Evidence of delayed nigrostriatal dysfunction in corticobasal syndrome: A SPECT follow-up study

Objective: To demonstrate that degeneration of substantia nigra neurons may occur at later stages of disease in some patients with corticobasal syndrome (CBS) who evidenced preserved nigrostriatal pathway at a baseline FP-CIT SPECT study. Background: Current pathological criteria for the definite diagnosis of corticobasal degeneration consider substantia nigra cell loss as a mandatory finding. However, dopamine transporter SPECT imaging performed in a large cohort of CBS patients showed about 10% of normal scans. Methods: We describe 4 patients with clinical diagnosis of CBS and normal FP-CIT SPECT at baseline whose tracer uptake resulted pathological at 1-year follow-up scan. Clinical assessment has been performed at the time of SPECT scan. A semi-quantitative approach was performed for striatal FP-CIT binding values. Results: Baseline SPECT scans have been performed after 2.3 ± 1.5 years from onset. All CBS patients presented asymmetric rigid-akinetic parkinsonism (mean Hoehn-Yahr stage 2.5; UPDRS motor score 18) with poor levodopa response and ideo-motor limb apraxia. At follow-up, neurological examination revealed some additional features, including limb dystonia, language impairment, postural instability, ocular gaze impairment, alien limb. All patients showed pathological FP-CIT uptake at the SPECT performed 10-15 months apart from the baseline scan. Conclusions: Our longitudinal FP-CIT SPECT findings support in vivo the hypothesis that substantia nigra neuronal loss may occur at later stages in some patients with CBS, despite early extrapyramidal symptoms.