Table 1
Comparison between initial vs. current monopolar reviews, tremor scales, and brain atrophy measurements. Table 1 shows the patient’s narrowed threshold for sensorimotor side effects on monopolar reviews over time. While patient has sustained tremor benefit from stimulation (as depicted by continued improvement of FTM scores), he is currently programmed on low stimulation settings. In this patient, the change in stimulation-induced side effects is likely related to increased brain atrophy, as shown across 4 atrophy indices.
| Contact | Initial monopolar review* Voltage (Side effect) | Current monopolar review* Voltage (Side effect) | Change in voltage | Change in time (months) | ||
|---|---|---|---|---|---|---|
| 0 | 0.6 (right hand paresthesia) | 0.5 (right hand paresthesia; also right jaw and leg pulling at ~1V) | –0.1 | 78 | ||
| 1 | 0.8 (right arm paresthesia) | 0.9 (right jaw pulling and right oral paresthesia) | +0.1 | |||
| 2 | 2.3 (right face paresthesia) | 1.9 (right jaw pulling; also right arm tingling at ~2V) | –0.4 | |||
| 3 | 4.5 (right face paresthesia) | 2.9 (right arm and jaw paresthesia; also concurrent pulling at ~3.4V) | –1.6 | |||
| Pre-operative tremor scores | 1-year tremor scores, after left VIM-DBS | Current tremor scores** | ||||
| FTM | 55 (motor); 18 (ADL) | 23 (motor, DBS-ON); 37 (motor, DBS-OFF); 6 (ADL) | 21 (motor, DBS-ON); 43 (motor, DBS-OFF); 2 (ADL) | |||
| Change in brain atrophy measurements and lead localizations1–3 | ||||||
| Evans index (normal < ~0.3) | Bifrontal index (normal < ~0.3) | Ventricular index (normal < ~0.3) | Cella media index (normal < ~0.25) | |||
| CT after initial left VIM-DBS (2013) | 0.27 | 0.32 | 0.31 | 0.16 | ||
| Most recent CT (2019) | 0.31 | 0.38 | 0.37 | 0.18 | ||
| % change | 15% | 19% | 19% | 13% | ||
[i] * Monopolar threshold reviews were performed with PW 90 Freq 135.
** Most recent tremor scale was performed 7 years after left VIM-DBS implantation; 3 months after activation of right VIM-DBS but 6 years since original right VIM-DBS implantation.
Left VIM-DBS lead = contacts 0–3.
PW = pulse width (μs); Freq = frequency (Hz); VIM = ventralis intermedius nucleus; DBS = deep brain stimulation; FTM = Fahn-Tolosa-Marin Clinical Rating Scale for Tremor; ADL = activities of daily living.
Figure 1
3D rendering of bilateral DBS VIM electrodes, initial vs. current. Sections A–C depict bilateral VIM leads in relation to targeted grey structure of VIM proper (A), yellow structure of thalamus (B), and overlay of VIM within the thalamus (C). Section D shows relative lateral shift of current VIM electrodes. The original DBS lead location is depicted in blue, and current DBS lead location in orange. His current optimized DBS settings are: 2- C+1.7V PW 90 Freq 135 (left VIM), and 10- C+ 1.0V PW 90 Freq 135 (right VIM).
Figure 2
Changes in noncontrast head CT over time. Initial postoperative CT in 2014 (A) was normal, with bilateral VIM-DBS leads in place. Recent CT in 2019 (B) shows increased ventricular size and subtle left > right hemispheric atrophy.
Supplementary Table 1
DBS stimulation parameters.
| DBS lead | Initial programming after monopolar review of left VIM-DBS | 1-year after left VIM-DBS, optimized programming | Current optimized programming, after new IPG |
|---|---|---|---|
| Left VIM-DBS | 2- C+ 2.0v PW 90 Freq 180 | 2- C+ 2.5v PW 120 Freq 185 | 2- C+ 1.7v PW 90 Freq 135 |
| Impedance | 1412 | 1277 | 770 |
| Right VIM-DBS | N/A | N/A | 10- C+ 1.1v PW 90 Freq 135 |
| Impedance | N/A | N/A | 813 |
[i] PW = pulse width (μs); Freq = frequency (Hz); Impedance = Ohms (Ω); VIM = ventralis intermedius nucleus; DBS = deep brain stimulation; IPG = implantable pulse generator.