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Perturbation of precision grip in Friedreich's ataxia and late-onset cerebellar ataxia.

Perturbations of precision grip were tested in 7 patients with Friedreich's ataxia (FA) and 11 patients with late-onset cerebellar ataxia (CA). Subjects were instructed to hold a small compressible manipulandum between thumb and index finger and to resist any perturbation of maintained finger position. A sudden increase of load induced a displacement of fingers until this was stopped by subjects' active intervention. The amount of initial displacement emerged as a highly sensitive parameter to differentiate the clinical subgroups: Responses in FA patients were missing or massively delayed, whereas displacements in CA patients were normal or only moderately abnormal. This discrimination of impaired hand function in FA and CA patients has not been possible by using only tasks of isometric grip force control. We concluded that our task relies more on intact sensory afferents, which are known to be impaired in FA, than on cerebellar function. In a second task the stiffness of the maintained grip was determined. On the average, preresponse stiffness was lower in FA patients as compared with CA patients and normal controls. However, stiffness appeared to be an independent parameter that did not influence the amount of displacement in the perturbation task.

Adolescent↗

Is the sensory neuropathy in ataxia-telangiectasia distinguishable from that in Friedreich's ataxia? Morphometric and ultrastructural study of the sural nerve in a case of Louis Bar syndrome.

The bioptical morphometric and ultrastructural study of sural nerve in a 17-year-old boy with ataxia-telangiectasia (AT) is reported. Our findings include a loss of fibers, particularly of large ones, axonal degenerative changes, Schwann cell inclusions of various type, and rare signs of primary demyelination. Teased-fiber study showed paranodal myelin enlargements, segmental demyelination, shortening, and/or variability of internodal length. This picture is similar to that in Friedreich's ataxia (FA), although they differ in degree and time of onset. A correct neuropathologic diagnosis of AT cannot be made on the basis of sural nerve biopsy alone.

Adolescent↗

Familial myoclonic epilepsy with ataxia and neuropathy with additional features of Friedreich's ataxia and peroneal muscular atrophy.

A family is described in which a mother and three of her five children showed myoclonic epilepsy. The mother and one son were also ataxic; one other son had additional features of Friedreich's ataxia, and a daughter had peroneal muscular atrophy as well as myoclonic epilepsy and ataxia. Although some of these disorders have been associated in previously reported families, the occurrence of all three disorders in members of one family seems to be unique. It is concluded that this family shows the manifestations of one, probably dominant, gene. The differences in age of onset and manifestations may be explained by the action of one or more subsidiary genes.

Adult↗

International Cooperative Ataxia Rating Scale (ICARS): appropriate for studies of Friedreich's ataxia?

Clinicians require scientifically rigorous, clinically meaningful rating scales to evaluate the health impact of disease and treatment that cannot be measured using conventional laboratory instruments. This study evaluated the psychometric properties of the International Cooperative Ataxia Rating Scale (ICARS), a commonly used clinician-rated measure, in Friedreich's ataxia (FRDA). People with confirmed FRDA were assessed by using the ICARS. Two assumptions of its measurement model were tested: the legitimacy of reporting ICARS scores in FRDA, and the acceptability, reliability, and validity of total and subscale scores. Seventy-seven people with FRDA were assessed. The ICARS total score effectively satisfied all psychometric criteria tested. The posture and gait disturbances subscale also performed well. The other three subscales did not pass standard criteria for tests of scaling assumptions, reliability, and validity. This small study recommends only the use of the ICARS total score as a measure of FRDA. However, the extent to which this score quantifies the true extent of FRDA remains uncertain as our validity testing was limited, partly by the lack of appropriate validating measures. Further validity testing, and examination of responsiveness, is required before the ICARS can be recommended as an outcome measure for treatment trials of FDRA.

Adolescent↗

Molecular characterization of ataxia telangiectasia T cell clones. II. The clonal inv(14) in ataxia telangiectasia differs from the inv(14) in T cell lymphoma.

We compared inversions of chromosome 14 in an ataxia telangiectasia clone and in a malignant T cell line (SUP-T1). The R-banding chromosome analysis showed a clear difference between the distal breakpoint of the two inversions. Fine mapping of the distal breakpoint in the ataxia telangiectasia inv(14) was performed by in situ hybridization. We conclude that this breakpoint is centromeric to the immunoglobulin heavy chain locus and to the D14S1 anonymous locus. Our results favor the existence of an unknown oncogene in band 14q32.1.

