Study aim: The aim is to evaluate the effect of transcranial direct current stimulation (tDCS) alone and combined with cognitive rehabilitation on attention, memory, and neuroplasticity markers including brain derived neurotrophic factor (BDNF) and diffusion tensor imaging (DTI) in multiple sclerosis patients. Design: Interventional randomized controlled trial with block randomization, parallel design, double blind, sham controlled, phase not applicable, on 45 patients. Random sequence generated by statistical software and allocation concealment maintained using sealed opaque envelopes. Settings and conduct: The study will be conducted at a multiple sclerosis center in tehran loghman hospital. After baseline assessment, patients will be randomly assigned to three groups. tDCS sessions will be delivered using preprogrammed devices. Patients, caregivers, and outcome assessors are blinded. Blood sampling for BDNF measurement and DTI imaging will be performed before and after the intervention. Participants/Inclusion and exclusion criteria: Inclusion criteria: Age 18 to 50 years, diagnosis of relapsing remitting multiple sclerosis, EDSS less than five, presence of cognitive impairment based on neuropsychological tests, willingness and informed consent. Exclusion criteria: History of seizure, psychiatric disorder requiring antipsychotics, pregnancy, left handedness, recent relapse requiring steroids, history of brain surgery or intracranial metallic clip, unwillingness or inability to complete sessions. Intervention groups: Group 1: Transcranial direct current stimulation (tDCS). Group 2: Transcranial direct current stimulation combined with cognitive rehabilitation. Group 3: Sham stimulation (inactive stimulation without effective current). Main outcome variables: Improvement of attention; improvement of verbal and spatial memory; improvement of inhibitory control; change in BDNF level; change in DTI indices.