Parkinson’s Disease and Deep Brain Stimulator Insertion

PARKINSON’S DISEASE

A. General

B. Pathophysiology

C. Pharmacologic treatment

1. Dopamine agonists

2. Non-dopamine agonists

D. Anesthetic considerations for PD

SURGICAL TREATMENT OF PD

A. Definitions

B. Deep brain stimulation (DBS)

C. Patient selection for DBS in PD

D. Technique: Stages of DBS insertion

ANESTHETIC CONSIDERATIONS FOR DBS INSERTION

Anesthetic options

A. Local anesthesia and sedation

B. General anesthesia

ANESTHETIC MANAGEMENT

PERIOPERATIVE COMPLICATIONS

FUTURE DIRECTIONS

A. New indications

B. Neuroprotection

C. Stem cell transplantation

I. PARKINSON’S DISEASE

A. General

1. Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by muscle rigidity, bradykinesia, tremor at rest, and postural instability.

a. The largest risk factor for PD is increasing age with an incidence of 0.1% and prevalence of 1% in people over 65 years of age. There is a slightly higher incidence in men than women.

b. Idiopathic PD comprises 85% of Parkinsonian syndromes. Secondary causes are rare and include drug-induced (primarily neuroleptic medications), cerebrovascular disease, head trauma, and metabolic causes.

c. PD causes non-motor signs and symptoms in addition to the motor symptoms. These include

1. Autonomic instability

2. Sleep disturbance

3. Sensory abnormalities (e.g., akathisia)

4. Cognitive impairment

5. Depression and anxiety

B. Pathophysiology

1. Movement is regulated by complex interactions among the basal ganglia, thalamus, cerebellum, and cerebral cortex.

2. Loss of dopaminergic cells in the pars compacta region of the substantia nigra in the basal ganglia results in an imbalance between acetylcholine-induced excitation and dopaminergic inhibition of the striatum. Increased excitation leads to excessive inhibition of the thalamus and brain stem nuclei. Suppression of the cortical motor system produces akinisia, rigidity, and tremor while suppression of the brain stem motor areas results in postural instability and gait abnormalities.

3. The non-motor manifestations of PD likely result from dopaminergic neurons outside these pathways as well as non-dopaminergic changes elsewhere in the central nervous system (CNS).

C. Pharmacologic treatment of PD is targeted at restoring the balance between the neurotransmitters dopamine and acetylcholine in the brain. Over time, however, patients become less responsive to the pharmacologic treatments of PD with progressive impairment in their quality of life.

1. Dopamine agonists

a. Levodopa, a dopamine precursor, is converted to dopamine in the CNS. Carbidopa, an enzyme that limits conversion of levodopa to dopamine outside the CNS, is commonly coadministered (Sinemet). Dopaminergic drugs are effective against all the motor symptoms of PD.

b. Apomorphine is the only parenterally available dopaminergic medication and is generally reserved for use as a rescue therapy. Nausea and vomiting are common side effects, and antiemetics should be coadministered.

2. Other medications

a. Monoamine oxidase (MAO) inhibitors. As MAO B degrades dopamine in the CNS, MAO inhibitors are a potential therapy for patients who have PD.

b. Amantadine, an antiviral medication, improves symptoms in mild PD although the mechanism is unknown.

c. Anticholinergics (e.g., benzotropine) may improve tremor and rigidity although are of limited use.

D. Anesthetic considerations for PD

1. Airway complications such as aspiration, laryngospasm, and inability to manage secretions can result from pharyngeal and laryngeal dysfunction.

2. Autonomic instability may be manifest as hypotension, hypovolemia, and arrhythmias.

3. Respiratory complications are more common owing to poor cough, recurrent infection, and rigidity-induced restrictive lung disease.

4. Dementia and depression are common which may impair intraoperative communication and cooperation. The risk of postoperative delirium is increased.

5. Difficult monitoring and vascular access may result from severe tremor and abnormal posturing.

6. Pharmacologic management of dopaminergic medications and consideration of their interactions with anesthetic drugs in the perioperative period are paramount.

a. Dopaminergic medications should be continued in the perioperative period to avoid significant motor impairment. The exception is in patients undergoing surgical management of PD with DBS insertion for which these medications will typically be held.

b. Anticholinergic medications may worsen the symptoms of PD and should be avoided. These include common antiemetics (e.g., metaclopramide, prochlorperazine, phenothiazines) and antipsychotic medications (e.g., haloperidol, loxapine).

7. Presence of a DBS has specific anesthetic implications including potential damage or reprogramming by electrocautery or magnetic resonance imaging (MRI). The DBS may also interfere with electrocardiographic (ECG) monitoring.

II. SURGICAL TREATMENT OF PARKINSON’S DISEASE

A. Definitions: Pallidotomy involves permanent lesioning of cells within the globus pallidus internus primarily to alleviate involuntary movements and rigidity. Thalamotomy involves permanent lesioning of cells within the thalamus primarily to alleviate tremor.

B. DBS

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