Extended Interval Dosing Natalizumab and impact on neuropsychological deficits in Relapsing-Remitting Multiple Sclerosis.

Cognitive impairment and neuropsychiatric symptoms are frequently reported in Relapsing-Remitting Multiple Sclerosis (RRMS). Natalizumab (NTZ) is usually administered on a 4-weekly Standard Interval Dosing (SID) schedule. However, Extended Interval Dosing (EID) at 6-8 weekly intervals has been proven non-inferior regarding relapse risk, with a lower risk of Progressive Multifocal Leukoencephalopathy (PML). The impact of EID NTZ on neuropsychological deficits in RRMS has not been studied. To determine if EID NTZ demonstrates an improvement in neuropsychological parameters in RRMS patients. We performed a retrospective, observational analysis of 34 RRMS patients treated between August 2015-2017. Patients underwent baseline neuropsychological testing before commencing EID NTZ. A second evaluation was performed, on average 28 months after commencing treatment. Z scores at the initial assessment showed baseline cognitive impairment in multiple domains. 14/20 Z-scores showed an improvement post-NTZ and 5/14 reached statistical significance; namely Trails A (visual attention/processing speed), Line-orientation (visual-spatial), Picture-naming (word finding), Digital-Span (attention, executive function and memory) and Story-recall (memory). The Hospital Anxiety and Depression Scale (HADS) data remained unchanged. Correlation matrix showed no association between HADS scores, the time between assessments and the changes in Z scores. This data suggests the efficacy of EID NTZ in improving cognitive impairment in RRMS. A prospective observational study is warranted.