Increased fracture risk in Parkinson's disease - An exploration of mechanisms and consequences for fracture prediction with FRAX

The relative contributions of factors such as muscle strength, falls risk and low bone mineral density (BMD) to increased fracture risk in Parkinson's Disease (PD) were examined in an analysis of 5212 community-dwelling women age 75 years or more recruited to a randomised, double-blind, placebo-controlled study of the oral bisphosphonate, clodronate. Similar number of PD and non-PD subjects received treatment. Each participant had measurements of hip and forearm BMD, muscle strength (hand grip strength and maximum isometric quadriceps strength), ability in the sit-to-stand test, and postural stability. Incident radiographic and/or surgically verified fractures, and deaths, were recorded over an average follow-up of 3.8 years. A diagnosis of PD was made if it was self-reported and appropriate medication was recorded at the study entry. 47 of the women (0.9 %) had a diagnosis of PD at baseline. They were of similar age to those without PD, but reported higher disability scores and lower quality of life. While BMD at the forearm and hip regions was lower in PD, this only reached statistical significance at the femoral neck (0.61 ± 0.12 vs 0.65 ± 0.12 g/cm², p = 0.037). Right hand grip strength was non-significantly lower in PD, but maximum right quadriceps strength was much reduced (96.9 ± 49.3 vs 126.3 ± 59.2 N, p = 0.003). Eleven (23.4 %) of the women with PD sustained 12 fractures, while 609 women (11.8 %) without PD sustained 742 osteoporotic fractures. The risk of osteoporotic fracture associated with PD was 2.24-fold higher in women with PD (Cox-regression HR 2.24, 95 % CI 1.23-4.06) and this remained high when adjusted for death as a competing risk (2.17, 95 % CI 1.17-4.01, p = 0.013). Following adjustment for femoral neck BMD, PD remained a significant predictor of fracture (HR 2.04, 1.12-3.70, p = 0.020). Entering PD as a risk variable using the rheumatoid arthritis input as a surrogate resulted in a reduction in PD as a FRAX-independent risk factor, particularly when BMD was included in FRAX (1.65, 95 % CI), but the relationship between PD and fracture risk appears to remain of clinical significance. The study suggests that PD may be an independent input in future iterations of FRAX, possibly due to non-skeletal components of risk such as reduced lower limb muscle strength. Introducing measures of muscle strength and performance in FRAX could also be considered.

Ursodeoxycholic acid as a novel disease-modifying treatment for Parkinson's disease: protocol for a two-centre, randomised, double-blind, placebo-controlled trial, The 'UP' study

INTRODUCTION

There are no disease-modifying treatments for Parkinson's disease (PD). We undertook the first drug screen in PD patient tissue and idntified ursodeoxycholic acid (UDCA) as a promising mitochondrial rescue agent. The aims of this trial are to determine safety and tolerability of UDCA in PD at 30 mg/kg, confirm the target engagement of UDCA, apply a novel motion sensor-based approach to quantify disease progression objectively, and estimate the mean effect size and its variance on the change in motor severity.

METHODS AND ANALYSIS

This is a phase II, two-centre, double-blind, randomised, placebo-controlled trial of UDCA at a dose of 30 mg/kg in 30 participants with early PD. Treatment duration is 48 weeks, followed by an 8-week washout phase. Randomisation is 2:1, drug to placebo. Assessments are performed at baseline, week 12, 24, 36, 48 and 56. The primary outcome is safety and tolerability. Secondary outcomes will compare the change between baseline and week 48 using the following three approaches: the Movement Disorders Society Unified Parkinson's Disease Rating Scale Part 3 in the practically defined 'OFF' medication state; confirmation of target engagement, applying 31Phosphorus MR Spectroscopy to assess the levels of ATP and relevant metabolites in the brain; and objective quantification of motor impairment, using a validated, motion sensor-based approach. The primary outcome will be reported using descriptive statistics and comparisons between treatment groups. For each secondary outcome, the change from baseline will be summarised within treatment groups using summary statistics and appropriate statistical tests assessing for significant differences. All outcomes will use an intention-to-treat analysis population.

ETHICS AND DISSEMINATION

This trial has been approved by the East of England - Cambridgeshire and Hertfordshire Research Ethics committee. Results will be disseminated in peer-reviewed journals, presentations at scientific meetings and to patients in a lay-summary format.

