Neurocognitive profile in 22q11 deletion syndrome and schizophrenia

OBJECTIVE: Schizophrenia is associated with neurocognitive deficits, but its etiologic heterogeneity may complicate the delineation of a neurocognitive profile. Schizophrenia associated with 22q11 Deletion Syndrome (22qDS) represents a more genetically homogeneous subtype for study. We hypothesized that in adults with 22qDS the neurocognitive profiles would differ between those with and without schizophrenia. METHOD: Using a comprehensive battery of tests, we compared the neurocognitive performance profiles in those with schizophrenia (n=27; 14 M, 13 F; mean age=30.6 years, SD=7.7 years) and those with no history of psychosis (n=29; 16 M, 13 F; mean age=25.0 years, SD=9.0 years). RESULTS: The 22qDS groups with and without schizophrenia had similar mean estimated IQ (71.6, SD=8.2 and 74.8, SD=6.1, respectively) and academic achievement, however the neurocognitive profiles of the two groups differed significantly on multivariate analysis (F(24,31)=2.25, p=0.017). The group with schizophrenia performed significantly more poorly on tests of motor skills, verbal learning, and social cognition (effect sizes>or=0.8) after correction for multiple comparisons. Other tests, but not the attentional measures used, showed nominally significant differences. CONCLUSIONS: In adults with 22qDS, the pattern of neurocognitive differences between those with and without schizophrenia appears similar to that between patients with schizophrenia and controls. Attentional dysfunction may be a more general feature of 22qDS. The findings support 22qDS-schizophrenia as a genetic model for neurodevelopmental investigations of schizophrenia.     

Velo-cardio-facial syndrome, schizophrenia and deletion at chromosome 22q11

A man with intellectual disability presented with schizophrenia, hypocalcaemia, facial dysmorphism and cleft soft palate. Velo-cardio-facial syndrome was diagnosed and deletion at 22q11 was confirmed by fluorescent in situ hybridization.     

22q11 deletion syndrome: a genetic subtype of schizophrenia.

Schizophrenia is likely to be caused by several susceptibility genes and may have environmental factors that interact with susceptibility genes and/or nongenetic causes. Recent evidence supports the likelihood that 22q11 Deletion Syndrome (22qDS) represents an identifiable genetic subtype of schizophrenia. 22qDS is an under-recognized genetic syndrome associated with microdeletions on chromosome 22 and a variable expression that often includes mild congenital dysmorphic features, hypernasal speech, and learning difficulties. Initial evidence indicates that a minority of patients with schizophrenia (approximately 2%) may have 22qDS and that prevalence may be somewhat higher in subpopulations with developmental delay. This paper proposes clinical criteria (including facial features, learning disabilities, hypernasal speech, congenital heart defects and other congenital anomalies) to aid in identifying patients with schizophrenia who may have this subtype and outlines features that may increase the index of suspicion for this syndrome. Although no specific causal gene or genes have yet been identified in the deletion region, 22qDS may represent a more homogeneous subtype of schizophrenia. This subtype may serve as a model for neurodevelopmental origins of schizophrenia that could aid in delineating etiologic and pathogenetic mechanisms.     

Low platelet count in a 22q11 deletion syndrome subtype of schizophrenia

Background: 22q11 Deletion Syndrome (22qDS) is a genetic syndrome associated with various physical features and schizophrenia. Some reports have identified thrombocytopenia (platelet count <150×10⁹/l) in individuals with 22qDS, especially children. We investigated whether adults with 22qDS and schizophrenia (22qDS-SZ) have lower platelet counts than other patients with schizophrenia (SZ).

Method: Complete blood counts (CBC) were recorded from medical records for 18 22qDS-SZ and 60 SZ subjects. Five CBCs per subject were randomly selected and used to calculate a within-subject mean for analyses.

