**Abstract**

Most commonly used for the treatment of Parkinson's disease (PD), the deep brain stimulation (DBS) is a new neurosurgical method whose other applications are still under development. Neuroimaging has a variety of main roles in DBS including evaluating the final electrode contact position, localizing the target nucleus, and detecting complications. Despite being a neurosurgical method, successful DBS intervention is highly dependent on an appropriate neuroimaging technique. For achieving satisfying clinical results, DBS needs the presence of neuroradiologists. In this chapter, we have reviewed the role of neuroimaging in all stages of deep brain stimulation as well as the underlying mechanism in this domain.

**Keywords:** neuroimaging, neurostimulation, deep brain stimulation, functional neurosurgery

### **1. Introduction**

Most commonly used for the treatment of Parkinson's disease (PD), the deep brain stimulation (DBS) is a new neurosurgical method which its other applications is still under development [1]. Neuroimaging has a variety of main roles in DBS including evaluating the final electrode contact position, localizing the target nucleus, and detecting complications.

Benabid et al. were the very first researchers who introduced the chronic highfrequency stimulation of the ventral intermediate nucleus (VIM) of the thalamus in early 1990s [2]. The authors used a subcutaneous pulse generator, which was implanted in the thoracic region, connected to chronic stimulating electrodes in the VIM for treatment of 6 patients with essential tremor and 26 patients with Parkinson's disease (PD). The patients maintained improvement up to 29 months. As the first clinical effort to introduce the chronic high-frequency stimulation of nuclei (deep brain stimulation), this study showed that this newly come up method could be used instead of common destructive surgeries such as thalamotomy.

Another similar technique, bilateral DBS of the subthalamic nucleus (STN), was then introduced by the Benabid team for the treatment of severe motor fluctuations and akinetic rigid Parkinson's disease [3]. In 2002, the USA food and drug

administration (FDA) approved the treatment of Parkinson's disease by stimulation of bilateral STN and the stimulation of internal globus pallidus (GPi) was approved in 2003. Although advanced Parkinson's disease is the main indication for DBS, a number of different additional uses have been mentioned for DBS, such as Tourette syndrome, cluster headache, and dystonia as well as psychiatric indications such as major depression (MDD) and obsessive-compulsion disorders (OCDs).

Despite being a neurosurgical method, successful DBS intervention is highly dependent on an appropriate neuroimaging technique. For achieving satisfying clinical results, DBS needs the presence of neuroradiologists. In this chapter, we have reviewed the role of neuroimaging in all stages of deep brain stimulation.

### **2. Targets for DBS**

A variety of indications and targets have been proposed for DBS since its starting era. Essential tremor and Parkinson's disease are among the most common and ancient indications of DBS, which are managed by stimulation of VIM nucleus [4–6]. On the other hand, STN and GPi are the most effective targets for Parkinson's disease DBS. It has also been reported that VIM DBS may relieve orthostatic tremor [6]. Tourette syndrome is another indication for DBS that is done through bilateral thalamic stimulation [7, 8].

Subthalamic nucleus (STN) stimulation by bilateral implantation of electrodes comprises a majority of DBS interventions for management of advanced Parkinson's disease [9, 10]. Intractable epilepsy is another described indication for STN DBS [11]. Recently, different psychologic disorders, such as OCD, have been discussed as possible indications for STN DBS [12]. Internal globus pallidus (GPi) is another target for DBS, which is more commonly indicated for managing dystonia and advanced Parkinson's disease [13–16]. Also, winter's cramp and Tourette syndrome have been managed by DBS of GPi [17–19]. Previous studies have shown that GPi DBS improves Yale Global Tic Severity Scale and reduces Tic in a range of 65–96%. An older reported indication for DBS is chronic pain for which a variety of targets have been proposed from internal capsule and periventricular gray matter to sensory thalamus [20, 21].

A variety of other targets have been come up for DBS in management of psychiatric disorders such as major depression or OCD [22–25]. On the other hand, cluster headache has been treated by hypothalamic DBS [26]. Also, seizures that are resistant to medical treatment have been managed by DBS of cerebellum, centromedian, or anterior nucleus of thalamus and hippocampus [26–28].

