Noninvasive transcranial magnetic stimulation (TMS) may help improve cognitive performance in patients with Parkinson disease (PD) and mild cognitive impairment, according to a recent study.
The preliminary findings from this study with 28 patients suggest that the intervention might improve overall cognitive performance in patients with PD with mild cognitive impairment for as long as 1 month.
PD is the second most frequent neurodegenerative disease, with symptoms consisting of motor deficits caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. Nonmotor symptoms can include cognitive difficulties, depression, anxiety, hallucinations, and other issues. Cognitive impairment, which can occur in the early phase of PD, increases the risk of developing dementia. Previously, cognitive deficits were shown to be associated with functional alterations in the dorsolateral prefrontal cortex (DLPFC) and caudate nucleus. Two studies of TMS previous transcranial magnetic stimulation studies over the left DLPFC showed short-term improvement in cognitive performance and focused on specific task.
The researchers in this study used intermittent theta burst stimulation (iTBS) over the left DLPFC, which another study reported is best suited for enhancing executive function in patients with medication-resistant depression. This study looked to replicate those findings with repeated sessions of iTBS over DLPFC in patients with PD and mild cognitive impairment.
Each patient underwent a comprehensive neuropsychological assessment that measured 5 cognitive domains with at least 2 tests for each domain, as suggested by the Movement Disorders Society Task Force: (1) attention and working memory, (2) executive function, (3) language, (4) memory and verbal learning, and (5) visuospatial abilities. Each participant also had other clinical evaluations, including the Unified Parkinson's Disease Rating Scale Part III to quantify the motor severity of the disease, the Beck Anxiety Inventory, the Beck Depression Inventory and the Apathy Evaluation Scale in order to assess the level of anxiety, depressive and apathy symptoms, in addition to the Parkinson Daily Questionnaire to assess quality of life changes.
Subjects were split in 2 groups and randomized to receive either active iTBS (n = 14; 6 women and 8 men, mean age 71) or sham stimulation (n = 14; 3 women and 11 men, mean age 67). Study team members were not blinded to the type of stimulation used, although the study participants were blinded.
On the second, fourth and seventh day researchers administered 2 iTBS sessions per day, separated by a 1-hour break between sessions. A post-TMS assessment consisted of alternative versions of the neuropsychological tests and clinical tests on the first, tenth and thirtieth day of the study.
The results showed an increase in overall cognition up to 1 month in both groups, but the effect was only significant in the active group. Visuospatial improvements were also limited to the active group only. Improvements were seen in the attention domain for both the active and shame groups.
TMS had no effect on executive performance, language or memory.
Additional studies are needed to explore the potential of iTBS as a tool to slow cognitive decline related to PD.
Trung J, Hanganu A, Jobert S, et al. Transcranial magnetic stimulation improves cognition over time in Parkinson's disease Parkinsonism Relat Disord. 2019;(66)9:3-8. doi: 10.1016/j.parkreldis.2019.07.006.