Neurologic examination abnormalities in children with bipolar disorder or attention-deficit/hyperactivity disorder

A longitudinal study of neurological soft signs from late childhood into early adulthood

Neurological examination of children includes the screening for soft neurological signs (NSS). There is little knowledge about their evolution during adolescence, except that their lasting presence has been associated with developmental, psychological, and cognitive disorders. We report the results of a NSS exam (assessing gross and fine motor function and the presence of hyperactivity and motor impersistence) over a 5-year period, among a group of healthy children who were followed annually as part of a dental study. Their ages ranged from 11 to 15 years at onset to 14 to 18 years at the end. Participants were divided into four groups by age (younger and older) and sex. At the first evaluation there were 191 males and 150 females. NSS score diminished both with increasing age and follow-up time in both groups, but at different rates in males and females. Females reached the lowest scores two years before the younger subgroup of males. These results show that NSS change rapidly in adolescence and at different rates in males and females, which must be taken into account in clinical contexts. The evolution of NSS suggests that they are a signature of neural development.

Frontiers between attention deficit hyperactivity disorder and bipolar disorder

The co-occurrence of attention deficit hyperactivity disorder (ADHD) and bipolar disorder has received much recent attention in the literature. The authors review the literature examining associations between ADHD and bipolar disorder in children, and data concerning severe irritability in youth with ADHD. This article focuses on (1) population-based studies examining ADHD and bipolar disorder or ADHD and co-occurring irritability, (2) the co-occurrence and prospective relationships of ADHD and bipolar disorder in clinical samples, (3) phenomenology and assessment of bipolar disorder and ADHD, (4) treatment of comorbid ADHD and bipolar disorder, (5) family and genetic studies of ADHD and bipolar disorder, and (6) pathophysiologic comparisons between children with ADHD and irritability and bipolar disorder. We draw on the research to make clinical recommendations and highlight important directions for future research.

Neurological outcomes in children with and without amalgam-related mercury exposure: seven years of longitudinal observations in a randomized trial

BACKGROUND

Although large-scale, randomized trials involving children have been completed and their results demonstrate an absence of neurobehavioral effects from clinical exposure to mercury amalgam, neurological findings from such studies have not been reported.

METHODS

The authors conducted a randomized, prospective trial examining the safety of dental amalgam in which 507 children aged 8 through 12 years were assigned to treatment with either amalgam or resin-based composite. During seven years of follow-up, the authors performed annual clinical neurological examinations, including an evaluation of neurological hard signs (NHSs), presence of tremor and neurological soft signs (NSSs).

RESULTS

The authors found no significant differences between treatment groups in any of the neurological measures. Groups did not differ with respect to the presence or absence of NHSs or tremor, nor the presence or absence or severity of NSSs at any point. As expected, NSS severity scores diminished with increasing age.

CONCLUSIONS

Even at the levels of amalgam exposure in this study (a mean of 7.7-10.7 amalgam surfaces per subject across the seven years of follow-up), the authors conclude that exposure to mercury from dental amalgam does not adversely affect neurological status.

CLINICAL IMPLICATIONS

The current evidence is that potential neurobehavioral or neurological effects from dental amalgam mercury exposure in children are inconsequential.

Neural activation during encoding of emotional faces in pediatric bipolar disorder

OBJECTIVE

Neurobiological understanding of bipolar disorder (BD) is limited by a paucity of functional magnetic resonance imaging (fMRI) research examining correlates of psychological processes. To begin to address these limitations, the current study tests the hypothesis that pediatric BD (PBD) subjects exhibit altered neural activation during encoding of emotional faces compared to typically developing controls.

METHODS

Pediatric BD subjects (n=23; mean age=14.2+/-3.1 years) and controls (n=22; mean age=14.7+/-2.3 years) were matched on age, gender, and IQ. In this event-related fMRI study, subjects were scanned while viewing emotional faces and given a surprise recognition memory test 30 min postscan. Our main outcome measure was between-group differences in neural activation during successful versus unsuccessful face encoding.

RESULTS

Pediatric BD youth exhibited reduced memory for emotional faces, relative to healthy comparisons, particularly on fearful faces. Event-related fMRI analyses controlling for this behavioral difference showed that PBD subjects, compared to controls, had increased neural activation in the striatum and anterior cingulate cortex when successfully encoding happy faces and in the orbitofrontal cortex when successfully encoding angry faces. There were no between-group differences in neural activation during fearful face encoding.

