GBA mutations in Parkinson disease: earlier death but similar neuropathological features.

BACKGROUND AND PURPOSE: Mutations in the glucocerebrosidase (GBA) gene are known to be a risk factor for Parkinson's disease (PD). Data on clinicopathological correlation are limited. The purpose of this study was to determine the clinicopathological findings that might distinguish PD cases with and without mutations in the GBA gene. METHODS: Data from the Arizona Study of Aging and Neurodegenerative Disorders were used to identify autopsied PD cases that did or did not have a GBA gene mutation. Clinical and neuropathological data were compared. RESULTS: Twelve PD cases had a GBA mutation and 102 did not. The GBA mutation cases died younger (76 vs. 81 years of age) but there was no difference in disease duration or clinical examination findings. No neuropathological differences were found in total or regional semi-quantitative scores for Lewy-type synucleinopathy, senile plaques, neurofibrillary tangles, white matter rarefaction or cerebral amyloid angiopathy scores. CONCLUSIONS: In longitudinally assessed, autopsied PD cases, those with GBA mutations had a younger age at death but there was no evidence for clinical or neuropathological differences compared to cases without GBA mutations. Due to the small GBA group size, small differences cannot be excluded.

Differential spectral quantitative electroencephalography patterns between control and Parkinson's disease cohorts.

BACKGROUND AND PURPOSE: It is believed that progressive Lewy-type synucleinopathy (LTS) is primarily responsible for the worsening of motor and non-motor Parkinson's disease (PD) signs and symptoms. Characterization of quantitative electroencephalography (QEEG) abnormalities across the spectrum of LTS to PD dementia (PD-D) may provide insight into the pathophysiology of PD cortical dysfunction. Here our enlarged EEG database was leveraged to characterize spectral QEEG abnormalities in asymptomatic autopsy-defined groups of control participants and incidental Lewy body disease (ILBD) and three clinically defined groups of participants with PD (cognitively normal PD, mild cognitive impairment PD, and PD-D). METHODS: The PD cohort was studied as part of the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). AZSAND utilizes its Brain and Body Donation Program to perform prospective, standardized, regular longitudinal pre-mortem assessments until death. Resting EEG from subjects was analyzed for spectral domain QEEG measures of background rhythm frequency and global relative power in delta, theta, alpha and beta bands. RESULTS: The various spectral QEEG measures showed differential changes specific to the groups compared. Important findings were background rhythm frequency showing the most pairwise differences across the groups, and this also was the only significant difference between control and ILBD. An increase in delta bandpower was characteristic of worsening cognitive deficits. CONCLUSIONS: Different patterns of change amongst QEEG measures across LTS and PD cognitive states suggest that they correlate with heterogeneous pathophysiologies of cortical dysfunction within the PD clinical spectrum. In addition, the biomarker application of a specific spectral QEEG measure needs to be selectively suited to its study purpose.

Quantitative EEG as a predictive biomarker for Parkinson disease dementia.

OBJECTIVE: We evaluated quantitative EEG (QEEG) measures as predictive biomarkers for the development of dementia in Parkinson disease (PD). Preliminary work shows that QEEG measures correlate with current PD cognitive state. A reliable predictive QEEG biomarker for PD dementia (PD-D) incidence would be valuable for studying PD-D, including treatment trials aimed at preventing cognitive decline in PD. METHODS: A cohort of subjects with PD in our brain donation program utilizes annual premortem longitudinal movement and cognitive evaluation. These subjects also undergo biennial EEG recording. EEG from subjects with PD without dementia with follow-up cognitive evaluation was analyzed for QEEG measures of background rhythm frequency and relative power in δ, , α, and ß bands. The relationship between the time to onset of dementia and QEEG and other possible predictors was assessed by using Cox regression. RESULTS: The hazard of developing dementia was 13 times higher for those with low background rhythm frequency (lower than the grand median of 8.5 Hz) than for those with high background rhythm frequency (p < 0.001). Hazard ratios (HRs) were also significant for > median bandpower (HR = 3.0; p = 0.004) compared to below, and for certain neuropsychological measures. The HRs for δ, α, and ß bandpower as well as baseline demographic and clinical characteristics were not significant. CONCLUSION: The QEEG measures of background rhythm frequency and relative power in the band are potential predictive biomarkers for dementia incidence in PD. These QEEG biomarkers may be useful in complementing neuropsychological testing for studying PD-D incidence.

Haplotypes and gene expression implicate the MAPT region for Parkinson disease: the GenePD Study.

