Classification of the hereditary ataxias and paraplegias

Hereditary spastic paraparesis (HSP) or the Strumpell-Lorrain syndrome is the name given to a heterogeneous group of inherited disorders in which the main clinical feature is progressive lower limb spasticity. Before the advent of molecular genetic studies into these disorders, several classifications had been proposed, based on the mode of inheritance, the age of onset of symptoms, and the presence or otherwise of additional clinical features. Families with autosomal dominant, autosomal recessive, and X-linked inheritance have been described.

https://jnnp.bmj.com/content/jnnp/69/2/150.full.pdf

Hereditary spastic paraparesis: a review of new developments

The system of assigning locus symbols to specify chromosomal regions that are associated with a familial disorder has a number of problems when used as a reference list of genetically determined disorders,including (I) erroneously assigned loci, (II) duplicated loci, (III) missing symbols or loci, (IV) unconfirmed loci and genes, (V) a combination of causative genes and risk factor genes in the same list, and (VI) discordance between phenotype and list assignment. In this article, we report on the recommendations of the International Parkinson and Movement Disorder Society Task Force for Nomenclature of Genetic Movement Disorders and present a system for naming genetically determined movement disorders that addresses these problems. We demonstrate how the system would be applied to currently known genetically determined parkinsonism, dystonia, dominantly inherited ataxia, spastic paraparesis, chorea, paroxysmal movement disorders, neurodegeneration with brain iron accumulation, and primary familial brain calcifications. This system provides a resource for clinicians and researchers that, unlike the previous system, can be considered an accurate and criterion-based list of confirmed genetically determined movement disorders at the time it was last updated.

Nomenclature of genetic movement disorders: Recommendations of the International Parkinson and Movement Disorder Society task force

Knowledge of the genetic demography of Quebec is useful for gene mapping, diagnosis, treatment, community genetics and public health. The French-Canadian population of Quebec, currently about 6 million people, descends from about 8500 French settlers who arrived in Nouvelle-France between 1608 and 1759. The migrations of those settlers and their descendants led to a series of regional founder effects, reflected in the geographical distribution of genetic diseases in Quebec. This review describes elements of population history and clinical genetics pertinent to the treatment of French Canadians and other population groups from Quebec and summarizes the cardinal features of over 30 conditions reported in French Canadians. Some were discovered in French Canadians, such as autosomal recessive ataxia of the Charlevoix-Saguenay (MIM 270550), agenesis of corpus callosum and peripheral neuropathy (MIM 218000) and French-Canadian-type Leigh syndrome (MIM 220111). Other conditions are particularly frequent or have special genetic characteristics in French Canadians, including oculopharyngeal muscular dystrophy, hepatorenal tyrosinaemia, cystic fibrosis, Leber hereditary optic neuropathy and familial hypercholesterolaemia. Three genetic diseases of Quebec First Nations children are also discussed: Cree encephalitis (MIM 608505), Cree leukoencephalopathy (MIM 603896) and North American Indian childhood cirrhosis (MIM 604901).

Population history and its impact on medical genetics in Quebec.

Mitochondrial dysfunction and oxidative damage are at the origin of numerous neurodegenerative diseases like Friedreich ataxia and Alzheimer and Parkinson diseases. Friedreich ataxia (FRDA) is the most common hereditary ataxia, with one individual affected in 50,000. This disease is characterized by progressive degeneration of the central and peripheral nervous systems, cardiomyopathy, and increased incidence of diabetes mellitus. FRDA is caused by a dynamic mutation, a GAA trinucleotide repeat expansion, in the first intron of the FXN gene. Fewer than 5% of the patients are heterozygous and carry point mutations in the other allele. The molecular consequences of the GAA triplet expansion is transcription silencing and reduced expression of the encoded mitochondrial protein, frataxin. The precise cellular role of frataxin is not known; however, it is clear now that several mitochondrial functions are not performed correctly in patient cells. The affected functions include respiration, iron–sulfur...

