Abundant nigral neuronal cytoplasmic inclusions in multiple system atrophy with slowly progressive levodopa-responsive parkinsonism

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To the Editor, Multiple system atrophy (MSA) is a rare and fatal neurodegenerative disorder characterized by progressive autonomic failure, parkinsonism, cerebellar ataxia, and pyramidal features, leading to death 6-10 years after symptom onset.1 Previous studies have also reported cases with pathologically confirmed MSA that clinically mimic Parkinson disease (PD).2–4 These studies focused on the clinical differences between typical and atypical MSA; however, the neuropathological differences between them remain unclear. Herein, we report a case of MSA with a PD-mimicking clinical course and unique pathological findings. A 54-year-old Japanese man developed a right leg resting tremor and became aware of a right-hand resting tremor at age 57 years. At age 58, he developed gait disturbances and right-handed clumsiness and visited our hospital for the first time. Neurological findings indicated cogwheel rigidity in the right limbs, mild bilateral bradykinesia, and resting tremors. Autonomic dysfunction and ataxia were not observed. He responded well to levodopa administration. Brain magnetic resonance imaging (MRI) undertaken at age 58 was unremarkable (Figure 1A). The patient was diagnosed with PD and treated with carbidopa-levodopa and selegiline. He experienced a wearing-off phenomenon at age 62 and presented with remarkable gait freezing at age 66. His cognitive function was preserved (Mini-Mental State Examination [MMSE] score, 29/30; Frontal Assessment Battery [FAB] score, 15/18). 123I-metaiodobenzylguanidine myocardial scintigraphy revealed a mildly reduced uptake in the delayed phase (Figure 1B). Dopamine transporter 123I-Ioflupane single-photon emission computed tomography showed reduced uptake in both striata (Figure 1C). His wearing-off partially improved with an increased dose of levodopa. At age 67, his gait disturbance worsened and he developed slurred speech. Neurological examination revealed truncal and bilateral limb ataxia, ataxic dysarthria, severe orthostatic hypotension, and mild cognitive impairment (MMSE score, 18/30; FAB score, 8/18). Brain MRI revealed progressive atrophy of the basis pontis, the middle cerebellar peduncle, the cerebellum, and the left putamen (Figure 1A). The patient died of aspiration pneumonia at 68 years. The final clinical diagnosis at 14 years from disease onset was PD and subsequent MSA in the last year.

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