Genotype-phenotype correlation of paroxysmal nonkinesigenic dyskinesia.

BACKGROUND: Paroxysmal nonkinesigenic dyskinesia (PNKD) is a rare disorder characterized by episodic hyperkinetic movement attacks. We have recently identified mutations in the MR-1 gene causing familial PNKD. METHODS: We reviewed the clinical features of 14 kindreds with familial dyskinesia that was not clearly induced by movement or during sleep. Of these 14 kindreds, 8 had MR-1 mutations and 6 did not. RESULTS: Patients with PNKD with MR-1 mutations had their attack onset in youth (infancy and early childhood). Typical attacks consisted of a mixture of chorea and dystonia in the limbs, face, and trunk, and typical attack duration lasted from 10 minutes to 1 hour. Caffeine, alcohol, and emotional stress were prominent precipitants. Attacks had a favorable response to benzodiazepines, such as clonazepam and diazepam. Attacks in families without MR-1 mutations were more variable in their age at onset, precipitants, clinical features, and response to medications. Several were induced by persistent exercise. CONCLUSIONS: Paroxysmal nonkinesigenic dyskinesia (PNKD) should be strictly defined based on age at onset and ability to precipitate attacks with caffeine and alcohol. Patients with this clinical presentation (which is similar to the phenotype initially reported by Mount and Reback) are likely to harbor myofibrillogenesis regulator 1 (MR-1) gene mutations. Other "PNKD-like" families exist, but atypical features suggests that these subjects are clinically distinct from PNKD and do not have MR-1 mutations. Some may represent paroxysmal exertional dyskinesia.

DLB and PDD boundary issues: diagnosis, treatment, molecular pathology, and biomarkers.

For more than a decade, researchers have refined criteria for the diagnosis of dementia with Lewy bodies (DLB) and at the same time have recognized that cognitive impairment and dementia occur commonly in patients with Parkinson disease (PD). This article addresses the relationship between DLB, PD, and PD with dementia (PDD). The authors agreed to endorse "Lewy body disorders" as the umbrella term for PD, PDD, and DLB, to promote the continued practical use of these three clinical terms, and to encourage efforts at drug discovery that target the mechanisms of neurodegeneration shared by these disorders of alpha-synuclein metabolism. We concluded that the differing temporal sequence of symptoms and clinical features of PDD and DLB justify distinguishing these disorders. However, a single Lewy body disorder model was deemed more useful for studying disease pathogenesis because abnormal neuronal alpha-synuclein inclusions are the defining pathologic process common to both PDD and DLB. There was consensus that improved understanding of the pathobiology of alpha-synuclein should be a major focus of efforts to develop new disease-modifying therapies for these disorders. The group agreed on four important priorities: 1) continued communication between experts who specialize in PDD or DLB; 2) initiation of prospective validation studies with autopsy confirmation of DLB and PDD; 3) development of practical biomarkers for alpha-synuclein pathologies; 4) accelerated efforts to find more effective treatments for these diseases.

BDNF tagging polymorphisms and haplotype analysis in sporadic Parkinson's disease in diverse ethnic groups.

Experimental and clinical data suggest that genetic variations in brain-derived neurotrophic factor (BDNF) gene may affect risk for Parkinson's disease (PD). We performed a case-control association analysis of BDNF in three independent Caucasian cohorts (Greek, North American, and Finnish) of PD using eight tagging SNPs and five constructed haplotypes. No statistically significant differences in genotype and allele frequencies were found between cases and controls in all series. A relatively rare BDNF haplotype showed a trend towards association in the Greek (p=0.02) and the Finnish (p=0.03) series (this haplotype was not detected in the North American series). However, given the large number of comparisons these associations are considered non-significant. In conclusion, our results do not provide statistically significant evidence that common genetic variability in BDNF would associate with the risk for PD in the Caucasian populations studied here.

How common are the "common" neurologic disorders?

OBJECTIVE: To estimate the current incidence and prevalence in the United States of 12 neurologic disorders. METHODS: We summarize the strongest evidence available, using data from the United States or from other developed countries when US data were insufficient. RESULTS: For some disorders, prevalence is a better descriptor of impact; for others, incidence is preferable. Per 1,000 children, estimated prevalence was 5.8 for autism spectrum disorder and 2.4 for cerebral palsy; for Tourette syndrome, the data were insufficient. In the general population, per 1,000, the 1-year prevalence for migraine was 121, 7.1 for epilepsy, and 0.9 for multiple sclerosis. Among the elderly, the prevalence of Alzheimer disease was 67 and that of Parkinson disease was 9.5. For diseases best described by annual incidence per 100,000, the rate for stroke was 183, 101 for major traumatic brain injury, 4.5 for spinal cord injury, and 1.6 for ALS. CONCLUSIONS: Using the best available data, our survey of a limited number of disorders shows that the burden of neurologic illness affects many millions of people in the United States.

