Correlation of walking disorder and freezing with cognitive function in parkinson's disease

Parkinson's disease is a cognitive disorder with non-motor findings that is commonly observed. The degree of cognitive disorder may be at varying levels from mild cognitive impairment (MCI) to dementia. In 2012 the Movement Disorder Society published diagnostic criteria for mild cognitive impairment in Parkinson's disease. The potentials related to the event were used as marker to assess cognitive functions. A previous study clearly showed P300 changes in Parkinson's disease dementia, but the results obtained by investigating P300 changes in Parkinson cases without dementia were controversial. Currently as the etiopathogenesis of PD is unknown, the pathophysiology of walking disorder and freezing in the disease is not fully understood and is correlated to different mechanisms. Disruption of the normal stepping pattern of patients is thought to reflect an error in activation of the motor control system for walking hypokinesia. The regulation of walking disorder in some patients with dopaminergic medications leads to consideration that striatal dopamine insufficiency may play a role. However, the lack of regulation with medication for all patients brings to mind the contribution of the non-dopaminergic system, with possible neuradrenergic system insufficiency and/or loss of cholinergic neurons or suppression of neuron activity in the PPN. For all these reasons, it is thought that walking disorder and freezing is a pathophysiology affecting the degree of cognitive function loss of patients, in addition to being a motor disorder. This study aimed to assess the relationship between cognitive characteristics of patients and walking disorder and freezing, in addition to correlations with P300 variations. To achieve this, 3 separate Parkinson's disease groups with diagnosis according to 2012 MDS 2nd stage diagnostic criteria were examined. Each group contained 20 patients with normal cognition, mild cognitive impairment or dementia in stage 2-4 and were compared in terms of walking disorder and incidence of freezing. Twenty Parkinson patients without cognitive disorder identified (PD-Normal), 20 Parkinson's patients with mild cognitive impairment (PD-MCI) and 20 Parkinson patients with dementia (PH-dementia) were included in the study and all participants had P300 test evaluated with the standard audio "odd ball paradigm" method. From the obtained traces, the N100, P200, N200 and P300 latencies and the peak-to-peak N100-P200, P200-N200, and N200-P300 amplitudes were measured and analyzed. The patients walking and freezing traits were investigated with the 6 minute walking test and FOG-Q test. One of the aims of our study was to identify whether there was a correlation between the degree of cognitive disorder of Parkinson patients and the audio P300 test. The results of the analysis using Fz, Cz and Pz electrode recordings to obtain P300 potential acquisition rates in MCI group were significantly low compared to the normal group. There was no significant difference between the P300 latencies in the 3 groups. The P300 amplitudes in the PD-dementia group were found to be shorter than the other two groups and this difference was statistically significant on Cz and Pz electrode recordings. Comparing the other late endogenous component of N200 potential acquisition rate, there was no statistically significant difference observed between the PD-normal, PD-MCI and PD-dementia groups. There was no statistically significant difference observed for N200 latencies recorded between Fz and Cz electrodes. Only on recordings with the Pz electrode was the latency duration in the PD-MCI group observed to be shorter and this was statistically significant. Comparing the early exogenous components, generally linked to physical properties of the stimulus, of N100 and P200 latency and amplitudes between the groups, apart from N100 latency recorded on the Fz electrode being longer in the dementia group, there was no statistically significant difference observed. In our study, there was no significant correlation between P300 potential acquisition and walking disorder and freezing. In the dementia group with highest P300 potential acquisition rate, comparison of patients with P300 potential acquisition and those without found no significant difference on FOG-Q and 6 minute walking test. These findings may be a sign of heterogeneity of their demographic and disease clinical characteristics, apart from cognitive characteristics. Tests of the MCI and normal cognition groups in terms of walking and freezing functions did not observe any significant difference between the two groups. As these two groups are similar in terms of parameters like age, disease stage, disease duration and educational level, it may be possible to assess the effect of cognitive process on walking functions. Contrary to other studies, in our study results led to the conclusion that MCI did not significantly negatively affect walking function. In our study we showed a correlation between advanced cognitive impairment and P300 potential acquisition rates. However, due to the heterogeneous groups in terms of demographic and disease characteristics, we could not show the correlation of cognitive disorder and walking disorder independent of other factors. In conclusion, the P300 test is an electrophysiologic parameter that may assess the cognitive process in PD. Definition of the normative values for PD patients may provide information about the cognitive situation of patients. Periodic control P300 tests may be used to monitor worsening of the patient's cognitive functions, and positive or negative effects of Parkinson medications or medications administered for cognitive disorders. It may be predicted that the incidence and severity of walking disorder and freezing in PD will increase in direct proportion to cognitive disorder. During this process P300 records may be used for cognitive evaluation