Magnetization transfer ratio measurements of the brain in children with tuberous sclerosis complex

Background: Magnetization transfer contrast and magnetization transfer ratio (MTR) in brain are mainly related to the presence of myelin. Neuropathological studies of brain lesions in tuberous sclerosis complex (TSC) have demonstrated disordered myelin sheaths. Objective: To evaluate the MTR of the brain in children with TSC and to compare with that in controls. Materials and methods: Four patients (aged 0.41–8.4 years, mean 2.5 years) with TSC and four age- and sex-matched controls were evaluated with classic MR sequences and with a three-dimensional gradient-echo sequence without and with magnetization transfer pre-pulse. The MTR was calculated as: (SI₀−SI_m)/SI₀×100%, where SI_m refers to signal intensity from an image acquired with a magnetization transfer pre-pulse and SI₀ the signal intensity from the image acquired without a magnetization transfer pre-pulse. Results: The MTR values of cortical tubers (44.1±4.1), of subependymal nodules (51.6±4.8) and of white matter lesions (52.4±1.8) were significantly lower than those of cortex (58.7±3.53), of basal ganglia (caudate nucleus 58.2±2.8, putamen 59.6±2.5, thalamus 61.3±2.4) and of white matter (64.2±2.5) in controls (P<0.001). The MTR of normal-appearing white matter (61.2±3.0) in patients was lower than that of white matter in controls (P<0.01). The MTR of cortex and basal ganglia in patients was not significantly different from that in controls. Conclusions: MTR measurements not only provide semiquantitative information for TSC lesions but also reveal more extensive disease.