Olof Sydow

Multicentre European study of thalamic stimulation in essential tremor: a six year follow up

Background: Thalamic stimulation is an efficient treatment for disabling essential tremor, as previously shown, but follow up has mostly been short term. Objectives: To see whether good results can be maintained in the longer term. Methods: 37 patients with essential tremor had implantation of a thalamic stimulator, either unilaterally or bilaterally. The results at one year have been reported earlier. After six years, 19 patients were available for follow up. The main instrument for evaluation was the essential tremor rating scale. The patients were examined with pulse generators turned on and off. Results: In the majority of patients, the very good results with stimulation seen at one year were maintained after a mean of 6.5 years. The reduction in tremor scores and improvement in activities of daily living were highly significant compared with baseline and with the stimulation turned off. There were few serious adverse events. Minor side effects related to stimulation were common. Few device related complications were observed and most could be resolved. Conclusions: Good reduction in tremor can be maintained for more than six years in the majority of these severely disabled patients. Thalamic stimulation can be recommended in essential tremor where there is insufficient response to drug treatment. Surgical procedures and follow up should be concentrated in relatively few centres, which will thereby acquire a high degree of expertise.

LRRK2 expression linked to dopamine-innervated areas

Leucine‐rich repeat kinase 2 (LRRK2) has been linked to Parkinsons disease. Our study explores the expression of LRRK2 in human and rodent brain tissue.

Multicentre European study of thalamic stimulation for parkinsonian tremor: a 6 year follow-up

Aim: To evaluate the results of ventral intermediate (Vim) thalamic deep brain stimulation (DBS) in patients with tremor predominant Parkinson’s disease (PD) at 6 years post surgery. Methods: This was a prolonged follow-up study of 38 patients from eight centres who participated in a multicentre study, the 1 year results of which have been published previously. Total scores as well as scores for individual items of the motor part and the disability part of the Unified Parkinson’s Disease Rating Scale were used for evaluation. Results: Tremor was still effectively controlled by DBS and appendicular rigidity and akinesia remained stable compared with baseline. Axial scores (speech, gait and postural instability), however, worsened, and in parallel the initial improvement in activities of daily living scores at the 1 year follow-up had disappeared at 6 years, despite sustained improvement of tremor. Remarkably, neither daily doses of dopaminergic medication nor fluctuations and dyskinesias had changed at 6 years compared with baseline in this particular patient group. Conclusion: This study confirms that patients with tremor dominant PD who do not present with fluctuations and dyskinesias may have a relatively benign progression of the disease. Vim DBS, although having no effect on akinesia and rigidity, is a relatively lenient surgical procedure and may still have a place for long term symptomatic control of PD tremor in selected patients.

Selecting deep brain stimulation or infusion therapies in advanced Parkinson's disease: an evidence-based review

Motor complications in Parkinson’s disease (PD) result from the short half-life and irregular plasma fluctuations of oral levodopa. When strategies of providing more continuous dopaminergic stimulation by adjusting oral medication fail, patients may be candidates for one of three device-aided therapies: deep brain stimulation (DBS), continuous subcutaneous apomorphine infusion, or continuous duodenal/jejunal levodopa/carbidopa pump infusion (DLI). These therapies differ in their invasiveness, side-effect profile, and the need for nursing care. So far, very few comparative studies have evaluated the efficacy of the three device-aided therapies for specific motor problems in advanced PD. As a result, neurologists currently lack guidance as to which therapy could be most appropriate for a particular PD patient. A group of experts knowledgeable in all three therapies reviewed the currently available literature for each treatment and identified variables of clinical relevance for choosing one of the three options such as type of motor problems, age, and cognitive and psychiatric status. For each scenario, pragmatic and (if available) evidence-based recommendations are provided as to which patients could be candidates for either DBS, DLI, or subcutaneous apomorphine.

Interim analysis of long-term intraduodenal levodopa infusion in advanced Parkinson disease

This interim 12‐month analysis is a part of an open‐label, observational, prospective study on health outcomes and cost impact of levodopa/carbidopa intestinal gel (LCIG, Duodopa) in Parkinson disease (PD). The specific aim was to investigate clinical and health‐related quality of life (HRQoL) effects in routine care.

Association study of two genetic variants in mitochondrial transcription factor A (TFAM) in Alzheimer's and Parkinson's disease

Mitochondrial (mt) dysfunction has been implicated in Alzheimers (AD) and Parkinsons disease (PD). Mitochondrial transcription factor A (TFAM) is needed for mtDNA maintenance, regulating mtDNA copy number and is absolutely required for transcriptional initiation at mtDNA promoters. Two genetic variants in TFAM have been reported to be associated with AD in a Caucasian case-control material collected from Germany, Switzerland and Italy. One of these variants was reported to show a tendency for association with AD in a pooled Scottish and Swedish case-control material and the other variant was reported to be associated with AD in a recent meta-analysis. We investigated these two genetic variants, rs1937 and rs2306604, in an AD and a PD case-control material, both from Sweden and found significant genotypic as well as allelic association to marker rs2306604 in the AD case-control material (P=0.05 and P=0.03, respectively), where the A-allele appears to increase risk for developing AD. No association was observed for marker rs1937. We did not find any association in the PD case-control material for either of the two markers. The distribution of the two-locus haplotype frequencies (based on rs1937 and rs2306604) did not differ significantly between affected individuals and controls in the two sample sets. However, the global P-value for haplotypic association testing indicated borderline association in the AD sample set. Our data suggests that the rs2306604 A-allele could be a moderate risk factor for AD, which is supported by the recent meta-analysis.