### **3. Pre-interventional imaging**

Magnetic resonance imaging (MRI) is the most commonly used modality for pre-interventional brain assessment in Parkinson's disease patients who are candidates for DBS, whether STN DBS or bilateral GPi. Multiple lacunae, severe atrophy, or leukoencephalopathy are among the MRI abnormalities that contraindicate DBS surgery [29, 30]. Some features in MRI imaging are predictors of desired or nonappropriate postoperative results. For example, a normalized surface measure of mesencephalon is correlated with satisfying clinical effects of bilateral STN stimulation on motor disability in Parkinson's disease; while, a smaller surface of mesencephalon is more associated with non-desired results of stimulation [31]. Also, it has been mentioned that brain atrophy is not related to non-desired postoperative

**19**

*Neuromodulation in the Age of Modern Neuroimaging Technologies*

clinical results in patients who are candidates for bilateral STN stimulation. There is a supporting hypothesis for connecting these imaging features to post-interventional clinical results that believes that a small mesencephalic surface area is correlated with cognitive impairment and non-dopaminergic non-levodopa responsive axial motor symptoms that do not appropriately respond to STN stimulation. Imaging modalities have an important role in targeting for DBS. Appropriate placement of electrodes is a sensitive and difficult neurosurgical technique, which involves highly skilled surgeons. In the first stage of DBS, anatomical landmarks are determined by MR imaging. Previously, invasive ventriculography was used to determine the anatomical landmarks for STN implantation; however, it is very uncommon these days [32]. MR imaging has two remarkable benefits: first of, it can be easily used for stereotactic targeting in DBS surgery and second, electrodes can be accurately implanted with no additional negative effects [33, 34]. Another option for targeting is MR imaging/CT fusion technique in which the data acquired from the two modalities are fused and MR imaging with stereotactic condition is not used anymore [35].

Plain control radiographs are more commonly used by most of the neurosurgery

Although it has remained a controversy, electrophysiological study of brain has been used intraoperatively for checking electrode placement in DBS surgery. Some neurosurgeons consider electrophysiologic mapping of the anatomic target during STN electrode implantation while others prefer not to apply it, as it prolongs the

In most of the cases, postoperative imaging is performed to detect the possible complications. CT scan is the most common modality that is used for this purpose. It seems that MR imaging has a higher sensitivity in comparison with CT scan for some complications; for example, electrode-related infections are more detected by MR imaging. Also, MR imaging correctly indicates the position of contact of implanted electrodes. MR imaging study provides a bunch of valuable data including the exact position of electrodes in case of clinical failure and also relationships between electrode and the target. Neurosurgeons more commonly register an atlas on postoperative MR imaging for checking the exact position of contact. Electrode heating is the most common complication of MR imaging, which is induced by

Post-interventional imaging has provided a remarkable source of data for discovering new therapeutic methods for many neurologic and psychiatric diseases. When undesired symptoms and manifestations are presented after DBS, researchers can assess the effect by imaging and this will lead to identification of new targets for managing a variety of disorders. It was found that bilateral hypothalamic DBS, which was used for treating morbid obesity, has evoked detailed autobiographic memories [44]. Also, the correlation of severe obsession and hyperactivity of caudate nucleus was found during intraoperative electrophysiologic study of caudate

teams during placement of implants to ensure that the electrodes are accurately following the predetermined pathway [36]. In addition, intraoperative use of MR

imaging or CT scan has been recently developed for this purpose [37, 38].

surgery and may be associated with risks and complications [39–41].

*DOI: http://dx.doi.org/10.5772/intechopen.92737*

**4. Imaging during intervention**

**5. Postoperative imaging**

electromagnetic waves [42, 43].

nucleus DBS in patients with OCD [45].

### *Neuromodulation in the Age of Modern Neuroimaging Technologies DOI: http://dx.doi.org/10.5772/intechopen.92737*

*Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

major depression (MDD) and obsessive-compulsion disorders (OCDs).

