Cognitive deficits in essential tremor patients

Essential tremor is one of the most common neurological disorders. Its most recognizable feature is a kinetic tremor of upper limbs, but it can also affect other parts of the body. For many years essential tremor has been treated as a benign, monosymptomatic disorder with little progression. A vast number of research in the last decade underpinned this view. The tremor can be accompanied with a broad spectrum of other motor and non-motor features. The latter include psychiatric symptoms and cognitive dysfunction. The configuration of these features varies between cases. The etiology, progression and underlying neuropathology of the disease is also heterogeneous. Thus, essential tremor should be rather treated as a complex and progressive neurodegenerative disease. In the cognitive domain the most common deficits are found in memory and executive functions, but deficits are also noted in attention, language and visuospatial functions. Similar pattern emerges in Parkinson's disease. This indicates dysfunctions of the frontal system, which includes the prefrontal cortex and subcortical structures like basal ganglia and cerebellum. The magnitude of cognitive dysfunction is partially independent from other manifestations of the disease, which indicates different underlying neuropathology of motor and non-motor features. Determination of the relationship between signs of the disease and underlying neuropathological mechanisms is an important goal of future research. The magnitude of cognitive deficits might have more significant influence on the quality of life in ET patients than the magnitude of motor signs. Despite that fact assessment of cognitive functions is omitted in standard diagnostic procedures. Presented data suggest that this practice should be revised.