TRIAL REGISTRATION NUMBER

NCT03840005.

Rescue of mitochondrial function in parkin-mutant fibroblasts using drug loaded PMPC-PDPA polymersomes and tubular polymersomes

Mutations in parkin cause autosomal recessive Parkinsonism and mitochondrial defects. A recent drug screen identified a class of steroid-like hydrophobic compounds able to rescue mitochondrial function in parkin-mutant fibroblasts. Whilst these possess therapeutic potential, the size and high hydrophobicity of some may limit their ability to penetrate the blood-brain barrier from systemic circulation, something that could be improved by novel drug formulations. In the present study, the steroid-like compounds Ursolic Acid (UA) and Ursocholanic Acid (UCA) were successfully encapsulated within nanoscopic polymersomes formed by poly(2-(methacryloyloxy)ethyl phosphorylcholine)-poly(2-di-isopropylamino)ethyl methacrylate) (PMPC-PDPA) and separated into spherical and tubular morphologies to assess the effects of nanoparticle mediated delivery on drug efficacy. Following incubation with either morphology, parkin-mutant fibroblasts demonstrated time and concentration dependent increases in intracellular ATP levels, resembling those resulting from treatment with nascent UA and UCA formulated in 0.1% DMSO, as used in the original drug screen. Empty PMPC-PDPA polymersomes did not alter physiological measures related to mitochondrial function or induce cytotoxicity. In combination with other techniques such as ligand functionalisation, PMPC-PDPA nanoparticles of well-defined morphology may prove a promising platform for tailoring the pharmacokinetic profile and organ specific bio-distribution of highly hydrophobic compounds.

Corpus callosum morphology and microstructure assessed using structural MR imaging and diffusion tensor imaging: initial findings in adults with neurofibromatosis type 1

BACKGROUND AND PURPOSE

Imaging studies have shown that children with NF-1 have increased brain volumes compared with age-matched controls and the CCs are disproportionately large. The purpose of this study was to determine if the CC in adults with NF-1 differed from that in matched controls by using DTI and volumetric imaging.

MATERIALS AND METHODS

MR imaging with DTI was performed in 10 adults with NF-1 and in 10 age-, sex-, and handedness-matched controls by using a 3T system. Total brain volumes and the areas and central lengths of the CC were calculated, along with the radial width of callosal subdivisions, in the 2 groups.

RESULTS

Our results showed that the total brain volume was not significantly different between adults with NF-1 and matched controls. The length and total cross-sectional area of the CC were statistically larger in adults with NF-1 compared with controls (approximately 10% longer and 20% greater area). On DTI we found a preservation of the primary eigenvalue with increases in the minor eigenvalues at the genu.

CONCLUSIONS

We have shown that the increased size of the CC found in children with NF-1 is also present in adults with the syndrome, whereas no difference in total brain volume was found.

CNS involvement in hereditary neuropathy with pressure palsies (HNPP)

We assessed seven patients with hereditary neuropathy with liability to pressure palsies (HNPP) with 16 electrophysiological tests and cranial MRI for CNS abnormalities. Mean latencies differed between patients with HNPP and controls for the blink reflex, the jaw-opening reflex, and acoustic evoked potentials. MRI abnormalities were observed in four patients. Our study suggests subclinical but functionally relevant CNS myelin damage in HNPP.

Neurodegenerative disorders: Parkinson's disease and Huntington's disease

Parkinson's disease and Huntington's disease are both model diseases. Parkinson's disease is the most common of several akinetic-rigid syndromes and Huntington's disease is only one of an ever growing number of trinucleotide repeat disorders. Molecular genetic studies and subsequent molecular biological studies have provided fascinating new insights into the pathogenesis of both disorders and there is now real hope for disease modifying treatment in the not too distant future for patients with Parkinson's disease or Huntington's disease.

