Microstructural Thalamic and Cortico-Thalamic Correlates of Cognitive Impairment in Pediatric Multiple Sclerosis (P6.267)

OBJECTIVE: To assess the role of microstructural abnormalities of thalamic connectivity defined regions and their cortical connections to cognitive impairment in pediatric multiple sclerosis (MS) patients. BACKGROUND: A large proportion of pediatric MS patients experience cognitive deficits, which have been related to the degree of thalamic atrophy. DESIGN/METHODS: Using a 3.0 T scanner, dual-echo, 3D T1-weighted and diffusion tensor MRI scans were acquired from 50 consecutive pediatric MS patients and 26 gender- and age-matched healthy controls (HC). Patients with abnormalities in 2 or more neuropsychological tests were classified as cognitively impaired (CI). Thalamic connectivity defined regions (CDRs) were segmented on the basis of their cortical connectivity using Diffusion Tractography-Based Parcellations. Between-group differences of CDRs and cortico-thalamic tract DT MRI metrics were assessed using Mann-Whitney and ANOVA tests. RESULTS: Seventeen pediatric MS patients (38.3[percnt]) were classified as CI. Thalamic volume did not differ between pediatric MS patients and HC, whereas it was significantly reduced in CI vs cognitively preserved (CP) pediatric MS patients. Compared to HC, MS patients showed reduced fractional anisotropy (FA) and increased mean diffusivity (MD) in the temporal connected CDRs, bilaterally, as well as in frontal, occipital, post-parietal, post-central and temporal cortico-thalamic tracts. Compared to CP, CI MS patients had an increased FA in motor and post-central connected CDRs, bilaterally, and in right occipital connected CDR. They also showed an increased MD in the right temporal connected CDR and motor cortico-thalamic tracts, bilaterally. CONCLUSIONS: In pediatric patients with MS, cognitive impairment seems to be mostly due to microstructural abnormalities in the thalami rather than to a cortico-thalamic disconnection. Study Supported by: Partially supported by a grant from Italian Ministry of Health (GR-2009-1529671).