Objective: To characterize posture and balance dysfunction in patients with essential tremor (ET) after undergoing deep brain stimulation (DBS) of the thalamic nucleus ventralis intermedius (Vim).

Background: Essential tremor is characterized by progressive, symmetric, moderate-to-high frequency postural and action tremor. ET is also associated with cerebellar dysfunction including impaired gait and ataxia. Though DBS of the thalamic nucleus Vim is an effective treatment modality for medically-refractory ET, its effect on posture and balance is not clearly defined.

Methods: Eight patients with a clinical diagnosis of ET (3 pre-Vim-DBS, 5 post-Vim-DBS) underwent standardized balance assessment using body accelerometers (Mobility Lab, APDM Inc.). Sway testing was carried out with the patients standing with eyes open and closed. The following parameters were measured and averaged in both groups of patients, to then be compared with normative data: sway smoothness or JERK (m²/s⁵), sway area (m²/s²), RMS sway and path length (m/s²), mean velocity (m/s), range of acceleration (m/s²), mean distance (m²/s⁵) and total power (m²/s⁴).

Results: In pre-DBS patients, all measured balance parameters were either normal or mildly abnormal. In post-DBS patients, these parameters were moderately to severely abnormal (Table 1).

[Table 1]

Conclusions: While patients with ET may experience mild-to-moderate balance and postural problems as a result of disease progression, DBS of the thalamic nucleus Vim could significantly aggravate them potentially resulting in significant postural imbalance and falls.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-thalamic-deep-brain-stimulation-on-posture-and-balance-in-patients-with-essential-tremor/