Objective: To investigate the non-motor signs among essential tremor (ET) patients presenting with midline tremor (Mid-ET).

Background: Midline essential tremor represents a distinctive group of ET characterized by the presence of tremor within the neck, jaw, tongue and/or voice. It has been considered as an ultimate stage of the disease progression and a marker of its severity. However, recent studies pointed its complexity in terms of non-motor presentation.

Method: We conducted a retrospective study in a tertiary Neurology referral center including ET patients classified into two groups based on the presence or not of midline tremor (Mid-ET vs. No-Mid-ET). We assessed non-motor signs (NMS) using the non-motor severity scale (NMSS). We used the Mini Mental State Examination (MMSE) for global cognitive evaluation, the frontal assessment battery (FAB) for executive function and Free and Cued Selective Reminding Test (FCSRT) for episodic memory, Beck’s Depression Inventory (BDI) or Geriatric Depression Scale (GDS) to assess depression. Quality index of sleep of Pittsburgh (PSQI) was used to assess sleep quality and RBD-screening questionnaire to look for Rapid eye movement sleep behavior disorder (RBD). Dysautonomia was evaluated using the SCOPA-Aut score and the neurophysiological study of the autonomic system.

Results: We included 163 patients: Mid-ET (n=79) and No-Mid-ET (n=84). Mid-ET patients had older age of onset (p=0.002) and more extrapyramidal signs (p=0.005). For NMS, Mid-ET was characterized with greater cognitive dysfunction (p=0.008). The hallmarks of the neuropsychiatric profile of Mid-ET were: Executive dysfunction (p=0.004), attention deficits (p<0.000), episodic memory impairment (p=0.003) with an insufficient memory retrieval process (p=0.006) and more severe depression (p=0.010). The presence of RBD was a characteristic trait of Mid-ET (p=0.039).

Conclusion: Mid-ET patients had older age of onset and greater cognitive dysfunction. The disparity of NMS between patients, with and without midline tremor, provides a redesigned insight into the underlying pathophysiology of Mid-ET indicative of a greater cerebellar dysfunction. The presence of RBD could also point toward a possible presence of synucleinopathy as a potential additional anatomopathological feature of Mid-ET.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-non-motor-features-of-essential-tremor-with-midline-distribution/