Results: 22qDS-SZ subjects had significantly lower mean platelet counts than comparison SZ subjects (142.2×10⁹/l versus 282.5×10⁹/l, t=−11.5, p<0.0001). Ten 22qDS-SZ (55%) and no comparison subjects had thrombocytopenia.

Conclusions: These results suggest that thrombocytopenia may be a common feature of 22qDS and that low platelet counts may comprise a readily available screening criterion to help identify this genetic syndrome among adults with schizophrenia.     

Molecular mechanisms in 22q11 deletion syndrome

It is now well recognized that as well as having a characteristic facial dysmorphology and a range of congenital abnormalities, individuals with chromosome 22q11 deletion syndrome (22q11DS) have a greatly increased risk of developing psychosis, in particular schizophrenia. The majority of deletions span a large 3Mb region at 22q11. However, the presence of affected individuals carrying smaller deletions have not been sufficient to satisfactorily reduce the critical region for the behavioral phenotype beyond a ~1.5Mb region that contains at least 28 genes. By having a shared genetic variant that greatly increases risk to psychosis, individuals with 22q11DS are a relatively homogeneous population to study psychiatric disease. Despite this, the large volume of research performed over the last 15 years suggest that the mechanism by which haploinsufficiency at 22q11 increases risk to psychiatric illness is likely to be complex and it remains uncertain why individuals carrying identical 22q11 deletions can present with such a wide range of neuropsychiatric phenotypes. This review will therefore consider the ways in which deletions at 22q11 are expected to increase risk to develop psychiatric disease by summarizing the work that has been done to investigate three of the most likely disease causing mechanisms: (a) gene dosage sensitivity; (b) unmasking of recessive alleles or functional polymorphism; and (c) position effect.     

Structural brain abnormalities in patients with schizophrenia and 22q11 deletion syndrome.

BACKGROUND: 22q11 Deletion Syndrome is a genetic syndrome associated with an increased risk for developing schizophrenia. Brain abnormalities have been reported in 22q11 Deletion Syndrome, but little is known about whether differences in brain structure underlie the psychotic disorders associated with this syndrome. In the current study, we used magnetic resonance imaging to characterize the structural brain abnormalities found in adults who have both 22q11 Deletion Syndrome and schizophrenia. METHODS: Magnetic resonance imaging brain scans of 14 adults (7 male, 7 female) with 22q11 Deletion Syndrome and schizophrenia and 14 age- and gender-matched healthy volunteers were analyzed to derive measures of gray matter, white matter, and cerebrospinal fluid. Differences between the two groups were tested using student t tests. RESULTS: 22q11 Deletion Syndrome and schizophrenia subjects had significantly smaller total gray matter volume (t = 2.88, p <.01) and larger lateral ventricles (t = 4.08, p <.001) than healthy controls. Gray matter deficits were most prominent in the frontal and temporal lobes. Total white matter volumes did not differ between the two groups. CONCLUSIONS: Findings from this 22q11 Deletion Syndrome and schizophrenia study are similar to those reported in other patients with schizophrenia, but only partially consistent with those reported in nonpsychotic children with 22q11 Deletion Syndrome. 22q11 Deletion Syndrome may provide a valuable genetic neurodevelopmental model for investigating the relationship between abnormalities in brain development and the expression of schizophrenia.     

Qualitative MRI findings in adults with 22q11 deletion syndrome and schizophrenia.

BACKGROUND: A genetic syndrome associated with schizophrenia, 22q11 deletion syndrome (22qDS), may represent a genetic subtype of schizophrenia (22qDS-Sz). Structural brain changes are common in schizophrenia and may involve developmental anomalies, but there are no data yet for 22qDS-Sz. The objective of this study was to assess brain structure in adults with 22qDS-Sz using magnetic resonance imaging (MRI). METHODS: Brain and arterial MRI scans of 11 adults with 22qDS-Sz (mean age = 28.4 years, SD = 6.5) were systematically assessed by a neuroradiologist for qualitative anomalies. RESULTS: A high frequency of abnormalities were found: T2 white matter bright foci (BF), 90%; developmental midline anomalies, 45%; cerebral atrophy or ventricular enlargement, 54%; mild cerebellar atrophy, 36%; skull base abnormalities, 55%; and minor vascular abnormalities, 36%. CONCLUSIONS: BF and skull base abnormalities, especially in association with neurodevelopmental midline abnormalities, may be distinguishing MRI features for a genetic subtype of schizophrenia involving a deletion on chromosome 22.     

