Deep Brain Stimulator Placement
DBS is a well-tolerated and effective surgical treatment for movement disorders, chronic pain, psychiatric disorders and a growing number of neurological disorders (epilepsy, depression, Tourette syndrome, headache, obesity, Alzheimer’s disease). Frame based systems are used to obtain accurate electrode placement. Microelectrode recordings (MER) and macro stimulation confirm, verify and optimize electrode target placement. Proper anesthetic management is important to balance patient comfort without interfering with neuro physiology.
Subthalamic Nucleus (STN), Globus Pallidus Interna (GPi), and the Ventralis intermedius nucleus of the thalamus.
Subcallosal cingulate gyrus, anterior limb of the internal capsule, and the nucleus accumbens.
Performed is a single or two stage operation.
In 2 stage procedure, the electrode is implanted in the brain separately from the Pulse generator if there are infection concerns.
Stereotactic frame placed under local anesthetic
MRI or CT obtained to choose the appropriate target coordinates based on anatomic imaging using computer software.
Frame is secured to the OR table and a geometric arc is placed to allow the target to be obtained from any angle given a stable radius.
Skin incision is planned, local anesthetic, burr hole drilled and dura opened.
Intraoperative electrode(s) inserted into brain and advanced 10-25 mm above the target site then advanced in .5-1 mm increments along the planned trajectory.
MER and macro electrode stimulation are used to confirm accurate localization of the therapeutic target.
Typically MAC with sedation is used for Stage 1 or electrode implantation in adults.
Mac provides best conditions for intra-operative neurophysiology and stimulation testing.
All medications are stopped at least 15 minutes prior to MER for best results.
Blood pressure control is of paramount importance at this time. Systolic blood pressure less than 140 can easily be achieved using nicardepine infusions.
Autonomic dysfunction is common. Watch for orthostatic hypotension, excessive sweating, incontinence can lead to sudden, exaggerated, or uncertain responses to central nervous system blockade.
Respiratory dysfunction for uncoordinated involuntary muscle movement is also possible
GI symptoms can result in nausea and vomiting.
Administer pre-operative aspiration prophylaxis with sodium citrate, Ondansetron and dexamethasone.
Avoid beta blockers (mask tremor testing), midazolam (over sedation/paradoxical agitation), droperidol (dystonia), metoclopramide (blocks dopamine receptors and can cause extra pyramidal symptoms).
Avoid Propofol. Abolishes MER and alters threshold stimulation. Parkinson’s patients may require lower doses and can induce dyskinesia.
Remifentanil is the best choice for ultra-short acting narcotic infusion. Can cause bradykinesia and bradycardia when used with dexmeditomidine.
Most anesthetics are GABA receptor agonists which inhibit basal ganglion activity thus affecting the spontaneous firing and spike activity making MER less reliable or unobtainable.
Avoid benzodiazepines, barbiturates, propofol, etomidate and volatile agents.
Ketamine has few side effects on MER and more useful on peds patients.
Dexmedetomidine is the most popular agent for sedation as it has no effect on GABA receptors, has sedative, analgesic and anxiolytic effects and minimal respiratory depression.
Dexmedetomidine can cause hypotension especially in Parkinson’s patients. Can have paradoxical agitation in doses greater than 1.1 mic/kg/hr.
Once testing is completed sedation can be resumed for closure.
If both stages being completed in same setting, electrodes are placed first then skin is closed, frame removed, drapes down and general anesthesia can be induced with an ETT for tunneling wires and placing the generator.