New clinical findings in the fragile X-associated tremor ataxia syndrome (FXTAS)

Abstract

The objective of this paper was to assess the phenotypic variance in patients with the Fragile X-associated Tremor Ataxia Syndrome (FXTAS) and to further elucidate genotype–phenotype correlations in the illness. A second goal was to generate hypotheses regarding symptom progression based on careful histories in our sample that can now be tested in ongoing longitudinal studies. The variability of clinical signs and symptom progression in FXTAS complicates our understanding of its phenotype and presents a series of problems in clinical trial design. Similarly, pre-motor and non-motor symptoms have not been adequately explored to answer outstanding questions regarding genotype–phenotype associations in FXTAS. This was a cross-sectional study of FMR1 premutation carriers from known fragile X syndrome pedigrees. We report on the first 50 subjects who have completed a full neurologic evaluation and a brain MRI. Subjects were selected on the basis of motor symptoms or abnormal results (>1 SD) on a quantitative instrument designed to detect mild tremor and ataxia (CATSYS 1994). A neuropsychological battery included the WAIS-III, COWA, and WCST. Statistical analysis used ANOVA and Fisher's exact test with p<0.05. All FMR1 premutation carriers were men of mean age 65±7 years. According to the diagnostic criteria of Jacquemont et al. (Am J Hum Genet 72(4):869–878, 2003), 21 subjects met criteria for definite FXTAS, 10 for probable, 9 for possible, and 10 were indeterminate. Duration of motor symptoms was significantly longer in the definitive group (8.6±6) compared to the other groups (p<0.01). The presentations in 40 subjects, excluding the indeterminate group, included: tremor 24, ataxia 5, memory symptoms 3, parkinsonism 2, and torticollis 1. The data suggest at least two dominant phenotypic presentations: (a) a tremor-dominant subtype in which the onset of ataxia is delayed; (b) a second in which ataxia is the dominant presentation from the outset. In both subtypes, once ataxia emerges it tends to track frontal cognitive changes (p<0.01). The data support the view that FXTAS is a late-life neurodegenerative disorder with involvement of motor, non-motor, and cognitive systems. The results suggest at least two presentations with tremor-and ataxia-predominant phenotypes. In both, global cognitive decline appears to track ataxia. Prospective longitudinal studies are needed to validate this proposed evolution of FXTAS and its relevance to future clinical trials design.

Relevance of corpus callosum splenium versus middle cerebellar peduncle hyperintensity for FXTAS diagnosis in clinical practice

“…Thus, MCP was found to be more frequent in FXTAS than in MSA-C which needs to be confirmed by further larger prospective studies. Whereas MCP hyperintensity was observed in only 13 % of FXTAS women in a previous series [16], no women in our study presented MCP hyperintensity. Alternately, 3 of the 5 women of our series had CCS hyperintensity.…”

Fragile X-associated tremor/ataxia syndrome — features, mechanisms and management

“…FXTAS can present with an intention tremor, cerebellar ataxia or cognitive decline [56][57][58] . Neuropathy -although not a major criterion for FXTAS -is commonly seen at the time of presentation and typically develops before tremor and ataxia 37,45,46,59,60 . Vestibular dysfunction is common before the onset of FXTAS, manifesting as frequent episodes of dizziness that are sometimes diagnosed as benign positional vertigo.…”

Current research, diagnosis, and treatment of fragile X-associated tremor/ataxia syndrome

“…Migraine headache were reported in a higher rate in females (54.2%) when prefrontal cortices that are critical for cognitive control (54). Correspondingly, those with FXTAS and the MCP sign are likely to have more severe cognitive deficits and a longer history of symptoms than those without the MCP sign (55). Asymptomatic FMR1 premutation carriers show white matter alterations (demyelination and axonal damage) of the afferent projections of the MCPs and superior cerebellar peduncles (53,56,57), which may be the earliest neuroanatomical marker of the onset of cognitive and motor symptoms associated with FXTAS (58).…”