Psychological symptoms correlate with reduced hippocampal volume in fragile X premutation carriers

Abstract

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder occurring in male and occasional female carriers of a premutation expansion (55-200 CGG repeats) of the fragile X mental retardation 1 gene (FMR1). This study assessed the relationship between hippocampal volume and psychological symptoms in carriers, both with and without FXTAS, and controls. Volumetric MRI measures, clinical staging, cognitive testing, molecular analysis, and measures of psychological symptoms were performed for female premutation carriers both with FXTAS (n = 16, age: 57.50 + or - 12.46) and without FXTAS (n = 17, age: 44.94 + or - 11.23), in genetically normal female controls (n = 8, age: 50.63 + or - 11.43), male carriers with FXTAS (n = 34, age: 66.44 + or - 6.77) and without FXTAS (n = 21, age: 52.38 + or - 12.11), and genetically normal male controls (n = 30, age: 57.20 + or - 14.12). We examined the relationship between psychological symptom severity and hippocampal volume, as well as correlations with molecular data. We found a significant negative correlation between total hippocampal volume and anxiety in female carriers, with and without FXTAS. This finding was mainly driven by the significant negative correlation between right hippocampal volume and anxiety. Other anxiety-related subscales also correlated with the right hippocampus in females. In male carriers with and without FXTAS, only paranoid ideation negatively correlated with hippocampal volume. Female premutation carriers demonstrated a negative association between hippocampal volume and the severity of anxiety-related psychological symptoms. Though the presentation of FXTAS symptoms is less common in females, anxiety-related problems are common both prior to and after the onset of FXTAS, and may be related to hippocampal changes.

FIG. 1

Comparison of anxiety score on SCL-90-R for males and females, with and without FXTAS, and controls. Closed diamonds indicate female data points, while open circles depict male data points. P-values are for comparisons of predicted means at the age of 60 (fitted ANCOVA model). We found female premutation carriers with FXTAS had significantly higher predicted scores at age 60 in the ANCOVA model as compared to female carriers without FXTAS (P=0.023), and controls (P=0.001*). In the same analysis, male premutation carriers with FXTAS also had higher levels of anxiety compared to male carriers without FXTAS (P=0.028) and controls (P=0.003*). *P-value retains significance following correction for multiple comparisons.

FIG. 2

Comparison of anxiety score on the SCL-90-R with right hippocampal volume (normalized by TCV) in female premutation carriers (both with and without FXTAS). Closed triangles indicate female premutation carriers without FXTAS, whereas open circles represent female carriers with FXTAS. We found that anxiety score correlated significantly with the size of the right hippocampus (R=−0.634, P<0.001*). The same was true for several other subscales on the SCL-90-R. *P-value retains significance following correction for multiple comparisons.