Frontotemporoparietal asymmetry and lack of illness awareness in schizophrenia.
BACKGROUND
Lack of illness awareness or anosognosia occurs in both schizophrenia and right hemisphere lesions due to stroke, dementia, and traumatic brain injury. In the latter conditions, anosognosia is thought to arise from unilateral hemispheric dysfunction or interhemispheric disequilibrium, which provides an anatomical model for exploring illness unawareness in other neuropsychiatric disorders, such as schizophrenia.


METHODS
Both voxel-based morphometry using Diffeomorphic Anatomical Registration through Exponentiated Lie Algebra (DARTEL) and a deformation-based morphology analysis of hemispheric asymmetry were performed on 52 treated schizophrenia subjects, exploring the relationship between illness awareness and gray matter volume. Analyses included age, gender, and total intracranial volume as covariates.


RESULTS
Hemispheric asymmetry analyses revealed illness unawareness was significantly associated with right < left hemisphere volumes in the anteroinferior temporal lobe (t = 4.83, P = 0.051) using DARTEL, and the dorsolateral prefrontal cortex (t = 5.80, P = 0.003) and parietal lobe (t = 4.3, P = 0.050) using the deformation-based approach. Trend level associations were identified in the right medial prefrontal cortex (t = 4.49, P = 0.127) using DARTEL. Lack of illness awareness was also strongly associated with reduced total white matter volume (r = 0.401, P < 0.01) and illness severity (r = 0.559, P < 0.01).


CONCLUSIONS
These results suggest a relationship between anosognosia and hemispheric asymmetry in schizophrenia, supporting previous volume-based MRI studies in schizophrenia that found a relationship between illness unawareness and reduced right hemisphere gray matter volume. Functional imaging studies are required to examine the neural mechanisms contributing to these structural observations.
Multimodal Imaging Group, Centre for Addiction and Mental Health, Toronto, Ontario, Canada.
Philip
P
Gerretsen
M Mallar
MM
Chakravarty
David
D
Mamo
Mahesh
M
Menon
Bruce G
BG
Pollock
Tarek K
TK
Rajji
Ariel
A
Graff-Guerrero
D000328:Adult; D000368:Aged; D001364:Awareness / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000473:pathology*; D012565:Schizophrenic Psychology; D013702:Temporal Lobe / Q000473:pathology*; D055815:Young Adult