Ataxia Telangiectasia↗

Genomic organisation of the spinocerebellar ataxia type 7 (SCA7) gene responsible for autosomal dominant cerebellar ataxia with retinal degeneration.

Autosomal dominant cerebellar ataxia with retinal degeneration (ADCA type II) is a progressive neurodegenerative disorder caused by a CAG expansion in the spinocerebellar ataxia 7 (SCA7) gene. Here, we describe the genomic organisation of the human SCA7 gene. The exon-intron boundaries were identified by sequencing plasmid subclones of a P1 artificial chromosome (PAC) clone containing the entire SCA7 gene. We found 13 exons, ranging in size from 69 to 979 bp, with all exon-intron boundaries following the GT-AG rule. The ATG initiation codon at position 554 of the cDNA occurs in exon 3 at position 12 and the coding region extends to the first five codons of exon 13, with the CAG repeat being located in exon 3 starting at codon 30. The intron sizes were determined by long-distance polymerase chain reaction with primers from neighbouring exons and by restriction mapping of the SCA7 PAC clone. The introns varied in size from 233 bp to about 40 kb, resulting in an overall size estimate for the SCA7 gene of 140 kb. Sequence analysis of intron 7 (491 bp) revealed a polymorphic GT/AC repeat, a useful intragenic marker for SCA7 in segregation studies.

Base Sequence↗

Ionizing radiation-dependent gamma-H2AX focus formation requires ataxia telangiectasia mutated and ataxia telangiectasia mutated and Rad3-related.

The histone variant H2AX is rapidly phosphorylated at the sites of DNA double-strand breaks (DSBs). This phosphorylated H2AX (gamma-H2AX) is involved in the retention of repair and signaling factor complexes at sites of DNA damage. The dependency of this phosphorylation on the various PI3K-related protein kinases (in mammals, ataxia telangiectasia mutated and Rad3-related [ATR], ataxia telangiectasia mutated [ATM], and DNA-PKCs) has been a subject of debate; it has been suggested that ATM is required for the induction of foci at DSBs, whereas ATR is involved in the recognition of stalled replication forks. In this study, using Arabidopsis as a model system, we investigated the ATR and ATM dependency of the formation of gamma-H2AX foci in M-phase cells exposed to ionizing radiation (IR). We find that although the majority of these foci are ATM-dependent, approximately 10% of IR-induced gamma-H2AX foci require, instead, functional ATR. This indicates that even in the absence of DNA replication, a distinct subset of IR-induced damage is recognized by ATR. In addition, we find that in plants, gamma-H2AX foci are induced at only one-third the rate observed in yeasts and mammals. This result may partly account for the relatively high radioresistance of plants versus yeast and mammals.

Arabidopsis↗

Autosomal dominant cerebellar ataxia type I. MRI-based volumetry of posterior fossa structures and basal ganglia in spinocerebellar ataxia types 1, 2 and 3.

Twenty-six patients suffering from autosomal dominant cerebellar ataxia type I were subjected to a genotype-phenotype correlation analysis using molecular genetic assignment to the genetic loci for spinocerebellar ataxia type 1, 2 or 3 (SCA1, SCA2, SCA3) and MRI-based volumetry of posterior fossa structures and basal ganglia nuclei. There was significant atrophy of the cerebellum and brainstem in all three SCA mutations compared with a group of 31 age- and sex-matched controls. Comparison between the SCA groups showed that cerebellar and brainstem atrophy was more severe in SCA2 than in SCA1 and SCA3. Putaminal and caudate volume was reduced only in SCA3, but not in SCA1 and SCA2. A set of three morphological criteria was defined that enabled us to assign all SCA2 and SCA3 patients correctly to the underlying genotype. In contrast, these criteria did not distinguish SCA1 from SCA2 and SCA3. Regression analysis failed to reveal a significant association between CAG repeat length and the volumes of the respective brain structures in any of the SCA mutant types. The present data provide in vivo evidence that SCA2 and SCA3 lead to distinct patterns of brain atrophy, while the atrophy changes in SCA1 overlap with both SCA2 and SCA3.