Challenges and opportunities in clinical trials for spinal muscular atrophy.

Spinal muscular atrophy (SMA) is the most common fatal neuromuscular disease of infancy. SMA type I is the most severe and mortality is usually due to respiratory failure. In type II the disability is of later onset and less severe, and prognosis has improved primarily due to supportive care. Type III is the mildest form with onset usually of weakness in adolescence or young adulthood. SMA is an autosomal recessive disorder with deletions or mutations of the gene at the 5 q11 locus. There is no specific prevention or treatment, but current progress toward potential therapies has been substantial and several candidates including histone deacetylase (HDAC) inhibitors are under consideration for further evaluation. The authors sought to address the challenges and opportunities for testing new therapies for SMA.

Evidence suggesting that Homo neanderthalensis contributed the H2 MAPT haplotype to Homo sapiens.

The tau (MAPT) locus exists as two distinct clades, H1 and H2. The H1 clade has a normal linkage disequilibrium structure and is the only haplotype found in all populations except those derived from Caucasians. The H2 haplotype is the minor haplotype in Caucasian populations and is not found in other populations. It shows no recombination over a region of 2 Mb with the more common H1 haplotype. The distribution of the haplotype and analysis of the slippage of dinucleotide repeat markers within the haplotype suggest that it entered Homo sapiens populations between approx. 10000 and 30000 years ago. However, sequence comparison of the H2 haplotype with the H1 haplotype and with the chimp sequence suggests that the common founder of the H1 and H2 haplotypes was far earlier than this. We suggest that the H2 haplotype is derived from Homo neanderthalensis and entered H. sapiens populations during the co-existence of these species in Europe from approx. 45000 to 18000 years ago and that the H2 haplotype has been under selection pressure since that time, possibly because of the role of this H1 haplotype in neurodegenerative disease.

The role of radiotracer imaging in Parkinson disease.

Radiotracer imaging (RTI) of the nigrostriatal dopaminergic system is a widely used but controversial biomarker in Parkinson disease (PD). Here the authors review the concepts of biomarker development and the evidence to support the use of four radiotracers as biomarkers in PD: [18F]fluorodopa PET, (+)-[11C]dihydrotetrabenazine PET, [123I]beta-CIT SPECT, and [18F]fluorodeoxyglucose PET. Biomarkers used to study disease biology and facilitate drug discovery and early human trials rely on evidence that they are measuring relevant biologic processes. The four tracers fulfill this criterion, although they do not measure the number or density of dopaminergic neurons. Biomarkers used as diagnostic tests, prognostic tools, or surrogate endpoints must not only have biologic relevance but also a strong linkage to the clinical outcome of interest. No radiotracers fulfill these criteria, and current evidence does not support the use of imaging as a diagnostic tool in clinical practice or as a surrogate endpoint in clinical trials. Mechanistic information added by RTI to clinical trials may be difficult to interpret because of uncertainty about the interaction between the interventions and the tracer.

Analysis of polyglutamine-coding repeats in the TATA-binding protein in different neurodegenerative diseases.

Trinucleotide repeat (TNR) expansion in the gene for TATA binding protein (TBP) has recently been described as causal for spinocerebellar ataxia type 17. The normal number of repeats has been considered to be 42 or less. An intermediate range with reduced penetrance has been assumed to be 43-47 CAA/CAG repeats. We examined this gene in 30 patients with autosomal-dominant cerebellar ataxia (ADCA), 35 patients with sporadic ataxia, 11 patients with Huntington's disease (HD), 351 patients with idiopathic Parkinson's disease (PD), 105 patients with Alzheimer's disease (AD), and 291 controls with no history of neurodegenerative disease. Three patients (one with sporadic PD and two with AD) carrying more than 42 TNRs in the TBP gene were identified. This reveals that the phenotype associated with CAG/CAA expansion in the TBP gene may be heterogeneous.

Clinical evaluation of idiopathic paroxysmal kinesigenic dyskinesia: new diagnostic criteria.

