Brain Vascular Damage in Essential Tremor: Observational Study and Statistical Analysis in An Affected Population Compared with A Group with Parkinsons Disease and A Control Group
Author(s): Zarola F
Previous studies of the Author pointed out that the incidence of vascular brain disease (cerebrovascular disease, CVD) in several expression modalities was statistically significant and relevant in Parkinson′s Disease (PD); subsequently the Author investigated the incidence of CVD in an extrapyramidal disease frequently detected in clinical practice and involved in the differential diagnostics within movement disorders, that is Essential Tremor (ET). The statistical chi-square calculator test for association between two categorical variables was applied in a first step between a population of 60 patients (2 patients without information on CVD were not included in the statistics) with ET and a control population (patients suffering from various central nervous system diseases excluding PD and ET but including the so-called Vascular Parkinsonism –VP-) of 145 subjects (16 patients without information on CVD were not included in the statistics). The result was negative (p-value is 0.696914. This result is not significant at p<0.01). In a second step a statistical comparison was performed between the same group of 60 patients with ET and the group of 85 patients with PD (1 patients without information on CVD was not included in the statistics) obtaining a highly significant result (the p-value is 0.000003. This result is significant at p<0.01). The statistical analysis concerns the presence or not of morphologically imaging signs of CVD (TC and RM Scan) in the two groups. These results demonstrate that while there is a correlation in the incidence of CVD and PD according with previous observations (actual p-value is 0.000001. This result is significant at p<0.01), the same correlation does not occur with the ET. The incidence of CVD in the ET has a random feature comparable to the randomness of the general population. Therefore it is hypothesized that the CVD in the ET is a pure comorbidity without pathogenetic value - even if apparently in contrast with what assumed in the classifications defining the atherosclerotic senile tremor as a variant of the same ET - according with hypothesized different neurotransmitter networks (dopaminergic vs supposed GABAergic). We can also speculate that the different therapeutic approach may depend on the different pathogenesis of the two pathologies (ET and PD). Further investigations result of particular interest also considering the fact often observed in clinical practice that the ET can over time evolve into PD or that in same cases there is an overlapping between PD and ET mainly in the in the tremorigen symptom.