Increased hippocampal volume in schizophrenics' parents with ancestral history of schizophrenia

Hippocampal volume in first-episode schizophrenia and longitudinal course of the illness

OBJECTIVES

Several lines of evidence suggest an adverse effect of psychotic episodes on brain morphology. It is not clear if this relationship reflects the cumulative effect of psychotic outbursts on the gradual progressive reduction of hippocampal tissue or an increased tendency toward psychotic episodes in patients with a smaller hippocampus at the beginning of the illness.

METHODS

This is a longitudinal 4-year prospective study of patients with first-episode schizophrenia (FES, N = 58). Baseline brain anatomical scans (at FES) were analysed using voxel-based morphometry and atlas-based volumetry of the hippocampal subfields. The effects of first-episode duration on the hippocampal morphology, and the effect of baseline hippocampal morphology on illness course with relapses, number of psychotic episodes and residual symptoms were analysed.

RESULTS

A significant negative correlation was detected between first-episode duration and baseline hippocampal morphology. Relapse, number of psychotic episodes and residual symptoms had no correlation with baseline hippocampal volume.

CONCLUSIONS

We replicated the effect of psychosis duration on hippocampal volume already at the time first-episode, which supports the concept of toxicity of psychosis. The indices of a later unfavourable course of schizophrenia had no correlation with baseline brain morphology, suggesting that there is no baseline morphological abnormality of the hippocampus that predisposes the patient to frequent psychotic outbursts.

Neural Correlates of Enhanced Genetic Risk for Schizophrenia

Schizophrenia is a disabling psychotic disorder characterized by hallucinations, delusions, and impaired functioning in many aspects of everyday life. The established condition generally becomes manifest in early adulthood, and evidence suggests that one of the most important risk factors for developing the disorder is inherited vulnerability. The established illness has been shown to be associated with deficits in many domains of cognitive function, along with structural and functional brain abnormalities, most notably in pre-frontal and temporal lobes. However, such studies have not been able to determine the extent to which such deficits relate to the presence of a schizophrenic predisposition, the presence of symptoms, and/or medication effects. A number of research groups have therefore turned to the study of relatives of affected individuals with the aim of determining if similar cognitive deficits and brain abnormalities are also found in those with increased genetic vulnerability to the disorder. In this article, studies on such individuals are discussed. It is concluded that deficits are apparent in relatives that are similar to but less marked than those seen in patients with schizophrenia.

Putative structural neuroimaging endophenotypes in schizophrenia: a comprehensive review of the current evidence

The genetic contribution to schizophrenia etiopathogenesis is underscored by the fact that the best predictor of developing schizophrenia is having an affected first-degree relative, which increases lifetime risk by tenfold, as well as the observation that when both parents are affected, the risk of schizophrenia increases to approximately 50%, compared with 1% in the general population. The search to elucidate the complex genetic architecture of schizophrenia has employed various approaches, including twin and family studies to examine co-aggregation of brain abnormalities, studies on genetic linkage and studies using genome-wide association to identify genetic variations associated with schizophrenia. ‘Endophenotypes’, or ‘intermediate phenotypes’, are potentially narrower constructs of genetic risk. Hypothetically, they are intermediate in the pathway between genetic variation and clinical phenotypes and can supposedly be implemented to assist in the identification of genetic diathesis for schizophrenia and, possibly, in redefining clinical phenomenology.

Maternal immune activation in mice delays myelination and axonal development in the hippocampus of the offspring

Epidemiological data suggest a relationship between maternal infection and a high incidence of schizophrenia in offspring. An animal model based on this hypothesis was made by injecting double-stranded RNA, polyinosinic-polycytidylic acid (poly-I:C), into early pregnant mice, and their offspring were examined for biochemical and histological abnormalities. Mouse brains were examined with special reference to oligodendrocytes, which have been implicated in several neurodevelopmental disorders. We detected a significant decrease of myelin basic protein (MBP) mRNA and protein at early postnatal periods in poly-I:C mice. MBP immunocytochemistry and electron microscopy revealed that the hippocampus of juvenile poly-I:C mice was less myelinated than in PBS mice, with no significant loss of oligodendrocytes. In addition, axonal diameters were significantly smaller in juvenile poly-I:C mice than in control mice. These abnormalities reverted to normal levels when the animals reached the adult stage. These findings suggest that retarded myelination and axonal abnormalities in early postnatal stages caused by maternal immune activation could be related to schizophrenia-related behaviors in adulthood.

