Microsurgical management of lateral lumbar disc herniations: combined lateral and interlaminar approach.

Seventy-three patients presenting either with biradicular symptoms caused by involvement of the upper and lower root or with monoradicular symptoms caused by affection of the upper root were treated between January 1993 and July 1995 in our department. An interlaminar and lateral access was used to decompress both the upper and lower root by combining the conventional interlaminar approach and a lateral partial facetectomy. With this technique, satisfactory to excellent results were obtained in 92% of the patients. The advantages of the combined approach are (i) optimized visualization of the disc and surrounding anatomical structures, (ii) improved exposure of the lateral foramen and thorough removal of disc material, (iii) minimal risk of root injury by improved visualization, (iv) preservation of a functional facet joint and thereby reduction of postoperative instability with persistent back pain. Since occasionally lateral disc herniations are poorly visualized by computed tomography or magnetic resonance imaging, the decision to use the combined approach should be guided by the patient's clinical presentation rather than by radiological findings.

Cognitive impairment in Alzheimer's disease correlates with ventricular width and atrophy-corrected cortical glucose metabolism.

We compared the correlation of PET and MRI with neuropsychological tests in 26 patients with probable Alzheimer's disease (AD). The width of the temporal horns and the third ventricle, regional metabolic rates of glucose (rCMRGlu) and the proportion of cerebrospinal fluid space in mesial temporal and temporoparietal cortical regions were measured with three-dimensionally coregistered PET and MRI in two planes perpendicular to the Sylvian fissure. Highly significant correlations between rCMRGlu and neuropsychological tests were found mainly in the temporoparietal cortex, with and without correction for atrophy. Correlations of similar magnitude were seen also between most tests and the width of the temporal horns and third ventricle. Changes in the third ventricle and mesial temporal lobe were best seen with MRI, whereas PET most clearly depicted alterations in neocortical association areas. These two aspects of the disease correlated with the severity of dementia to a similar degree.

An interactive technique for three-dimensional image registration: validation for PET, SPECT, MRI and CT brain studies.

UNLABELLED: A multipurpose three-dimensional registration technique was validated with PET, SPECT, CT and MRI scans, which had been obtained under normal clinical conditions. In contrast to fully automated procedures, this coregistration method is highly interactive, which has the advantage that it does not impose rigid restrictions by data type and by alterations in normal anatomy or brain function resulting from disease. METHODS: Basically, a computer program provides a variety of tools to examine the accuracy of coregistration visually and to specify necessary translations and rotations in all three dimensions. Tools and criteria to accept coregistration were applied according to a standardized protocol. Reproducibility was assessed with five independent users on nine pairs of image sets. In two pairs of these image sets, coregistration was repeated three times by each user. RESULTS: Depending on the resolution of the images involved, the reproducibility of translation distances ranged from 0.32 to 2.22 mm (s.d.) and of rotation angles from 0.32 to 1.70 degrees. It was always much smaller than the point-spread full-width half maximum of the device with the lower resolution. The accuracy of coregistration was examined using two arbitrarily misplaced image sets. Interindividual and intraindividual variance were similar, which suggested that the influence of subjectivity was not significant. Average displacements after coregistration were 0.43 and 0.29 mm or less for PET and MRI data, respectively, which indicated the absence of a systematic bias. CONCLUSION: The results indicate the high reproducibility and accuracy of this three-dimensional coregistration technique, which is comparable or superior to those of automated techniques and methods based on external artificial landmarks.

Difference of regional cerebral metabolic pattern between presenile and senile dementia of the Alzheimer type: a factor analytic study.

Positron emission tomographic studies using metabolic ratios to represent the contrast between certain brain regions have shown differences of cerebral glucose metabolism between presenile and senile dementia of Alzheimer type (DAT). In this study, factors for regional variance of cerebral metabolism in 61 patients with probable Alzheimer's disease were obtained using principal component analysis (PCA). The difference between two age groups of DAT patients according to age at onset < or = 65 years (n = 30) and > 65 years (n = 31) were investigated. A PCA using nine pairs of cerebral regions normalized to cerebellum for reduction of intersubject variability identified five regional factors for cerebral metabolism: one each for the left and right temporo-parietal cortex, and the other three for frontal cortex, primary visual and sensorimotor cortex, and mesial temporal sensorimotor cortex, and mesial temporal cortex. The age groups differed significantly only in the factor for the right temporo-parietal cortex, with a more prominent metabolic reduction in presenile than senile DAT. Severity of dementia was correlated with the factors for the right and left temporo-parietal cortex. The effect of age at onset on glucose metabolism of the right temporo-parietal cortex was independent from that of dementia severity in DAT.

Activation PET as an instrument to determine therapeutic efficacy in Alzheimer's disease.

Forty patients with probable Alzheimer's disease (AD) were selected from a pool of 80 patients and assigned to 4 groups. Each received either social support, cognitive training only, or cognitive training in combination with pyritinol or phosphatidylserine. Treatment duration was 6 months. Before and after treatment the patients underwent neuropsychological testing as well as measurement of the regional cerebral metabolic rate for glucose using positron emission tomography (PET) and 2[18F]-fluoro-2-deoxy-D-glucose (FDG). Before treatment, the groups were comparable in respect to resting and activated glucose pattern achieved by a visual recognition task. They did not differ in scores of a neuropsychological test battery. After the treatment period the group with cognitive training + phosphatidylserine showed a significant glucose enhancement during the stimulation tasks in various brain regions, and an improvement in cognitive functioning compared to the other groups. The group with cognitive training + pyritinol had better stimulation effect as that of the social support group indicating that a combination of cognitive training + pharmacological intervention was superior than that of cognitive training alone.