Adult↗

Thalamic involvement in a spinocerebellar ataxia type 2 (SCA2) and a spinocerebellar ataxia type 3 (SCA3) patient, and its clinical relevance.

In spite of the considerable progress in clinical and molecular research, knowledge regarding brain damage in spinocerebellar ataxia type 2 (SCA2) and type 3 (SCA3) still is limited and the extent to which the thalamus is involved in both diseases is uncertain. Accordingly, we performed a pathoanatomical analysis on serial thick sections stained for lipofuscin granules and Nissl substance through the thalami of two genetically confirmed cases: one an SCA2 patient, the other an SCA3 patient. During this systematic study, we detected severe destruction of the reticular (RT), fasciculosus (FA), ventral anterior (VA), ventral lateral (VL), ventral posterior lateral (VPL), ventral posterior medial (VPM), cucullar (CU) and mediodorsal thalamic nuclei (MD), the lateral geniculate body (LGB) and inferior nucleus of the pulvinar (PU i) in the SCA2 case, and a severe neuronal loss in the RT, FA, VA and PU i of the SCA3 case. In the SCA2 patient, additional obvious neuronal loss was observed in all nuclei of the anterior and rostral intra laminar groups, in the lateral posterior nucleus (LP), the lateral (PU l) and the medial subnuclei of the pulvinar (PU m), whereas in the SCA3 patient only two of the nuclei that belong to the anterior thalamic group, the VL, VPL, VPM, LP, LGB, PU l and PU m, displayed marked neurodegeneration. These novel findings indicate that thalamic involvement in SCA2 and SCA3 patients has been underestimated in the past. In view of what is known about the functions of the affected thalamic nuclei, the present findings provide an appropriate pathoanatomical explanation for some of the disease-related symptoms seen in both of our and other SCA2 and SCA3 patients: gait, stance, truncal and limb ataxia, dysarthria or anarthria, falls, dysdiadochokinesia and bradykinesia, problems with writing, somatosensory deficits, saccadic dysfunctions, executive dysfunctions and abnormalities of visual evoked potentials.

Adolescent↗

Broadened Friedreich's ataxia phenotype after gene cloning. Minimal GAA expansion causes late-onset spastic ataxia.

We describe three siblings from an Italian family affected by an autosomal recessive spinocerebellar degeneration. Gait ataxia, presenting between 38 and 45 years, was the first symptom in all three patients. Dysarthria, dysmetria, brisk tendon reflexes, extensor plantar response, and scoliosis were constant features. Disease progression was slow. Electrophysiologic studies demonstrated a slight reduction in sural nerve sensory action potential in only one patient. Analysis of GAA expansion within the X25 gene showed that patients were homozygous for the expansion, with the shorter expanded allele ranging from 120 to 156 triplets. The size of the GAA expansion may be smaller than we previously described. Such minimal expansions may result in atypical forms of Friedreich's ataxia.

Action Potentials↗

Early onset hereditary spinocerebellar ataxia: an autosomal recessive disorder distinct from Friedreich's ataxia.

The important clinical features of seven patients with an early onset slowly progressive heredofamilial spinocerebellar degenerative disorder of probably autosomal recessive inheritance included limb ataxia, retained and/or exaggerated tendon reflexes (biceps and knee), pyramidal weakness of lower limbs and normal sensory action potentials. This rare disorder is probably distinct from Friedreich's ataxia and carries a better prognosis.

Adolescent↗

Hereditary paroxysmal ataxia with mental retardation: a clinicopathological study in relation to episodic ataxia type 2.

A case of hereditary acetazolamide-responsive paroxysmal ataxia with mild mental retardation in an autopsied Japanese man is described. His ataxic attacks had occurred for approximately 65 years since the age of 6. One of his daughters had severe mental retardation and epilepsy, and the other had paroxysmal ataxic attacks and mild mental retardation. Analysis of the subject's CACNA1A gene and that in his daughter revealed neither mutations nor CAG expansion. Neuropathologically, cortical degeneration consisting of the marked loss of Purkinje and granule cells was found exclusively in the cerebellar vermis. This was consistent with findings at autopsy for cases reported as spinocerebellar ataxia 6. In addition, there were minor anomalies, such as hypoplastic cerebellum and brainstem, heterotopic Purkinje cells, and cortical microdysgenesis of the temporal lobe. It is considered that the cerebellar cortical degeneration and the minor malformations found in the brain are closely related to one another, rather than having occurred independently.