The fragile X tremor ataxia syndrome in the differential diagnosis of multiple system atrophy: data from the EMSA Study Group

The recent identification of fragile X-associated tremor ataxia syndrome (FXTAS) associated with premutations in the FMR1 gene and the possibility of clinical overlap with multiple system atrophy (MSA) has raised important questions, such as whether genetic testing for FXTAS should be performed routinely in MSA and whether positive cases might affect the specificity of current MSA diagnostic criteria. We genotyped 507 patients with clinically diagnosed or pathologically proven MSA for FMR1 repeat length. Among the 426 clinically diagnosed cases, we identified four patients carrying FMR1 premutations (0.94%). Within the subgroup of patients with probable MSA-C, three of 76 patients (3.95%) carried premutations. We identified no premutation carriers among 81 patients with pathologically proven MSA and only one carrier among 622 controls (0.16%). Our results suggest that, with proper application of current diagnostic criteria, FXTAS is very unlikely to be confused with MSA. However, slowly progressive disease or predominant tremor are useful red flags and should prompt the consideration of FXTAS. On the basis of our data, the EMSA Study Group does not recommend routine FMR1 genotyping in typical MSA patients.

Slow N -acetyltransferase 2 status leads to enhanced intrastriatal dopamine depletion in 6-hydroxydopamine-lesioned rats

We previously reported an association between the N-acetyltransferase 2 (NAT2) slow acetylator status and Parkinson's disease (PD). We have now investigated the possible functional relevance of this association by treating Fischer 344 (F344) rapid and Wistar-Kyoto (WKY) slow NAT2 acetylator rat strains with the neurotoxin 6-hydroxydopamine (6-OHDA). Intrastriatal treatment with either 10 or 20 microg of 6-OHDA lead to a significantly greater reduction of striatal dopamine concentrations in the WKY slow acetylator rat strain than in the F344 rapid acetylator rat strain (P < 0.004), reflecting a more marked degree of dopaminergic denervation. Nigral dopaminergic cell counts were also lower in the WKY rats, but this difference failed to reach statistical significance, suggesting that slow acetylation is especially deleterious at the level of striatal nerve endings.

Candidate gene studies in focal dystonia

BACKGROUND

Genetic susceptibility factors for focal idiopathic torsion dystonia (F-ITD) are not established. Mutations in the DYT1 gene can cause focal dystonia, and an association with a polymorphism in the D5 receptor gene (DRD5) has been reported but not confirmed.

OBJECTIVE

To investigate a possible role of DYT1 polymorphisms, a CA repeat in the D5 receptor gene (DRD5), the human leukocyte antigen (HLA)-DRB locus, and four polymorphisms in the homocysteine metabolism in the pathogenesis of F-ITD.

METHODS

Initially, 100 German patients and 100 matched control subjects were investigated. A second French population with 121 F-ITD patients and matched control subjects was also studied.

RESULTS

Two polymorphisms of the beta-cystathionine synthase gene were associated with F-ITD in the German population, but this finding was not replicated in a second independent F-ITD patient and control group of French origin. None of the other investigated polymorphisms was associated with F-ITD. The authors failed to confirm a previously reported association with a polymorphism in DRD5.

CONCLUSION

No evidence for an involvement of DYT1, DRD5, HLA-DRB, or polymorphisms in the homocysteine pathway in the pathogenesis of F-ITD was found.

The phenylalanine loading test in the differential diagnosis of dystonia

Early diagnosis of dopa-responsive dystonia (DRD) and its delineation from other dystonic syndromes is of great relevance because DRD is an eminently treatable condition. The possible relevance of the phenylalanine loading test (Phe-L) in differentiating DRD from primary focal and generalized dystonia was investigated. A marked difference in the phenylalanine/tyrosine ratio between patients with DRD and patients with other types of dystonia was observed. This indicates that Phe-L may be helpful in the differential diagnosis of dystonias.

Steele-Richardson-Olszewski-syndrome: the relation of dopamine D2 receptor binding and subcortical lesions in MRI

We compared (123)I-iodobenzamide single photon emission computed tomography (IBZM-SPECT) for imaging of striatal dopamine D(2) receptors in vivo, and MRI in 32 patients with the clinical diagnosis of progressive supranuclear palsy (PSP). We found a significant inter-dependence of reduction of specific striatal IBZM binding indicative of striatal degeneration and of the absence of multiple signal hyperintensities in MRI; age had no influence neither on IBZM binding nor on signal hyperintensities. We conclude that the presence of multiple signal hyperintensities should raise doubt on the correct clinical diagnosis.

