Diffusion tensor imaging identifies deficits in white matter microstructure in subjects with type 1 diabetes that correlate with reduced neurocognitive function

Abstract

Objective: Long-standing type 1 diabetes is associated with deficits on neurocognitive testing that suggest central white matter dysfunction. This study investigated whether diffusion tensor imaging (DTI), a type of magnetic resonance imaging that measures white matter integrity quantitatively, could identify white matter microstructural deficits in patients with long-standing type 1 diabetes and whether these differences would be associated with deficits found by neurocognitive tests.

Research design and methods: Twenty-five subjects with type 1 diabetes for at least 15 years and 25 age- and sex-matched control subjects completed DTI on a 3.0 Tesla scanner and a battery of neurocognitive tests. Fractional anisotropy was calculated for the major white matter tracts of the brain.

Results: Diabetic subjects had significantly lower mean fractional anisotropy than control subjects in the posterior corona radiata and the optic radiation (P < 0.002). In type 1 diabetic subjects, reduced fractional anisotropy correlated with poorer performance on the copy portion of the Rey-Osterreith Complex Figure Drawing Test and the Grooved Peg Board Test, both of which are believed to assess white matter function. Reduced fractional anisotropy also correlated with duration of diabetes and increased A1C. A history of severe hypoglycemia did not correlate with fractional anisotropy.

Conclusions: DTI can detect white matter microstructural deficits in subjects with long-standing type 1 diabetes. These deficits correlate with poorer performance on selected neurocognitive tests of white matter function.

FIG. 1.

Fractional anisotropy in major brain regions. A: Superior frontal region, inferior frontal region, occipital region, and region superior to corpus callosum (going clockwise starting at top left). There is ∼15% overlap between the frontal regions and the region superior to the corpus callosum. B: Fractional anisotropy in major brain regions; there was no significant difference in any of the major regions. □, type 1 diabetic subjects; ▪, control subjects. Data are means ± SE.

FIG. 2.

Fractional anisotropy of specific white matter tracts. A: Left-coronal view: corona radiata* (red), superior longitudinal fasciculus (yellow), corpus callosum isthmus (blue), and cingulum (green). Middle-saggital view: genu (green), rostral body (purple), anterior midbody (yellow), posterior midbody (red), isthmus (blue), and splenium (teal) of corpus callosum. Right-axial view: optic radiation* (orange). *P < 0.002 between diabetic subjects and controls. B: Fractional anisotropy in posterior corona radiata and optic radiation. □, type 1 diabetic subjects; ▪, control subjects. *P < 0.002 between diabetic subjects and controls. Data are means ± SE. (Please see http://dx.doi.org/10.2337/db08-0724 for a high-quality digital representation of this image.)

FIG. 3.

Rey-O copy score versus fractional anisotropy in the posterior corona radiata. Overall Spearman correlation = 0.43 (P = 0.0018). ○, Control subjects; , diabetic subjects without microvascular complications; ▴, diabetic subjects with microvascular complications.