White matter abnormalities in adults with 22q11 deletion syndrome with and without schizophrenia

Dysfunction of cerebral white matter (WM) is a potential factor underlying the neurobiology of schizophrenia. People with 22q11 deletion syndrome have altered brain morphology and increased risk for schizophrenia, therefore decreased WM integrity may be related to schizophrenia in 22q11DS. We measured fractional anisotropy (FA) and WM volume in 27 adults with 22q11DS with schizophrenia (n = 12, 22q11DS SCZ+) and without schizophrenia (n = 15, 22q11DS SCZ−), 12 individuals with idiopathic schizophrenia and 31 age-matched healthy controls. We found widespread decreased WM volume in posterior and temporal brain areas and decreased FA in areas of the frontal cortex in the whole 22q11DS group compared to healthy controls. In 22q11DS SCZ+ compromised WM integrity included inferior frontal areas of parietal and occipital lobe. Idiopathic schizophrenia patients showed decreased FA in inferior frontal and insular regions compared to healthy controls. We found no WM alterations in 22q11DS SCZ+ vs. 22q11DS SCZ−. However, there was a negative correlation between FA and PANSS scores (Positive and Negative Symptom Scale) in the whole 22q11DS group in the inferior frontal, cingulate, insular and temporal areas. This is the first study to investigate WM integrity in adults with 22q11DS. Our results suggest that pervasive WM dysfunction is intrinsic to 22q11DS and that psychotic development in adults with 22q11DS involves similar brain areas as seen in schizophrenia in the general population.     

Mouse models of 22q11 deletion syndrome.

22q11 deletion syndrome (22q11DS) is caused by an interstitial chromosomal microdeletion that encompasses about 40 genes. It is the most common of the microdeletion syndromes. The clinical phenotype, which is complex and variable, includes specific congenital defects of the cardiovascular system, craniofacies, and immune system. In early childhood, patients manifest cognitive impairment, behavioral disorders, and delays in motor development and language acquisition. Adult patients have a high risk for developing serious psychiatric disorders, especially schizophrenia, schizoaffective disorder, and bipolar disorder. The great majority of patients have an identical or near identical chromosomal deletion, and genotype-phenotype correlations have not been established. Indeed, little progress was made toward resolving the complex clinical phenotype until the deletion was successfully modeled in the mouse. In recent years, through a variety of mouse mutants that carry multigene and single gene mutations, we have learned that mutation in a single gene, Tbx1, is responsible for most of the congenital defects seen in the mouse models and in patients. We now face a greater challenge as we attempt to use the mouse to address the pathogenesis of the behavioral and psychiatric disorders associated with 22q11DS. Significant progress has already been made, and recent studies in the mouse suggest that several genes from the deleted region affect behavior and might contribute to disease burden in patients.     

Catechol-O-methyl transferase and expression of schizophrenia in 73 adults with 22q11 deletion syndrome.