BACKGROUND: Microtubule-associated protein tau (MAPT) has been associated with several neurodegenerative disorders including forms of parkinsonism and Parkinson disease (PD). We evaluated the association of the MAPT region with PD in a large cohort of familial PD cases recruited by the GenePD Study. In addition, postmortem brain samples from patients with PD and neurologically normal controls were used to evaluate whether the expression of the 3-repeat and 4-repeat isoforms of MAPT, and neighboring genes Saitohin (STH) and KIAA1267, are altered in PD cerebellum. METHODS: Twenty-one single-nucleotide polymorphisms (SNPs) in the region of MAPT on chromosome 17q21 were genotyped in the GenePD Study. Single SNPs and haplotypes, including the H1 haplotype, were evaluated for association to PD. Relative quantification of gene expression was performed using real-time RT-PCR. RESULTS: After adjusting for multiple comparisons, SNP rs1800547 was significantly associated with PD affection. While the H1 haplotype was associated with a significantly increased risk for PD, a novel H1 subhaplotype was identified that predicted a greater increased risk for PD. The expression of 4-repeat MAPT, STH, and KIAA1267 was significantly increased in PD brains relative to controls. No difference in expression was observed for 3-repeat MAPT. CONCLUSIONS: This study supports a role for MAPT in the pathogenesis of familial and idiopathic Parkinson disease (PD). Interestingly, the results of the gene expression studies suggest that other genes in the vicinity of MAPT, specifically STH and KIAA1267, may also have a role in PD and suggest complex effects for the genes in this region on PD risk.

Pathologic findings in prospectively ascertained essential tremor subjects.

OBJECTIVE: To assess pathologic changes in prospectively characterized subjects with essential tremor (ET). METHODS: Subjects enrolled in the Sun Health Research Institute Brain and Body Donation Program were examined annually by a movement disorders neurologist, and semiannually by a behavioral neurologist and neuropsychologist. Twenty-four subjects without a prior diagnosis of dementia or other major movement disorder met clinical criteria for ET and came to autopsy. Subjects with mild cognitive impairment (n = 3) were included. These subjects were compared with 21 controls. Brains were examined postmortem according to standardized protocols for assessment of age-related changes and specific pathologic conditions (e.g., Parkinson disease, Alzheimer disease). RESULTS: Subjects had a mean age of 86.2 years and a mean duration of tremor of 11.1 years. Seven subjects had evidence for cerebellar pathology (Purkinje cell loss, cerebellar cortical sclerosis, and proliferation of Bergmann glia). Pigmented neurons were qualitatively depleted in the locus ceruleus in eight subjects and in the substantia nigra in five subjects. Of these, three had Lewy bodies, one subject had brainstem predominant disease, and two had limbic stage. Three subjects had a nonspecific cerebral tauopathy and another met pathologic criteria for progressive supranuclear palsy. However, when compared with controls, only changes in the locus ceruleus and gliosis of the cerebellum remained significant findings. CONCLUSIONS: This study supports previous findings of heterogenous pathology in essential tremor (ET). There is an increased frequency of cerebellar gliosis and locus ceruleus depletion. We did not find an increased incidence of Lewy bodies in subjects with ET.

Both early and late cognitive dysfunction affects the electroencephalogram in Parkinson's disease.

We sought to define quantitative electroencephalographic (EEG) measures as biomarkers of both early and late cognitive decline in Parkinson's disease (PD). PD subjects classified as cognitively normal (PD-CogNL), mild cognitive impairment (PD-MCI), and dementia (PD-D) were studied. Cognitive status and neuropsychological testing was correlated with background rhythm and frequency band EEG power across five frequency bands. We conclude that global EEG measures have potential use as biomarkers in the study of both early and late cognitive deterioration in PD, including for evaluating its treatment. PD-MCI has mean quantitative EEG characteristics that represent an intermediate electrophysiological state between PD-CogNL and PD-D.

Herbicide exposure modifies GSTP1 haplotype association to Parkinson onset age: the GenePD Study.

BACKGROUND: Polymorphisms in the glutathione S-transferase pi gene (GSTP1), encoding GSTP1-1, a detoxification enzyme, may increase the risk of Parkinson disease (PD) with exposure to pesticides. Using the GenePD Study sample of familial PD cases, we explored whether GSTP1 polymorphisms were associated with the age at onset of PD symptoms and whether that relation was modified by exposure to herbicides. METHODS: Seven single-nucleotide polymorphisms (SNPs) were genotyped and tested for association with PD onset age in men in three strata: no exposure to herbicides, residential exposure to herbicides, and occupational exposure to herbicides. Haplotypes were similarly evaluated in stratified analyses. RESULTS: Three SNPs were associated with PD onset age in the group of men occupationally exposed to herbicides. Three additional SNPs had significant trends for the association of PD onset age across the herbicide exposure groups. Haplotype results also provided evidence that the relation between GSTP1 and onset age is modified by herbicide exposure. One haplotype was associated with an approximately 8-years-earlier onset in the occupationally exposed group and a 2.8-years-later onset in the nonexposed group. CONCLUSIONS: Herbicide exposure may be an effect modifier of the relation between glutathione S-transferase pi gene polymorphisms and onset age in familial PD.

