Feature GPi STN VIM Speech Less affects but also does not help More problems Dysarthria is common Dystonia GPi helps for both medication-responsive and –nonresponsive STN helps for dystonia (GPi better for “on-meds” dystonia) Dyskinesia GPi helps for both medication-on and –off dyskinesias parkinsonism-plus syndromes / parkinsonism unresponsiveness to levodopa ≥ moderate cognitive dysfunction Dementia usually starts 10 years* after PD diagnosis (protective factors – tremor-predominant, no axial symptoms, young-onset PD [dementia is delayed until age 70]) *if much earlier – Lewy body dementia Patient must be able to properly operate the neurostimulator. Dementia, as well as cognitive deficits, are not improved by DBS and might even be made worse by trauma of surgery. N.B. patients with cognitive decline or full-blown dementia may be at increased risk for DBS Limousin P, P, Pollak P et al. (1998). Electrical stimulation of the subthalamic nucleus in advanced Parkinson’s disease. N Engl J Med 339: 1105–1111. MI, Johansson F, Shamsgovara P (2000). Bilateral subthalamic nucleus stimulation in a Parkinsonian patient with preoperative deficits in speech and cognition: persisting improvement in mobility but increased dependency: a case study. Mov Disord 15: 136–139. anxiety – difficulty postop DBS programming; if anxiety is reactive to PD, then DBS helps; if anxiety is lifelong, then patient knows how to cope with it; worst if anxiety is due to PD affecting limbic circuits – patients very difficult to program. depression – risk of postop suicide, so must be controlled and psychiatrist established preop. general surgical contraindications (anticoagulants, terminal cancer, infectious disease, immunodeficiency, poorly controlled HTN, and so on); for diabetics, HbA1c has to be < 8.0% DBS – achieve the best score as patient had on meds* preop and smoothen fluctuations! *this applies only to early stages of PD; in advanced stages, PD patients are frozen no matter how much medication they get (becomes obvious if DBS battery dies)
CT – stereotactic, without contrast 0.6 mm – reference exam; MRI provides high anatomical resolution, while CT eliminates MRI distortion. T2: axial (VCU) cube – GE (VA) dark fluid SPACE - Siemens T1: T1-weighted 3D Magnetization Prepared-Rapid Acquisition Gradient Echo (MPRAGE) - sagittal (VCU) or axial (VA); postcontrast – to see vessels. Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR) on 3T MRI scanner DTI (2NEX scan duration 8 minutes; or 3NEX – 12 minutes) MRI must be 3D (volumetric), i.e. without gaps between slices. CT O-arm Ceretom – small bore Bodytom, Airo – large bore, good soft tissue resolution if patient cannot have MRI (e.g. pacemaker), intraop ventriculogram can be used: standard EVD catheter is passed free-hand through the right frontal burr hole into the lateral ventricle → Omnipaque 3 cm3 (180 mg/mL) is injected into the ventricle → immediate O-arm; anterior commissure is not well visualized in the ventriculogram as a result of gravitational layering of the contrast but still be estimated from the preop CT scan (fused to O-arm). A. - target visually chosen directly from CT / MRI); prior to introduction of CT / MRI, target localization involved injecting air or positive contrast into lateral ventricle to outline third ventricular structures (ventriculography) adjacent to diencephalic targets with current MRI, GPi and STN are visualized directly, but VIM is derived from Schaltenbrand and Wahren atlas, utilizing intercommissural plane and midcommissural point for reference. ongoing debates should stereotaxis be just image-guided (without MER); Larson et al. place DBS on first trajectory in 98% patients. Montgomery et al. (2012) found that imaging-based targeting was consistent with the physiologically defined target only 70% of the time; in 30% of subjects, additional MER trajectories were required (25% required 2 additional MER penetrations and remaining 5% required 3 additional penetrations). B. MRI - based upon position of AC-PC:
Manual Brochure ClearPoint® (MRI Interventions, Inc., Irvine, California, USA, ) Flexible headcoil is a must (esp. for kids) load exams from CD: VA: CT, axial T1 with contrast, axial T1 without, sagittal CUBE FLAIR, hybrid exam (if using DTI fibers). VCU: CT, sagittal T1 with contrast, axial T2 if need to remove exams: END → Remove exam – shows exam numbers and preview select patient (if exams come under different names, use “Manage Series” to rename) → will automatically show available images (uncheck undesired ones). will need CT (as reference exam), axial T1 with contrast (axial T1 without is usually not needed), sagittal CUBE FLAIR, hybrid exam (if using DTI fibers). just click “Verify Orientation” (there is no way to really verify it). click “Auto Merge” (may use on all images at the same time) “Point Merge” – click on corresponding points on the scan and then “+” sign. Once 4 points are added it starts showing accuracy. Once happy, click “Verify” “Verify merge” (axial, coronal, sagittal planes – look for sella) → NEXT (we don’t care about 3D model) → NEXT (make sure it says NEXFRAME as software automatically detects frameless when no frame is on CT). How to achieve best levels on CT – move both sliders to the left → move “L” (top slider) to the right until brain shows “salt & pepper” granularity → move “W” (bottom slider) to the right until see perfect parenchymal view.
