Basal ganglia volumes in children with attention-deficit hyperactivity disorder.

Previous research has demonstrated volume reduction of the left globus pallidus in children with the codiagnoses of Tourette syndrome and attention-deficit hyperactivity disorder (ADHD), in comparison with children who have Tourette syndrome alone and with normal controls. The purpose of this study was to determine whether children with ADHD alone also had volume reduction of the globus pallidus or other basal ganglia structures. Subjects were 10 boys with ADHD, 16 boys with Tourette syndrome and ADHD, and 11 normal control boys. Groups were matched for age. Boys with ADHD were individually matched for age, handedness, and IQ to 10 of the 16 boys with Tourette syndrome and ADHD. Volumes of caudate, putamen, and globus pallidus were measured and corrected for brain volume. The boys with ADHD had significantly smaller left globus pallidus volume and total globus pallidus volume (corrected for brain volume) than the normal controls. The Tourette syndrome plus ADHD group did not differ from the ADHD group on any of the measures. We conclude that small globus pallidus volume, particularly on the left side, is associated with ADHD.

Executive function in children with Tourette syndrome and/or attention deficit hyperactivity disorder.

Tourette Syndrome (TS) in children is associated with various neurobehavioral disorders including attention deficit hyperactivity disorder (ADHD). Children with TS and ADHD show some difficulties with neuropsychological tasks, but we do not know if children with TS alone have neuropsychological deficits. To assess specific cognitive differences among children with TS and/or ADHD, we administered a battery of neuropsychological tests, including 10 tasks related to executive function (EF), to 10 children with TS-only, 48 with ADHD-only, and 32 with TS + ADHD. Children in all groups could not efficiently produce output on a timed continuous performance task [Test of Variables of Attention (TOVA) mean reaction time and reaction time variability]. Children with TS-only appeared to have fewer EF impairments and significantly higher perceptual organization scores than children with TS + ADHD or ADHD-only. These findings suggest that deficiencies in choice reaction time and consistency of timed responses are common to all three groups, but children with TS-only have relatively less EF impairment than children with TS + ADHD or ADHD-only.

Volumetric MRI changes in basal ganglia of children with Tourette's syndrome.

To define the site of pathology in Tourette's syndrome (TS), we performed a volumetric MRI study of basal ganglia structures and lateral ventricles on 37 children with this disorder and 18 controls. There were no statistically significant differences in the size of the right or left caudate, putamen, globus pallidus, or ventricles in these populations. In contrast, there were significant differences for measures of symmetry in the putamen and the lenticular region. Virtually all controls (17 right- and one left-handed) had a left-sided predominance of the putamen, whereas in 13 of 37 TS subjects, a right predominance exceeded that of any control. Statistical comparisons among TS patients, with (n = 18) or without (n = 19) attention-deficit hyperactivity disorder (ADHD), and controls showed significant differences for the volume of the left globus pallidus and for lenticular asymmetry. Post hoc evaluations showed that in the TS + ADHD group, the volume of the left globus pallidus was significantly smaller than the volume of the right and that lenticular asymmetry was due to a greater right-sided predominance in the TS+ADHD group. This study lends further support to proposals that claim the basal ganglia is involved in the pathogenesis of TS and also suggests that the comorbid problem of ADHD is related to regional changes that differ from those primarily associated with tics.

Influence of isotonic agents on the stability of thimerosal in ophthalmic formulations.

Storage tests on the stability of thimerosal in trimethoprim-polymyxin B eyedrop formulations containing isotonic agents other than sodium chloride have been carried out. The HPLC assay of thimerosal in stored formulations containing boric acid and EDTA decreased with time and temperature, while formulations containing propylene glycol, glycerol, and mannitol showed no significant decrease in thimerosal assay compared with a formulation containing no isotonic agent. The latter group provide suitable alternatives to sodium chloride, which has been shown to have a seriously detrimental effect on thimerosal stability.

Decomposition of thimerosal in aqueous solution and its determination by high-performance liquid chromatography.

Studies on the decomposition of thimerosal in aqueous solution have confirmed that thiosalicylic acid and ethylmercuric hydroxide are the initial products. On prolonged reaction, thiosalicylic acid was oxidized to 2,2'-dithiosalicylic acid, while ethylmercuric hydroxide was reduced to elemental mercury. As a result, a specific, reverse-phase high-performance liquid chromatographic assay has been developed for thimerosal in the presence of its decomposition products. By comparison, an existing colorimetric assay procedure employing dithizone was shown to be not fully specific. The presence of sodium chloride in the solution accelerated the decomposition of thimerosal. There was evidence that thimerosal was sorbed onto plastic containers on storage.

Validity of the Missouri Children's Picture Series as a predictor of childhood sleep disturbances.

In view of recent findings in a retrospective study by two of the authors, the present research was designed to systematically assess the validity of the Missouri Children's Picture Series sleep disturbances scale. Study I compared groups of restless sleepers and nocturnal enuretics with matched cohorts attending a summer residential program for children with communication-related disorders. Study II examined the relation of two MCPS scales to parent reports of corresponding problems, using a multitrait-multimethod matrix, individual correlations, and cluster analysis. Neither study provided convincing evidence for the validity of the sleep disturbance scale.