Katherine Schweitzer

Genetic variability in the SNCA gene influences alpha-synuclein levels in the blood and brain

Genetic variability in the promoter and 3′ region of the SNCA gene coding α‐synuclein modulates the risk to develop sporadic Parkinsons disease (PD). Whether this is mediated by regulating a‐synuclein expression levels remains unknown. Therefore, we analyzed levels of α‐synuclein in blood and human post mortem brain tissue including the substantia nigra using quantitative real‐time reverse transcriptase‐ polymerase chain reaction and enzyme linked immu‐nosorbent assay in vivo. Single nucleotide polymor‐phism (SNP) rs356219, a tagging SNP for a disease‐ associated haplotype in the 3′ region of the SNCA gene, has a significant effect on SNCA mRNA levels in the substantia nigra and the cerebellum. Further, the “protective” genotype 259/259 of the PD‐associated promoter repeat NACP‐Repl is associated with lower protein levels in blood than genotypes 261/261, 259/261, and 259/263. In conclusion, we provide evidence that a‐synuclein levels are influenced by genetic variability in the promoter and 3′ region of the SNCA gene in vivo.—Fuchs, J., Tichopad, A., Golub, Y., Munz, M., Schweitzer, K. J., Wolf, B., Berg, D., Mueller, J. C., Gasser, T. Genetic variability in the SNCA gene influences α‐synuclein levels in the blood and brain. FASEB J. 22, 1327–1334 (2008)

The specificity and sensitivity of transcranial ultrasound in the differential diagnosis of Parkinson's disease: a prospective blinded study

BACKGROUND Increased echogenicity of the substantia nigra (SN), as determined by transcranial sonography (TCS), is characteristic of idiopathic Parkinsons disease (iPD). The results of initial retrospective studies indicate that this ultrasound sign is specific for iPD and can help to differentiate it from atypical parkinsonian syndromes (aPS); however, these early studies were done in patients with later disease stages and known clinical diagnosis. We aimed to determine the diagnostic value of TCS in the early stages of parkinsonian syndromes, when the clinical symptoms often do not enable a definite diagnosis to be made. METHODS 60 patients who presented with the first, but still unclear, clinical symptoms of parkinsonism had TCS in this prospective blinded study. Investigators were blinded to the results of the clinical investigations, the ultrasound findings, and the diagnosis at time of investigation. The patients were followed-up every 3 months for 1 year to assess and re-evaluate the clinical symptoms. The patients in whom a clinical diagnosis could not be made with certainty were investigated with raclopride PET or dopamine transporter single-photon emission computed tomography (SPECT), or both. FINDINGS A clinical diagnosis of parkinsonism could not be established at baseline in 38 patients. At 12 months, 39 patients were clinically categorised as having iPD. Compared with endpoint diagnosis, the sensitivity of TCS at baseline was 90%7% and the specificity was 82.4%; the positive predictive value of TCS for iPD was 92.9% and the classification accuracy was 88.3%. INTERPRETATION TCS is an easy to implement, non-invasive, and inexpensive technique that could help in the early differential diagnosis of parkinsonian syndromes. The routine use of TCS in the clinic could enable disease-specific therapy to be started earlier. FUNDING Michael J Fox Foundation for Parkinsons Research.

Enlarged Substantia Nigra Hyperechogenicity and Risk for Parkinson Disease: A 37-Month 3-Center Study of 1847 Older Persons

OBJECTIVE To evaluate whether enlarged substantia nigra hyperechogenicity (SN+) is associated with an increased risk for Parkinson disease (PD) in a healthy elderly population. DESIGN Longitudinal 3-center observational study with 37 months of prospective follow-up. SETTING Individuals 50 years or older without evidence of PD or any other neurodegenerative disease. PARTICIPANTS Of 1847 participants who underwent a full medical history, neurological assessment, and transcranial sonography at baseline, 1535 could undergo reassessment. MAIN OUTCOME MEASURE Incidence of new-onset PD in relation to baseline transcranial sonography status. RESULTS There were 11 cases of incident PD during the follow-up period. In participants with SN+ at baseline, the relative risk for incident PD was 17.37 (95% confidence interval, 3.71-81.34) times higher compared with normoechogenic participants. CONCLUSIONS In this prospective study, we demonstrate for the first time a highly increased risk for PD in elderly individuals with SN+. Transcranial sonography of the midbrain may therefore be a promising primary screening procedure to define a risk population for imminent PD.

