Dramatic unilateral decrease in uptake via the dopamine transporter: Imaging in a patient with hemiparkinsonism following the lacunar stroke in substantia nigra

Vascular parkinsonism (VaP) is typically defined as having predominant lower body involvement, postural instability, less prominent rest tremor and little or no response to treatment with levodopa. In this study, we report a patient with VaP with clear demonstration of a dramatic unilateral decrease of radiotracer uptake in a 18F-FP-CIT-PET study. A 62-year-old right-handed woman was referred to the neurology department due to rest tremor and rigidity in the right hand, which began after undergoing resection surgery for a left acoustic neuroma 7 years prior. Brain MRI, taken at 1 year after surgery showed an ischemic stroke lesion in the left medial pons and the left substantia nigra. 18F-FP-CIT-PET revealed a marked reduction of radiotracer uptake in left striatum compared to that of the right. We treated the patient with 100 mg of levodopa, 200 mg of entacarpone and 25 mg of carbidopa. There was an improvement in bradykinesia and tremor, but the symptoms persisted, and there was no deterioration during 6 months of observation. After acoustic neuroma surgery, ischemic complications are uncommon, and even a small lesion in the nigrostriatal pathway can cause a hemiparkinsonism. If a patient experience sudden onset hemiparkinsonism, they should be carefully examined for lesions in the nigrostriatal pathways. Under these conditions, the 18F-FP-CIT-PET scan can enable visualization of a unilateral decrease and is a useful tool for diagnosis and differentiation from idiopathic Parkinson’s disease.