Cognitive deficits in Essential Tremor

Essential tremor

From International Journal of Pharmaceutical Research

Essential tremor (ET) is the most common adult onset movements’ disorders affecting 1% of general population and 4% of those above the age of 40 years and characterized by bilateral symmetrical postural and kinetic tremors of the forearms and hands.

In summary, recent clinical, pathological, and neuroimaging findings are consistent with the hypothesis that ET is a disorder of the cerebellum and its brain connections rather than a monosymptomatic tremor disorder. Essential tremor is no longer considered as the benign mono symptomatic illness but a progressive neurodegenerative disorder with both motor and non-motor manifestations.

Moreover, pathological studies have shown that the majority of patients with essential tremor have cerebellar atrophy. 

Patients with ET often experience varieties of cognitive deficits affecting memory, attention and executive functions markedly reducing their activities of daily living. Other non-tremor manifestations of ET include ataxia, personality changes, depressive symptoms, mild hearing dysfunctions, upper airways dysfunction and sleep disorders.

Cognitive decline is a common under diagnosed ET manifestation and due to its slow progression, most ET patients are unaware of its existence resulting in progressive decline in their activity of daily living.

The study showed mild but significant decrease in the global cognitive functions in ET patients. This cognitive decline is higher in patients with longer tremor durations and connected with higher risk of dementia.

The executive functions that were at the heart of cognitive deficits, included mental flexibility, problem solving, abstraction, set shifting, use of feedback and the ability to modify incorrect strategies.

The tests showed significant impairment in attention and working memory of ET patients as measured by arithmetic test, digit span forwards and backwards but language vocabulary was nearly normal.

Brain MRI volumetric study showed symmetrical reduction in total white matter, thalamic, cerebellar cortical and white matter volumes in ET patients with the cerebellum was the most affected. The degree of cognitive decline was proportional with the severity of thalamic, cerebellar cortex and white matter volumes reduction.

The results of both audio-logical evaluation tests (using tone and speech stimuli) and brain MRI volumetry are in accordance with that cognitive dysfunction in ET patients is mainly subcortical and related to impaired cerebello-cortical connections and reduced cerebral white matter volume.

АФФЕКТИВНЫЕ РАССТРОЙСТВА ПРИ ЭССЕНЦИАЛЬНОМ ТРЕМОРЕ

В настоящее время большинством исследователей подтверждается наличие при эссенциальном треморе (ЭТ) не только двигательных нарушений, но и изменений в когнитивной, аффективной сферах, наличие значительной степени инвалидизации и нарушений социального функционирования.

Испытуемые характеризуют себя как замкнутых, отстраненных от других людей. Обращает на себя внимание высокая степень неуверенности в социальном одобрении, склонность к подчинению, зависимости, уступчивости, а также избыточный контроль.

Galina Toktalieva

Kyrgyzstan-born author residing in Graz, Austria

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