ORIGINAL ARTICLE Value of Combining Activated Brain FDG-PET and Cardiac MIBG for the Differential Diagnosis of Dementia Differentiation of Dementia With Lewy Bodies and Alzheimer Disease When the Diagnoses Based on Clinical and Neuroimaging Criteria Are Difficult Sergio L. Schmidt, MD, PhD,* Patricia L. Correa, MD,† Julio C. Tolentino, MD,* Alex C. Manha ˜es, MD, PhD,* Renata M. Felix, MD,† Jader C. Azevedo, MD,† Gustavo B. Barbirato, MD,† Marcelo H. F. Mendes, MD,* Yolanda Boechat, MD,‡ Herbert Cabral, MD,‡ Guilherme J. Schmidt,* Hans F. Dohmann, MD,† and Claudio T. Mesquita, MD, PhD† Abstract: Dementia with Lewy bodies (DLB) is the second most common cause of dementia. The diagnosis of DLB is particularly important because these patients show good response to cholinest- erase inhibitors. Clinical and neuroimaging criteria for DLB have not been acceptable for predictive accuracy. We report a case of progressive dementia in which the differentiation of DLB and Alzheimer disease (AD) on the basis of clinical criteria alone was not possible. The patient was admitted to the hospital because he became worse after he had started treatment for severe AD. Both MRI and brain magnetic resonance spectroscopy were normal. The patient underwent myocardial scintigraphy with I-123 MIBG show- ing marked reduction in cardiac MIBG accumulation. The heart to mediastinum ratio of MIBG uptake was impaired in both early and delayed images. FDG-PET scan before and after activation with a visual attention task showed occipital cortex hypometabolism as compared with AD and a normal control. This case illustrates the value of combining activated brain FDG PET and cardiac MIBG. The association of these 2 techniques could be used as a potential diagnostic tool in a patient with dementia misdiagnosed as AD. Key Words: visual attention, brain FDG PET, cardiac MIBG, Lewy body dementia (Clin Nucl Med 2008;33: 398 – 401) D ementia is a common neuropsychiatric condition occur- ring in 5% to 11% of the population by age 65 and up to 40% beyond age 85. 1 Despite the fact that neurodegenerative diseases account for most cases, multiple medical conditions are also known to result in dementia. 2 Therefore, evaluation to exclude treatable causes of cognitive dysfunction is essen- tial for proper diagnosis and treatment. Regarding neurode- generative diseases, Alzheimer disease (AD) and vascular dementia either alone or in combination account for most cases. 3 Dementia with Lewy bodies (DLB) is the second most common cause of dementia, accounting for about 15% of cases at autopsy. 4 The diagnosis of DLB is particularly im- portant because these patients are responsive to cholinester- ase inhibitors and are extremely sensitive to the side effects of neuroleptic drugs. 5 Several retrospective and prospective studies have examined the predictive accuracy of clinical criteria for DLB 6 –10 showing low sensitivity in most studies. There is, therefore, a need to develop ways of increasing accuracy of the diagnosis of DLB. Neuroimaging modalities based on morphology such as MRI and CT scans as well as functional MRI have failed to differentiate DLB and AD. 11 In this regard, the utility of FDG-PET has been extensively reported. 12 These studies show high sensitivity but low specificity for the diagnosis of AD and other dementias. It is expected that neuropsycholog- ical protocols applied at the time of imaging should increase the specificity of FDG-PET for the diagnosis of AD, DLB, and other dementias. 13,14 The etiology of DLB is still un- known, but the disease is characterized pathologically by Lewy bodies in many brain regions. 15 In particular, Lewy body degeneration in the cardiac plexus is observed in pa- tients with DLB. 16 MIBG is an analogue of noradrenaline and is actively transported into noradrenaline granules of sympa- thetic nerve terminals by the noradrenaline transporter. 17,18 I-123 MIBG myocardial scintigraphy can be performed Received for publication February 6, 2007; revision accepted January 13, 2008. From the *State University of Rio de Janeiro (UERJ); †Hospital Procardiaco; and ‡Fluminense Federal University (UFF), Niteroi, Rio de Janerio, Brazil. This work was performed at Hospital Procardiaco and State University of Rio de Janeiro UERJ. Reprints: Patricia Lavatori Corre ˆa, MD, Rua General Polidoro 192, Botafogo, Rio de Janeiro, RJ, Brazil. E-mail: patricialavatori@oi.com.br. Copyright © 2008 by Lippincott Williams & Wilkins ISSN: 0363-9762/08/3306-0398 Clinical Nuclear Medicine • Volume 33, Number 6, June 2008 398