Dopa-responsive dystonia -- the story so far

Dopa-responsive dystonia (DRD) is an eminently treatable condition and its recognition is therefore of crucial importance. In classical cases, the disease manifests in early childhood with walking problems due to dystonia of the lower limbs. The dystonia is frequently accompanied by "parkinsonian" features such as reduced facial expression or slowing of fine finger movements. Biochemically, the disorder is typically characterized by low levels of the neurotransmitter metabolite homovanillic acid and reduced levels of neopterin and tetrahydrobiopterin (BH4) in the cerebrospinal fluid. This is due to heterozygote mutations of the GTP cyclohydrolase I gene, which is the rate-limiting enzyme in the synthesis of BH4. BH4 is an essential co-factor for tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of dopamine. Reduced levels of BH4 lead to the dopamine-deficit syndrome DRD because of reduced TH activity. Other genes implicated in the pathogenesis of this disorder are the TH gene itself and the parkin gene. This article summarizes all relevant aspects of DRD including recent advances in the genetics of this disorder and the widening phenotype. Particular emphasis is given to clinically relevant aspects such as diagnostic difficulties and atypical presentations in infancy and early childhood.

Detailed genotyping demonstrates association between the slow acetylator genotype for N-acetyltransferase 2 (NAT2) and familial Parkinson's disease

In a preliminary report we demonstrated an association between the slow acetylator genotype of N-acetyltransferase 2 (NAT2) and familial cases of Parkinson's disease (FPD). Using a considerably more precise NAT2 typing method, which detects all mutant NAT2 alleles with a frequency of >1% in the white population, we have now retyped all the original patients and control subjects to investigate the reliability of our initial findings. The slow acetylator genotype remained considerably more common among FPD (73%) than normal control subjects (NPC, 43%) or the disease (Huntington's disease [HD]) control group (52%) with an odds ratio (OR) of 3.58 (95% confidence interval (CI): 1.96-6.56; p = 0.00003) for FPD versus NPC and an OR of 2.50 (95% CI: 1.37-4.56, p = 0.003) for FPD versus HD. Furthermore, the wild-type allele 4 conferred a protective effect with an OR of 0.39 (95% CI: 0.23-0.64; p = 0.0025) for FPD versus NPC and an OR of 0.50 (95% CI: 0.30-0.85, p = 0.01) for FPD versus HD. The results of this study support an association between the NAT2 slow acetylator genotype and FPD in our population.

Different postural reaction patterns for expected and unexpected perturbations in patients with idiopathic Parkinson's disease and other parkinsonian syndromes

Different postural reaction patterns after predictable and unpredictable perturbations during free stance were studied in 8 patients with idiopathic Parkinson's disease (iPD), in 4 patients with other parkinsonian syndromes (PS) and in 5 healthy controls. First, the amplitude of leaning maximally backward and forward was measured (condition I). Secondly, the body equilibrium was disturbed by self-paced, predictable, rapid arm elevations (condition II) and by sudden unpredictable toe-down and toe-up rotations of a supporting platform (condition III). Patients with PS particularly had difficulties in regaining body equilibrium after unexpected perturbations. In controls and patients with PS, unpredictable disturbances were better compensated in toe-down than in toe-up direction, whereas the opposite was true for patients with iPD. These results correspond to the fact that patients with PS had a specific leaning-backward impairment and patients with iPD, a leaning-forward impairment. The authors conclude that the differences in postural stability between patients with iPD and PS are caused by different pathophysiological mechanisms. These differences in postural stability could serve as an additional tool for differential diagnosis.

Multiple system atrophy

Multiple system atrophy (MSA) is a degenerative central nervous system disease of unclear origin. Patients affected typically show symptoms attributable to the combined involvement of the extrapyramidal, pyramidal, cerebellar and autonomic nervous systems. At onset patients mostly see a doctor because of extrapyramidal or--more rarely--cerebellar symptoms. Evidence of autonomic nervous system involvement is often not apparent, at least to the neurologist, before the history is taken. In later stages, by contrast, involvement of all of the above systems is clinically detectable.

