Early detection of dementia with Lewy bodies in patients with amnestic mild cognitive impairment using 123I-MIBG cardiac scintigraphy

Abstract

Increasing clinical attention has been focused on cardiac sympathetic denervation for the differential diagnosis of dementia with Lewy bodies (DLB) from Alzheimer's disease (AD) with the development of [123I] metaiodobenzylguanidine (MIBG) scintigraphy. Decreased MIBG uptake, which reflects cardiac sympathetic denervation, has been detected in DLB, but not in AD. However, the time course of detected cardiac sympathetic degeneration is poorly understood in DLB. Herein, the authors report two patients with a clinical diagnosis of amnestic mild cognitive impairment (MCI) who had cardiac sympathetic denervation, detected by cardiac 123I-MIBG scintigraphy, without the core clinical features of DLB. One amnestic MCI patient had nocturnal dream enactment behavior, consistent with clinically probable REM sleep behavior disorder (RBD), and converted to probable DLB with the development of recurrent visual hallucination and spontaneous parkinsonism two years after MCI is diagnosed. The other amnestic MCI patient exhibited occipital metabolic reduction on [18F]-fluoro-d-glucose (FDG) positron emission tomography (PET) scan, which is the preferentially affected region in DLB patients, although she had no core or suggestive clinical features of DLB. Both patients had abnormal findings on electrocardiogram at annual health checkups despite having no cardiac-related symptoms. Detailed clinical examinations, including angiography and echocardiogram, revealed no overt etiology, supporting the idea that cardiac sympathetic denervation is due to underlying Lewy body disease. The clinical courses of these patients suggest that 123I-MIBG cardiac scintigraphy is useful for the detection of DLB in the predementia phase, even before core clinical features appear.