BACKGROUND: Paroxysmal kinesigenic dyskinesia (PKD) is a rare disorder characterized by short episodes of involuntary movement attacks triggered by sudden voluntary movements. Although a genetic basis is suspected in idiopathic cases, the gene has not been discovered. Establishing strict diagnostic criteria will help genetic studies. METHODS: The authors reviewed the clinical features of 121 affected individuals, who were referred for genetic study with a presumptive diagnosis of idiopathic PKD. RESULTS: The majority (79%) of affected subjects had a distinctive homogeneous phenotype. The authors propose the following diagnostic criteria for idiopathic PKD based on this phenotype: identified trigger for the attacks (sudden movements), short duration of attacks (<1 minute), lack of loss of consciousness or pain during attacks, antiepileptic drug responsiveness, exclusion of other organic diseases, and age at onset between 1 and 20 years if there is no family history (age at onset may be applied less stringently in those with family history). In comparing familial and sporadic cases, sporadic cases were more frequently male, and infantile convulsions were more common in the familial kindreds. Females had a higher remission rate than males. An infantile-onset group with a different set of characteristics was identified. A clear kinesigenic trigger was not elicited in all cases, antiepileptic response was not universal, and some infants had attacks while asleep. CONCLUSIONS: The diagnosis of idiopathic paroxysmal kinesigenic dyskinesia (PKD) can be made based on historical features. The correct diagnosis has implications for treatment and prognosis, and the diagnostic scheme may allow better focus in the search for the PKD gene(s).

SNCA multiplication is not a common cause of Parkinson disease or dementia with Lewy bodies.

The authors recently have shown that triplication of the alpha-synuclein gene (SNCA) can cause Parkinson disease (PD) and diffuse Lewy body disease within the same kindred. The authors assessed 101 familial PD probands, 325 sporadic PD cases, 65 patients with dementia with Lewy bodies, and 366 neurologically normal control subjects for SNCA multiplication. The authors did not identify any subjects with multiplication of SNCA and conclude this mutation is a rare cause of disease.

DNA haplotype analysis of CAG repeat in Taiwanese Huntington's disease patients.

We studied the expanded CAG repeat and adjacent CCG repeat in 53 Huntington's disease (HD) patients and 172 unrelated normal subjects matched to the patients for ethnic origin. The range of the CAG repeat varied from 38 to 109 in the HD patients and from 10 to 29 in the control group. A significant negative correlation was found between the age at onset and the CAG expansion, with no significant influence of the adjacent CCG repeat on the age at onset by multiple regression analysis. Allelic association using CCG repeat and 2 flanking dinucleotide repeat markers within 150 kb of the HD gene revealed linkage disequilibrium for 2 of 3 markers. Haplotype analysis of 24 HD families using these markers identified 3 major haplotypes underlying 87.5% of HD chromosomes. The data suggested frequent haplotypes in the Taiwanese population on which one or more mutational events leading to the disease occurred.

Alpha-synuclein in blood and brain from familial Parkinson disease with SNCA locus triplication.

The authors recently demonstrated that genetic triplication of the SNCA locus causes Parkinson disease. Here it is shown that SNCA triplication results in a doubling in the amount of alpha-synuclein protein in blood. Examination of brain tissue showed a doubling in the level of SNCA message. However, at the protein level in brain, there was a greater effect on deposition of aggregated forms into insoluble fractions than on net expression of soluble alpha-synuclein.

Genetic testing in spinocerebellar ataxia in Taiwan: expansions of trinucleotide repeats in SCA8 and SCA17 are associated with typical Parkinson's disease.

DNA tests in normal subjects and patients with ataxia and Parkinson's disease (PD) were carried out to assess the frequency of spinocerebellar ataxia (SCA) and to document the distribution of SCA mutations underlying ethnic Chinese in Taiwan. MJD/SCA3 (46%) was the most common autosomal dominant SCA in the Taiwanese cohort, followed by SCA6 (18%) and SCA1 (3%). No expansions of SCA types 2, 10, 12, or dentatorubropallidoluysian atrophy (DRPLA) were detected. The clinical phenotypes of these affected SCA patients were very heterogeneous. All of them showed clinical symptoms of cerebellar ataxia, with or without other associated features. The frequencies of large normal alleles are closely associated with the prevalence of SCA1, SCA2, MJD/SCA3, SCA6, and DRPLA among Taiwanese, Japanese, and Caucasians. Interestingly, abnormal expansions of SCA8 and SCA17 genes were detected in patients with PD. The clinical presentation for these patients is typical of idiopathic PD with the following characteristics: late onset of disease, resting tremor in the limbs, rigidity, bradykinesia, and a good response to levodopa. This study appears to be the first report describing the PD phenotype in association with an expanded allele in the TATA-binding protein gene and suggests that SCA8 may also be a cause of typical PD.

Neuropathology of two members of a German-American kindred (Family C) with late onset parkinsonism.

We present genealogical and longitudinal clinical observations and autopsy findings of a previously reported kindred, Family C (German-American), with late-onset autosomal dominant parkinsonism with evidence for linkage on chromosome 2p13. The clinical phenotype includes the cardinal features of idiopathic Parkinson's disease. In addition, postural tremor and dementia are detected in some individuals. Two members of the kindred, one affected and one unaffected have recently come to autopsy. The unaffected family member was an 82-year-old woman whose brain showed only mild age-related pathology and no evidence of subclinical Lewy body disease. In contrast, the affected family member was an 83-year-old man whose brain had neuronal loss, gliosis and Lewy bodies in the substantia nigra and other monoaminergic brain stem nuclei, as well as the basal forebrain and amygdala. Lewy bodies and Lewy neurites had a distribution typical of cases of idiopathic Parkinson's disease. Thus, the clinical and pathological findings in this family with autosomal dominant parkinsonism are similar to those of sporadic Parkinson's disease.

