Cognitive functions in neuromyelitis optica

Abstract

Background: Neuromyelitis optica (NMO) is characterized by optic neuritis and longitudinally extensive acute transverse myelitis. The brain is generally considered healthy in NMO, though very recent studies have demonstrated that magnetic resonance imaging abnormalities may be observed in various brain regions of NMO patients. To date, cognitive functions have never been investigated in NMO.

Objective: To investigate cognitive functions in a cohort of 30 patients with NMO.

Design: Observational, prospective study.

Patients: We studied 30 patients with NMO and compared them with 30 patients with multiple sclerosis and 30 healthy controls matched for age, sex, and educational level. Main Outcome Measure We applied a French translation of the Brief Repeatable Battery of Neuropsychological Tests for Multiple Sclerosis and 3 additional tests.

Results: Cognitive performance was significantly lower in the NMO and multiple sclerosis groups than in healthy controls for the 2-second (P< .001) and 3-second (P= .001) Paced Auditory Serial Addition Test, the digit symbol modality test (P= .005), word generation (P= .02), and forward (P= .002) and backward (P= .007) digit span test. We did not observe any difference in test performance between NMO and multiple sclerosis patients. We found no differences between the 3 groups for the other tests. We did not find any correlation between clinical, biological, or magnetic resonance imaging results and cognitive dysfunction.

Conclusions: This study confirms the recent concept of a possible brain involvement in NMO. Additional studies are needed to confirm these initial results and to better understand the mechanisms of such abnormalities.