Axonal injury develops in the course of multiple sclerosis and results in Wallerian degeneration. This contributes to neuronal injury and brain tissue atrophy. The magnitude of the atrophy depends on the disease duration and severity of the inflammatory processes and the degree of neurodegeneration is difficult to predict a priori.

To identify the range of annually adjusted brain volume loss in multiple sclerosis patients between 2005 and 2017.

To address the problem T1-weighted volumetric sequence was included routine MRI acquisition in multiple sclerosis patients between 2005 and 2009 to identify the pattern of atrophy. The structural analysis protocol was restarted in 2014 and enabled the acquisition of T1-weighted MPRAGE images in yearly follow-up MRI scans performed in all MS patients. We identified the patients who were scanned in both periods to detect the magnitude of brain volume loss during the interval of 7 to 12 years. Brain volume segmentation was performed using longitudinal evaluation pipeline of the Freesurfer 5.3. The volume of the whole brain,  lateral ventricles, thalamus and corpus callosum were analyzed using R-CRAN open statistical analysis environment (www.r-project.org). Average Annual atrophy rate was calculated by dividing the percent difference by the number of years of follow-up duration. 

We analyzed 45 patients (26 female). Median age was 41.5 years (IQR 36-48; range 31-61). Disease duration median follow-up was 8.5 years (IQR 8-10).  Median annualized percent volume change for the whole brain volume was -0.08 (IQR -0.14 - -0.04, range -0.37-0.06). There was no association of disease follow-up duration and annualized atrophy rate.

Long-term follow-up indicates that there is a large variation in the annualized atrophy rate in the treated cohort of patients.  Study limitations include: each of the MRI study timepoints was acquired on a different scanner and large attrition rate caused by the long duration of the follow-up.