PET measurement of cardiac and nigrostriatal denervation in Parkinsonian syndromes.

UNLABELLED: Scintigraphic imaging with (123)I-metaiodobenzylguanidine ((123)I-MIBG) has demonstrated extensive losses of cardiac sympathetic neurons in idiopathic Parkinson's disease (IPD). In contrast, normal cardiac innervation has been observed in (123)I-MIBG studies of multiple-system atrophy (MSA) and progressive supranuclear palsy (PSP). Consequently, it has been hypothesized that cardiac denervation can be used to differentiate IPD from MSA and PSP. We sought to test this hypothesis by mapping the distribution of cardiac sympathetic neurons in patients with IPD, MSA, and PSP by using PET and (11)C-meta-hydroxyephedrine ((11)C-HED). Also, the relationship between cardiac denervation and nigrostriatal denervation was investigated by measuring striatal presynaptic monoaminergic nerve density with PET and (11)C-dihydrotetrabenazine ((11)C-DTBZ). METHODS: (11)C-HED and (11)C-DTBZ scans were obtained for patients with IPD (n = 9), MSA (n = 10), and PSP (n = 8) and for age-matched control subjects (n = 10). Global and regional measurements of (11)C-HED retention were obtained to assess the extent of cardiac sympathetic denervation. (11)C-DTBZ binding was measured in the caudate nucleus, anterior putamen, and posterior putamen. RESULTS: As expected, extensive cardiac denervation was observed in several of the patients with IPD. However, substantial cardiac denervation was also seen in some patients with MSA and PSP. (11)C-DTBZ studies demonstrated striatal denervation in all patients with IPD and in most patients with MSA and PSP. No correlation was found between cardiac (11)C-HED retention and striatal (11)C-DTBZ binding. CONCLUSION: Cardiac sympathetic denervation was found to occur not only in IPD but also in other movement disorders, such as MSA and PSP. This finding implies that scintigraphic detection of cardiac sympathetic denervation cannot be used independently to discriminate IPD from other movement disorders, such as MSA and PSP. Cardiac sympathetic denervation was not correlated with striatal denervation, suggesting that the pathophysiologic processes underlying cardiac denervation and striatal denervation occur independently in patients with parkinsonian syndromes. These findings provide novel information about central and peripheral denervation in patients with neurodegenerative disorders.

Validation of a polysomnographic score for REM sleep behavior disorder.

STUDY OBJECTIVES: Rapid eye movement (REM) sleep behavior disorder (RBD) was described more than 2 decades ago, but only 1 report on 5 patients and 5 normal subjects has tested the effectiveness of a method by which relevant polysomnographic findings can be quantified. We sought to validate this method in a larger sample of patients and control subjects. DESIGN: Cross-sectional. SETTING: Academic hospital. INTERVENTIONS: A clinician interviewed 17 patients at risk for RBD secondary to neurodegenerative disorders and 6 controls to assess whether RBD was present by history. Bed partners completed a questionnaire that quantified RBD symptom severity. From 2 consecutive nocturnal studies in each patient, 2 different polysomnographic RBD scores were generated: the percentage of 30-second REM epochs with at least 15 seconds of tonically maintained electromyographic activity, and the percentage of 3-second REM mini-epochs that contained phasic electromyographic bursts. MEASUREMENTS AND RESULTS: The tonic and phasic measures, combined together, were higher in patients with clinical determinations of probable or possible RBD (n=9) than in patients judged unlikely to have RBD (n=4, P = .023). The overall polysomnographic measure correlated with the symptom scores (rho = 0.42, P = .048). Specific polysomnographic RBD measures on night 1 correlated highly with those on night 2 (rho > 0.70, P < .0001). CONCLUSIONS: This quantitative method to assess the severity of RBD polysomnographic features appears to be both valid and reliable in patients at risk for RBD because of neurodegenerative disorders.

11C-DTBZ and 18F-FDG PET measures in differentiating dementias.