BACKGROUND: Catechol-O-methyl transferase (COMT) is a candidate gene for schizophrenia with a role in dopamine metabolism, particularly in frontal cortex. COMT is within the region commonly deleted in 22q11 deletion syndrome (22q11DS), a syndrome with high prevalence of schizophrenia. We examined the role of COMT in schizophrenia-related expression in 22q11DS. METHODS: We genotyped the COMT functional Val(158/108)Met allele in 73 Caucasian adults with 22q11DS (36 men, 37 women; aged 33.8, SD 10.1 years; 37 Met, 36 Val hemizygosity) blind to clinical data and assessed effects on symptoms and frontal functioning. RESULTS: The lower activity Met allele was not significantly more prevalent than the Val allele in 33 subjects with schizophrenia. Excitement symptoms were more severe, however, and three frontal cognitive tests (theory of mind, Trails B, and olfactory identification), communication, and social functioning measures showed significantly worse performance with Met allele hemizygosity, even after accounting for effects of schizophrenia. CONCLUSIONS: The results suggest that hemizygosity of the COMT functional allele exerts an effect on some measures of frontal functioning in 22q11DS. Elevated levels of tonic dopamine activation associated with the COMT Met allele may underlie these aspects of expression. We must look elsewhere for causes of the high prevalence of schizophrenia in 22q11DS, however.     

Attention deficits in children with 22q.11 deletion syndrome

This study examined attention abilities of children with 22q.11 deletion syndrome. Thirty children (14 males, 16 females; age range 7 to 13y) were given comprehensive neuropsychological and neuropsychiatric assessments. Learning disability was found in 13 children. Superiority in verbal over performance IQ was very common. Attention-deficit-hyperactivity disorder (mainly of inattentive subtype) was diagnosed in 13 children. There appeared to be a relation between low IQ and presence of autism spectrum problems. The presence of attention deficits was clearly supported by the scores on the Child Behavior Checklist and the Conners Questionnaire. On the Becker attention tests the reaction times were significantly longer in the two visual and auditory tests, indicating that the ability to sustain attention is critically impaired in this group. A tendency of inferiority on auditory compared with visual tests was noted but there were no specific problems with the focus-execute aspect of attention.     

Neuromotor deficits in children with the 22q11 deletion syndrome.

The 22q11 chromosomal deletion syndrome (22q11DS) is associated with a heterogeneous physical phenotype, neurocognitive deficits, and increased risk of later psychiatric illness. Sporadic clinical reports suggested motor differences, but quantitative studies of movement in children with 22q11DS are rare. If present in a majority of affected school-age children, characterization of neuromotor deficits may prove to be critical for intervention, neurocognitive test interpretation, and understanding etiology. We administered the Movement Assessment Battery for Children to 72 children ages 4.3 to 16.1, including 49 children confirmed positive for the 22q11 deletion and 23 control siblings. We predicted a higher frequency of global and domain impairment in manual dexterity, eye-hand coordination, and balance among affected children. Ninety-four percent of affected children had marked neuromotor deficits, and group scores differed broadly for both global and subarea measures. Secondary analyses showed no impairment differences between younger and older children with 22q11DS, and longitudinal trajectories for 12 affected children suggested stability of deficits over 3-year intervals. Neuromotor deficits in children with 22q11DS occur early in development, continue throughout the school-age years, should be considered in the interpretation of motor-based achievement and IQ tests, and require targeted and ongoing remediation throughout childhood and adolescence. Further studies examining the specificity of motor impairment to 22q11DS are needed.     

Lower prepulse inhibition in children with the 22q11 deletion syndrome

OBJECTIVE: The 22q11 deletion syndrome is associated with a range of possible physical anomalies, probable ongoing learning disabilities, and a specific constellation of neuropsychological deficits, including impairments in selective and executive visual attention, working memory, and sensorimotor functioning. It has been estimated that 25% of the children with 22q11 deletion syndrome go on to develop schizophrenia in late adolescence or adulthood. This is of urgent concern. Specification of early brain network vulnerabilities may provide a basis for early intervention while indicating critical links between genes and severe psychiatric illness. Neuropsychological studies of children with 22q11 deletion syndrome have implicated an array of potentially aberrant brain pathways. This study was conducted to determine whether preattentive processing ("sensorimotor gating") deficits are present in this population. METHOD: The authors administered a test of prepulse inhibition to 25 children with 22q11 deletion syndrome and their 23 sibling comparison subjects, ages 6-13. It was predicted that the children with 22q11 deletion syndrome would have lower prepulse inhibition than the comparison subjects. RESULTS: Prepulse inhibition in the children with 22q11 deletion syndrome (26.06%) was significantly less than that of the sibling comparison subjects (46.41%). Secondary analyses suggested that this decrement did not reflect developmental delay, and lower prepulse inhibition was associated with particular subsyndromal symptoms in some children. CONCLUSIONS: Sensorimotor gating is lower in children with 22q11 deletion syndrome. These findings may indicate specific brain circuits that are anomalous in 22q11 deletion syndrome.     

