Improvement of Glucose Metabolism in the Visual Cortex Accompanies Visual Field Recovery in a Patient with Hemianopia.

Damage to the visual cortex or the geniculostriatal pathways could cause homonymous visual field (VF) defects at the contralateral side of the lesion. In clinical practice, it is known that the VF defects are gradually recovered over months on the cases. We report a case with recovered homonymous hemianopia following an infarction in the visual cortex by positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) and (11)C-flumazenil (FMZ). A 58-year-old man experienced defect of left VF, and magnetic resonance imaging (MRI) revealed a localized infarction in the right occipital lobe. Goldmann VF perimetry revealed left homonymous hemianopia, but central VF was intact. Three months after the onset of infarction, we measured cerebral glucose metabolism with FDG and FMZ binding using PET. FMZ binding reflects the density of surviving neurons. Moreover, eight months after the onset, FDG-PET scan was performed. Goldmann VF perimetry was also performed at the same times of PET examinations. Decrease of cerebral glucose metabolism in the right anterior striate cortex was observed at three months after onset, while FMZ binding in the same area did not decrease in the patient. At eight months after onset, we observed recovery of VF and improvement of cerebral glucose metabolism in the anterior striate cortex. We presented change of cerebral glucose metabolism using PET accompanying improvement of VF. Evaluation of cerebral glucose metabolism and FMZ binding in the striate cortex is useful for estimating the prognosis of hemianopia caused by organic brain damage.

Adenosine receptor PET imaging in human brain.

Positron emission tomography (PET) is a nuclear medicine imaging technique that allows in vivo imaging of regional receptor-binding capacity. Advances in radiotracer chemistry have led to the development of novel imaging probes for adenosine receptors, especially adenosine A1 and A2A receptors. In this chapter, we discuss brain PET imaging for adenosine receptors and comparison of radioligands for PET imaging in health and diseases.

Increased adenosine A1 receptor levels in hemianopia patients after cerebral injury: an application of PET using 11C-8-dicyclopropylmethyl-1-methyl-3-propylxanthine.

PURPOSE: The aim of this study was to apply positron emission tomography (PET) with C-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. PATIENTS AND METHODS: Four patients with homonymous hemianopia and 15 healthy subjects were examined using PET to measure cerebral glucose metabolism, C-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]. RESULTS: 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. CONCLUSIONS: 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.

Measurement of the 11C-flumazenil binding in the visual cortex predicts the prognosis of hemianopia.

In order to determine whether functional neuroimaging studies can predict the prognosis of hemianopia due to organic cerebral disorders, we studied 8 patients (6 men and 2 women; age, 56.0+/-8.6 years) with homonymous hemianopia and compared them with 15 normal subjects (6 men and 9 women; age, 54.3+/-4.4 years). The cerebral glucose metabolism and 11C-flumazenil (FMZ) binding were measured by positron emission tomography, more than 1 month after the onset of the condition. Bilateral regions of interest (ROIs) were selected in the striate cortex, extrastriate cortex, cuneus and thalamus. Further, semi-quantitative data on the cerebral glucose metabolism and FMZ binding were obtained for the ROIs and compared with the data obtained for homologous regions in the contralateral hemisphere by calculating the ipsilateral/contralateral (I/C) ratio. The I/C ratios for the cerebral glucose metabolism and FMZ binding in the striate cortex were significantly low in the patients (glucose metabolism, P<0.0005; FMZ binding, P<0.005), while the ratio for the FMZ binding in the cuneus increased (P<0.0005). We observed that 5 patients, whose I/C ratio for the FMZ binding in the striate cortex was >0.850, experienced an improvement in their visual field, while that 3 patients with lower I/C ratios did not. The FMZ-PET may be useful to predict the prognosis of hemianopia in the chronic phase.