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Slide 1-

Functional Neurosurgery and Anesthetic Considerations Susan M Ryan, PhD, MD Associate Clinical Professor Department of Anesthesia, UCSF 2006
Slide 2-

What is Functional Neurosurgery? “Neurosurgery intended to improve or restore function by altering underlying physiology”
Slide 3-

Areas of Functional Neurosurgery Movement disorders Seizures Pain syndromes Psychiatric disorders Peripheral nerve injuries
Slide 4-

Areas of Expansion Movement disorders Seizures Psychiatric disorders
Slide 5-

Neurosurgical Techniques Deep brain stimulation (DBS) Selective ablation electrodes Implantation viral vectors stem cells Cranial nerve/ peripheral electrical stimulation
Slide 6-

Functional Neurosurgery Began in mid-1900’s Eclipsed by effective medications Now: Non-responders Advanced cases
Slide 7-

Neurosurgical Techniques Deep brain stimulation Best established use: Parkinson’s Disease Vagal nerve stimulation Best established use: Seizure disorders
Slide 8-

DBS/VNS Studies in Progress Obesity Fibromyalgia Cluster headache Tourette’s Syndrome Depression Obsessive Compulsive Disorder
Slide 9-

DBS for Parkinson’s Disease
Slide 10-

Clinical Features ‘Pill-rolling’ tremor Masked faces ‘Cog-wheel’ rigidity Festinating gate Bradykinesia
Slide 11-

Pathologic Features Progressive neuronal death Dopamine neurons of substantia nigra Non- dopamine populations in CNS and PNS Bulbar function Sympathetic chain Parasympathetics of the gut
Slide 12-

Basal Ganglia in PD
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Treatment Medications L-dopa + periph. inhibitor (Sinamet) Dopamine agonists MAO inhibitors COMT inhibitors Amantadine
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DBS Surgery Goal: Improvement in PD symptoms Tremor Rigidity Hypokinesia Gait Balance
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Slide 17-

DBS Surgery Placement of stereotactic frame prior to procedure MRI to confirm coordinates
Slide 18-

DBS Surgery Stereotactic head frame attached to bed Pt placed in sitting position
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DBS Stereotactic Surgery Drill hole in skull to allow electrode placement for recording & stimulation
Slide 20-

DBS Stereotactic Surgery Electrode passed slowly to record single cells in nucleus of interest
Slide 21-

DBS Stereotactic Surgery Visual and auditory feedback of cell location and characteristics
Slide 22-

DBS Stereotactic Surgery Listening for cell response during leg movement
Slide 23-

DBS Surgery Find best location within the nucleus Place stimulating electrode Close burr hole, remove frame Induce general anesthesia Tunnel leads Place generator in upper chest wall Wait to activate stimulator in outpatient setting
Slide 24-

Anesthesia: DBS Generator placement General anesthesia for generator placement No particular anesthetic Propofol or inhaled agent work well Avoid dopamine antagonists Avoid demerol Muscle relaxants OK Prevent or treat emergence hypertension Not much pain in post-op setting
Slide 25-

PD: Specific Issues Risk of exacerbation Consider intraoperative continuation of medications Hemodynamics may be labile Degeneration of sympathetic ganglia Dopamine-related hypotension, hypovolemia
Slide 26-

PD: Specific Issues Airway or pulmonary compromise Upper airway obstruction Dysarthria and history of choking Restrictive ventilatory pattern Aspiration risk
Slide 27-

Patients with Existing DBS DBS is usually on 24/7 for PD pts May be off at night in other conditions Consider turning off prior to surgery
Slide 28-

DBS: Surgical Risks Intracerebral hemorrhage Venous air embolism Emotional lability
Slide 29-

DBS: Surgical Risks Intracerebral hemorrhage Monitor patient for neurologic changes Risk: 1.6% per lead Avoid hypertension Keep SBP < 140 Consider arterial line Antihypertensives: labetalol, hydralazine
Slide 30-

DBS: Surgical Risks Venous air embolism Early detection Communicate with surgeon Support blood pressure Provide O2 Airway plan
Slide 31-

DBS: Surgical Risks Emotional Lability Usually no treatment needed Consider sedation PRN
Slide 32-

DBS Outcomes Bilateral DBS of STN: N = 49 Assessed at 1,3, and 5 years Assessed on and off meds and stimulation (Krack, et al, NEJM 349, 2003)
Slide 33-

