Transcranial Magnetic Stimulation (TMS) is a non-invasive method that can change the brain functions. It is used for therapeutic purposes in many psychiatric disorders. In addition to its clinical effect, TMS has also another effect increasing the cognitive performance.
The impairment in cognitive skills observed in neurodegenerative disorders like Dementia can be improved by the effects of TMS performed with correct implementation and methods.
Two of the most common neurodegenerative disorders, Alzheimer (AH) and Parkinson, have similar attributes. They mainly affect the elderly population. They cause structural and functional changes in the brain. Impairment in cognitive functions, along with psychological and behavioral problems, are observed in Alzheimer and Parkinson. Individuals, who are not diagnosed with dementia but have less cognitive skills than expected when compared to their peers and their levels of education, are included in the mild cognitive impairment (MCI) group.
Various brain imaging studies indicate that the memory disorders observed in MCI and AH are related to the increased activation in the right DLPFC.
In a case study carried out with an MCI patient, it was shown that the high-frequency repetitive TMS (rTMS), which was implemented for a total of 10 sessions on the inferior parietal lobe for 2 weeks, achieved an increase in the memory performance. In another rTMS study repressing the right DLPFC, it was shown that that there was an increase in the verbal and non-verbal recognition memory duties.
High frequency stimulation (excitation) is implemented on the dorsolateral prefrontal cortex by rTMS in nearly all of the studies. Bilateral stimulation is preferred more in the rTMS studies carried out on the elders, because the hemispheric asymmetry decreases in the elders, according to a theory. Furthermore, it was shown that rTMS was more effective in mild dementia patients, and that the change of the brain plasticity was performed quite difficultly in the dementia patients showing advanced cognitive impairment.
It was shown that the stimulation implemented on the DLPFC area at bilateral (left and right) high frequency enabled a positive increase in the cognitive performance showing dementia-based impairment (like memory, attention) in the patients having an Alzheimer history of 2-6 years. There is a study showing that this state of improvement still continued at the end of a 3-month follow-up.
The TMS studies carried out on Parkinson patients focus on the treatment of depression.
The studies carried out on Parkinson patients showed that the stimulation implemented on the left DLPFC area at high frequencies provided a decrease in the depression and anxiety scores, in other words, a decrease in the symptoms of depression.
In a study comparing rTMS to Fluoxetin (antidepressant) used to treat depression in patients with Parkinson, it was shown that rTMS treated the depression in Parkinson more effectively.
Despite the limited amount of studies conducted, the therapeutic effect observed in neurodegenerative disorders show that rTMS can potentially be an alternative treatment.