**2. Targets for DBS**

thalamic stimulation [7, 8].

sensory thalamus [20, 21].

**3. Pre-interventional imaging**

administration (FDA) approved the treatment of Parkinson's disease by stimulation of bilateral STN and the stimulation of internal globus pallidus (GPi) was approved in 2003. Although advanced Parkinson's disease is the main indication for DBS, a number of different additional uses have been mentioned for DBS, such as Tourette syndrome, cluster headache, and dystonia as well as psychiatric indications such as

Despite being a neurosurgical method, successful DBS intervention is highly dependent on an appropriate neuroimaging technique. For achieving satisfying clinical results, DBS needs the presence of neuroradiologists. In this chapter, we have reviewed the role of neuroimaging in all stages of deep brain stimulation.

A variety of indications and targets have been proposed for DBS since its starting era. Essential tremor and Parkinson's disease are among the most common and ancient indications of DBS, which are managed by stimulation of VIM nucleus [4–6]. On the other hand, STN and GPi are the most effective targets for Parkinson's disease DBS. It has also been reported that VIM DBS may relieve orthostatic tremor [6]. Tourette syndrome is another indication for DBS that is done through bilateral

Subthalamic nucleus (STN) stimulation by bilateral implantation of electrodes comprises a majority of DBS interventions for management of advanced Parkinson's disease [9, 10]. Intractable epilepsy is another described indication for STN DBS [11]. Recently, different psychologic disorders, such as OCD, have been discussed as possible indications for STN DBS [12]. Internal globus pallidus (GPi) is another target for DBS, which is more commonly indicated for managing dystonia and advanced Parkinson's disease [13–16]. Also, winter's cramp and Tourette syndrome have been managed by DBS of GPi [17–19]. Previous studies have shown that GPi DBS improves Yale Global Tic Severity Scale and reduces Tic in a range of 65–96%. An older reported indication for DBS is chronic pain for which a variety of targets have been proposed from internal capsule and periventricular gray matter to

A variety of other targets have been come up for DBS in management of psychiatric disorders such as major depression or OCD [22–25]. On the other hand, cluster headache has been treated by hypothalamic DBS [26]. Also, seizures that are resistant to medical treatment have been managed by DBS of cerebellum,

Magnetic resonance imaging (MRI) is the most commonly used modality for pre-interventional brain assessment in Parkinson's disease patients who are candidates for DBS, whether STN DBS or bilateral GPi. Multiple lacunae, severe atrophy, or leukoencephalopathy are among the MRI abnormalities that contraindicate DBS surgery [29, 30]. Some features in MRI imaging are predictors of desired or nonappropriate postoperative results. For example, a normalized surface measure of mesencephalon is correlated with satisfying clinical effects of bilateral STN stimulation on motor disability in Parkinson's disease; while, a smaller surface of mesencephalon is more associated with non-desired results of stimulation [31]. Also, it has been mentioned that brain atrophy is not related to non-desired postoperative

centromedian, or anterior nucleus of thalamus and hippocampus [26–28].

**18**

clinical results in patients who are candidates for bilateral STN stimulation. There is a supporting hypothesis for connecting these imaging features to post-interventional clinical results that believes that a small mesencephalic surface area is correlated with cognitive impairment and non-dopaminergic non-levodopa responsive axial motor symptoms that do not appropriately respond to STN stimulation.

Imaging modalities have an important role in targeting for DBS. Appropriate placement of electrodes is a sensitive and difficult neurosurgical technique, which involves highly skilled surgeons. In the first stage of DBS, anatomical landmarks are determined by MR imaging. Previously, invasive ventriculography was used to determine the anatomical landmarks for STN implantation; however, it is very uncommon these days [32]. MR imaging has two remarkable benefits: first of, it can be easily used for stereotactic targeting in DBS surgery and second, electrodes can be accurately implanted with no additional negative effects [33, 34]. Another option for targeting is MR imaging/CT fusion technique in which the data acquired from the two modalities are fused and MR imaging with stereotactic condition is not used anymore [35].