The tau gene A0 polymorphism in progressive supranuclear palsy and related neurodegenerative diseases

Progressive supranuclear palsy is characterised pathologically by the deposition of neurofibrillary tangles consisting of tau protein. Patients with the disease have been reported to have a more frequent occurrence of one allele of an intronic polymorphism of the tau gene. Other diseases which may involve tau deposition include frontotemporal dementia and corticobasal degeneration. This polymorphism has been studied in a series of subjects with progressive supranuclear palsy, corticobasal degeneration, frontotemporal dementia, idiopathic Parkinson's disease, and normal controls to (1) confirm this association in a large series and (2) to investigate a possible role for this association in other disorders which involve tau deposition. The results confirm the finding of an overrepresentation of the A0 allele and the A0/A0 genotype in patients with progressive supranuclear palsy, in the largest series reported to date. The A0 allele was found in 91% of patients with progressive supranuclear palsy as opposed to 73% of controls (p<0.001) and the A0/A0 genotype was seen in 84% of patients as compared with 53% of controls (p<0.01). There was no significant difference between patients with Parkinson's disease, frontotemporal dementia, or corticobasal degeneration, and controls. The A0 allele may have a direct effect on tau isoform expression in progressive supranuclear palsy or it may be in linkage disequilibrium with an adjacent determinant of tau gene expression. The explanation for this difference between a predisposition factor to progressive supranuclear palsy and the other conditions may lie in the molecular pathology of these diseases.

GTP cyclohydrolase deficiency; intrafamilial variation in clinical phenotype, including levodopa responsiveness

A family with a dominant form of partial GTP cyclohydrolase deficiency is described. Clinical severity varied from mild involvement with complete responsiveness to levodopa to severe dystonia precluding any voluntary activity including talking, progressive contractures, and only partial responsiveness to levodopa. Although there are several possible reasons for intrafamilial variability, any patient with dystonia, the cause of which is not clearly identified, should receive a trial of levodopa.

Dopa-responsive dystonia: a clinical and molecular genetic study

We have studied the GTP-cyclohydrolase 1 (GCH-1) gene in 30 patients with the diagnosis of clinically definite (n = 20) or possible (n = 10) dopa-responsive dystonia (DRD) as well as in a child with atypical phenylketonuria due to complete GCH-1 deficiency. A large number of new heterozygote mutations (seven point mutations, two splice site mutations, and one deletion) as well as a new homozygote mutation in the child with atypical phenylketonuria were detected. In addition, two previously described mutations were found in two other cases. We further extended our investigation of GCH-1 to the 5' and 3' regulatory regions and report the first detection of point mutations in the 5' untranslated region. Demethylation of CpG islands does not appear to be an important causative factor for the GCH-1 mutations in DRD. In addition, we have extended the clinical phenotype of genetically proven DRD to focal dystonia, dystonia with relapsing and remitting course, and DRD with onset in the first week of life. None of our DRD patients without a mutation in GCH-1 had the 3-bp deletion recently detected in DYT1, the causative gene for idiopathic torsion dystonia with linkage to 9q34.

The alpha-synuclein Ala53Thr mutation is not a common cause of familial Parkinson's disease: a study of 230 European cases. European Consortium on Genetic Susceptibility in Parkinson's Disease

We report the results of a screen of 230 European familial index cases of Parkinson's disease for the recently described Ala53Thr mutation in the alpha-synuclein gene in an autosomal dominant Parkinson's disease kindred. No mutations were found from this broad white population, and we therefore conclude that although of great interest, this mutation is a very rare cause of familial Parkinson's disease.

Multiple-system atrophy is genetically distinct from identified inherited causes of spinocerebellar degeneration

Multiple system atrophy (MSA) is a neurodegenerative disorder of unknown cause. The only case-control study conducted in MSA patients to date suggested a possible contributory genetic component in the pathogenesis of this disorder. The aim of this study was to evaluate a possible overlap between clinically or pathologically well-defined MSA and other conditions with an identified genetic defect causing spinocerebellar degeneration in humans or mutant mice strains. The spinocerebellar ataxia type 1 and 3 genes (SCA1 and SCA3) were analyzed for a pathologic expansion in 80 patients with MSA to evaluate a possible overlap between MSA and SCA1 or SCA3. Weaver mice and lurcher mice are animal models for spinocerebellar degeneration; both share pathologic features with MSA. We sequenced the H5 pore region of the human homologue of the weaver mouse gene, hiGIRK2, in all our patients. In lurcher mice, previous biochemical studies have shown a decreased intracellular response to insulin-like growth factor 1 (IGF-1) in the cerebellar cortex, and we thus investigated the possibility of an allelic association between MSA and the receptor for IGF-1. In addition, we evaluated a possible involvement of the ciliary neurotrophic factor gene (CNTF) and examined the role of HLA-A32 to clarify the conflicting data from previous studies. No changes were detected in any of the analyzed genes. Our studies strongly suggest that MSA is an autonomous syndrome distinct from identified genetic causes for spinocerebellar degeneration.

