Glucose hypermetabolism in the thalamus of patients with essential blepharospasm.

Essential blepharospasm (EB) is classified as a form of focal dystonia characterized by involuntary spasms of the musculature of the upper face. The basic neurological process causing EB is not known. The purpose of this study was to investigate cerebral glucose metabolism in patients with EB whose symptoms were suppressed by an injection of botulinum-A toxin. Earlier studies were confounded by sensory feedback activities derived from dystonic symptom itself. Cerebral glucose metabolism was examined by positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) in 25 patients (8 men and 17 women; age 52.6 +/- 10.1 years) with EB. The patients were awake but with the spasms suppressed by an injection of botulinum-A toxin. Thirty-eight normal volunteers (14 men and 24 women; age 58.2 +/- 7.3 years) were examined as controls. The difference between the two groups was examined by statistical parametric mapping (SPM99). A significant increase in the glucose metabolism was detected in the thalamus and pons in the EB patients. Hyperactivity in the thalamus may be a key pathophysiological change common to EB and other types of focal dystonia. The activity of the striatum and cerebellum are likely to be sensory dependent.

Differential activation of cerebral blood flow by stimulating amblyopic and fellow eye.

PURPOSE: Positron emission tomography (PET), the blood flow response in the primary visual cortex (V1) to two visual stimuli, low temporal frequency (6 Hz) to activate the parvocellular system, and high temporal frequency (25 Hz) to activate the magnocellular system were used to investigate pathophysiologic mechanism of amblyopia. METHODS: Five women and one man who were aged between 26 and 60 years, who were ophthalmologically normal except for amblyopia, and who had corrected visual acuity in the amblyopic eye of 0.6 or worse were examined. An intravenous injection of the H(2)(15)O was given, and the regional cerebral blood flow was measured by PET during full-field stimulation with either 6 Hz or 25 Hz flicker to the amblyopic or the sound eye. RESULT: The activation of blood flow in the contra-lateral area V1 by the 6-Hz stimulation of the sound eye was greater than that during the stimulation of the amblyopic eye (P<0.05, small volume correction, n=6). With 25-Hz stimulation of the sound and amblyopic eyes, the blood flow in the contra-lateral and ipsi-lateral areas V1 was not significantly different. CONCLUSION: The decreased activation of blood flow in the contra-lateral V1 by low temporal frequency stimuli supports the hypothesis that the parvocellular pathway in amblyopic eyes is depressed.

A case of multiple sclerosis with homonymous hemianopia examined by positron emission tomography.

BACKGROUND: To demonstrate the efficacy of positron emission tomography (PET) for examining multiple sclerosis (MS) patients with hemianopia. CASE: A 20-year-old man visited us with a complaint of left homonymous hemianopia and headache. OBSERVATIONS: The patient's visual acuity was 1.2 (n.c.) OD and 0.9 (1.0) OS. Magnetic resonance imaging (MRI) showed a mass in the temporoparietal lobe. A pathological diagnosis of MS was made by brain biopsy. Low glucose metabolism in the lesion and visual cortex was observed by PET with (18)F-fluorodeoxy glucose. PET with (11)C-flumazenyl revealed a reduction of (11)C-uptake in the demyelinated optic radiation, and only a slight reduction of (11)C-uptake in the primary visual cortex. The results of (11)C-flumazenyl PET suggested a slight reduction of neuronal density. In 2 years, the visual field recovered to the normal state. CONCLUSION: PET can be a useful tool for estimating the visual outcome of patients with hemianopia in MS.

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.

Detection of visual activation of lateral geniculate nucleus by positron emission tomography.

PURPOSE: Although activation of the lateral geniculate nucleus (LGN) has been shown by functional magnetic resonance imaging, a quantitative evaluation of the activity has not been reported by positron emission tomography (PET). The purpose of this study was to quantify the degree of activation of the LGN and other vision-related structures by visual stimuli as detected by PET. METHODS: PET activation was induced by a bolus injection of 15O-labelled water (H2(15)O) in six normal volunteers. The regional cerebral blood flow (rCBF) was measured under three conditions: eyes closed, binocular flickering light stimulation, and binocular viewing of a video movie. Single-subject analysis, group analysis, and correlation analysis were performed. RESULTS: Although single-subject analysis did not show significant changes, group analysis revealed a significant increase in rCBF in the left LGN induced by flickering light stimulation ( P<0.01) and video stimulation ( P<0.05). Localization of the activation foci in the LGN agreed with the retinotopic organization of the LGN. CONCLUSION: Although the LGN is relatively small compared with the resolution of the PET image, visually activated blood flow changes could be determined by H2(15)O PET: