Functional Neurosurgery and Anesthetic Considerations

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Functional Neurosurgery and Anesthetic
Considerations

• Susan M Ryan, PhD, MD
• Associate Clinical Professor
• Department of Anesthesia, UCSF
• 2006

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What is Functional Neurosurgery?

• Neurosurgery intended to improve
• or restore function by altering underlying
  physiology

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Areas of Functional Neurosurgery

• Movement disorders
• Seizures
• Pain syndromes
• Psychiatric disorders
• Peripheral nerve injuries

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Areas of Expansion

• Movement disorders
• Seizures
• Psychiatric disorders

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Neurosurgical Techniques

• Deep brain stimulation (DBS)
• Selective ablation
• electrodes
• Implantation
• viral vectors
• stem cells
• Cranial nerve/ peripheral electrical stimulation

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Functional Neurosurgery

• Began in mid-1900s
• Eclipsed by effective medications
• Now Non-responders
• Advanced cases

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Neurosurgical Techniques

• Deep brain stimulation
• Best established use
• Parkinsons Disease
• Vagal nerve stimulation
• Best established use
• Seizure disorders

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DBS/VNS Studies in Progress

• Obesity
• Fibromyalgia
• Cluster headache
• Tourettes Syndrome
• Depression
• Obsessive Compulsive Disorder

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• DBS for Parkinsons Disease

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Clinical Features

• Pill-rolling tremor
• Masked faces
• Cog-wheel rigidity
• Festinating gate
• Bradykinesia

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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

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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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DBS Surgery

• Placement of stereotactic frame prior to
  procedure
• MRI to confirm coordinates

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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

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DBS Stereotactic Surgery

• Electrode passed slowly to record single cells in
  nucleus of interest

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DBS Stereotactic Surgery

• Visual and auditory feedback of cell location and
  characteristics

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DBS Stereotactic Surgery

• Listening for cell response during leg movement

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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

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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

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PD Specific Issues

• Risk of exacerbation
• Consider intraoperative continuation of
  medications
• Hemodynamics may be labile
• Degeneration of sympathetic ganglia
• Dopamine-related hypotension, hypovolemia

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PD Specific Issues

• Airway or pulmonary compromise
• Upper airway obstruction
• Dysarthria and history of choking
• Restrictive ventilatory pattern
• Aspiration risk

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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

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DBS Surgical Risks

• Intracerebral hemorrhage
• Venous air embolism
• Emotional lability

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DBS Surgical Risks

• Intracerebral hemorrhage
• Monitor patient for neurologic changes
• Risk 1.6 per lead
• Avoid hypertension
• Keep SBP lt 140
• Consider arterial line
• Antihypertensives labetalol, hydralazine

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DBS Surgical Risks

• Venous air embolism
• Early detection
• Communicate with surgeon
• Support blood pressure
• Provide O2
• Airway plan

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DBS Surgical Risks

• Emotional Lability
• Usually no treatment needed
• Consider sedation PRN

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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)

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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)

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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)

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DBS other motor diseases

• Essential tremor
• Dystonia
• More sedation during MRI

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DBS and Tourettes

• Motor/speech tics
• Up to 1 school age children
• 1/3 persist into adulthood

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DBS for Tourettes(Visser-Vandewalle, J.
Neurosurg 99 2003)
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DBS and Psychiatric Disease

• Depression
• Pilot in 2005
• 4/6 patients improved gt50 on testing
• Currently at least 3 ongoing NIH trials
• 10 to 20 patients per study

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• Vagus Nerve Stimulation

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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

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Vagal Nerve Stimulation

• Approved device made by Cyberonics
• Chronic, intermittent stimulation to cervical
  vagus
• Prevents and aborts seizures

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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

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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

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VNS Surgery

• Performed under general anesthesia
• Leads wrapped around L vagus in neck
• Only L, and only unilateral
• Generator placed upper left chest

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Final Electrode/tether Placement
Anchor Tether
Negative Electrode
Positive Electrode
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VNS Surgery

• Possible intraop complications with lead testing
• Arrhythmias- transient sinus arrest
• Labile hemodynamics
• Airway obstruction (vocal cord stimulation)- if
  not intubated

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VNS Surgery

• Surgical complications
• Infection 2.9
• Hoarseness or temporary vocal cord paralysis
  0.7
• Hypesthesia or lower left facial paralysis 0.7

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VNS Surgery Chronic Side Effects

• Hoarseness
• Cough
• Paresthesias
• Dyspepsia
• Disrupted sleep
• Worsening sleep apnea

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VNS Anesthesia

• Pre-op considerations
• Take usual seizure medications
• CBC, electrolytes
• EKG
• cardiac medications?

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VNS Anesthesia

• May use local, MAC, or GA
• Usually GA- no restriction on agents
• Endotracheal tube
• Blood loss is minimal

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VNS Anesthesia

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

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Chronic VNS

• Turn off for other surgery
• Restart in recovery

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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

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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

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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

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Other ongoing VNS studies

• Cervical VNS
• PTSD
• Panic disorder
• OCD
• Rapid-cycling bipolar disorder
• Bilateral diaphragmatic VNS
• Morbid obesity

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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?