Association of slow acetylator genotype for N-acetyltransferase 2 with familial Parkinson's disease

BACKGROUND

Epidemiological studies have identified positive family history and exposure to environmental toxins as risk factors for Parkinson's disease (PD). An inherited defect of xenobiotic metabolism could result in increased susceptibility to such toxins. We investigated the frequency of functionally relevant polymorphisms in six detoxification enzymes among patients with PD to elucidate the relation between these polymorphisms and the disease.

METHODS

We obtained brain-tissue samples from 100 patients with apparently sporadic PD and blood samples from 100 living patients with familial PD. For the control group, we extracted DNA from the tissue of 100 pathologically normal brains. The six enzymes analysed in these three groups were: CYP2D6, CYP2E1, NAD(P)H-menadione reductase, glutathione transferases M1 and T1, and N-acetyltransferase 2. We also investigated N-acetyltransferase 2 in 100 blood samples from patients with genetically proven Huntington's disease. We used PCR-based methods and restriction-enzyme analysis to detect polymorphisms.

FINDINGS

The slow acetylator genotype for N-acetyltransferase 2 was more common in the familial PD group (69%) than in all controls (37%). Even after correction for multiple comparisons, this result remained highly significant (p = 0.002) for familial PD compared with normal controls (odds ratio 3.79 [95% CI 2.08-6.90]) and compared with Huntington's disease (2.45 [1.37-4.38], p = 0.004). The slow acetylator frequency for N-acetyltransferase 2 for sporadic PD was between that for Huntington's disease and familial PD. The frequencies of all the other polymorphisms were similar in the two study groups and the normal control group.

INTERPRETATION

We found an association between the slow acetylator genotype for N-acetyltransferase 2 and familial PD. Further studies are needed to investigate the biological relevance of these findings, but slow acetylation could lead to impaired ability of patients with familial PD to handle neurotoxic substances.

GTP cyclohydrolase I mutations in patients with dystonia responsive to anticholinergic drugs

OBJECTIVES

To investigate the hypothesis that GTP cyclohydrolase I (GCH1) mutations are responsible for the phenotype of highly anticholinergic responsive dystonia in patients with apparent primary torsion dystonia.

METHODS

From 107 British patients with clinically diagnosed primary torsion dystonia, seven patients were identified with an excellent response to anticholinergic drugs. All six exons of the GCH1 gene were sequenced in these patients to identify mutations.

RESULTS

Three novel GCH1 mutations were identified in two patients. One patient was a compound heterozygote with asymptomatic carrier parents. The clinical phenotype of patients with and without GCH1 mutations was similar.

CONCLUSIONS

These findings show that a proportion of patients with apparent primary torsion dystonia and a good response to anticholinergic drugs have GCH1 mutations and therefore have a variant of dopa responsive dystonia. The difficulty in distinguishing clinically between patients with and without mutations underscores the importance of considering the diagnosis of a levodopa responsive dystonia in all such patients.

Mitochondrial DNA polymorphisms in pathologically proven Parkinson's disease

To date, five single base pair changes of the mitochondrial DNA have been reported to occur either exclusively or with increased frequency in Caucasian patients with Parkinson's disease (PD) and it has been postulated that these mutations might be casually related to the observed inhibition of mitochondrial respiratory chain function in PD. To evaluate these findings, we analysed the frequency of all five polymorphisms in 100 cases of pathologically proven cases of PD. We were either unable to detect the previously described polymorphisms in our series or found them to be present with the same frequency among controls. Our data do not support the hypothesis of an involvement of the mitochondrial DNA in the pathogenesis of PD.