Open-label dose-escalation study of oral 1-octanol in patients with essential tremor.

Twenty-one single oral doses of 1-octanol were given to patients with essential tremor (ET) in an open-label dose-escalation study. The drug was well tolerated up to 64 mg/kg. The main side effect was an unusual taste. No overt intoxication was seen. There was evidence for efficacy, with a significant reduction in tremor amplitude as measured by accelerometry and handwriting that was maximal at 2 hours. Higher doses may produce more sustained benefit.

Accuracy of muscle localization without EMG: implications for treatment of limb dystonia.

Although botulinum toxin is an effective treatment for focal dystonia, the importance of electromyography (EMG) in identifying muscles and guiding injections is unclear. The authors examined the accuracy of muscle localization in 38 muscles in patients with focal hand dystonia without EMG guidance. Only 37% of needle placement attempts reached the target muscles or muscle fascicles. This study demonstrates that EMG guidance is needed for correct localization of desired muscles.

Assessment of silent embolism from carotid endarterectomy by use of diffusion-weighted imaging: work in progress.

BACKGROUND AND PURPOSE: Transcranial Doppler studies have suggested that microemboli are released into the arterial circulation during the majority of carotid endarterectomy (CEA) procedures. This, together with the observation that neuropsychological performance may decline postoperatively, has led to concern that cerebral infarction may occur unrecognized during CEA. Our objective was to examine this risk with diffusion-weighted imaging, a technique that is highly sensitive to acute cerebral infarction. METHODS: Eighteen participants (median age, 68 years; age range, 56-87 years) were assessed with diffusion-weighted imaging and the National Institutes of Health Stroke Scale before and after CEA. Imaging was performed using single-shot echo-planar imaging with a maximum diffusion sensitivity of b = 1000 s/mm(2) applied to three orthogonal planes. Preoperative imaging was performed a median of 2.5 hours before surgery (range, 0.5-12.5 hours) and 15 hours after surgery (range, 1.5-58.5 hours). Two neuroradiologists independently interpreted the diffusion-weighted images, blinded to operative status and clinical findings. RESULTS: There was no diffusion-weighted imaging evidence of silent embolism in this series of 18 participants (95% confidence interval limits, 0 to 10%). Clinical complications were confined to one case of confusion occurring after CEA; the diffusion-weighted imaging results were normal in this case. CONCLUSION: There is no evidence from our series that silent cerebral infarction is a common occurrence during CEA. These data provide further support for the safety of CEA.

Incidence of postangiographic abnormalities revealed by diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: Occasionally we have observed anecdotal cases of asymptomatic hyperintensities on diffusion-weighted MR (DW-MR) examinations of the brain of patients who previously underwent routine cerebral angiography. These observations, as well as MR imaging and transcranial Doppler data in the literature suggesting a high rate of procedure-associated emboli, raise concern regarding the underdiagnosis of asymptomatic focal infarction associated with cerebral angiography. In order to determine whether asymptomatic diffusion abnormalities are frequently associated with procedures, we prospectively obtained DW-MR images before and after routine cerebral angiography. METHODS: Twenty consecutive patients, who met protocol criteria and received a routine three- or four-vessel diagnostic cerebral angiogram at our institution, were evaluated. Using a Bayesian estimate to establish an upper bound for the incidence of an event with zero occurrences in a study sample, the study group size was selected to exclude a 10% incidence of abnormalities revealed by DW-MR imaging of patients who underwent previous cerebral angiography. Two neuroradiologists evaluated imaging studies. RESULTS: Neither clinical signs nor abnormalities on DW-MR images were found, which suggested no infarction after angiography in our patient sample. Based on this data, an upper bound of 9% (95% confidence) is predicted for the appearance of abnormalities revealed by DW-MR imaging after cerebral angiography. CONCLUSION: Cerebral angiography is associated with an incidence of asymptomatic cerebral infarction of no more than 9%. It well may be substantially lower than this estimate; a more accurate evaluation of the true incidence would require a significantly larger study population. This test provides a convenient noninvasive means of assessing procedure-related cerebral infarction, such as that which occurs after carotid endarterectomy or vascular angioplasty and stenting.