Parkinsonian traits in amyotrophic lateral sclerosis (ALS): a prospective population-based study

Background Amyotrophic Lateral Sclerosis (ALS) is characterized by a spectrum of phenotypes, but a few study addressed the presence of parkinsonian (PK) symptoms. Aim of our study was to investigate the occurrence of PK features in a prospective population-based cohort of ALS patients, determining their demographic, clinical, neuropsychological and genetic characteristics, and identifying their morphological and functional imaging correlates. Methods A consecutive series of ALS patients were enrolled and prospectively followed for two years. Patients were classified according to the presence (ALS-PK) or absence (ALS) of PK signs, and they underwent neuropsychological testing, genetic analysis for the main ALS and PD genes, brain MRI and 18F-FDG-PET. ALS-PK patients underwent 123I-ioflupane SPECT Results Out of 114 eligible patients, 101 (64 men; mean age at onset 65.1 years) were recruited. Thirty-one patients (30.7%) were classified as ALS-PK. Compared to ALS patients, ALS-PK patients were more frequently male, but did not differ for any other clinical, demographic or neuropsychological factor. 123I-ioflupane SPECT was normal in all but two ALS-PK patients. At 18F-FDG-PET, ALSPK patients showed a relative hypometabolism in left cerebellum and a relatively more preserved metabolism in right insula and frontal regions; MRI fractional anisotropy was reduced in the sagittal stratum and increased in the retrolenticular part of the internal capsule. Conclusions In our study about 30% of ALS patients showed PK signs. Neuroimaging data indicate that PK signs are due to the involvement of brain circuitries other than classical nigrostriatal ones, strengthening the hypothesis of ALS as complex multisystem disease.