Figure 1.1

Implanted components of the deep brain stimulation (DBS) system include the DBS leads, extensions, and neurostimulator.

Figure courtesy of Medtronic; used with permission.

The DBS lead, containing an array of electrodes (presently four or eight, but soon more) on its distal end, is implanted into the deep brain target using stereotactic neurosurgical techniques. Such procedures typically use image-based targeting and intraoperative physiological confirmation to accurately implant the DBS lead into the appropriate target. DBS lead implantation is often performed using local anesthesia in the awake patient to optimize the recording of physiological data during the mapping procedure, as well as to elicit the patient’s report of stimulation-induced adverse effects during intraoperative test stimulation of the lead. Newer techniques harness the power of real-time interventional magnetic resonance imaging (iMRI) to guide and confirm DBS lead placement while the patient is under general anesthesia.

Following implantation of DBS leads, the neurostimulator (also called an implantable pulse generator) is implanted under general anesthesia. The neurostimulator is typically placed in the subclavicular region, although it can be located elsewhere. Bilateral stimulation necessitates the implantation of two single-channel neurostimulators or one dual-channel neurostimulator. Extension wires (extensions), tunneled under the skin, connect the brain leads to the neurostimulator(s). Days to weeks after device implantation, stimulation is activated. Using the DBS programmer, the clinician can select which electrodes (sometimes colloquially referred to as “contacts”) on the DBS lead to use to deliver stimulation, as well as the stimulation parameters themselves (including amplitude, pulse width, and rate of stimulation).

Indications for DBS

Table 1.1 summarizes the disorders for which DBS is presently indicated.

Table 1.1

Indications for deep brain stimulation.

Disorder	DBS target(s)	Year of FDA approval in the USA	Comments
Essential tremor and parkinsonian tremor	Ventral intermediate nucleus of thalamus (Vim)	1997	Vim thalamic target rarely used now for parkinsonian tremor, as DBS at other targets (STN and GPi) effective for tremor suppression, as well as improvement of other cardinal PD motor features
Parkinson’s disease	Subthalamic nucleus (STN) or globus pallidus internus (GPi)	2002	DBS of STN tends to be used more often for PD than DBS of GPi, although there are relative merits to both targets
Dystonia	Globus pallidus internus (GPi) or subthalamic nucleus (STN)	2003 (Humanitarian Device Exemption)	The vast majority of experience in dystonia to date is with DBS of GPi, although STN DBS is being explored
Epilepsy	Seizure focus Anterior nucleus of the thalamus (ANT)	2013 Pending approval in US	“Closed loop,” responsive stimulation delivered when electrographic seizure activity is detected to abort seizures “Open loop,” cyclical stimulation delivered on a regular basis to suppress seizure occurrence
Obsessive–compulsive disorder	Anterior limb of internal capsule	2009 (Humanitarian Device Exemption)	Target also referred to as ventral capsule/ventral striatum (VC/VS)