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Corpus callosal signal intensity in treatment-naive pediatric obsessive compulsive disorders
F P Mac Master1, M S Keshavan, E L Dick
1Wayne State University School of Medicine, Detroit, MI, USA.
Insights
Pediatric obsessive compulsive disorder (OCD) shows abnormal myelinization in the corpus callosum, specifically the genu region. This myelinization abnormality correlates with OCD symptom severity and may impact brain circuit function.
Area of Science:
- Neuroscience
- Child Psychiatry
- Radiology
Background:
- Obsessive compulsive disorder (OCD) is a prevalent childhood disorder.
- Previous research indicated corpus callosum (CC) abnormalities in pediatric OCD.
- Aberrant myelinization was hypothesized as a potential cause for these CC abnormalities.
Purpose of the Study:
- To investigate myelinization in the CC of pediatric OCD patients.
- To characterize CC signal intensity (SI) as an index of myelinization.
- To correlate CC SI with OCD symptom severity.
Main Methods:
- Compared CC signal intensity (SI) from MRI scans.
- Analyzed 21 treatment-naive pediatric OCD patients and 21 matched controls.
- Examined regional CC SI, focusing on the genu, body, and splenium.
Main Results:
- OCD patients exhibited significantly lower mean total genu SI compared to controls.
- This abnormality was localized to the anterior genu, connecting ventral prefrontal cortex and striatum.
- Lower genu SI correlated inversely with OCD symptom severity.
Conclusions:
- Developmental abnormalities in genu myelination may occur in early-onset OCD.
- Altered genu myelination in OCD patients could affect prefrontal cortex-striatal circuit function.
- Findings suggest myelinization as a key factor in pediatric OCD pathophysiology.
Abstract:
1. Obsessive compulsive disorder (OCD) is increasingly recognized as a severe, highly prevalent and chronically disabling disorder, emerging during childhood in as many as 80% of cases. The authors previously found significant abnormalities in the region of the corpus callosum (CC) connecting ventral prefrontal cortex and striatum in pediatric OCD patients compared to controls that correlated significantly with OCD symptom severity. We speculated that this abnormality might reflect aberrant myelinization in OCD patients. 2. In order to better characterize the abnormality, the authors examined CC signal intensity (SI), believed to be a reliable index of myelinization of the CC. Lower numbers would indicate a greater concentration of white matter, while higher numbers indicate higher concentrations of gray matter. We compared the SI from midsagittal magnetic resonance images of 21 treatment-naive OCD patients, 7.2-17.7 years, and 21 case-matched healthy controls to examine regional CC signal intensity of the anterior, middle and posterior genu, body, isthmus, and the anterior, middle and the posterior splenii. 3. Mean total genu SI for the patient group (.993 + .006) was significantly less than the total genu SI of controls (.994 + .006) at F(1,37) = 4.73; p = .036. This abnormality in SI was localized to the CC region connecting ventral PFC and striatum, the anterior genu for the OCD group (.991 + .007) which was also less than control (.995 + .007) at F(1,37) = 5.47; p = .025., with no abnormality observed in middle or posterior genu regions. Genu SI was also inversely correlated with OCD symptom severity (r = -.55, p = .013) but not illness duration. Genu SI also correlated positively with genu area (r = .52, p = .020) in OCD patients but not controls. 4. Developmental abnormalities in genu size may arise from abnormalities in myelination in early onset OCD patients. The increased genu myelination observed in OCD patients may alter signal transduction and function of VPFC-striatal association circuits.