670 cant deficits in visual-motor abilities. 4-9 Although attention-deficit/hyperactivity disorder is fairly common in WS, 4,5,10,11 epilepsy and autism are rare features of this condition. 9,12 Parents of children with WS often re- port significant sleep-related symptoms that include difficulty falling asleep, rest- less sleep, and frequent and prolonged awakenings from sleep. A movement arousal disorder, such as periodic limb movement in sleep, could contribute to these symptoms. Therefore we decided to screen these patients by a telephone survey for a possible movement arousal disorder and later study a subset of chil- dren with polysomnography to evaluate for PLMS in these patients. METHODS Study Group and Telephone Survey The parents of 28 younger children with WS (mean age, 4.7 ± 2.3 years; range, 1.5 to 10 years), who were fol- lowed up in the multispecialty WS clinic of the Children’s Hospital of Philadel- phia, participated in a telephone survey regarding sleep habits of their children. We interviewed one parent of each child. This survey, performed by one of the in- vestigators, included 8 questions aimed to differentiate between sleep-disordered breathing (Table I, questions 1 and 2) Williams syndrome is a complex dys- morphic and developmental disorder linked to a deletion in chromosome 7q11.23 encompassing the elastin gene and genes involved in brain develop- ment. 1,2 This disorder involves alter- ations in vascular and connective tissues P Periodic limb movement in sleep in children with Williams syndrome Raanan Arens, MD, Bryan Wright, BS, Joanne Elliott, RPFT, Huaqing Zhao, MA, Paul P. Wang, MD, Lawrence W. Brown, MD, Tara Namey, BS, and Paige Kaplan, MBBCh and is associated with mental retardation and neurologic disorders. 3 Children with WS have cognitive and behavioral disor- ders with a unique neurobehavioral pro- file. They display a distinctive preserva- tion of face recognition skills and many language and memory skills but signifi- From the Divisions of Pulmonary Medicine, Neurology, Biostatistics, Child Development, and Genetics, The Children’s Hospital of Philadelphia, Children’s Seashore House, and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania. Submitted for publication Jan 19, 1998; revisions received May 21, 1998, and Sept 3, 1998; accepted Sept 4, 1998. Reprint requests: Raanan Arens, MD, Division of Pulmonary Medicine, The Children’s Hospital of Philadel- phia, 34th St and Civic Center Blvd, Philadelphia, PA, 19104-4399. Copyright © 1998 by Mosby, Inc. 0022-3476/98/$5.00 + 0 9/21/94316 ADHD Attention-deficit/hyperactivity disorder NREM Non-rapid eye movement P ET CO 2 Expired end-tidal CO 2 tension PLMS Periodic limb movements in sleep REM Rapid eye movement RLS Restless leg syndrome S a O 2 Arterial oxygen saturation WS Williams syndrome Objective: Williams syndrome (WS) is associated with neurobehavioral abnor- malities that include irritability and attention-deficit/hyperactivity disorder. Par- ents often report children having difficulties initiating and maintaining sleep be- cause of restlessness and arousals. Therefore we evaluated a group of children with WS for the presence of a movement arousal sleep disorder. Methods: Twenty-eight families of children with WS participated in a tele- phone survey aimed to screen for a movement arousal disorder. Of the 16 chil- dren identified as having such a disorder, 7 (mean age, 3.9 ± 2.2 years) under- went polysomnography. Their studies were compared with those of 10 matched control subjects (mean age, 5.3 ± 2.0 years). Results: The 7 subjects with WS who were screened by the survey had sleep latency, total sleep time, arousals, and awakenings that were similar to those of control subjects. However, they presented with a disorder of periodic limb movement in sleep (PLMS). The PLMS index in the subjects with WS was 14.9 ± 6.2 versus 2.8 ± 1.9 in control subjects (P < .0001). In addition, arousal and awakening in subjects with WS were strongly associated with PLMS. Moreover, children with WS spend more time awake during sleep periods than control subjects (10.0% ± 7.0% vs 4.4% ± 4.7%; P < .05). Five children were treated with clonazepam, and in 4 a significant clinical response was noted. Conclusion: We report an association between WS and PLMS. Clonazepam may reduce the clinical symptoms of PLMS in some of these children. (J Pediatr 1998;133:670-4)