The GTP-cyclohydrolase I gene in atypical parkinsonian patients: a clinico-genetic study

GTP cyclohydrolase I (GTPCH) has recently been identified as the first causative gene for Dopa-responsive dystonia (DRD). DRD typically presents with dystonia in the lower limbs in childhood, but may produce an akinetic-rigid syndrome in middle and old age. We have sequenced the GTPCH gene in 29 Parkinsonian patients without a positive family history for DRD, but who shared at least one feature of the akinetic-rigid presentation of DRD: 23 patients had at least one living relative who also suffered from an akinetic-rigid syndrome; 2 patients had an abnormally mild course of their parkinsonism which was extremely dopa-responsive. DNA was also analysed from 4 brain samples of patients who were clinically diagnosed as suffering from Parkinson's disease, but then did not show any pathological findings at post mortem. No changes in the sequence of the GTPCH gene were detected. We conclude that so far there is no evidence that mutations of the GTPCH gene are responsible for the development of parkinsonism in patients without a positive family history of DRD.

The human homologue of the weaver mouse gene in familial and sporadic Parkinson's disease

The pathological hallmark of Parkinson's disease is cell death of dopaminergic neurons in the substantia nigra, resulting in striatal dopaminergic deficit and a clinical syndrome dominated by disorders of movement. The cause for this cell loss is unknown, but the possibility of a contributing genetic factor is increasingly recognized. Homozygous weaver mice, a mutant mouse strain, display progressive postnatal depletion of dopaminergic cells in the mesencephalon and have thus been proposed as an animal model for Parkinson's disease. Recently, mGIRK2, a putative G-protein inward rectifier K+ channel, has been identified as the causative gene in the weaver mouse and a homozygous mutation has been described in the H5 pore region of this channel. The human homologue of mGIRK2, KCNJ7 or hiGIRK2, has previously been isolated on chromosome 21q22.1. A possible involvement of this gene in the pathogenesis of Parkinson's disease has been discussed. To evaluate the possibility of a shared genetic defect in weaver mouse and Parkinson's disease, we analysed the H5 pore region of hiGIRK2 in familial and sporadic cases of Parkinson's disease. The sequence was normal in all cases examined, suggesting a differing aetiology of nigral cell loss in Parkinson's disease and weaver mice.

Dopa-responsive dystonia in British patients: new mutations of the GTP-cyclohydrolase I gene and evidence for genetic heterogeneity

Dopa-responsive dystonia (DRD) was originally described in a series of Japanese patients, but is now increasingly recognized in other countries. Recently the GTP cyclohydrolase I (GTPCH) gene was isolated as the first causative gene for dopa-responsive dystonia (DRD). Mutations were identified in three Japanese families with autosomal dominantly inherited DRD and in one sporadic Japanese patient. Characterisation of the exon-intron boundaries of this gene has now allowed the analysis of mutations at the level of genomic DNA. Amplifying all six exons, we analyzed the GTPCH gene in nine British families with 33 affected family members and in three sporadic cases and found six new mutations. Only point mutations were found, causing a stop codon in one family and an amino acid change in highly conserved regions of the gene in a further four families and in one sporadic case. None of these mutations were detected more than once and none of the mutations previously described were found in our patients. No mutations were identified in four families and in two sporadic cases.

Signal changes on MRI and increases in reactive microgliosis, astrogliosis, and iron in the putamen of two patients with multiple system atrophy

A correlation of clinical, MRI, and neuropathological data is reported in two patients with multiple system atrophy (MSA). On MRI, patient 1 showed striatal atrophy, reduction of T2 relaxation times within most of the putamen, and a band of hyperintense signal changes in the lateral putamen. In patient 2, MRI disclosed only shortening of the T2 signal in the putamen. Immunohistochemistry showed pronounced reactive microgliosis and astrogliosis in the affected brain regions. In patient 1, the area with the most pronounced microgliosis and astrogliosis most likely correlated with the area of hyperintense signal changes on MRI. This area also contained the highest amount of ferric iron, which was increased in the putamen of patient 1 but not patient 2. It is unlikely that the hypointense signal changes in the putamen are due to an increase of iron alone. Reactive microglial and astroglial cells may play a part in the pathogenesis of MSA.

Sequence of the superoxide dismutase 1 (SOD 1) gene in familial Parkinson's disease

Mutations in the superoxide dismutase 1 (SOD1) gene have been detected in affected members of some families with familial amyotrophic lateral sclerosis. To evaluate the possibility of a shared genetic defect in amyotrophic lateral sclerosis and Parkinson's disease, the SOD1 gene was sequenced in index patients with familial Parkinson's disease from 23 families. No changes were detected.

