Cognitive impairment in multiple sclerosis and neuromyelitis optica among Hong Kong Chinese

Abstract

INTRODUCTION: Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are important central nervous system inflammatory demyelinating disorders. Cognitive impairment is increasingly recognized in both MS and NMOSD. METHODS: We studied cognitive functions of Chinese MS and NMOSD patients followed up in Queen Mary Hospital by using a Chinese version of Rao’s Brief Repeatable Battery of Neuropsychological Tests (BRBN). The BRBN consisted of five groups of tests: (1) Symbol Digit Modalities Test (SDMT) and (2) Paced Auditory Serial Addition Test (PASAT) for sustained attention, concentration and speed of information processing; (3) Selective Reminding Test (SRT) for verbal immediate and delayed recall memory; (4) 10/36 Spatial Recall Test (SPART) for spatial immediate and delayed recall memory; and (5) Word List Generation Test (WLG) for verbal fluency on semantic stimulus; yielding a total of 9 test scores. An abnormal score is defined as that below the fifth percentile of the normative value derived from healthy subjects. Patients with abnormal scores in three or more tests were diagnosed as having cognitive impairment. RESULTS: A total of 30 healthy subjects (16 men; mean age, 37.3; range, 21-56 years), 17 NMOSD patients (15 women; mean age, 47; range, 28-69 years), and 21 MS patients (14 women; mean age, 40.5; range, 18-59 years) were studied. The mean disease duration was 80.5 months, the mean latest Expanded Disability Status Scale (EDSS) score was 2.7, 13 (76.5%) were AQP4 antibody positive and 10 (58.8%) had magnetic resonance imaging brain abnormalities for the NMOSD patients. The mean disease duration was 141.7 months and the mean latest EDSS score was 3.5 for the MS patients. Among the 17 NMOSD patients, five (29.4%) had impaired SDMT, six (35.3%) had impaired SRT, seven (41.2%) had impaired SPART, 7 (41.2%) had impaired PASAT, and 7 (41.2%) had impaired WLG. Overall, eight (47.1%) NMOSD patients had cognitive impairment. Among the 21 MS patients, 15 (71.4%) had impaired SDMT, 10 (47.6%) had impaired SRT, 9 (42.9%) had impaired SPART, 14 (66.7%) had impaired PASAT, and 14 (66.7%) had impaired WLG. Overall, 15 (71.4%) MS patients had cognitive impairment. CONCLUSION: Cognitive impairment is common among NMOSD and MS patients.