DTI-based tractography of the arcuate fasciculus in patients with polymicrogyria and language disorders

• Patients with PMG commonly present with language disorders.
• DTI-tractography allows parcellation and quantitative analysis of brain WM.
• The AF is a major association tract involved in human language.
• DTI-tractography demonstrates several qualitative and quantitative abnormalities of the AF in PMG.
• Disrupted AF may constitute an anatomical substrate for language disorders in PMG.

ObjectivesTo assess the integrity of the arcuate fasciculus (AF) with diffusion tensor imaging (DTI) and tractography in patients with congenital polymicrogyria (PMG) and language disorders.MethodsTwelve patients with PMG and 12 matched controls were prospectively evaluated with DTI (32 gradient encoding directions, b-value = 1000 s/mm2) at 3.0 T. The AF was virtually dissected with a deterministic streamline approach. DTI metrics included FA (fractional anisotropy), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). A subset of patients (n = 4) was evaluated to assess cognitive performance and language skills.ResultsQualitative evaluation revealed several abnormalities in tracts size and architecture in nearly all PMG patients. Remarkably, in 3 patients with bilateral PMG, the AF was not delineated on both hemispheres. In comparison to controls, patients exhibited significant decrease of FA (p = 0.003) in addition to increase of RD (p = 0.03) in the right AF, whereas there was significant increase of MD in the left AF (p = 0.04). All 4 patients with language evaluation had suboptimal performance on lexical fluency and prosodic linguistic.ConclusionsDTI and tractography suggest that the AF is severely disrupted in patients with PMG, providing an anatomical in vivo substrate for the language disorders commonly associated with these cortical malformations.