Severe Cognitive Impairment: Fragile X

Joseph Higgins & Lindsey Charbonneau

Description

       Many disorders or perinatal conditions can result in severe cognitive impairment (IQ below 39). One of these is Fragile X Syndrome. Fragile X Syndrome is a genetic disorder resulting in learning difficulties, autism (in 1/3 of cases), anxiety, and a range of physical identifying features (e.g., long face, large prominent ears, high arched palate, hyperextensive finger joints, flat feet, macroorchidism). It is caused by a triplet repeat mutation in the FMR1 gene on the X chromosome. It is an X-linked recessive disorder which is associated with nervous system abnormalities such as increased volume in the caudate nucleus and lateral ventricle. Along with Down Syndrome, it is one of the most common causes of mental retardation in children. Those with fragile X syndrome experience many expressive and receptive speech and language delays which may result from social anxiety, hyperarousal (e.g., hyperactivity, impulsivity, poor self-control) gaze aversion, tactile defensiveness, turning away from face-to-face interaction, and ritualistic greeting habits. Different genders may have different profiles of language impairments, but the research is limited. Some children have been reported to be completely nonverbal or limited to one-word utterances. Females have less compromised receptive language skills than males due to less severe cognitive impairments.

Prevalence - add prevalence here 

Links to Language/Literacy

• Effects on language and literacy: Many of the linguistic and pragmatic impairments may be related to co-occurring or undiagnosed Autism.
• Comprehension: Performance on the Test for Auditory Comprehension of Language was not significantly different than the typically developing comparison group. This suggests that those with fragile x have equal development in receptive syntax, receptive vocabulary, and nonverbal cognition in early years. If deficits are found, intervention should be across many receptive domains as opposed to focused solely on syntax or vocabulary. 
• Fluency: No differences in MLU were reported between those with the same mental age, though literature is limited.
• Phonology/Articulation: based on physical features, some articulatory problems are to be expected. For instance, high palatal vault may impair articulation of some consonants, and could impact resonance.  
• Vocabulary: Better scores on vocabulary tests than would be predicted by nonverbal mental age has been reported. However, some studies have reported higher rates of lexical errors. It is hypothesized that poor inhibitory control may impair efficient lexical retrieval. Once a word is retrieved, perseveration is common due to an inability to inhibit repeated activation of a single word in the semantic network. 
•  Writing: Comparable or slightly improved written language skills were found compared to mental age matched typically developing children in one study. Females in particular had significantly higher scores. 
•  Narratives: Research on narratives is limited by attention issues and distractibility in this population. E.g., when asked to recount a story, language was off topic and tangential. Limited use of sentences with complex clauses was found. Grammatical performance was improved when given a picture book to reference (possibly due to improved attentional focus).
•  Motivation / Social Linguistic Factors: echolalia, neologisms, dysprosody, poor conversational pragmatics, poor pronoun reference, theory of mind problems, increased tangential language in conversation (as opposed to answering questions), reduced initiation of conversation (e.g., asking questions).

Multimedia/Web Resources!

http://youtu.be/B6j8Dd-FDRI

http://www.fraxa.org/fragilex.aspx

http://www.fragilex.org/

http://www.fragilex.org/media-resources/videos-podcasts/

References

Abbeduto, L., Murphy, M. M., Cawthon, S. W., Richmond, E. K., Weissman, M. D., Karadottir, S., & O'Brien, A. (2003). Receptive language skills of adolescents and young adults with down or fragile X syndrome. American Journal on Mental Retardation, 108(3)¸ 149-160.

Sudhalter, V., & Belser, R. C. (2001). Conversation characteristics of children wtih fragile X syndrome: Tangential language. American Journal on Mental Retardation, 106(5), 389-400.

Levy, Y., Gottesman, R., Borochowitz, Z., Frydman, M., & Sagi, M. (2006). Language in boys with fragile X syndrome. Journal of Child Language, 33, 125-144.

Finestock, L. H., & Abbeduto, L. (2010). Expressive language profiles of verbally expressive adolescents and young adults with Down Syndrome or fragile X syndrome. Journal of Speech, Language, and Hearing Research, 53, 1334-1348.