Primary and transitional progressive MS - A clinical and MRI cross-sectional study

Background: Ten percent of patients with MS have a progressive course from onset with no history of relapses or remissions. A smaller subgroup follow a similar progressive course but have a single relapse at some point (transitional progressive [TP] MS). To date these patients have been excluded from receiving licensed treatments for MS and from most therapeutic trials. Objective: To document the clinical and MRI characteristics of a large cohort of progressive patients, including 158 with primary progressive (PP) MS and 33 with TPMS. Data from a small reference group of 20 patients with secondary progressive (SP) MS are also presented for reference. Methods: Patients were recruited from six European centers. All underwent a clinical assessment including scoring on the Expanded Disability Status Scale (EDSS) and MRI of the brain and spinal cord. Results: The men-to-women ratio was 81:77 (51% men) in the PP group, 14:19 (42% men) in the TP group, and 5:15 (25% men) in the SP group. The mean age at disease onset was significantly higher in the PP group than it was in the other two groups (PP 40.2 years, TP 34.9 years, SP 28.7 years). On MRI the PP group had lower mean brain T2 and T1 hypointensity lesion loads than the SP group (T2 12.02 versus 27.74 cm(3), p = 0.001; T1 4.34 versus 7.04 cm(3), p = 0.015). The SP and TP cohorts had significantly more T2-weighted lesions in the spinal cord than the PP patients, and the SP cohort had the greatest degree of atrophy. There was a correlation in the PP and TP patients between EDSS score and brain and spinal cord atrophy (r = 0.3, 0.2, p less than or equal to 0.006) but not with brain lesion load, The PP and TP patients who presented with spinal cord pathology had significantly lower brain T2 and T1 lesion loads than those with non-spinal cord presentations (p = 0.002). Conclusions: The monitoring of disease progression in PPMS is difficult, although measures of atrophy correlate with the EDSS and appear most promising. This study increases our understanding of this unique patient group, which will be further expanded with the acquisition of serial data.