DBS Outcomes Stimulation alone: significant improvement Synergy between meds and stimulation Allows decrease in medication doses Improvement in L-dopa dyskinesias Akinesia, speech, and freezing of gait all worsened (Krack, et al, NEJM 349, 2003)
Slide 34-

DBS vs Medical Therapy Randomized-pair trial: DBS + optimized medical tx Optimized medical tx 75% of pairs favored DBS + meds Quality of life Severity of motor sxs off medication (Deuschl et al, NEJM, 355, 2006)
Slide 35-

DBS: other motor diseases Essential tremor Dystonia More sedation during MRI
Slide 36-

DBS and Tourette’s Motor/speech tics Up to 1% school age children 1/3 persist into adulthood
Slide 37-

DBS for Tourette’s (Visser-Vandewalle, J. Neurosurg 99: 2003)
Slide 38-

DBS and Psychiatric Disease Depression Pilot in 2005 4/6 patients improved >50% on testing Currently at least 3 ongoing NIH trials 10 to 20 patients per study
Slide 39-

Vagus Nerve Stimulation
Slide 40-

Vagus: Mixed Sensory and Motor 20% efferent: parasympathetic control of the heart and gut viscera 80% afferent: extensive connections to limbic and higher cortical systems Animal studies VNS: EEG changes and seizure cessation
Slide 41-

Vagal Nerve Stimulation Approved device made by Cyberonics Chronic, intermittent stimulation to cervical vagus Prevents and aborts seizures
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Slide 43-

Vagal Nerve Stimulation Typical settings: Automatic: 30 sec stimulation q 5 min Additional manual: if pt feels aura, may wave wand over generator to activate stimulator
Slide 44-

Vagal Nerve Stimulation Results from 3 studies: Significant decrease in seizures: 24%-35% Controls: low-level stimulation Seizure frequency decreased further over time Decreased medication doses
Slide 45-

VNS Surgery Performed under general anesthesia Leads wrapped around L vagus in neck Only L, and only unilateral Generator placed upper left chest
Slide 46-

Final Electrode/tether Placement Negative Electrode Positive Electrode Anchor Tether
Slide 47-

VNS Surgery Possible intraop complications with lead testing: Arrhythmias- transient sinus arrest Labile hemodynamics Airway obstruction (vocal cord stimulation)- if not intubated
Slide 48-

VNS Surgery Surgical complications: Infection: 2.9% Hoarseness or temporary vocal cord paralysis: 0.7% Hypesthesia or lower left facial paralysis: 0.7%
Slide 49-

VNS Surgery: Chronic Side Effects Hoarseness Cough Paresthesias Dyspepsia Disrupted sleep Worsening sleep apnea
Slide 50-

VNS: Anesthesia Pre-op considerations: Take usual seizure medications CBC, electrolytes EKG cardiac medications?
Slide 51-

VNS: Anesthesia May use local, MAC, or GA Usually GA- no restriction on agents Endotracheal tube Blood loss is minimal
Slide 52-

VNS: Anesthesia Anti-seizure medications induce hepatic enzymes-- higher anesthetic doses? Post-op seizures are common- be prepared Incidence of transient vocal cord paralysis
Slide 53-

Chronic VNS Turn off for other surgery Restart in recovery
Slide 54-

VNS for Depression Seizure pts with VNS: happier over time! N = 60 pts previously failed numerous treatments 2 weeks on meds only 2 weeks stim adjust + meds 8 weeks fixed stimu + meds
Slide 55-

VNS for Depression Open label study: 30.5% of patients responded with significant decrease in depression rating scale 15% full remission Substantial functional improvement, even in non-responders
Slide 56-

VNS for Depression Placebo controlled study: N= 225 VNS-responding patients: 15% Placebo-responding patients: 10% Lower levels of stimulation Much to figure out, although now FDA approved
Slide 57-

Other ongoing VNS studies Cervical VNS: PTSD Panic disorder OCD Rapid-cycling bipolar disorder Bilateral diaphragmatic VNS Morbid obesity
Slide 58-

Functional Neurosurgery DBS Targets stimulation based on neuroanatomy. Tailors stim to the disorder. Invasive. Requires neurosurgery VNS Simultaneous stimulation of multiple tracts & nuclei. No specific target. Same stimulation for a number of disorders. Much less invasive. Does not require neurosurgeon. Procedure in search of an application?