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K C Rickler

Publications and source records attributed to K C Rickler.

8 recordsLinked to original sources
PubMed1999

EEG differences in monozygotic twins discordant and concordant for schizophrenia.

In an electroencephalographic (EEG) study of 27 pairs of monozygotic (MZ) twins discordant for schizophrenia, 13 pairs of MZ twins concordant for schizophrenia, 40 pairs of healthy MZ twins, and 91 healthy, unrelated subjects with repeated assessments, we investigated (a) the trait quality of brainwave patterns with respect to interindividual differences, intraindividual stability over time, and within-pair MZ concordance; (b) the EEG characteristics that enable discrimination between affected and unaffected individuals; and (c) the EEG characteristics that reflect the severity of illness. In comparison with healthy control subjects, the MZ twins who were discordant and concordant for schizophrenia exhibited a much lower within-pair EEG concordance, so that EEG abnormalities associated with schizophrenia and manifested differently in the co-twins concordant for schizophrenia seemed to reflect nongenetic, pathological developments of genetically identical brains.

Adolescent↗
PubMed1997

Sleep disorders.

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Child↗
PubMed1997

Pharmacology of the selective serotonin reuptake inhibitors in children and adolescents.

OBJECTIVE: To review the pharmacology of a new class of medications, the potent selective serotonin reuptake inhibitors (SSRIs), what is known about their metabolism in children and adolescents, and the practical clinical implications of such. METHOD: Articles were retrieved through index Medicus searches for articles published during the past 10 years on the SSRIs and on pediatric pharmacology. RESULTS: More than 300 articles were reviewed. Pharmacological data, derived from relevant adult literature, were summarized and extrapolated to children and from the limited pediatric literature. The SSRIs represent a new class of antidepressants with distinct advantages in their side effect profile and their broad therapeutic index over that seen with the tricyclic antidepressants. Their advantage of few anticholinergic side effects and limited cardiovascular toxicities are particularly relevant for the pediatric population. The SSRIs are metabolized via the hepatic cytochrome isoenzyme P450 system, and potential drug-drug interactions are reviewed. CONCLUSIONS: The SSRIs appear to offer advantages over the tricyclic antidepressants. Unfortunately, pharmacokinetic data are lacking, and systematic studies of safety and efficacy in the pediatric age group are limited. Preliminary reports are encouraging, but further study is required.

Adolescent↗
PubMed1995

Cerebral morphometric abnormalities in Tourette's syndrome: a quantitative MRI study of monozygotic twins.

Although the pathologic substrate of Tourette's syndrome (TS) is unknown, studies have implicated subtle changes in the basal ganglia. To further investigate structural basal ganglia pathology in TS, we performed morphometric analyses of MRIs of 10 monozygotic twin pairs discordant for severity of TS but concordant for the presence of tic disorders (mean age, 16.3 years; range, 9 to 31 years). Right caudate volume was slightly but significantly reduced in the relatively more severely affected twins as a group compared with the less affected twins (mean difference = 6%, p < 0.01). Most of this difference was attributable to volume reduction in the anterior right caudate (p < 0.02), which was smaller in the more severely affected twin in nine of 10 twin sets. The mean volume of the left lateral ventricle was 16% smaller in the more severely affected twins than in the less severely affected twins (p < 0.01). The normal asymmetry of the lateral ventricles (left greater than right) was not present in the more severely affected twins, who had a trend toward a larger right lateral ventricle. Moreover, the difference within a pair in the degree of loss of the normal ventricular asymmetry correlated with the difference within a pair in the severity of the tic disorder (r = 0.75, p < 0.02). There were no other basal ganglia, ventricular volumetric, or asymmetry abnormalities. These findings partially replicate other MRI studies and suggest that subtle structural abnormalities in the CNS, particularly in the caudate, may play a role in the pathophysiology of TS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Are neurological abnormalities in well discordant monozygotic co-twins of schizophrenic subjects the result of perinatal trauma?

OBJECTIVE: Neurological abnormalities found in schizophrenic subjects and their healthy relatives have raised questions concerning etiology. The aim of the present study was to investigate the genetic and environmental antecedents of neurological impairment in monozygotic twins discordant for schizophrenia, with particular focus on the well discordant twins. The etiological factors of interest were history of obstetric complications, family history of psychosis, history of substance abuse, and history of postnatal cerebral trauma. METHOD: History of obstetric complications, including information from pregnancy through the neonatal period, and data on neurological "hard" and "soft" signs were obtained blindly and separately for each member of 22 monozygotic twin pairs discordant for schizophrenia and seven normal comparison monozygotic twin pairs. Clinical and family interviews provided information about background factors. RESULTS: Degree of neurological impairment in the well discordant monozygotic twins was significantly positively related to history of both neonatal and total obstetric complications. None of the three other background factors investigated was related to degree of neurological impairment in the ill or well co-twins. CONCLUSIONS: The contribution of obstetric complications to the current level of neurological impairment in well discordant co-twins suggests that the spectrum of neuroabnormality, ranging from neurological signs to schizophrenia, in monozygotic discordant twins may be the result of subtle gene-environment interaction.

Adult↗
PubMed1994

Electroencephalographic abnormalities in monozygotic twins with Tourette's syndrome.

The association of attentional, neuropsychological, and behavioural abnormalities with Tourette's syndrome (TS) suggests that the abnormal function of the disorder extends beyond the motor circuits of the basal ganglia. To explore this possibility we studied, with conventional 18-channel electroencephalography, monozygotic twins ranging from 8 to 26 years of age, where at least one member of the twin pair suffered from TS. In nine out of the 11 twin pairs that differed in clinical severity of the tic disorder, the twin with the more severe course of illness had a significantly more abnormal electroencephalogram (EEG) by qualitative visual analysis. Most of the differences were due to excessive frontocentral theta activity, suggesting dysfunction outside the basal ganglia. There was also a significant relationship between a lower global neuropsychological testing score and a worse overall EEG. In eight of nine twin sets with different global neuropsychological testing scores, the twin with the lower score had a worse EEG. A similar relationship was found between birth weight and overall EEG quality. In the nine sets that differed in birth weight, the twin with a lower birth weight had a worse EEG in seven of the sets. The EEG findings are unlikely to be unlikely to be a medication effect because the same result was seen in the six twin pairs who had been medication-free for at least six months before entry into the study. The origin of this slowing may relate to the interaction between environmental insults to the central nervous system and the genetic component of TS, an interaction producing damage to the cortex, thalamus, or both.

Adolescent↗
PubMed1992

Relationship of birth weight to the phenotypic expression of Gilles de la Tourette's syndrome in monozygotic twins.

We studied 16 pairs of monozygotic twins (mean age, 12.8 +/- 1.4 years; age range, 8 to 26 years; sex, 12 male pairs, four female pairs) in whom at least one twin had Gilles de la Tourette's syndrome (TS) to determine the concordance rates for TS and tic disorders and to examine environmental factors accounting for intrapair differences in tic severity. In this cohort, the concordance rate for TS was 56%, and the concordance rate for tic disorders was 94%, supporting a primary genetic basis for TS and tic disorders with a high rate of penetrance for the gene. Thirteen of the pairs had differing birth weights and the lower birth-weight twin had a higher tic score in 12 of these pairs. The magnitude of the intrapair birth-weight difference (BWD) strongly predicted the magnitude of the intrapair tic score difference. The difference in tic severity could not be explained by any postnatal medical events. These findings suggest that crucial events affecting the phenotypic expression of TS occur in utero and that the factors causing the BWD also are related to tic severity.

Adolescent↗