinesia, even in MSA.