Neurodevelopmental mechanisms may underlie visual hallucinations in schizophrenia

By Will Boggs MD

Individuals with schizophrenia who have visual hallucinations show deviations in cortical sulcation, a marker of brain development, researchers from France report.

"This basic research provides for the first time evidences for neurodevelopmental deviations associated with visual hallucinations (VH)," Dr. Arnaud Cachia from Centre de Psychiatrie & Neurosciences in Paris and Dr. Renaud Jardri from Universite de Lille told Reuters Health in a joint email.

"Considering VH as a marker of deviations during early neurodevelopmental processes allows a reinterpretation of clinical aspects of VH," they say.

"Hence," the researchers suggest, "the greater clinical impairment and greater compromise of overall functioning reported by patients experiencing VH may relate to a greater neurodevelopmental weight in this subgroup of patients."

As many as 80% of patients with schizophrenia experience auditory hallucinations (AH), compared with only about a quarter who have visual hallucinations, Drs. Cachia and Jardri and their colleagues write in Molecular Psychiatry, online October 28. There have been no brain imaging studies to investigate the neurodevelopmental processes associated with VH in these patients.

The team compared the cortical sulcation in healthy controls, patients with schizophrenia with AH only and patients with schizophrenia with AH plus VH. (VH almost never occurs in isolation in patients with schizophrenia).

Patients with schizophrenia had significantly less sulcation than did healthy controls, the researchers found. In the right hemisphere, but not in the left, cortical sulcation was significantly decreased in patients with AH plus VH, compared with patients with AH alone.

In the AH plus VH group, regional analyses revealed decreases in sulcation in the right parietal cortex and in the left Sylvian fissure, compared with AH-only patients. But none of the differences were significant following Bonferroni correction for multiple testing.

There were no significant differences between the groups in hemispheric gray matter, white matter, or cerebrospinal fluid (CSF) volumes.

"The identification of schizophrenia subgroups with high neurodevelopmental deviations, like patients with VH, should optimize the possibility for translating knowledge of a high heritability in schizophrenia into the search for structural genomic variants since these variants have been consistently reported to affect genes implicated in brain development," Dr. Cachia and Dr. Jardri said.

"In addition, this work supports the notion that visual hallucinations do not only concern neurological conditions but also schizophrenia, contrary to what has long been proposed," they suggest. "We hope such findings will impact clinical detection of VH experiences in patients with schizophrenia."

Dr. Judith M. Ford from University of California San Francisco, who was not involved in the new work, has also studied the neural underpinnings of visual hallucinations.

"While VH are generally neglected in clinical assessments in psychiatry, the Cachia et al data provide biological support for their distressing reality," she told Reuters Health by email. "So, instead of clinicians dismissing reports of VH in patients with schizophrenia as being 'over-endorsing', they should consider that VH do have biological reality."

"VH are typically studied in neurological patients where the etiology is much better understood," Dr. Ford said. "For me this raises the possibility of equifinality -- if the symptom is the same in two different clinical groups, but the diagnosis and etiologies are different, can we assume the same mechanisms are involved? If so, this raises many opportunities for research into the neural basis of visual hallucinations."

SOURCE: http://bit.ly/10DAgOp

Mol Psychiatry 2014.

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