SWEDDs—Scans without Evidence of Dopamine Deficit

Scans without Evidence of Dopamine Deficit (SWEDDs)

パーキンソン病患者を対象とした複数の大規模研究において，臨床診断はパーキンソン病であるにもかかわらず，DaT SPECT/PETでドパミン細胞の変性・脱落がみられない患者が存在することが明らかになった。これらの患者はSWEDDsと呼ばれ，現在ではパーキンソン病と異なる病態と考えられている。パーキンソン症状を呈し，かつ黒質線条体系のドパミン細胞が障害されない神経疾患はSWEDDsと診断される可能性がある。

Abstract

Dopamine transporter (DaT) single-photon emission computed tomography (SPECT) and［¹⁸F］fluoro-L-DOPA (［¹⁸F］DOPA) positron emission tomography (PET) facilitate the investigation of dopaminergic hypofunction in neurodegenerative diseases. DaT SPECT and［¹⁸F］DOPA PET have been adopted as survey tools in clinical trials. In a large study on Parkinson's disease, 4-15% of subjects clinically diagnosed with early-stage Parkinson's disease had normal dopaminergic functional imaging scans. These are called Scans without Evidence of Dopamine Deficit (SWEDDs), and are considered to represent a state different from Parkinson's disease. Neurological diseases that exhibit parkinsonism and have normal dopaminergic cells in the nigrostriatal system (e.g., essential tremor, psychogenic parkinsonism, DOPA-responsive dystonia, vascular parkinsonism, drug-induced parkinsonism, manganism, brain tumor, myoclonus-dystonia (DYT11), and fragile X syndrome) might be diagnosed with SWEDDs. True bradykinesia with fatigue or decrement may be useful for distinguishing between Parkinson's disease and SWEDDs. However, because SWEDDs encompass many diseases, their properties may not be uniform. In this review, we discuss DaT SPECT, the concept of SWEDDs, and differential diagnosis.