Motor stereotypies in fragile X syndrome

The purpose of this study was to quantify the type and frequency of stereotypies in fragile X syndrome and to determine the relationship of observed stereotypies with gender, level of cognitive function, and parent-reported scores for repetitive behaviors. Subjects with fragile X syndrome were videotaped during the administration of a standardized conversation task, a standardized narrative task, and sitting alone. Two individuals rated the stereotypies on the videotapes (10 min each) using the stereotyped behavior scale. Intelligence quotient scores were collected and parents/guardians completed the Vineland adaptive behavior scale and the aberrant behavior checklist - community edition. Thirty-eight subjects were tested (mean age 17.1 +/- 7.1 yr). The mean total of stereotypies was 11 +/- 11.7 movements in 10 min and the mean stereotyped behavior scale score was 5.8 +/- 5.5. The most common type of movement was rubbing him/herself, followed by body movement and repetitive movement. There were correlations between the stereotyped behavior scale score and intelligence quotient (P = 0.0006), the aberrant behavior checklist total score (P = 0.01), and the stereotypy subscore (P = 0.0007). Stereotypies are common in fragile X syndrome and more frequent in individuals with lower intelligence quotients and more severe behavior. The stereotyped behavior scale measure correlated with parent completed checklists, but showed poor to moderate reliability for measurement of stereotypies by a single rater and test retest in fragile X syndrome.