Leucine-rich repeat kinase 2 (LRRK2) mutations in a Swedish parkinson cohort and a healthy nonagenarian

Specific variants of Leucine‐rich repeat kinase 2 (LRRK2) have been shown to associate with Parkinsons disease (PD). Several mutations have been found in PD populations from different parts of the world. We investigated the occurrence of three mutations (R1441G/C/H, G2019S, and I2020T) in our Swedish case–control material and identified four carriers of the G2019S mutation in 284 PD cases and 1 95‐year‐old carrier in 305 controls. The other two variants were absent in our material. We conclude that the LRRK2 G2019S mutation constitutes a significant factor for PD in the Swedish population and that it is not completely penetrant.

Association of a polymorphism in the ABCB1 gene with Parkinson's disease.

The ATP-binding cassette, sub-family B, member 1 (ABCB1) gene encoding the protein P-glycoprotein (P-gp) has been implicated in the pathophysiology of Parkinsons disease (PD) due to its role in regulating transport of endogenous molecules and exogenous toxins. In the present study, we analyzed the ABCB1 single nucleotide polymorphisms (SNPs) 1236C/T (exon 12), 2677G/T/A (exon 21) and 3435C/T (exon 26) in 288 Swedish PD patients and 313 control subjects and found a significant association of SNP 1236C/T with disease (p=0.0159; chi(2)=8.28), whereas the distributions of wild-type and mutated alleles were similar for 2677G/T/A and 3435C/T in patients and controls. Haplotype analysis revealed significant association of the 1236C-2677G haplotype with PD (p=0.026; chi(2)=4.955) and a trend towards association with disease of the 1236C-2677G-3435C haplotype (p=0.072; chi(2)=3.229). Altered ABCB1 and/or P-pg expression was recently shown in PD patients, and impaired drug efflux across barriers such as the gastrointestinal and nasal mucosal linings or the blood-brain barrier, might result in accumulation of drugs and/or endogenous molecules in toxic amounts, possibly contributing to disease. ABCB1 polymorphisms thus constitute an example of how genetic predisposition and environmental influences may combine to increase risk of PD.

Cerebellar α-synuclein levels are decreased in Parkinson’s disease and do not correlate with SNCA polymorphisms associated with disease in a Swedish material

Alterations of brain and plasma α‐synuclein levels and SNCA gene variability have been implicated in the pathogenesis of Parkinsons disease (PD). We therefore measured α‐synuclein protein levels in postmortem PD and control cerebellum tissue using Western blot and investigated whether the levels correlated to SNCA genotype. We found markedly decreased α‐synuclein levels in PD patients (n=16) compared to gender‐and age‐matched controls (n=14; P= 0.004) normalized to α‐tubulin. We also performed an association study of the noncoding polymorphisms rs2737029 (A/G) and rs356204 (A/G) (intron 4), and of rs356219 (T/C) (34′‐region) of SNCAin a Swedish PD case‐control material. Using a two‐sided χ test, we found significant association of rs2737029 (P= 0.003; χ2 =9.07) and rs356204 (P=0.048; χ2 =3.91) with disease, strengthening the involvement of SNCA polymorphisms in sporadic PD. Stratification of the human postmortem brain material by genotype of the three investigated polymorphisms, did not indicate any influence of genotype on α‐synuclein protein levels when comparing PD with controls. Taken together, our findings demonstrate that the investigated Parkinson patients have markedly reduced levels of α‐synuclein in cerebellum, and that this reduction is general, rather then correlated to the investigated polymorphisms, although two of the polymorphisms also associated with disease in a Swedish material.—Westerlund, M., Belin, A. C., Anvret, A., Håkansson, A., Nissbrandt, H., Lind, C., Sydow, O., Olson, L., and Galter, D. Cerebellar α‐synuclein levels are decreased in Parkinsons disease and do not correlate with SNCA polymorphisms associated with disease in a Swedish material. FASEB J. 22, 3509–3514 (2008)

Variations of the CAG trinucleotide repeat in DNA polymerase gamma (POLG1) is associated with Parkinson's disease in Sweden

DNA polymerase gamma (POLG1) is coding for the catalytic subunit of the heterotrimeric mitochondrial DNA polymerase and involved in replication and repair of mitochondrial DNA. In addition to its 5 to 3 polymerase activity, POLG1 has a 3 to 5 exonuclease activity important in the repair process. Mitochondrial dysfunction has been implicated in neurodegenerative disorders like Parkinsons disease (PD). Dopamine neurons, which degenerate in PD, are believed to be particularly susceptible to mitochondrial dysfunction, which makes POLG1 a possible candidate gene for the disease. POLG1 has a polyglutamine tract (poly-Q) in the N-terminal, encoded by a CAG sequence in exon 2. Most commonly the poly-Q tract comprises 10 repeats (10Q, frequency >80%) or moderately common 11Q (frequency 6-12%); however the composition of poly-Q alleles has been reported to vary from 6Q to 14Q. We analyzed this POLG1 trinucleotide repeat in a Swedish PD case-control material and detected variations from 5Q to 15Q. We report a significant association between the non-10/11Q repeats with PD (p=0.002). In silico analysis of poly-Q length effect on mRNA folding energy show a decrease in energy for <10/11Q mRNA (4.6%) and an increase for >10/11Q mRNA (4.8%) compared to 10/11Q mRNA. Our results strengthen the evidence for involvement of POLG1 and mitochondrial dysfunction in PD.