Posterior cortical atrophy with [11C] Pittsburgh compound B accumulation in the primary visual cortex

Abstract

Sirs, Posterior cortical atrophy (PCA) is a presenile dementia that presents primarily with signs and symptoms of cortical visual dysfunction [1]. The most common associated pathologic findings of PCA are amyloid plaques and neurofibrillary tangles predominantly affecting the visual association areas [8]. Although [C] Pittsburgh compound B (PIB) PET studies of amnestic Alzheimer’s disease (AD) have been conducted [2, 3, 5], the link between amyloid-b (Ab) and regional brain dysfunction remains controversial. However, two PIB studies of PCA supported the possible link between Ab deposition and clinical features [7, 10]. Here, we describe a patient with PCA who showed left homonymous hemianopsia and uncoupling between PIB uptake and glucose metabolism in the right occipital lobe. A 63-year-old woman consulted our hospital with a 5-year history of poor vision. She first noticed that characters on posters appeared to be shaking. One year later, she found difficulty in reading subtitles in movies and then she became unable to read books. On neurological examination, she showed left homonymous hemianopsia. A Goldmann dynamic visual field examination demonstrated macular-sparing left homonymous hemianopsia. Visual acuity was normal and bilateral light reflexes were prompt. Other neurological examinations were normal. On neuropsychological evaluations, she showed visuospatial dysfunction and dyscalculia. MMSE score was 26 of 30. Memory function was preserved. She demonstrated disturbed recognition of superimposed figures. Face and color recognition were normal. Cerebrospinal fluid (CSF) Ab42 was decreased (297 pg/ ml) and in normal controls, the levels are 874 ± 293 pg/ml (mean ± SD, INNOTEST b-AMYLOID(1-42), Innogenetics, Ghent, Belgium). CSF tau protein phosphorylated at serine 199 was increased (1.36 pM). In normal controls, these levels are 0.6 ± 0.4 pM [4]. [F] fluorodeoxyglucose (FDG) PET image was acquired for 6 min starting 45 min after the injection of 150 MBq of tracer. The accumulation of [C] PIB was evaluated by a standardized uptake value ratio (SUVR) on a summing image obtained 40–60 min after injection of 500 MBq of tracer taking the cerebellar cortex as a reference region. [F] FDG PET showed hypometabolism in the temporo-parieto-occipital lobe predominantly on the right (Fig. 1d–f). [C] PIB PET demonstrated increased uptake in the bilateral frontal lobes and parietal and occipital cortices with more intense uptake on the right (Fig. 1g–i). In the right occipital lobe, FDG uptake showed lower metabolism in the lateral occipital cortex (Fig. 1d, e, arrow) than in the calcarine cortex (Fig. 1d, e, arrowhead). In contrast, amyloid imaging demonstrated high PIB uptake in the right calcarine cortex (Fig. 1g, h, arrowhhead) while the adjacent lateral occipital cortex showed normal PIB uptake (Fig. 1g, h, arrow). It was shown that macular sparing occurred when the posterior part of the calcarine cortex was spared in patients with striate cortical disease such as infarction, neoplasm and cerebromalacia, while macular splitting occurred when the occipital pole and operculum were involved [6]. Neuroimaging studies of our patient demonstrated that in the occipital lobe, there were two regions showing different T. Kambe Y. Motoi (&) N. Hattori Department of Neurology, Juntendo University School of Medicine, 2-1-1, Hongo Bunkyo-ku, Tokyo 113-8421, Japan e-mail: motoi@juntendo.ac.jp