The aim of this study was to assess cognitive complaints among Egyptian MS patients and to validate the CSQND as a screening tool for cognitive complaints in Egyptian MS patients.
After taking the CSQND questionnaire, 34% of our patients were found to have memory problems, 51% had concentration difficulties, 34% had language difficulties and 22.5% had space and time disorientation. In a multi-center study carried out across Italy, Nocentini et al. found that 33% of MS patients suffered from memory dysfunction, 43% suffered from reduced processing speed, 20% suffered from language difficulties and 23% suffered from visuo-perceptual dysfunction . In a cohort of 291 MS patients, Benedict and colleagues found 51.9% of patients to suffer impaired processing speed and 54.3% to suffer from memory dysfunction.  Other cohorts estimate memory problems to exist in up to 65% of MS patients , around 12–25% of MS patients suffer from attention difficulties , and around 25% of MS patients suffer from visuo-perceptual impairment .
Sadigh-Eteghad in a cohort of 115 MS patients, found that similar to this study, EDSS scores and disease duration were positively correlated with severity of CI, while unlike this study, age at disease onset and relapse rate were not correlated. However, in that study all variables except EDSS score significantly predicted CI severity . In another cohort of 125 MS patients, a significant association between age at onset, disease duration, and EDSS score and the risk of developing CI was found . Sandi and colleagues in a cohort of 553 CIS and RRMS patients found EDSS score to be significant predictor of CI, but they found no association between age at onset, disease duration and cognitive dysfunction . This can be explained by the different sample sizes and methodologies used in these studies.
In this study patients with MS performed poorly in SDMT, SDMT was affected in about 26% of patients with significant difference between patients and healthy controls. These results are similar to previous reports which found that 31% of Egyptian MS patients performed poorly in SDMT . Different studies showed relatively higher percentages with a range of 28–67% for SDMT total score [19,20,21], this may be explained by the relatively younger age, shorter disease duration and less disability in our cohort.
A statistically significant difference was found between patients and controls as regards the CSQND total score, where MS patients significantly had more cognitive complaints than controls as expected. This establishes the construct validity of the CSQND through “Known groups validity” which is a form of construct validation in which the validity is determined by the degree to which an instrument can demonstrate different scores for groups known to vary on the variables being measured .
The CSQND results were in agreement with results of SDMT of BICAMS establishing the concurrent validity of CSQND. The SDMT has been found to be the most sensitive individual cognitive measure for use in MS due to its predictive validity, high sensitivity and specificity, ease of administration, and patient-friendliness . The agreement of CSQND with SDMT which assesses the cognitive processing speed may suggest that cognitive symptoms in MS patients may be explained by affection in processing speed rather than true memory or executive dysfunction.
The test–retest reliability of CSQND was confirmed by correlating the CSQND results at the first application and 1 week later upon retesting both in patients and controls and a significantly positive correlation was found.
This study has proven the CSQND to be a valid and reliable tool for screening cognitive complaints of Egyptian MS patients. Limitations in this study were difficulty to assess objectively other masked MS symptoms other than CI which may affect cognition due to lack of resources. Further studies in different cohorts and different disease areas are still needed to establish the validity of CSQND as a screening tool for cognitive complaints in different neurological disorders.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.