CYP2D6-debrisoquine hydroxylase gene polymorphism in multiple system atrophy

Molecular genetic studies of the cytochrome P450 system enzyme CYP2D6, which hydroxylates debrisoquine, have indicated an excess of mutant alleles in large series of patients with Parkinson's disease (PD) when compared with controls. We have investigated CYP2D6 polymorphism in 91 patients with multiple system atrophy (MSA) in order to determine if this finding is specific to PD or if there is similar evidence of genetic susceptibility to neurotoxicity in MSA. The distribution of CYP2D6 alleles was not significantly different between MSA patients and controls, and there were fewer poor metabolisers in the MSA group than in the control group.

Apo E genotypes in multiple sclerosis, Parkinson's disease, schwannomas and late-onset Alzheimer's disease

Apolipoprotein E (apo E) exists in three allelic, functionally distinct isoforms (apo E2, E3 and E4). Recent work has suggested that apo-E-dependent uptake of lipoproteins may play important roles in the development and maintenance of the nervous system and in the responses to both peripheral and central nervous system injury. If apo-E-mediated transport of lipids were a rate-limiting step in these processes, one might expect that the functional differences between the alleles would be associated with varying predispositions to neurodegenerative and demyelinating diseases. Thus, we looked for an association between particular apo E genotypes and susceptibility to multiple sclerosis and Parkinson's disease. If apo-E-mediated cholesterol uptake were limiting in neuronal growth, one might also expect that apo E2 alleles would slow CNS tumour growth. Accordingly, apo E genotypes were investigated in individuals with sporadic vestibular schwannomas and neurofibromatosis type 2 (NF-2). No significant alteration in the apo E allele distributions was observed in any of these conditions, nor did the apo E genotypes correlate with disease severity. However, we confirmed the previous findings of an over-representation of the apo E4 allele in autopsy-diagnosed late-onset Alzheimer's disease patients. In addition, our data supported the recent observations that apo E2 may be associated with a protective effect for late-onset Alzheimer's disease. These contrasting risks associated with the apo E2 and E4 alleles strengthen the suggestions that this gene is directly involved in the pathogenesis of Alzheimer's disease.

A contrast enhanced lesion of the III nerve on MR of a patient with ophthalmoplegic migraine as evidence for a Tolosa-Hunt syndrome

A 23-year-old female with a six year history of migraine without aura twice developed a nearly complete internal and external III nerve paresis ipsilateral to her headache, two days after the onset of migraineous headache. An MR scan performed one week after the second episode showed a contrast enhanced lesion of the prepontine III nerve, where it enters the cavernous sinus on the left side. The headache, as well as the paresis ameliorated spontaneously. We suggest this is a further well documented case of "ophthalmoplegic migraine" which might reflect Tolosa-Hunt syndrome.

3H-spiperone binding to lymphocytes fails in the differential diagnosis of de novo Parkinson syndromes

In order to investigate the diagnostic value of 3H-spiperone binding capacity to lymphocytes in the differential diagnosis of de novo Parkinson's disease (idiopathic Parkinson syndrome, PD), we performed a double blind prospective study of spiperone binding capacity of 123 patients and 23 healthy control persons, belonging to different diagnostic groups (PD, Parkinsonian syndrome due to vascular lesions, multiple system atrophy [MSA], essential tremor). Diagnoses were based on medical history, clinical examination, CT or MRI scan, acute response to dopamimetic drugs, one year follow up, and long term response to L-DOPA treatment. Spiperone binding was assayed using ten different concentrations (0.03-3 nmol) in absence or presence of 1 mumol (+)-butaclamol to determine nonspecific binding. There was no significant difference in spiperone binding between patients with PD not treated with L-DOPA, and patients with other basal ganglia disorders including parkinsonian syndrome due to vascular lesions, multiple system atrophy, or progressive supranuclear palsy, and age matched controls. Binding was significantly higher in parkinsonian patients with PD treated with L-DOPA and patients with essential tremor. It is concluded that at present 3H-spiperone binding gives no further information in the differential diagnosis of de novo Parkinson's disease.