Volumetric MRI Assessment of Brain and Spinal Cord in Finnish Twins Discordant for Multiple Sclerosis

Background and Objective. Brain size, white matter hyperintensity, and the development of brain atrophy are known to be highly heritable. The decrease of brain volume starts from the very onset of multiple sclerosis and is 10-fold compared with normal aging. The aim of this study was to assess whether the brain and spinal cord volumes and the volume of white matter lesions differed between twins with multiple sclerosis and their asymptomatic co-twins.
Material and Methods. A co-twin control method was used to evaluate whether the brain and spinal cord volumes differ between twins with multiple sclerosis and their co-twins. Nineteen twin pairs were studied neurologically, and the volumes of T1, T2, FLAIR, and gadolinium-enhanced lesions and those of the brain and the spinal cord were obtained by magnetic resonance imaging. Results. Significant differences in the brain (P=0.064) or spinal cord (P=0.648) volumes were not detected. Four of the 7 monozygotic and 5 of the 12 dizygotic co-twins had focal brain white matter lesions, but none fulfilled the magnetic resonance imaging criteria of Barkhof. Spinal cord lesions were not seen in any of the co-twins.
Conclusions. The absence of a significant difference in the brain or spinal cord volume between the twins with multiple sclerosis and their co-twins supports the recent observation of brain size and the development of brain atrophy being highly heritable.