Objective: To evaluate corpus callosum thickness and area in Parkinson’s disease (PD) subjects and the relationship of these measures with cognitive impairment.

Background: Many PD patients develop dementia (PDD) that may be preceded by mild cognitive impairment (PD-MCI). The corpus callosum is of particular interest in the setting of cognitive impairment given its critical role in interhemispheric communication. Decreased corpus callosum thickness and area have been demonstrated in subjects with other forms of cognitive impairment, but this finding has not been described previously in PD.

Methods: 94 PD and 24 healthy control (HC) subjects underwent MRI brain scans, clinical and neuropsychological evaluation, and cognitive classification using the International Parkinson and Movement Disorder Society criteria (cognitively normal [PD-NC], n = 26; PD-MCI, n = 46; PDD, n = 22; HC, n = 24). Z-scores for cognitive domains (attention/working memory, executive function, memory, language, visuospatial function) were calculated. Using the C8 image analysis program, callosal mean thickness and area values were calculated and normalized by total intracranial volume. Five callosal segments (anterior to posterior) were defined by the Hofer and Frahm parcellation scheme. Regional mean thickness and area values were compared with ANCOVA (age as covariate) between HC and PD subjects and then among PD cognitive groups, correcting for multiple comparisons. Stepwise linear regression analyses were performed on PD subjects’ cognitive domain scores and callosal segment thickness/area values, controlling for age.

Results: Compared to HCs, PD subjects had reduced mean thickness in anterior and mid-anterior segments (p’s<0.005) and reduced area in the other callosal segments (all p’s<0.005). No significant differences were seen in these measures among PD cognitive groups. Regression analyses showed significant associations among several cognitive domain scores and anterior callosal thicknesses and area.

Conclusions: PD subjects have reduced thickness in anterior segments of the corpus callosum and reduced area in multiple callosal regions as compared to HC subjects suggesting a relationship with the neurodegenerative process. The association between reduced anterior callosal thicknesses in PD and worse cognitive performance raises the possibility that disrupted connections to frontal cortical regions may play a role in certain PD cognitive functions.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/corpus-callosum-thickness-and-area-in-parkinsons-disease/