MRI brain volume abnormalities in young, nonpsychotic relatives of schizophrenia probands are associated with subsequent prodromal symptoms

Schizophrenia is characterized by subtle but well-replicated total and regional (frontal and temporal) brain tissue volume deficits. Studies of individuals at-risk for developing schizophrenia suggest that the onset of brain volume decrement may closely pre-date overt manifestations of schizophrenia, making brain volume abnormalities potential predictors for early identification. In an ongoing longitudinal morphometric MRI study of young, nonpsychotic first- or second-degree relatives of schizophrenia probands, we compared brain volumes in 46 relatives who are still within age range for developing schizophrenia against comparison groups of 46 schizophrenia patients and 46 healthy volunteers without family history of schizophrenia. Relatives had similar brain volume abnormalities as schizophrenia patients albeit less severe. Relatives had significantly larger whole brain, frontal, temporal and parietal gray matter (GM) volumes than patients. Relatives also had significantly smaller frontal GM volumes than healthy volunteers. Both relatives and patients had significantly larger whole brain WM (specifically parietal WM) volumes compared to healthy volunteers. Abnormally greater WM volumes in relatives and patients are suggestive of genetically-mediated dysmaturation of the age-expected myelination during adolescence through mid adulthood. On prodromal symptoms assessed in relatives one year after MRI brain scans, initial GM deficits as well as larger WM volumes correlated significantly with greater severity of subsequent prodromal symptoms. Together with previous genetic high-risk studies of adolescent or young adult relatives, these findings indicate that premorbid MRI brain abnormalities may be of predictive value for the early identification of schizophrenia.

Magnetic resonance imaging study of the ventricle-brain ratio in parents of schizophrenia subjects

Structural abnormalities found in probands with schizophrenia have been reported to occur to some degree in their unaffected relatives. However, there has yet to be a study that has focused on brain changes of parents of schizophrenics who are not the presumed obligate carriers. Using MRI, the authors studied the ventricle-brain ratio (VBR) of 9 pairs of parents of schizophrenics and 18 age- and sex-matched healthy controls. VBRs of the unaffected parents of schizophrenics were significantly larger than those of the controls. Our results suggest that large VBRs aggregate in the parents of schizophrenics and may serve as an indicator of vulnerability to the disorder.

Verbal memory processes in schizophrenia patients and biological relatives of schizophrenia patients: intact implicit memory, impaired explicit recollection

Verbal memory deficits are arguably the most common cognitive abnormalities in biological relatives of schizophrenia patients. Because verbal memory is a complex cognitive function, it is necessary to differentiate its intact and compromised aspects in order to reveal aberrant neural systems that reflect genetic risk in relatives of schizophrenia patients. Using an experimental verbal memory task, we examined encoding, free-recall, repetition priming, and recognition of verbal material in 22 schizophrenia patients, 22 first-degree biological relatives of schizophrenia patients, and 23 nonpsychiatric control participants. Schizophrenia patients exhibited intact repetition priming, but worse size judgment task performance (encoding), recall, and recognition than the control participants. Biological relatives of schizophrenia patients exhibited intact size judgment task performance, repetition priming, and recognition, but a free-recall deficit. Although size judgment task performance at encoding was associated with recall of verbal material in schizophrenia and control groups, in the relative group encoding performance was associated with the degree of repetition priming. Findings are consistent with impaired explicit recollection of verbal material, but intact implicit verbal memory in schizophrenia patients and biological relatives of schizophrenia patients.

Hippocampal volume in familial and nonfamilial schizophrenic probands and their unaffected relatives

BACKGROUND

There is evidence for hippocampal volume loss in schizophrenia, but the etiology of this remains unclear. The aim of our study was to assess the contribution of familial liability and obstetric complications to hippocampal volume reduction in schizophrenia.

METHODS

Hippocampal volumes were obtained using stereological methods from magnetic resonance scans performed on 35 schizophrenic probands from multiply affected families and 63 of their unaffected relatives, as well as 31 schizophrenic probands from families with no other affected members, 33 of their unaffected relatives, and 68 control subjects.

RESULTS

Probands with schizophrenia, regardless of family history, had significant volume reduction of the left hippocampus. Hippocampal volume was not significantly reduced in either group of relatives. Obstetric complications were associated with left hippocampal volume reduction.

CONCLUSIONS

We failed to find evidence that hippocampal volume loss is associated with familial liability to schizophrenia but have confirmed the association between hippocampal volume reduction and exposure to obstetric complications.