The behavioral and neuropsychological characteristics of tic disorder, with or without attention-deficit hyperactivity disorder (ADHD), were examined in 78 children followed at Seoul National University College of Medicine, Korea. Sixteen had tic disorder alone, 19 had comorbid tics and ADHD, 21 had ADHD alone, and 22 were normal controls. Seven neuropsychological tests involving global cognitive function, attention, information-processing, and fine motor coordination were compared in the 4 groups. Tic disorder with ADHD and ADHD patients had similar findings and marked deficits compared to the tic disorder and control groups. In tests of attention, the ADHD group made more errors of commission than the tic disorder with ADHD group. ADHD symptoms found in children with tic disorder may be a true comorbid condition and not secondary to tic symptoms. 
COMMENT. Tic disorder comorbid with ADHD carries an increased risk of cognitive deficits and behavioral disturbance similar to that found with ADHD alone, whereas tic disorder alone is not a risk factor. This report confirms previous findings in a study using transcranial magnetic stimulation to demonstrate additive deficits in inhibitory cortical motor mechanisms in children with ADHD comorbid with tic disorder (Moll GH et al. 2001; see Ped Neur Briefs March 2001;15:22-23).
The prevalence of ADHD in patients with tic disorder has been estimated at more than 50%. Although the use of stimulants for ADHD associated with tics is controversial, the authors favored early intervention to correct attention and behavioral problems. An exacerbation of tics would probably mandate immediate stimulant withdrawal. For studies of treatments of ADHD and Tics, see Progress in Pediatric Neurology III, PNB Publ, 1997;pp318-321.