Essential tremor: what is beyond the oscillatory monosymptomatic illness?

Background Essential tremor (ET) is now considered as a slowly progressive neurodegenerative disorder with a variety of motor and non-motor manifestations. The objectives of this work were to study the existence of cognitive, mood, olfactory, and balance dysfunctions in ET patients and their relation to tremor severity as well as patients’ activity of daily livings. Methods This study was performed on 36 ET patients and 24 healthy controls subjects (HCS) submitted to The Essential Tremor Rating Assessment Scale (TETRAS), advanced activity of daily living scale (AADLs), Montreal cognitive assessment scale (MoCA), Montgomery–Åsberg Depression Rating Scale (MADRS), auditory mismatch negativity (MMN), Sniffin’ Sticks test (SST), computerized dynamic posturography (CDP), and brain MRI diffusion tensor tractography (DTT). Results ET patients showed significant decrease in AADLs, MoCA, SST (threshold, identification, and discrimination subscales) as well as visual and vestibular ratios of CDP compared to HCS. Auditory MMN showed significant reduction in the amplitude and prolongation of latencies while corticospinal tracts, thalamo-cortical connectivity, and middle cerebellar peduncles DTT revealed reduced fractional anisotropy in ET patients with normal tracts densities. Conclusion ET patients exhibit a wide variety of non-motor manifestations including cognitive impairment, depressive symptoms, hyposmia, and increased risk of falls with consecutive reduced activity of daily living beyond the deleterious effects of the kinetic tremor.