The deficit subtype of schizophrenia is characterized by white matter tract disruption, while all subtypes of schizophrenia feature a reduction in cortical thickness, a cross-sectional neuroimaging study has found.
Patients with deficit schizophrenia showed significant disruption of white matter at the right inferior longitudinal fasciculus, the right arcuate fasciculus, and the left uncinate fasciculus, compared with nondeficit patients and healthy controls, according to a study published in the March 6 online issue of JAMA Psychiatry (doi:10.1001/jamapsychiatry.2013.786).
The study, which used high-resolution MRI to compare 77 patients with schizophrenia – 18 with deficit and 59 nondeficit – and 79 healthy controls, found these features also were present within first-episode patients who showed deficit-like characteristics. The main characteristics of the deficit subtype include primary, enduring negative symptoms and impaired emotion processing, emotion expression, and social function.
“Our finding within first-episode patients that a more ‘deficit-like’ clinical picture was associated with greater impairment within these same white matter tracts supports the fact that white matter disruption in these patients is a feature of the clinical deficit subtype, rather than other factors such as long-term medication exposure or duration of illness,” wrote Dr. Aristotle N. Voineskos of the Centre for Addiction and Mental Health, Toronto, and his colleagues.
“In contrast, we also found that cortical thickness reductions were present in the same regions in both deficit and nondeficit patients compared with healthy controls, which supports the consistency of cortical thickness findings in different clinical subtypes,” they noted.
The areas of white matter most significantly altered in deficit patients connect regions of the brain involved in the expression and processing of emotion and in socioemotional functioning – functions that are typically impaired in patients with deficit schizophrenia and are present from the first episode.
“The major impairments and low recovery rates of these patients make this group a high priority for investigation,” the researchers wrote. “Furthermore, studying this more clinically homogeneous subgroup may facilitate biomarker discovery which has been a challenge not only for schizophrenia but for psychiatry research as a whole.”
The finding of cortical thickness reductions in the same regions of the brain in both deficit and nondeficit subtype patients supports the idea that this is a characteristic clinical feature of schizophrenia, Dr. Voineskos and his associates said.
Although most of the patients included in the study had a long history of schizophrenia and a history of antipsychotic medication use, researchers also included patients with first-episode schizophrenia to account for age, illness duration, and effects of medication.
“These data were particularly helpful in light of recent, somewhat conflicting reports regarding the effects of these variables on cortical brain structure,” the researchers wrote.
Individual researchers were supported by the Canadian Institutes of Health, American Psychiatric Association/American Psychiatric Institute for Research and Education, the Brain and Behavior Research Foundation, the Ontario Mental Health Foundation, and the Centre for Addiction and Mental Health and the CAMH Foundation.
Dr. Voineskos had no disclosures. His coauthors disclosed various involvements with numerous pharmaceutical companies, including Forest Laboratories, Wyeth, Takeda, and Lundbeck Canada.