Figure 1
Confirming Final Electrode Placement. Post-operative CT scan showing position of contacts later chosen as active cathodes for stimulation.
Video 1.
Presurgical Assessment of Tremor. Off primidone >48 hours. Stimulation Setting − Left VIM: N/A; Right VIM: N/A. Observations − Head tremor nearly 100% of time, 3−5 cm amplitude. +Jaw tremor. Bilateral hand tremor 3−10 cm postural, 1−3 cm intention. Moderately wide base with constant mild gait ataxia. Tandem documented as constant moderate deviation but not filmed. Video 2. Omnidirectional Bipolar Volume of Tissue Activation (VTA). Off primidone >7 days. Typical bipolar configuration, nonsegmented. Stimulation Setting − Left VIM: Contacts: 3(−) 1(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz; Right VIM: Contacts: 11(−) 9(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz. Observations − Head tremor 25−50% of time, 1−3 cm amplitude. No jaw tremor. Bilateral hand tremor 1−3 cm postural and intention. Mildly widened base with frequent gait ataxia, with frequent moderate tandem deviation. Video 3. Directional Monopolar VTA. Off primidone >7 days. Typical monopolar configuration, segmented, left VIM contact A points laterally. Stimulation Setting − Left VIM: Contacts: 3A(−) Case(+), Current: 1.2 mA, Pulse Width: 90 μs, Freq: 170 Hz; Right VIM: Contacts: 11A(−) Case (+), Current: 1.2 mA, Pulse Width: 90 μs, Freq: 170 Hz. Observations − Head tremor >75% of time, 3−5 cm amplitude. +Jaw tremor. Bilateral hand tremor 3−10 cm posture and intention. Moderately wide base, constant mild tandem deviation. Video 4. Directional, Medial Bipolar VTA. Off primidone >7 days. Segmented bipolar configuration, left VIM contact B points medially/posteriorly. Stimulation Setting − Left VIM: Contacts: 3B(−) 1(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz; Right VIM: Contacts: 11A(−) 9(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz. Observations − Head tremor 25−50% of time, 1−3 cm amplitude. No jaw tremor. Bilateral hand tremor 1−3 cm postural, 3−10 cm intention. Narrowed base but constant gait/lower limb ataxia, with constant moderate tandem deviation. Video 5. Directional, Lateral Bipolar VTA. Off primidone >7 days. Segmented bipolar configuration, left VIM contact A points laterally. Stimulation Setting − Left VIM: Contacts: 3A(−) 1(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz; Right VIM: Contacts: 11A(−) 9(+), Current: 1.5 mA, Pulse Width: 90 μs, Freq: 170 Hz. Observations − Head tremor <25% of time, <1 cm amplitude. No jaw tremor. Bilateral hand tremor 1−3 cm postural and intention. Mildly widened base with rare gait ataxia, with occasional mild tandem deviation.
Table 1
Monopolar Symptom Threshold Assessment. Through this Monopolar Survey, Thresholds for Tremor Amplitude Improvement and the Development of Irreversible, Stimulation-induced Side Effects were Identified per Traditional Contact Assessment. Segmented Monopolar Survey was not Conducted
| Improvement Threshold* | Irreversible SE Threshold+ | SE Description+ | |
|---|---|---|---|
| Left VIM | |||
| 4 | 1.0 mA | 1.2 mA | Limb ataxia |
| 3 | 0.6 mA | 1.2 mA | Limb ataxia |
| 2 | 1.2 mA | 1.0 mA | Limb ataxia and tingling |
| 1 | >2.0 mA ˆ | 1.0 mA | Tingling |
| Right VIM | |||
| 12 | 0.8 mA | 1.2 mA | Limb ataxia |
| 11 | 0.6 mA | 1.2 mA | Limb ataxia |
| 10 | 1.4 mA | 1.6 mA | Limb ataxia and tingling |
| 9 | >2.0 mA ˆ | 1.4 mA | Tingling |