Substantia nigra hypoechogenicity: Definition and findings in restless legs syndrome

Pathological studies demonstrate a decreased iron content in the substantia nigra (SN) contributing to the pathophysiology of restless legs syndrome (RLS). SN echogenicity as measured by transcranial sonography (TCS) correlates with the SN iron content. The objective of this study was to determine a critical value to define SN hypoechogenicity as a potential marker for RLS. There were 49 RLS patients (39 idiopathic, 10 secondary) and 49 age‐ and sex‐matched controls who underwent TCS by 2 independent and blinded examiners to determine the area of SN echogenicity. We found that SN echogenicity is significantly decreased in RLS patients compared to healthy controls (P < 0.001). SN hypoechogenicity (sum area of SN echogenicity of both sides < 0.2 cm2) is more common in idiopathic than in secondary RLS patients. The area under curve for idiopathic RLS versus controls (receiver operating characteristics) is 0.91, specificity is 0.90, and sensitivity is 0.82. TCS provides an interesting additional instrument in the diagnosis of RLS. Therefore, SN hypoechogenicity (SN sum area < 0.2 cm2), which is supposed to indicate a decreased SN iron content, is a marker for RLS. Further studies are needed to investigate its significance for the pathophysiology of this frequent movement disorder and possible clinical applications.

Multiregional brain iron deficiency in restless legs syndrome

Evidence for tissue iron deficiency in restless legs syndrome (RLS) is limited to the substantia nigra (SN). Using MRI, we assessed T2 values of various brain regions in 6 RLS patients and 19 controls and correlated them with sonographically assessed SN echogenicity. Both neuroimaging features are supposed to correlate with tissue iron content. Mean T2 values of all regions were higher in patients (2.9–7.8%), though significantly increased only in four regions; the mean T2 over all voxels was higher in patients (5.1%, P < 0.001) and correlated inversely with SN echogenicity (r = −0.61, P < 0.001). This indicates multiregional (global) brain iron deficiency in RLS and proposes SN echogenicity as a potential morphological marker for brain iron status.

Disturbance of iron metabolism in Parkinson’s disease — ultrasonography as a biomarker

A central role of iron in the pathogenesis of Parkinson’s disease (PD) has been discussed for many years. So far, however, a biomarker indicating increased iron levels in the substantia nigra (SN) in PD patients has been missing. Performing transcranial ultrasound we detected an increased area of SN echogenicity as a typical echofeature in PD, visible already in the early stages of the disease and in subjects with subclinical impairment of the nigrostriatal system. Animal studies and post mortem analyses of human brain tissue revealed that this echofeature is associated with increased iron levels of the substantia nigra as well as a reduced neuromelanin content. The apparently autosomal dominant inheritance of this echofeature in relatives of patients with idiopathic PD indicates a primary role of disturbances of iron metabolism in PD. Consequently performed mutation analyses in genes involved in brain iron metabolism lead to the discovery of specific mutations in theferritin-H, IRP2 andHFE gene in single PD patients. Moreover, variations in the ceruloplasmin gene were found to be associated with PD or SN hyperechogenicity. Functional relevance of some of these mutations for iron metabolism could be proven. Therefore, SN hyperechogenicity can be regarded as biomarker for both: impairment of the nigrostriatal system and increased iron levels of the SN. Future studies aim at substantiating the hypothesis that healthy subjects with SN hyperechogenicity indeed represent a population at risk for nigrostriatal degeneration, which would have a significant impact on therapeutical options.

