functional neurosurgery and anesthetic considerations susan m ryan, phd, md associate clinical...
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Functional Neurosurgery and
Anesthetic Considerations
Susan M Ryan, PhD, MD
Associate Clinical Professor
Department of Anesthesia, UCSF
2006
What is Functional Neurosurgery?
“Neurosurgery intended to improve
or restore function by altering underlying
physiology”
Areas of Functional Neurosurgery
• Movement disorders
• Seizures
• Pain syndromes
• Psychiatric disorders
• Peripheral nerve injuries
Areas of Expansion
• Movement disorders
• Seizures
• Psychiatric disorders
Neurosurgical Techniques
• Deep brain stimulation (DBS)
• Selective ablationelectrodes
• Implantationviral vectors
stem cells
• Cranial nerve/ peripheral electrical stimulation
Functional Neurosurgery
• Began in mid-1900’s
• Eclipsed by effective medications
• Now: Non-responders Advanced cases
Neurosurgical Techniques
• Deep brain stimulationBest established use:
Parkinson’s Disease
• Vagal nerve stimulationBest established use:
Seizure disorders
DBS/VNS Studies in Progress
• Obesity
• Fibromyalgia
• Cluster headache
• Tourette’s Syndrome
• Depression
• Obsessive Compulsive Disorder
DBS for Parkinson’s Disease
Clinical Features
• ‘Pill-rolling’ tremor
• Masked faces
• ‘Cog-wheel’ rigidity
• Festinating gate
• Bradykinesia
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
Basal Ganglia in PD
Treatment
• Medications• L-dopa + periph. inhibitor (Sinamet)
• Dopamine agonists
• MAO inhibitors
• COMT inhibitors
• Amantadine
DBS Surgery
• Goal: Improvement in PD symptoms
• Tremor• Rigidity• Hypokinesia• Gait• Balance
DBS Surgery
• Placement of stereotactic frame prior to procedure
• MRI to confirm coordinates
DBS Surgery
• Stereotactic head frame attached to bed
• Pt placed in sitting position
DBS Stereotactic Surgery
• Drill hole in skull to allow electrode placement for recording & stimulation
DBS Stereotactic Surgery
• Electrode passed slowly to record single cells in nucleus of interest
DBS Stereotactic Surgery
• Visual and auditory feedback of cell location and characteristics
DBS Stereotactic Surgery
• Listening for cell response during leg movement
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
Anesthesia: DBS Generator placement
• General anesthesia for generator placement
• No particular anestheticPropofol or inhaled agent work wellAvoid dopamine antagonistsAvoid demerol Muscle relaxants OK
• Prevent or treat emergence hypertension
• Not much pain in post-op setting
PD: Specific Issues
• Risk of exacerbation
Consider intraoperative continuation of medications
• Hemodynamics may be labile
Degeneration of sympathetic gangliaDopamine-related hypotension, hypovolemia
PD: Specific Issues
• Airway or pulmonary compromise
• Upper airway obstruction
• Dysarthria and history of choking
• Restrictive ventilatory pattern
• Aspiration risk
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
DBS: Surgical Risks
• Intracerebral hemorrhage
• Venous air embolism
• Emotional lability
DBS: Surgical Risks
Intracerebral hemorrhageIntracerebral hemorrhage
• Monitor patient for neurologic changes• Risk: 1.6% per lead
• Avoid hypertensionKeep SBP < 140Consider arterial line Antihypertensives: labetalol, hydralazine
DBS: Surgical Risks
Venous air embolismVenous air embolism• Early detection
• Communicate with surgeon
• Support blood pressure
• Provide O2
• Airway plan
DBS: Surgical Risks
Emotional LabilityEmotional Lability
• Usually no treatment needed• Consider sedation PRN
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)
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)
DBS vs Medical Therapy
• Randomized-pair trial:• DBS + optimized medical tx• Optimized medical tx
• 75% of pairs favored DBS + meds Quality of lifeSeverity of motor sxs off medication
(Deuschl et al, NEJM, 355, 2006)
DBS: other motor diseases
• Essential tremor
• Dystonia• More sedation during MRI
DBS and Tourette’s
• Motor/speech tics
• Up to 1% school age children
• 1/3 persist into adulthood
DBS for Tourette’s(Visser-Vandewalle, J. Neurosurg 99: 2003)
05
1015202530354045
# Tics Per Minute
#1 #2 #3
Pre DBS1 wk PostLong-term
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
Vagus Nerve Stimulation
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
Vagal Nerve Stimulation
• Approved device made by Cyberonics
• Chronic, intermittent stimulation to cervical vagus
• Prevents and aborts seizures
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
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
VNS Surgery
• Performed under general anesthesia
• Leads wrapped around L vagus in neck
• Only L, and only unilateral
• Generator placed upper left chest
Final Electrode/tether Placement
Negative Electrode
Positive Electrode
Anchor Tether
VNS Surgery
• Possible intraop complications with lead testing:
• Arrhythmias- transient sinus arrest
• Labile hemodynamics
• Airway obstruction (vocal cord stimulation)- if not intubated
VNS Surgery
• Surgical complications:
• Infection: 2.9%
• Hoarseness or temporary vocal cord paralysis: 0.7%
• Hypesthesia or lower left facial paralysis: 0.7%
VNS Surgery: Chronic Side Effects
• Hoarseness
• Cough
• Paresthesias
• Dyspepsia
• Disrupted sleep
• Worsening sleep apnea
VNS: Anesthesia
• Pre-op considerations:
• Take usual seizure medications
• CBC, electrolytes
• EKG
• cardiac medications?
VNS: Anesthesia
• May use local, MAC, or GA
• Usually GA- no restriction on agents
• Endotracheal tube
• Blood loss is minimal
VNS: Anesthesia
• Anti-seizure medications induce hepatic enzymes-- higher anesthetic doses?
• Post-op seizures are common- be prepared
• Incidence of transient vocal cord paralysis
Chronic VNS
• Turn off for other surgery
• Restart in recovery
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
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
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
Other ongoing VNS studies
• Cervical VNS:• PTSD
• Panic disorder
• OCD
• Rapid-cycling bipolar disorder
• Bilateral diaphragmatic VNS• Morbid obesity
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?