Cognitive functions in radiological isolated syndrome

Introduction: Radiologically isolated syndrome is defined as incidentally detecting lesions consistent with multiple sclerosis (MS) on magnetic resonance imaging (MRI) taken for other reasons than any symptoms or signs in the subjects not having symptoms or signs clinically consistent with MS. The studies have reported that in the subjects with diagnosis of radiologically isolated syndrome, clinical condition consistent with MS develop within 5 years in one third of them and in within 10 years in 51.2% of them. The accumulated data has given rise to the view that the radiologically isolated syndrome reflects preclinical or subclinical pahse of MS. Frequency of cognitive impairment ranges between 43% and 70% in the patients with MS. It has been reported that the cases of radiologically isolated syndrome have cognitive impairment at a rate of 27-31% on the cognitive tests even though it is not clinically obvious. Furthermore, cognitive impairment patters of such cases is similar to that in MS. May be the first manifestation of such cases is subclinical cognitive involvement. Objectives: In the present study, it was aimed to assess cognitive function using the battery of Symbol Digit Modalities Test, California Verbal Learning Test-II, Brief Visuospatial Memory Test-Revised testlerini içeren Brief International Cognitive Assessment for MS in the subjects presenting to the outpatient clinic of Neurology Department of Medical Faculty of Celal Bayar University and being diagnosed as having radiologically isolated syndrome. Methods: The present study included 28 subjects presenting to outpatient clinic of Neurology Department of Medical Faculty of Celal Bayar University with signs and symptoms not suggestive of multiple sclerosis and having lesions consistent with MS on cranial MRI and being diagnosed as having radiologically isolated syndrome according to diagnostic criteria of 2017 Magnetic Resonance Imaging in Multiple Sclerosis. Control subjects included 20 healthy individuals matched for age, educational level, and sex. Battery of Brief International Cognitive Assessment for MS was used to measure cognitive functioning in both groups. Findings: Although the subjects had no any signs of cognitive impairment, scores on the Symbol Digit Modalities Test, California Verbal Learning Test-II, and Brief Visuospatial Memory Test-Revised were found to be significantly lower in the group of radiologically isolated syndrome than in the control group. No significant relationship was found between the cognitive test scores and total number of lesions and number of lesions on different locations. Additionally, no significant relationship was found between the cognitive test scores and oligoclonal band and immunoglobulin G index in the cerebro-spinal fluid and visual evoked potentials in the subjects undergoing these investigations. Conclusions: As in other studies, cognitive impairment not being manifested was reported in the present study. This subclinical cognitive involvement is highly likely due to demyelinating process. Thus, all cases of radiologically isolated syndrome should be assessed for cognitive functioning and their follow-up should be performed using not only clinical and magnetic resonance imaging but also cognitive tests. Those with cognitive impairment detected in the first assessment should be followed closely and at more frequent intervals, and thus they should be given chance of having diagnosis of multiple sclerosis and starting the treatment earlier. Additionally, studies with higher number of subjects should be performed to determine predictive value of the cognitive impairment.