Cognitive phenotype and psychiatric disorder in 22q11.2 deletion syndrome: A review

The behavioural phenotype of 22q11.2 deletion syndrome syndrome (22q11DS), one of the most common human multiple anomaly syndromes, frequently includes intellectual disability (ID) together with high risk of diagnosis of psychotic disorders including schizophrenia. Candidate cognitive endophenotypes include problems with retrieval of contextual information from memory and in executive control and focussing of attention. 22q11DS may offer a model of the relationship between ID and risk of psychiatric disorder. This paper reviews research on the relationship between the cognitive phenotype and the development of psychiatric disorders in 22q11DS.Aspects of cognitive function including verbal I.Q., visual memory, and executive function, are associated with mental health outcome in people with 22q11DS. This relationship may result from a common neurobiological basis for the cognitive difficulties and psychiatric disorders. Some of the cognitive difficulties experienced by people with 22q11DS, especially in attention, memory retrieval, and face processing, may, however, in themselves constitute risk factors for development of hallucinations and paranoid delusions.Future research into factors leading to psychiatric disorder in people with 22q11DS should include assessment of social and psychological factors including life events, symptoms associated with trauma, attachment, and self-esteem, which together with cognitive risk factors may mediate mental health outcome.     

Disabilities and cognition in children and adolescents with 22q11 deletion syndrome

The purpose of this study was to investigate cognitive and other disabilities in children and adolescents with 22q11 deletion syndrome. Thirty-three children (15 females, 18 males; age range 3 to 19y, median 7y 6mo) with 22q11 deletion were investigated for growth, development, neurology, cognition, motor function, and participation (measured as handicap**). Half of the children had never crawled, although they had shuffled, and commencement of walking was delayed (mean 18mo, SD 6mo). Hypotonia was found in 25 and poor balance in 24 of the 33 children; 17 out of 27 had definite motor problems, including two with spastic hemiplegia. Intelligence quotient (IQ) range was 50 to 100. Eleven patients had an IQ below 70, and 15 between 70 and 84. Verbal IQ was higher than Performance IQ. Level of handicap within the study group was considered moderate, and all but one child had extra support at school. We conclude that children with 22q11 deletion syndrome have multiple neurological, motor, and cognitive problems. Although the severity and number of problems varies, the combination of impairments and disabilities results in a low level of participation.     

Chromosome 22q11 deletion syndrome (CATCH 22): neuropsychiatric and neuropsychological aspects

Twenty children and young adults (age range 5 to 33 years, 12 females and eight males) with genetically confirmed 22q11 deletion syndrome (CATCH 22: Cardiac anomaly, Anomalous face, Thymus hypoplasia/aplasia, Cleft palate, and Hypocalcaemia), recruited from a large ongoing study, were given comprehensive assessments with a view to determining the pattern of neuropsychiatric and neuropsychological deficits thought to be part of the syndrome in many cases. IQ ranged between 46 and 100 with a mean score of 70. Half the group had an IQ <70. In 13 individuals, attention-deficit-hyperactivity disorder (ADHD), mainly inattentive or combined type in most cases, and/or autism spectrum problems were diagnosed. Many participants, even among those who had an IQ within the normal range and had neither ADHD nor autistic spectrum problems, showed a characteristic and pronounced behavioural profile with low mental energy, initiation difficulties, deficits in sustained attention, and social interaction (often augmented by limited facial expression and communication and speech problems).