The New ACLS Guidelines

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 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 • • • • • •

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 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: • • • •

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?