The aim of this study was to apply positron emission tomography (PET) with 11C-8-dicyclopropylmethyl-1-methyl-3-propylxanthine (MPDX), a radioligand for adenosine A1 receptor (A1R), to patients with hemianopia caused by brain injury to study neurorepair mechanisms in the brain.
Four patients with homonymous hemianopia and 15 healthy subjects were examined using PET to measure cerebral glucose metabolism, 11C-flumazenil (FMZ) binding to the central benzodiazepine receptor, and MPDX binding to A1R. Left and right regions of interest (ROIs) were selected, and semiquantitative data on the 3 kinds of PET examinations were obtained. The ROIs were referenced using the data for homologous regions in the contralateral hemisphere [ipsilateral/contralateral (I/C) ratio].
The I/C ratios for cerebral glucose metabolism and FMZ binding were low in the primary visual cortex (PVC) and visual association cortex in all the patients, whereas MPDX binding increased in the PVC in patients 1 and 2. Patients 1 and 2 experienced improvement in their visual field after 1 year. However, the other 2 patients showed no changes. We observed an increase in MPDX binding to A1R in the injured portion of the PVC in the patients who recovered.
Evaluation of A1R by MPDX-PET may be useful for predicting prognosis and understanding the compensatory and reorganization processes in hemianopia caused by organic brain damage.
From the *Department of Ophthalmology and Visual Science and †Department of Neurosurgery, Tokyo Medical and Dental University, Graduate School, Tokyo; ‡Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Tokyo; and §Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
Received for publication February 4, 2012; revision accepted May 15, 2012.
Conflicts of interest and sources of funding: none declared.
This research was performed at the Positron Medical Center, Tokyo Metropolitan Institute of Gerontology.
Reprints: Yukihisa Suzuki, MD, PhD, Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Graduate School, Yushima 1 chome-5-45, Bunkyo-ku, Tokyo 113-8519, Japan. E-mail: email@example.com.