To investigate the clinical and neuropsychological correlates of The Essential Tremor Rating Assessment Scale (TETRAS) in the preoperative evaluation of patients treated with deep brain stimulation (DBS).

TETRAS is an essential tremor (ET) rating scale which includes a performance subscore, an objective rating of tremor by an examiner, and an activities of daily life (ADL) subscore, a subjective rating on the tremor’s impact on daily life. Prior studies demonstrated strong correlation between these subscores. Use of TETRAS for preoperative rating in patients treated with DBS is not well described.

This single center, retrospective study identified patients who received DBS for tremor treatment with preoperative TETRAS assessment. Clinical information, preoperative TETRAS scores, preoperative neuropsychological testing, and DBS data, including latest programming settings were collected. The total electrical energy delivered (TEED) was calculated. Pearson correlation was used to assess the relationship between TETRAS ADL and performance subscores, and continuous data  and TETRAS total and subscores.

In 22 patients, ADL and performance subscores showed moderate correlation (r=0.51, p=0.01). TEED in bilateral stimulation was strongly correlated with performance subscores (r=0.857, p=.0002) but was not significantly correlated with ADL subscores (r=0.164, p=0.59). Some neuropsychological measures were significantly correlated with ADL subscores, including converted MMSE scores (r=-0.559, p=0.01), estimated premorbid IQ (r=-0.602, p=0.01), and a composite executive function score (r=-0.489, p=0.04), but were not significantly correlated with performance subscores. Other neuropsychological scores non-significantly correlated with ADL subscores but not performance subscores. 

Preoperative TETRAS performance and ADL subscores were not as strongly correlated in patients with DBS as in previously reported nonsurgical populations. Performance subscores correlated strongly with TEED while ADL subscores did not. ADL subscores correlated with several neuropsychological measures, which should be taken into consideration when interpreting these scores in patients being considered for DBS.