A positron emission tomography study on the role of nigral lesions in parkinsonism in patients with amyotrophic lateral sclerosis

Background: Patients with amyotrophic lateral sclerosis (ALS) sometimes exhibit parkinsonism, but the lesion responsible for parkinsonism has not been extensively studied. Objective: To test whether nigrostriatal system dysfunction is responsible for parkinsonism in ALS. Design: From the 182 ALS patients who were admitted to our neurology ward during the past 10 years, we extracted all the patients who satisfied the criteria of both parkinsonism and ALS. Setting: The University of Tokyo Hospital. Methods: We conducted [F-18]L-dopa and [C-11]N-methylspiperone positron emission tomography and technetium Tc99m hexamethylpropyleneamine oxime single-photon emission computed tomography studies on 5 patients with ALS manifesting overt parkinsonism. Results: Two male and 3 female patients (average age, 63.2 +/- 5.8 years) had ALS for an average of 28.6 +/- 21.5 months and had parkinsonism for an average of 15.2 +/- 11.4 months. Features of their parkinsonism were characterized by outstanding bradykinesia without resting tremor or dementia. The results of positron emission tomography studies indicated normal nigrostriatal function, but those of single-photon emission computed tomography demonstrated decreased blood flow in the frontotemporal cortices. Conclusion: It is likely that parkinsonism in ALS is due to cortical lesions rather than nigrostriatal dysfunction and that both symptoms are the clinical manifestation of frontotemporal dementia with motor neuron diseases, including classic ALS.