Persistent chorea triggered by hyperglycemic crisis in diabetics.

Five female patients developed chorea concurrent with, or shortly after a hyperglycemic episode (admission glucose values 500-1,000 mg/dL). In four of these five patients, there was no prior history of diabetes mellitus. The chorea continued despite correction of blood glucose and persisted to the time of last follow-up, 6 months to 5 years later. The chorea developed subacutely over 2 days to 1 month and was generalized in one, unilateral in three, and involved right > left lower extremity in the other; the severity initially reached ballistic proportions in two. Associated clinical features were nil in four of these patients, but cognitive impairment and personality change occurred in one. The histories and laboratory studies identified no predisposing factors other than the hyperglycemia. The chorea was sufficiently troublesome to require administration of neuroleptic medication in all five cases. Four of the five cases had high signal intensity within basal ganglia on T1-weighted magnetic resonance (MR) imaging, as has previously been described; however, this was not seen in one case (who had the most severe clinical condition). Most previously described cases have involved a reversible clinical syndrome, in contrast to our patients. The pathogenic mechanisms remain uncertain.

Serum leptin concentrations and satiety in Parkinson's disease patients with and without weight loss.

We compared serum leptin and satiety measures in 18 Parkinson's disease (PD) patients with unintended weight loss (WL) and 18 PD patients whose weight was stable (WS). Mean serum leptin concentrations tended to be lower in WL than WS patients, but this did not reach statistical significance. Body mass index correlated with serum leptin concentrations. Ratings of hunger, satiety, fullness, and thirst did not differ between groups. However, the mean sensation of fullness before meals correlated with serum leptin in the entire cohort of patients, particularly in the WL group. The results indicate that unintended weight loss in PD patients is unlikely to be due to abnormal serum leptin concentrations.

A clinical and pathological study of motor neurone disease on Guam.

Despite over 40 years of intensive study, the cause of the high incidence of motor neurone disease (MND) on Guam, and the relationship between this disease and MND seen in the rest of the world are still uncertain. We present a series of 45 cases of Guamanian MND, which reaffirm the clinical similarity between this disease and MND seen in other countries. However, the occurrence of MND among the indigenous Chamorros of Guam is distinguished by four factors: (i) high prevalence; (ii) frequent familial occurrence; (iii) co-occurrence with the parkinsonism-dementia complex (PDC); and (iv) association with an unusual and distinctive linear retinopathy termed Guam retinal pigment epitheliopathy (GRPE). These distinguishing factors were not present in four non-Chamorros who resided on Guam when their MND symptoms occurred. Pathologically, the classical features of MND were seen in Guamanian Chamorro cases including ubiquitin inclusions. Neurofibrillary tangles were frequently seen. The neurofibrillary tangles appeared in the same distribution as described in the PDC but, unlike classical PDC, they were not usually associated with cell loss and occurred less frequently. While neurofibrillary tangle formation and the clinicopathological syndrome of MND may occur in parallel, observations from this series suggest that pathologically classical MND on Guam may occur independently of neurofibrillary degeneration and the clinical features of PDC.

Lewy bodies and parkinsonism in families with parkin mutations.

Previous work has established that compound mutations and homozygous loss of function of the parkin gene cause early-onset, autosomal recessive parkinsonism. Classically, this disease has been associated with loss of dopaminergic neurons in the substantia nigra pars compacta and locus ceruleus, without Lewy body pathology. We have sequenced the parkin gene of 38 patients with early-onset Parkinson's disease (<41 years). Two probands with mutations were followed up. Clinical evaluation of their families was performed, blinded to both genetic and pathological findings. Chromosome 6q25.2-27 haplotype analysis was carried out independently of the trait; parkin gene expression was examined at both the RNA and protein levels. Haplotype analysis of these families revealed a common chromosome 6, with a novel 40 bp exon 3 deletion that cosegregated with disease. In the proband of the smaller kindred, an exon 7 R275W substitution was identified in addition to the exon 3 deletion; RNA analysis demonstrated that the mutations were on alternate transcripts. However, Lewy body pathology typical of idiopathic Parkinson's disease was found at autopsy in the proband from the smaller kindred. These data suggest that compound heterozygous parkin mutations and loss of parkin protein may lead to early-onset parkinsonism with Lewy body pathology, while a hemizygous mutation may confer increased susceptibility to typical Parkinson's disease.