Combined Short-Pulse and Directional Deep Brain Stimulation of the Thalamic Ventral Intermediate Area for Essential Tremor.

OBJECTIVE: Novel deep brain stimulation (DBS) systems allow directional and short-pulse stimulation to potentially improve symptoms and reduce side effects. The aim of this study was to investigate the effect of short-pulse and directional stimulation, in addition to a combination of both, in the ventral intermediate thalamus (VIM)/posterior subthalamic area (PSA) on tremor and stimulation-induced side effects in patients with essential tremor. MATERIALS AND METHODS: We recruited 11 patients with essential tremor and VIM/PSA-DBS. Tremor severity (Fahn-Tolosa-Marin), ataxia (International Cooperative Ataxia Rating Scale), and paresthesia (visual analog scale) were assessed with conventional omnidirectional and directional stimulation with pulse width of 60 µs and 30 µs. RESULTS: All stimulation conditions reduced tremor. The best directional stimulation with 60 µs reduced more tremor than did most other stimulation settings. The best directional stimulation, regardless of pulse width, effectively reduced stimulation-induced ataxia compared with the conventional stimulation (ring 60 µs) or worst directional stimulation with 60 µs. All new stimulation modes reduced occurrence of paresthesia, but only the best directional stimulation with 30 µs attenuated paresthesia compared with the conventional stimulation (ring 60 µs) or worst directional stimulation with 60 µs. The best directional stimulation with 30 µs reduced tremor, ataxia, and paresthesia compared with conventional stimulation in most patients. Correlation analyses indicated that more anterior stimulation sites are associated with stronger ataxia reduction with directional 30 µs than with conventional 60 µs stimulation. CONCLUSION: Directional and short-pulse stimulation, and a combination of both, revealed beneficial effects on stimulation-induced adverse effects.

Short pulse and directional thalamic deep brain stimulation have differential effects in parkinsonian and essential tremor.

The aim of this study was to assess the effects of novel stimulation algorithms of deep brain stimulation (short pulse and directional stimulation) in the ventrointermediate thalamus and posterior subthalamic area (VIM/PSA-DBS) on tremor in Parkinson's disease (PD) and to compare the effects with those in essential tremor (ET). We recruited six PD patients (70.8 ± 10.4 years) and seven ET patients (64.4 ± 9.9 years) with implanted VIM/PSA-DBS in a stable treatment condition (> 3 months postoperatively). Tremor severity and ataxia were assessed in four different stimulation conditions in a randomized order: DBS switched off (STIM OFF), omnidirectional stimulation with 60 µs (oDBS60), omnidirectional stimulation with 30 µs (oDBS30), directional stimulation at the best segment with 60 µs (dDBS60). In both patient groups, all three DBS stimulation modes reduced the total tremor score compared to STIM OFF, whereas stimulation-induced ataxia was reduced by oDBS30 and partially by dDBS60 compared to oDBS60. Tremor reduction was more pronounced in PD than in ET due to a limited DBS effect on intention and action-specific drawing tremor in ET. In PD and ET tremor, short pulse or directional VIM/PSA-DBS is an effective and well tolerated therapeutic option.Trial registration: The study was registered in the DRKS (ID DRKS00025329, 18.05.2021, German Clinical Trials Register, DRKS-Deutsches Register Klinischer Studien).

Comparison of Montreal cognitive assessment and Mattis dementia rating scale in the preoperative evaluation of subthalamic stimulation in Parkinson's disease.

