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
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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 ablation
electrodes
• Implantation
viral 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 stimulation
Best established use:
Parkinson’s Disease
• Vagal nerve stimulation
Best established use:
Seizure disorders
DBS/VNS Studies in Progress
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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
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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 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
PD: Specific Issues
• Risk of exacerbation
Consider intraoperative continuation of medications
• Hemodynamics may be labile
Degeneration of sympathetic ganglia
Dopamine-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 hemorrhage
• Monitor patient for neurologic changes
• Risk: 1.6% per lead
• Avoid hypertension
Keep SBP < 140
Consider arterial line
Antihypertensives: labetalol, hydralazine
DBS: Surgical Risks
Venous air embolism
• Early detection
• Communicate with surgeon
• Support blood pressure
• Provide O2
• Airway plan
DBS: Surgical Risks
Emotional 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 life
Severity 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)
45
40
35
30
# Tics Per 25
Minute 20
15
10
5
0
Pre DBS
1 wk Post
Long-term
#1
#2
#3
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
Anchor
Tether
Positive
Electrode
Negative
Electrode
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:
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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:
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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?