StealthViz 3D objects in Mach rainbow color map – objects can be colored on FrameLink: Reformatting: select AC and PC (at ventricular surfaces – imitates historical ventriculogram landmarks), select 3 midline (interhemispheric fissure, aqueduct) apply SW atlas and Talairach grids; stretch grids to conform with patient’s anatomical exam (best to use CUBE FLAIR); mostly work on basal nuclei because impossible to achieve perfect match (SW atlas was created on cadavers with slightly deformed brains) Setting trajectory: choose “Plan 1”, rename it (use “Edit” button), then click “Sample” button to get suggestion from software N.B. software uses only AC-PC coordinates to suggest target at standard location (SW only serves for visual control) (adjust and) “Set Target” (adjust and) “Set play with trajectory by adjusting entry point alternate between “Anatomical” and “Trajectory” ideally, trajectory stretches 5-6 mm of target nucleus, ideally, entry point is on or 1-2 anterior to coronal suture (not too far anterior - to stay behind hairline), and 2-4 cm from midline. point must avoid: cortical vessels deep vessels in sulci (i.e. entry should be on gyrus top) trajectory must deep vessels ventricle caudate nucleus then choose “Plan 2” for the side. at the end may create copies of each plan (in case plan is by accident modified; H: may try “undo” button in lower right button row) - look in sagittal plane (how much in front to coronal suture on CT): - look in coronal plane (how much lateral to midline): CD / USB look what exam types are needed: Go back to very first PREP step (where merging exams) – note series # of each exam that is used
N.B. software always will label one worst fiducial as “Marginal” but that doesn’t mean it is bad per se. Goal of navigation accuracy is ≤ 0.2 mm (acceptable minimum 0.5 mm) Next → “Step” to accuracy (on registration series) by operator touching several fiducials. Go to appropriate plan, turn all scans off, check geometry on toolkit (after it gets close to target; may loosen screw and rotate NexProbe if geometry is unacceptable) brain pushes hardware posteriorly and medially so cheat (if unable to perfectly align to target) laterally and anteriorly (unless expect to use posterior track) After hardware secured to target → Next → Click “Set entry” Next → check distance to target (length of trajectory) – set Nexdrive Z-stage to that distance: Go to “Plan 10”: operator points to A → step → “Set operator points to E → step →“Set target”; check on axial window (turn crosspin on with F4) deviation from midline → operator adjusts by rotating dial. Go to Plan: Planning: turn on MRI and SW → move 6 mm (for VIM) or 10 mm (for STN, GPi) above target on trajectory. [If don’t hear beep when clicking “step” – means it is on “continuous update” (vs. “foot switch update”)] [If you don’t see study image once you turned it on – might be out of window; H: click “<” or “>” to get back on trajectory] After CT is done, create plan for each microelectrode (e.g. Plan 10 → rename to “R ctr”; Plan 9 → rename to “R post”) – check how they look on CUBE FLAIR. Specificities for FrameLink – Standard mode – for registration. High-definition mode – to analyze position of inserted ME or DBS Enhanced mode – at the end (to look for - automatic fiducial-less registration O-arm gantry cannot be tilted more than 15 degrees (in general, keep as vertical as can unless need to tilt). O-arm won’t let to scan if Stealth camera cannot see passive spinal frame (can leave even unattached to patient but within camera range).
irrigate with Bacitracin / vancomycin DuraSeal on whole plastic to prevent CSF leak. bur hole incision: close with 4-0 Vicryls for galea → staples → Aquacel Ag dressing (historically: Mepilex Ag→ Tegaderm). connector incision: 1-2 full thickness vertical mattress 2-0 nylons → staples → Aquacel Ag dressing bone fiducials removed and irrigated out with vancomycin → (Dermabond →) staples (Monocryl for frontal ones) → bacitracin stockinette. take to CT scanner (check for bleeding, lead placement, pneumocephalus) / do enhanced mode scan with O-arm. resume Parkinsonian medications immediately postoperatively (also will help a little bit with HTN BP; Dr. Baron says that Sinemet does not affect BP much); if frozen, OK to give extra dose of Sinemet. keep SBP < 155 for overnight or 24 hours (if requires PRN meds for BP, keep in ICU overnight), then relax parameters. NR mask for 24 hrs if large pneumocephalus. mupirocin ointment to bone fiducial sites TID. home after 24 hours if no problem. may be difficult with demented, frail patients. strongly consider doing awake – second side accuracy may be compromised due to pneumocephalus, so desirable to verify effects with patient awake. MER general anesthesia without muscle paralysis. on radiolucent headrest, egg crate (to prevent pressure sores), but no C-collar EMG monitoring in contralateral orbicularis oculi, orbicularis oris, arm, ± leg – i.e. internal capsule side effects: implant to target depth and increase voltage until EMG shows response, then try different contacts and wide array. DBS Only with patient awake!