Loss of nocturnal blood pressure fall in various extrapyramidal syndromes

Cardiovascular autonomic dysfunction has frequently been reported in some patients with extrapyramidal syndromes, especially multiple system atrophy (MSA) but also Parkinsons disease (PD). However, there are only few reports on the prevalence of cardiovascular autonomic dysfunction progressive in supranuclear palsy (PSP). Moreover, the relation of detailed cardiovascular testing and easy to assess 24‐hour ambulatory blood pressure (BP) is not known. Our study evaluates 24‐hour ambulatory BP monitoring in patients with PD, PSP, MSA, and corresponding controls (Con) and relates the findings to the results of comprehensive cardiovascular autonomic testing. Twenty‐three patients with PD, 25 patients with PSP, 25 patients with MSA, and 26 corresponding controls were studied by 24‐hour ambulatory BP monitoring (ABPM) in comparison to cardiovascular autonomic testing. Patients with PD, PSP, and MSA presented frequently with a pathological nocturnal BP regulation (no decrease or even an increase of nocturnal BP) in comparison to the control group (PD 48%, PSP 40%, MSA 68% vs. Con 8%). In MSA and PD patients, the frequent pathological BP increase during night was closely correlated to orthostatic hypotension. Since loss of nocturnal BP fall is frequent in patients with extrapyramidal syndromes, even if they are free of subjective autonomic dysfunction, we recommend 24‐hour ABPM as an easy to perform screening test, especially if detailed autonomic testing is not available. Pathological loss of nocturnal BP fall may account for increased cardiovascular mortality in extrapyramidal syndromes.

Transcranial ultrasound in different monogenetic subtypes of Parkinson's disease.

Hyperechogenicity of the substantia nigra (SN) has been found to be a typical sign in idiopathic Parkinsons disease (PD), prevalent in more than 90% of affected individuals. To see whether SN hyperechogenicity is also characteristic for monogenetically caused PD, we investigated PD patients with alpha-synuclein, LRRK2, parkin, PINK1 and DJ-1 mutations by transcranial sonography (TCS). In all these patients the area of SN echogenicity was significantly larger than in healthy controls, but smaller, than in idiopathic PD. As SN hyperechogenicity could be related to an increased iron content of the SN, these findings suggest that iron may play a less significant role in the pathogenesis of monogenetically caused compared to idiopathic PD.

Predictive value of transcranial sonography in the diagnosis of Parkinson's disease.

Transcanial sonography (TCS) is increasingly applied in the diagnosis of Parkinsons disease (PD), but investigator bias may influence the results of examination. Blinding the sonographer to the clinical diagnosis of 42 PD patients and 35 controls, we obtained a positive predictive value of 85.7% and a negative predictive value of 82.9% in the diagnosis of PD solely by interpreting the results of TCS, indicating that TCS is a valuable additional tool in the diagnosis of PD.

Substantia nigra hyperechogenicity as a marker of predisposition and slower progression in Parkinson's disease

Increased echogenic size (hyperechogenicity) of the substantia nigra (SN) is a characteristic transcranial sonography finding in patients with Parkinsons disease (PD). The SN echogenic size does not change in the course of the disease. In order to see whether this stable ultrasound marker may give any implications for the rate of PD progression, we sonographically investigated 16 PD patients in whom the rate of progression had been determined by serial 18‐fluorodopa positron emission tomography over a follow‐up period of 65.7 ± 26.7 months. We found a significant negative correlation between the right‐to‐left averaged SN echogenic size and the rate of disease progression in the caudate nucleus and in the putamen. There was a tendency towards a younger age at symptom onset in patients with SN hyperechogenicity. It may therefore be hypothesized that a differing influence of factors determining SN echogenicity early in life and impairing forces occurring later in life may account for different pathogenetic subgroups of idiopathic PD.