CONCLUSIONS

Our results extend what is known about memory and face emotion processing impairments in PBD subjects by showing increased fronto-striatal activation during encoding of emotional faces. Further work is required to determine the impact of mood state, medication, and comorbid illnesses on these findings.

Are Motor Inhibition and Cognitive Flexibility Dead Ends in ADHD?

Executive dysfunction has been postulated as the core deficit in ADHD, although many deficits in lower order cognitive processes have also been identified. By obtaining an appropriate baseline of lower order cognitive functioning light may be shed on as to whether executive deficits result from problems in lower order and/or higher order cognitive processes. We examined motor inhibition and cognitive flexibility in relation to a baseline measure in 816 children from ADHD and control families. Multiple children in a family were tested in order to examine the familiality of the measures. No evidence was found for deficits in motor inhibition or cognitive flexibility in children with ADHD or their nonaffected siblings: Compared to their baseline speed and accuracy of responding, children with ADHD and their (non)affected siblings were not disproportionally slower or inaccurate when demands for motor inhibition or cognitive flexibility were added to the task. However, children with ADHD and their (non)affected siblings were overall less accurate than controls, which could not be attributed to differences in response speed. This suggests that inaccuracy of responding is characteristic of children having (a familial risk for) ADHD. Motor inhibition and cognitive flexibility as operationalized with mean reaction time were found to be familial. It is concluded that poorer performance on executive tasks in children with ADHD and their (non)affected siblings may result from deficiencies in lower order cognitive processes and not (only) from higher order cognitive processes/executive functions.

Emotion regulation in children and adolescents: boundaries between normalcy and bipolar disorder

Much controversy has surrounded the diagnosis of bipolar disorder (BD) in children and adolescents. However, recent work from an affective neuroscience perspective has advanced what is known about the boundaries of emotion regulation in BD compared to typically developing youth. In this article, we first briefly review the clinical issues that have contributed to this diagnostic controversy. Second, we discuss our phenotyping system, which can be used to guide neurobiological research designed to address these controversial issues. Third, we review what is known about the fundamentals of emotion regulation in human and nonhuman primate models. Fourth, we present recent data demonstrating how children and adolescents with BD differ from those without psychopathology on measures of emotion regulation. Taken as a whole, this work implicates a neural circuit encompassing the prefrontal cortex, amygdala, and striatum in the pathophysiology of pediatric BD.

Cognitive flexibility in phenotypes of pediatric bipolar disorder

OBJECTIVE

Clinicians and researchers debate whether children with chronic, nonepisodic irritability should receive the diagnosis of bipolar disorder (BD). To address this debate, we evaluated cognitive flexibility, or the ability to adapt to changing contingencies, in three groups of children: narrow-phenotype BD (NP-BD; full-duration manic episodes of elevated/expansive mood; N = 50; 13.1 +/- 2.9 years), severe mood dysregulation (SMD; chronic, nonepisodic irritability; N = 44; 12.2 +/- 2.1 years), and healthy controls (N = 43; 13.6 +/- 2.4 years). Cognitive flexibility is relevant to symptoms of BD involving dysfunctional reward systems (e.g., excessive goal-directed activity and pleasure-seeking in mania; anhedonia in depression).

METHOD

We studied simple and compound reversal stages of the intra-/extradimensional shift task and change task that involves inhibiting a prepotent response and substituting a novel response.

RESULTS

On the simple reversal, NP-BD youths were significantly more impaired than both the SMD group and controls. On the compound reversal, NP-BD and SMD youths performed worse than controls. On the change task, NP-BD youths were slower to adapt than SMD subjects.

CONCLUSIONS

Phenotypic differences in cognitive flexibility may reflect different brain/behavior mechanisms in these two patient populations.

The cerebellum and motor dysfunction in neuropsychiatric disorders

The cerebellum is densely interconnected with sensory-motor areas of the cerebral cortex, and in man, the great expansion of the association areas of cerebral cortex is also paralleled by an expansion of the lateral cerebellar hemispheres. It is therefore likely that these circuits contribute to non-motor cognitive functions, but this is still a controversial issue. One approach is to examine evidence from neuropsychiatric disorders of cerebellar involvement. In this review, we narrow this search to test whether there is evidence of motor dysfunction associated with neuropsychiatric disorders consistent with disruption of cerebellar motor function. While we do find such evidence, especially in autism, schizophrenia and dyslexia, we caution that the restricted set of motor symptoms does not suggest global cerebellar dysfunction. Moreover, these symptoms may also reflect involvement of other, extra-cerebellar circuits and detailed examination of specific sub groups of individuals within each disorder may help to relate such motor symptoms to cerebellar morphology.