Friedreich Ataxia: Molecular Mechanisms, Redox Considerations, and Therapeutic Opportunities

A new syndrome of autosomal recessive spastic ataxia has been isolated in the Charlevoix-Saguenay region of Quebec. This syndrome is remarkably homogeneous and includes: spasticity, dysarthria, distal muscle wasting, foot deformities, truncal ataxia, absence of sensory evoked potentials in the lower limbs, retinal striation reminiscent of early Leber's atrophy and the frequent presence (57%) of a prolapse of the mitral valve. Biochemically, many cases show impaired pyruvate oxidation, others have hyperbilirubinaemia and some have low serum beta-lipoproteins and HDL apoproteins. These features are similar to those found in typical Friedreich's ataxia.

/pdf/autosomal-recessive-spastic-ataxia-of-charlevoix-saguenay-2vojldrz39.pdf

Autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Twenty four ataxic patients were investigated with electromyography and nerve conduction studies. They were divided in two groups according to the area they came from, the evolution of the disease, and the clinical signs. Group I patients from the Rimouski area displayed all the clinical and electrophysiological signs of Friedreich's ataxia. Group II comprised patients who presented with a new syndrome known as the autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Although the clinical evolution was better in the latter, there were more electromyographic signs of denervation and the motor conduction velocities were slower. Both groups showed identical and important abnormalities in sensory nerve conduction. The results of electrophysiological studies in spastic ataxia have not been reported to our knowledge. They underline the place of spastic ataxia as distinct from Friedreich's ataxia, spastic paraplegia, and the known familial neuropathies.

/pdf/electromyography-and-nerve-conduction-studies-in-friedreich-pfjpknllg9.pdf

Electromyography and nerve conduction studies in Friedreich's ataxia and autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS).

We described a cluster of 8 independent sibships of Friedreich's ataxia in the St-Fabien parish of Rimouski and have shown that they are all related within 6 generations. The study of this geographic and genetic isolate permitted the investigation of certain unusual features of the disease such as constant myopia, delayed reaction times to pain, flexor spasms, and a rapid evolution.

/pdf/a-cluster-of-friedreich-s-ataxia-in-rimouski-quebec-28s1au4dy5.pdf

A cluster of Friedreich's ataxia in Rimouski, Québec.

Electroencephalographie studies have heen done in two groups of hereditary ataxia: a group hearing the classical features of Friedreich's ataxia and a group clinically different described as autosomal recessive spastic ataxia of Charlevoix-Saguenay (A RSA CS). The qualitative anomalies observed in the two Ķroups were similar and were comparable with the data reported in the literature. However, the main difference between the two groups is the greater incidence of EEG abnormalities in the A RSA CS group, which suggests more involvement of the cortical and subcortical structures. This is reinforced by the lower I.Q. performance in the latter patients. Some comments are made about focal EEG findings, behavior and I.Q. In general, EEG was not considered a valuable instrument for diagnosis since no qualitative electric pattern could be identified. With regard to prognosis, EEG cannot be used as a criterion, since there is no relation between the degree of anomalies and the severity of the disease and since EEG does not worsen with the progression of the disease.

Electroencephalographic Findings in Friedreich's Ataxia and Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS)

The plasma distribution of alpha-keto acids was measured in 26 subjects including 8 patients with Friedreich's ataxia, 8 with the recessive spastic ataxia of Charlevoix-Sageunay and 10 healthy volunteers. The groups were matched with regards to age, sex, weight and the study was conducted under standardized dietary intake. The result indicate significant differences in the alpha-keto acids distribution between the groups.

R. Bouchard

Papers

Autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Electromyography and nerve conduction studies in Friedreich's ataxia and autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS).

A cluster of Friedreich's ataxia in Rimouski, Québec.

Electroencephalographic Findings in Friedreich's Ataxia and Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS)

Quantitative metabolic profiling of alpha-keto acids in Friedreich's ataxia.