Neurophys
-DBS activate axons
-DBS ↓excessive synchronization in motor network
-DBS activates multiple populations
Parts
-Brain electrode
-IPG/Battery
-Patient programmer
-Clinician programmer
Brain electrodes
Medtronic
-3389 ring (0.5mm spacing)
-3387 ring (1.5mm spacing)
-Segmented (Sensight), 0.5 or 1.5mm spacing
Abbott (formerly St. Jude)
-Segmented, 0.5 or 1.5mm spacing
Boston Scientific
-8 ring contacts
-Segmented 8 contact (Cartesia)
-Segmented 16 contacts (Cartesia X & HX)
-all 0.5mm spacing
Medtronic
-Activa
>PC (primary cell, dual channel)
>SC (primary cell, single channel)
>RC (rechargeable, dual channel)
-Percept PC (primary cell, dual channel, sensing)
-Percept RC (rechargeable, dual channel, sensing)
Abbott
-Infinity 5 (primary cell, dual channel, small)
-Infinity 7 (primary cell, dual channel, large)
-Liberta RC (rechargeable, dual channel)
Boston Scientific
-Vercise (rechargeable, dual channel)
-Vercise Gevia (rechargeable, dual channel, wand)
-Vercise Genus R16 or P32 (rechargeable, 2-4 leads, Bluetooth)
-Vercise Genus P16 or P32 (primary cell, 2-4 leads, Bluetooth)
Clinician programmer
-Medtronic tablet (Samsung)
-Abbott tablet (iPad)
-Boston Scientific tablet (Surface)
Patient programmer
-Medtronic (Samsung smartphone or remote)
-Abbott (iPad mini)
-Boston Scientific (remote; Gevia-gray; Genus-black)
Adjustable parameters
-Amplitude (2-3 mA or V)
>Spread of stimulation
-Pulse width (60-90 μs)
>Time linger in tissue
-Frequency (130-180 Hz)
>Least important
>↑Hz (180)→ tremor; ↓Hz→ gait
General
-Leads vs Electrodes vs Contact
-Negative contact = cathode
>active contact; most neural activation
-Positive contact = anode
>current return; some neural activation
-Contact labelling
-Therapy impedance and current
Medtronic Percept
Ring
>0–3(L); 8–11(R)
Segmented
>0, 1A, 1B, 1C, 2A, 2B, 2C, 3
>8, 9A, 9B, 9C, 10A, 10B, 10C, 11
*Segments labeled counter-clockwise
L brain: A (ant), B (lat), C (med)
R brain: A (ant), B (med), C (lat)
*Multiple current source, so each contact assigned its own amplitude
Abbott
-U/L: 1, 2A, 2B, 2C, 3A, 3B, 3C, 4
-R: 9, 10A, 10B, 10C, 11A, 11B, 11C, 12
*Segment A usually implanted anterior (but can rotate)
*Segments labeled clockwise
L brain: A (ant), B (med), C (lat)
R brain: A (ant), B (lat), C (med)
*Single current source, so one amplitude split between contacts
Boston Scientific
Ring
>U/L: 1–8
>R: 1–8 (old 9–16)
Segmented
>L: 1, 2A, 2B, 2C, 3A, 3B, 3C, 4 (previously 1, 2/3/4, 5/6/7, 8)
>R: same as Left (previously 9, 10/11/12, 13/14/15, 16)
*Segments labeled counter-clockwise
L brain: A (ant), B (lat), C (med)
R brain: A (ant), B (med), C (lat)
*Multiple current source, so each contact assigned its own amplitude
Segment leads - orientation
-Stereotactic marker for determining orientation of segments
-Leads typically implanted with segment A facing anterior
>Medtronic: proximal marker (triangle down) aligned with segment A; distal marker (triangle up) aligned with B
>Boston, Abbot: vertical marker aligned with segment A
-Repeat X-ray or CT for orientation
Contact configuration
-monopolar, double monopolar, fractionated monopolar, wide bipolar, narrow bipolar, double bipolar
-2-4wks after procedure 2/2 micro-lesioning effect
-For PD, hold meds
-Check surgical sites
-Monopolar mapping
>Explain side effects
>Choose 130hz and 60us, adjust amplitude
>Amplitude jumps 0.5 if paresthesias 0.1
>Neuro-exam, including speechs for every change in amplitude
Side effect map
Vim
-Muscle contraction→ Lat
-Dysarthria→ Lat/Posteromedial
-Paresthesia→ Post
-Ataxia→ Ventral
-No side effect >5mA→ Sup/Ant
-Paresthesia→ Medial/Post
-Muscle contraction→ Lat/Ant
-Dysarthria→ Lat/Ant
-Mood→ Inf/Med
-Autonomic→ no specific region
>Diplopia→ anteromedial
-Dyskinesia→ at the site!
-No side effect >5mA→ Sup/Ant
GPi
Electrode position
-Muscle contractions→ PostMed
-Dysarthria→ PostMed
-Phosphenes→ DeepMed
-Dyskinesia→ at the site!
-Bradykinesia→ Med
-FOG→ Med
-No side effect >5mA→ Ant/Lat/Dorsal
*High stimulation can worse tremor, dystonia
-bMRI
Tips
Impedance
-Always save old settings
-Teach patient
>patient programmer
>DBS do's and don'ts
-Fu every mo for 6mo
-Fu every mo for 6mo
-Refer to monopolar map, redo if needed
-If no benefit after 2 sessions, do imaging for lead position
Future adjustments
-ET→ Taper off after stimulation
-PD→ Meds for NMS
>STN→ med red 2/2 DKN
>GPi→ can maintain same regimen
-DTN→ retain pre-op meds
Warnings
-Diathermy (‘deep heating’)
-Electrical or radiofrequency therapeutic devices (keep away from head/chest)
-Electrocautery (surgery)
-Lithotripsy
-MRI (heating effect)
-TMS, ECT
-Magnetic fields
-Metal/theft detectors (airport report pacemaker and request pat down)
-Store refrigerators, industrial microwave ovens
-Arc welding equipment, high voltage power lines
-Effect on other medical devices (external defibrillation, cardiac pacemakers)
IPG longevity
PCs→ 3-5y
Impedance
>10,000ohm→ break along contact
Will not affect stimulation if that contact is unused
-3000-5000→ not problem (but ↑V if CV mode)
-Segments can have ‘high’ bipolar impedance (>10,000 ohm) but not a problem if monopolar impedances wnl
-Low impedance (10-100)→ short in circuit
>Stimulation will be applied to all shorted contacts even if they are not “turned on”
>Quick battery drain if stimulation applied between two shorted contacts (one +, the other -) so do not do
Refine parameters
-If low side effect thresholds, try bipolar or directional:
>Use most optimal contact as negative in bipolar configuration
>Perform monopolar mapping for each segment on the best level
-If unable to achieve benefit with single contact, try double-monopolar stimulation using two adjacent contacts
>Double monopolar if high side effects thresholds (or fractionate current to avoid side effects)
>Double bipolar if low side effects threshold
-Establish best contact first, before changing PW and frequency
>Lower PW if side effects
>Increase frequency for tremor
>Increase PW for more benefit (can also increase amplitude)