UNLABELLED: Accurate, early differentiation of dementias will become increasingly important as new therapies are introduced. Differential diagnosis by standard clinical criteria has limited accuracy. PET offers the potential to increase diagnostic accuracy. (18)F-FDG studies detect metabolic abnormalities in demented patients, but with limited specificity. PET also offers the ability to quantify other biochemical markers that can yield additional useful diagnostic information. We demonstrate that (+)-(11)C-dihydrotetrabenazine ((11)C-DTBZ) studies, which provide an index of nigrostriatal terminal density (distribution volume; DV), also provide a measure of transport (K(1)) that produces information comparable to the metabolic measure of (18)F-FDG. METHODS: Fifty-two patients and 19 control subjects underwent both (11)C-DTBZ and (18)F-FDG PET scans. Seven had the clinical diagnosis of frontotemporal dementia (FTD), 25 had Alzheimer's disease (AD), and 20 had dementia with Lewy bodies (DLB). DTBZ scans provided maps of K(1) and DV, whereas (18)F-FDG scans provided maps of glucose metabolism. Correlation analyses were performed between the different PET measures both within and across subjects. Discriminant analysis using logistic regression compared the performance of (11)C-DTBZ K(1) and (18)F-FDG in differentiating subject groups. Three experienced PET researchers participated in an interrater reliability study using both (11)C-DTBZ K(1) and (18)F-FDG images. RESULTS: Within-subject correspondence between (11)C-DTBZ K(1) and (18)F-FDG measures was high, with correlations averaging 0.92. Correlations between the (11)C-DTBZ DV and either K(1) or (18)F-FDG were far lower, averaging 0.37 and 0.31, respectively, indicating the much higher degree of similarity in information provided by K(1) and (18)F-FDG compared with the very different information provided by (11)C-DTBZ DV. Discriminant analysis demonstrated that (11)C-DTBZ K(1) and (18)F-FDG yielded similar levels of sensitivity and specificity for differentiating the subjects in this study. Including (11)C-DTBZ DV in addition to either K(1) or (18)F-FDG improved discrimination between groups. The raters classified PET scans nearly equivalently using K(1) and (18)F-FDG. CONCLUSION: Multiple PET measures, whether 2 parameters from a single PET study such as (11)C-DTBZ K(1) and DV, or 2 parameters from different studies such as (18)F-FDG and (11)C-DTBZ DV, offer complementary information useful for diagnosing dementias. K(1) and DV images generated from a single (11)C-DTBZ scan provide as much diagnostic information as 2-scan studies using both (11)C-DTBZ and (18)F-FDG.

Differentiation of Alzheimer's disease from dementia with Lewy bodies utilizing positron emission tomography with [18F]fluorodeoxyglucose and neuropsychological testing.

We compared the relative utility of neuropsychological testing and positron emission tomography (PET) with [18F]fluorodeoxyglucose ([18F]FDG) in differentiating Alzheimer's disease (AD) from dementia with Lewy bodies (DLB). We studied 25 patients with AD, 20 with DLB, and 19 normal elderly controls. There was no difference between patient groups for MMSE, confrontational naming, or verbal learning. The DLB group was significantly more impaired than the AD group for verbal fluency, and the AD group was significantly more impaired than the DLB group for verbal delayed recall. The DLB group had greater difficulty than the AD group on a visual discrimination task that does not require motor functioning, but the difference did not reach significance. Family ratings of motor functioning suggested significantly greater impairment in DLB patients than in AD patients. PET studies revealed significantly lower local cerebral metabolic rates for glucose (lCMRglc) for visual cortex (Brodmann areas 17, 18, and 19) in the DLB than the AD group, but no differences for other regions commonly affected in AD, including posterior cingulate, superior parietal lobe, lateral temporal lobe, and the prefrontal region. Motor ratings were significantly correlated with lCMRglc in all areas of cerebral cortex, including Brodmann areas 17, 18, and 19. The results demonstrate a similar profile of cerebral hypometabolism in the two patient groups except in the visual cortex, where the DLB group shows markedly lower lCMRglc than the AD group. Neuropsychological testing also differentiates the groups, and family ratings of motor functioning are as robust as PET in these later stages of the disorders.

Striatal monoamine terminals in Lewy body dementia and Alzheimer's disease.

We used positron emission tomography (PET) with (+)-[(11)C]dihydrotetrabenazine ([+]-[(11)C]DTBZ) to examine striatal monoaminergic presynaptic terminal density in 20 patients with dementia with Lewy bodies (DLB), 25 with Alzheimer's disease (AD), and 19 normal elderly controls. Six DLB patients developed parkinsonism at least 1 year before dementia (DLB/PD) and 14 developed dementia before parkinsonism or at about the same time (DLB/AD). Striatal mean binding potential was decreased by 62 to 77% in the DLB/PD group and 45 to 67% in the DLB/AD compared to AD and control. Binding was lower in the DLB/PD group than the DLB/AD, but the differences reached only marginal significance in the caudate nucleus. No differences were found between AD and control groups though a few AD patients had binding values below the range of the controls. Subsequent neuropathological examination in one AD patient revealed both AD and DLB changes despite the absence of clinical parkinsonism. Both DLB groups had an anterior to posterior binding deficit gradient relative to controls, largest in posterior putamen, smaller in anterior putamen, smallest in caudate nucleus. The DLB/AD group showed significant binding asymmetry only in posterior putamen. We conclude that PET with (+)-[(11)C]DTBZ differentiates DLB from AD, and decreased binding in AD may indicate subclinical DLB pathology in addition to AD pathology.