INTRODUCTION: The preoperative evaluation of Parkinson's Disease (PD) patients for subthalamic nucleus deep brain stimulation (STN-DBS) includes the assessment of the neuropsychological status of the patient. A widely used preoperative test is the Mattis Dementia rating scale (MDRS). However, the Montreal cognitive assessment (MoCA) has also been proven to be a sensitive, time-sparing tool with high diagnostic validity in PD. We evaluate the utility of the MoCA as a preoperative screening test for PD patients undergoing bilateral STN-DBS. METHODS: In this single-centre, retrospective study, we analysed pre- and postoperative assessments of MoCA, MDRS, Movement disorder society-Unified PD Rating Scale-motor examination, PD Questionnaire-39 and levodopa equivalent daily dose. Longitudinal outcome changes were analysed using paired t-test, Pearson's correlation coefficient, linear regression and CHAID (chi-square automatic interaction detector) regression tree model. RESULTS: Clinical motor and cognitive scores of 59 patients (61.05±7.73 years, 24 females) were analysed. The MoCA, but not the MDRS, identified significant postoperative cognitive decline in PD patients undergoing STN-DBS. The preoperative MoCA score correlated with postoperative quality of life improvement, whereas the MDRS did not. PD patients with a MoCA score ≤ 23 points had a significant decline of quality of life after DBS surgery compared to patients > 23 points. CONCLUSION: This study identifies the MoCA as an alternative test within the preoperative evaluation of PD patients for the detection of neuropsychological deficits and prediction of the postoperative improvement of quality of life.

Thalamic short pulse stimulation diminishes adverse effects in essential tremor patients.

OBJECTIVE: To investigate the effect of directional current steering and short pulse stimulation in the ventral intermediate thalamic nucleus (VIM) on stimulation-induced side effects in patients with essential tremor. METHODS: We recruited 8 patients with essential tremor in a stable postoperative condition (>3 months after electrode implantation of deep brain stimulation [DBS] electrodes) with segmented contacts implanted in the VIM. Tremor severity on acute stimulation was assessed by the Fahn-Tolosa-Marin Tremor Rating Scale. Cerebellar impairment was evaluated with the International Cooperative Ataxia Rating Scale. Patients rated paresthesia intensity with a visual analog scale. RESULTS: In all patients, tremor was reduced to the same extent by VIM stimulation regardless of pulse width using energy dose-equivalent amplitudes. Short pulse stimulation diminished stimulation-induced ataxia of the upper extremities and paresthesia compared with conventional parameters. Directional steering with monopolar stimulation of single segments successfully suppressed tremor but also induced ataxia. No differences in adverse effects were found between single-segment stimulation conditions. CONCLUSION: These proof-of-principle findings provide evidence that acute short pulse stimulation is superior to directional steering in the subthalamic area to decrease stimulation-induced side effects while preserving tremor suppression effects in patients with tremor. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with tremor with thalamic DBS, acute short pulse stimulation reduces adverse effects, while directional steering does not provide a generalizable benefit regarding adverse effects.

Differential effect of dopa and subthalamic stimulation on vestibular activity in Parkinson's disease.

Postural disturbances in advanced Parkinson's disease are less responsive to therapy than other cardinal motor signs. The vestibulocollic reflex represents one brain-stem neuronal circuit involved in postural adjustments. The objective of this study was to investigate the vestibulocollic reflex in parkinsonian patients and the effects of subthalamic stimulation and dopa by recording vestibular-evoked myogenic potentials. After overnight withdrawal of medication, 20 patients with Parkinson's disease with (6 men, 4 women; mean age, 64.4 ± 2.2 years) or without (8 men, 2 women; mean age, 62.7 ± 3.9 years) implanted subthalamic electrodes in different treatment conditions were compared with 10 age-matched controls (5 men, 5 women; mean age, 59.6 ± 2.4 years). Vestibular-evoked myogenic potentials were recorded by electromyographic surface electrodes applied to both sternocleidomastoid muscles (band-pass filter, 8-1600 Hz; sampling rate, 5 kHz) and averaged in response to bilateral auditory tone bursts (120 dB SPL; sine waves, 7 ms; 1000 Hz) applied through earphones. Adjusted vestibular-evoked myogenic potential amplitudes were significantly smaller in parkinsonian patients than in controls, in particular in patients without surgery. Administration of dopa, but not subthalamic stimulation, significantly increased amplitudes. Onset latencies were similar for all groups and treatment conditions. Decreased vestibular-evoked myogenic potential amplitudes in parkinsonian patients suggest reduced vestibular nuclei excitability within the brain stem, which is modulated by dopa but not by subthalamic stimulation. This suggests different pathways for the action of both treatment modalities in Parkinson's disease and may explain clinical differences in terms of postural disturbances. © 2012 Movement Disorder Society.