Measurement of Cerebral Glucose Metabolism in the Visual Cortex Predicts the Prognosis of Hemianopia.

BACKGROUND AND OBJECTIVE: Homonymous hemianopia caused by cerebrovascular disease may improve over time. This study investigated whether functional neuroimaging can predict the prognosis of hemianopia due to cerebral infarction. METHODS: We studied 19 patients (10 men and 9 women) with homonymous hemianopia and compared them with 34 healthy subjects (20 men and 14 women). Cerebral glucose metabolism was measured by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), 1 to 6 months after the onset. Bilateral regions of interest (ROIs) were selected from the posterior and, anterior striate cortices, extrastriate cortex, and thalamus. Furthermore, semi-quantitative data on cerebral glucose metabolism were obtained for ROIs and compared with the data obtained for homologous regions in the contralateral hemisphere by calculating the ipsilateral/contralateral (I/C) ratio. RESULTS: The I/C ratio for the cerebral glucose metabolism in the posterior striate cortex was high (>0.750) in 8 patients, and the central visual field of these patients improved or showed macular sparing. The I/C ratio for cerebral glucose metabolism in the anterior striate cortex was high (>0.830) in 7 patients, and the peripheral visual field of these patients improved. However, no improvement was observed in 9 patients with a low I/C ratio for cerebral glucose metabolism in both the posterior and anterior striate cortices. CONCLUSION: Measurement of cerebral glucose metabolism in the striate cortex is useful for estimating visual field prognosis. Furthermore, FDG-PET is useful in predicting the prognosis of hemianopia.

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.

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.

Neuroimaging analysis of a case with left homonymous hemianopia and left hemispatial neglect.

PURPOSE: To correlate the neuro-ophthalmological observations with the magnetic resonance images (MRI) and positron emission tomographic (PET) findings in a case with left homonymous hemianopia and left hemispatial neglect. CASE: A 57-year-old woman underwent surgery for a ruptured anterior communicating artery aneurysm. After she recovered consciousness, it was found that she had left homonymous hemianopia and left hemispatial neglect. Although the hemispatial neglect slowly improved, the homonymous hemianopia persisted. MRI and measurements of cerebral glucose metabolism by 2-fluoro-2-deoxy-D-glucose(FDG)-PET were performed 1 year later. RESULTS: MRI revealed infarctions on the medial surface of the frontal lobe, on the right medial surface of the occipital lobe, and global atrophy of the right cortical hemisphere. FDG-PET disclosed severe glucose hypometabolism in the entire right hemisphere. Glucose metabolism in the right occipital cortex was 61.1% of that in the homologous region on the left side, 62.8% in the right anterior cingulate gyrus, and 93.8% in the temporal-parietal-occipital junction. CONCLUSIONS: The low glucose metabolism in the right visual cortex explains the persistent left hemianopia, and that in the right anterior cingulate gyrus and the right temporal-parietal-occipital junction may be responsible for the left hemispatial neglect. The relatively mild damage in the right temporal-parietal-occipital junction explained the recovery of the neglect symptom. Measurements of regional cerebral glucose metabolism by PET are useful for determining the cause of cerebral visual dysfunction and its prognosis after a cerebral lesion.

Glucose utilization of visual cortex following extra-occipital interruptions of the visual pathways by tumor. A positron emission tomography study.

To assess the effect of extra-occipital lesions on the local cerebral glucose utilization of the primary and associative visual cortex, 29 patients were studied in the unstimulated state by positron emission tomography and [18F]2-deoxyglucose. Quantitative Goldmann perimetry was done in each patient at the time of the positron emission tomographic study. Nine patients showed homonymous defects, either hemianopsia or quadrantanopsia, whereas nine patients had heteronymous defects. Eleven control subjects, free of any neurological symptoms and with normal visual fields, were also studied with [18F]2-deoxyglucose positron emission tomography. In the normal control subjects and in patients with a heteronymous defect, left-to-right differences in the local cerebral metabolic rate for glucose of the visual cortex varied less than 10%. In patients with hemianopic defects, differences ranged from 8 to 38%, with the hypometabolic cortex always contralateral to the field defect. In patients with quadrantanopic defects, the visual cortex contralateral to the field defect demonstrated differences from 14 to 24% above and below the calcarine fissure, the cortex that received greater input from the affected field being hypometabolic.

Metabolic imaging in hemianopsia using positron emission tomography with 18F-deoxyfluoroglucose.

To evaluate the usefulness of metabolic mapping by positron emission tomography using 18F-deoxyfluoroglucose as a tracer in the diagnosis of hemianopsia, we examined eight patients who had had cerebrovascular accident, and four controls. Neuro-ophthalmologic examination disclosed hemianopsia in five and incomplete hemianopsia in three patients; computed tomography showed low-density areas in four patients; and nuclear magnetic resonance imaging demonstrated a prolonged T2 area in five patients. The cerebral metabolic rate for glucose without visual stimulation in the visual cortex was 7.4 +/- 1.0 mg/min/100 g of brain without interhemispheric asymmetry. Light stimulation increased cerebral metabolic rate for glucose in the visual cortex of the nonaffected hemisphere and decreased it in the affected hemisphere. Asymmetry in the metabolic rate in the posterior medial occipital cortex in complete hemianopsia was 22% 12% (P less than .01).

Local cerebral glucose metabolic response to audiovisual stimulation and deprivation: studies in human subjects with positron CT.

Positron computed tomography (CT) and 18-F fluorodeoxyglucose (FDG) were used to measure local cerebral glucose metabolism (LCMRGlc) in patients and normal subjects during auditory and visual stimulation and deprivation. Sixty-six studies were performed in 42 individuals. In normal subjects metabolic left-right symmetry was found in states of partial (eyes patched or ears plugged) sensory deprivation. Visual stimuli of increasing complexity produced symmetric increases in LCMRGlc of the primary and associative visual cortices. Patients with lesions of the visual pathway but sparing the visual cortex demonstrated abnormalities in visual cortical LCMRGlc that correlated with clinical symptoms. Auditory stimulation studies in normal subjects demonstrated metabolic evidence of hemispheric specialization. The side (left versus right) and site of maximal metabolic response correlated with the type (verbal versus nonverbal) and content (factual story, chords, tone sequences) of the stimulus as well as the strategy used by the subject to solve the listening task. There was no correlation between the site of metabolic response and side of stimulus presentation. The results of these studies demonstrate that positron CT provides new and previously unattainable information about local human brain physiology in normal and pathological states. The limitations, advantages and future prospects of using these methods to study human brain function are discussed.

Tomographic mapping of human cerebral metabolism visual stimulation and deprivation.

Positron computed tomography was used to investigate changes in the local cerebral metabolic rate for glucose (LCMRGlc) of the visual cortex. Progressive increases in LCMRGlc were found from eyes-closed control to stimulation with white light, alternating black/white checkerboard pattern, and a complex visual scene of a park, with the associative visual cortex increasing at a faster rate than the primary visual cortex as the visual scene complexity increased. A graded decrease in LCMRGlc of the visual cortex was found with a stepwise deletion of spontaneous cell firing at the retinal, geniculate and cortical level due to lesions. Left/right metabolic symmetry of the visual cortex during monocular stimulation confirms 50% crossing of the human visual system. Neonatal blindness showed no apparent degeneration of the visual cortex and was equivalent to eyes-closed controls. The interictal state of a patient with visual seizures demonstrated a hypometabolic visual cortex with a 2.5-fold increase in metabolism during an ictal visual hallucination.