Adult↗

Heterogeneous findings in four cases of cerebellar ataxia associated with hypogonadism (Holmes' type ataxia).

We report four sporadic cases of cerebellar ataxia associated with hypogonadism. All patients were female. The neurological symptoms appeared in the first three decades. Apart from ataxia, the most frequent features were nystagmus, dysarthria, mental impairment, brisk tendon reflexes, skeletal deformities, peripheral neuropathy, and tremor. Neuroimaging studies showed constant cerebellar atrophy, in some instances associated with involvement of either grey or white cerebral matter. Neurophysiological studies demonstrated an axonal neuropathy. Endocrine evaluation showed heterogeneity of the hypogonadism, which was hypogonadotrophic in one patient and hypergonadotrophic in the other three. One patient had partial deficiency of muscle cytochrome c oxidase. The syndrome appears to be a heterogeneous multisystem disorder and in some cases a mitochondrial metabolism deficiency could be suspected.

Adolescent↗

Spinocerebellar ataxia type 6 with positional vertigo and acetazolamide responsive episodic ataxia.

The SCA6 mutation, a small expansion of a CAG repeat in a calcium channel gene CACNA1A, was identified in three pedigrees. Point mutations in other parts of the gene CACNA1A were excluded and new clinical features of SCA6 reported--namely, central positional nystagmus and episodic ataxia responsive to acetazolamide. The three allelic disorders, episodic ataxia type 2, familial hemiplegic migraine, and SCA6, have overlapping clinical features.

Acetazolamide↗

Neuropsychological test performance in patients with dominantly inherited spinocerebellar ataxia: relationship to ataxia severity.

To determine whether the cognitive status of patients with dominantly inherited spinocerebellar ataxia (DSCA) might be related to neurologic severity, we administered a comprehensive neuropsychological test battery to 43 patients with DSCA, ranging in ataxia severity from mild to end-stage. As compared with the controls, the mildly ataxic patients scored normally or close to normal as a group on all of the neuropsychological tests. In contrast, approximately one-half of the moderately and all of the severely ataxic patients showed poor performance, independent of age, Hamilton Rating Scale for Depression score, or education, on the Wisconsin Card Sorting Test, suggesting impaired executive system function. In addition, a subgroup of these patients had a neuropsychological profile suggestive of mild generalized cognitive impairment. We conclude that DSCA is not a homogeneous group of disorders with respect to cognitive status and that the neurologic severity of the disorder is a major factor. Impaired executive system function could be explained by damage to olivopontocerebellar system control over cerebral cortical function or to damage to other neuronal systems (especially cholinergic) that degenerate in parallel with the olivopontocerebellar system.

Adult↗

Hereditary ataxia with sensory neuronopathy: Biemond's ataxia.

We report the case of a man with late-onset hereditary ataxia and sensory loss. Three of his sisters were affected by a similar disorder; to date no other members of his family have developed symptoms. The clinical features of this family are similar to a rare form of autosomal dominant hereditary ataxia, recently classified as SCA4. Postmortem findings indicate that this syndrome is marked by degeneration of cerebellar Purkinje cells, dorsal root sensory ganglion neurons, and the ascending posterior columns. Similar clinical and pathologic findings were reported by Biemond in 1954.

Adult↗

Is early onset cerebellar ataxia with retained tendon reflexes identifiable by electrophysiologic and histologic profile? A comparison with Friedreich's ataxia.

An electrophysiologic and histologic study was performed on 18 patients affected by early onset cerebellar ataxia with retained tendon reflexes (EOCA). Sensory and motor conduction velocity (SCV, MCV) was measured along peripheral nerves in all patients, somatosensory (SSEP) and brainstem auditory evoked potentials (BAEP) were recorded in 13; cortical stimulation (CS) in 12, and sural nerve biopsy in 4 patients were also performed. The results as a whole allow a division of EOCA patients into 2 groups: with (7 patients) and without (11 patients) peripheral neuropathy. Among EOCA patients with neuropathy a differential diagnosis with Friedreich's disease patients was not possible according to BAEPs and CS, while SSEPs could differentiate 2 out 5 patients in whom they were performed.

Adolescent↗