Visuospatial deficits in posterior cortical atrophy: structural and functional correlates
- Katia Andrade1,2,
- Aurélie Kas2,3,4,
- Romain Valabrègue5,
- Dalila Samri6,7,
- Marie Sarazin1,2,6,7,
- Marie-Odile Habert2,3,4,
- Bruno Dubois1,2,6,7,
- Paolo Bartolomeo1,2,6,7,8
- 1INSERM UMR_S 975, Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière (CRICM), Paris, France
- 2Université Pierre et Marie Curie (UPMC, Paris 6), Paris, France
- 3INSERM UMR_S 678, UPMC, Paris 6, Paris, France
- 4AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Médecine Nucléaire, Paris, France
- 5Centre de NeuroImagerie de Recherche (CENIR), Groupe Hospitalier Pitié-Salpêtrière, Paris, France
- 6AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Fédération des Maladies du Système Nerveux, Paris, France
- 7Institut de la Mémoire et de la Maladie d'Alzheimer (IM2A), Hôpital Pitié-Salpêtrière, Paris, France
- 8Department of Psychology, Catholic University, Milan, Italy
- Correspondence to Dr P Bartolomeo, Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, INSERM UMR_S 975, Hôpital de la Salpêtrière, Bâtiment de l'ICM, pièce 3.028, 47 Bd de l'Hôpital, 75651 Paris Cedex 13, France; paolo.bartolomeo{at}upmc.fr
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Contributors PB coordinated the study. PB and KA drafted and wrote the manuscript, and received patients in neurological consultations. KA reviewed and collected the medical, neuropsychological and MRI data. KA and RV performed image preprocessing and VBM analyses. AK and M-OH were responsible for SPECT acquisition and interpretation. AK performed SPECT analyses, helped write the manuscript and made figure 1. DS was responsible for the patients' neuropsychological assessments. MS and BD were responsible for the patients' first neurological evaluations and their management. All authors read and approved the final manuscript.
- Received 13 January 2012
- Revised 5 April 2012
- Accepted 30 April 2012
- Published Online First 29 May 2012
Abstract
Objective To determine the neural substrates of biased spatial orienting in posterior cortical atrophy (PCA) by using a combined structural and functional neuroimaging approach.
Background Patients with spatial neglect typically bisect horizontal long lines towards their brain lesions but the precise neural substrates of this spatial bias remain controversial and poorly explored in neurodegenerative disorders such as PCA.
Methods 15 patients with PCA underwent brain MRI and single photon emission computed tomography (SPECT) and were required to bisect five 20 cm long lines, each centred on an A4 horizontal sheet. Direct correlations between average deviations on the bisection task and both (1) the degree of grey matter density, as estimated by voxel based morphometry and (2) regional cerebral blood flow, as assessed by SPECT, were performed.
Results Seven patients (47%) had pathological bias on the bisection task, deviating consistently towards the non-neglected side for each of the five lines. Rightward bias (sign of left-sided neglect) was more frequent and severe than leftward bias (sign of right-sided neglect). Correlation analyses showed that rightward deviations correlated with atrophy and hypoperfusion exclusively in the right hemisphere, involving a large scale fronto-parietal network; cortical atrophy was prominent in the parieto-temporal cortex but extended to the frontal region; hypoperfusion was substantial both in the middle frontal gyrus and in the postcentral region. No correlations emerged from leftward deviations.
Conclusion The results indicate that rightward bias (sign of left-sided neglect) in PCA depends on dysfunction of a large fronto-parietal network in the right hemisphere, related to both cortical atrophy and decreased cerebral perfusion.
