**7. DBS in movement disorders**

DBS became the standard therapy refractory over the last 25 years for individuals with motor circuit disabilities, most notably PD, dystonia, and essential tremor. DBS use has now been confined to high-income and developing countries [34]. Hospital-discharge-based studies of US database has showed that >30,000 DBS surgeries were performed during 2002 and 2011, and the publications on DBS have also risen over the same period of time [35].

### **7.1 Parkinson's disease**

Over the last 10 years, STN is used as a target for DBS in PD [36]. GPi is also used as a target, but the choice between STN and GPi is often guided by the biomedical group based on the medical context of the patient.

Multiple studies have already shown that STN DBS produces continuous symptom relief even after 5–10 years of treatment, although with cognition and gait regression due to the unremitting development of the underlying degenerative disorder [37]. In PD diagnosis, DBS is called the "second honeymoon"

### *Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

(dopaminergic therapy is the first). Instability in posture and freezing can be improved by DBS at pedunculopontine nucleus region of the brain [38].

Based on previous studies, there is a general concept of DBS that it can improve PD patients with advance kind of symptoms like motor fluctuation, dyskinesias secondary to chronic levodopa as well as those with refractory and marked tremor. But based on studies of EARLYSTIM findings, DBS can also improve early stages of PD [39]. Due to these advantages of DBS, it is now been under clinical trials for those patients who are eliminated from surgery due to age factor, along with those patients with motor fluctuations in whom medication is effective. Due to the inherent risk of DBS like hemorrhage and infection, such trials face ethical issues [40].

### **7.2 Epilepsy**

Earlier it was thought that DBS can switch open resective surgery in epilepsy, but after studies on DBS of the anterior nucleus of the thalamus (ANT), it was stifled. These researches imposed well on the efficacy of DBS but simultaneously also demonstrated that many patients did not attain seizure freedom after the DBS treatment [41, 42]. Closed-loop stimulation is a hopeful technology in epilepsy that can sense seizure activity with electrode and also can send electrical stimulations to brain to thwart propagation of seizure [43].

### **7.3 Essential tremor**

After various studies, DBS was recommended by FDA in 1997 for the initial tremor symptoms of the movement disorder [44]. Along with DBS, other therapies such as lesional surgery have also been used for the treatment of essential tremors. DBS is a better choice due to its safety as well as adjustability of the stimulation, which is not provided by the lesional therapy [45]. Thalamic DBS is used in tremors of multiple sclerosis patients [46].

### **7.4 Dystonia**

DBS had played a crucial role in dystonia treatment [47, 48]. Pallidal DBS, for instance, is the first-line treatment in childhood generalized dystonic disease. The most significant determinant of results was age at which surgery was performed and the duration of disorder [49–51]. Genetic makeup of patients has also been important in evaluating the outcome, as individual with DYT1 dystonia are benefited more than the DYT6 dystonia [52]. Therefore, genetic testing of patients undergoing DBS treatment would suggest which candidate is going to be benefited more [53]. The posteroventral lateral GPi in dystonia is the utmost recognized target for DBS [54]. GPi stimulation offers significant recovery in dystonic patients with adversarial effects on low frequency. The STN and the thalamus are two other targets for DBS. Despite of positive outcomes of STN DBS, the therapeutic use is still restricted [55]. An additional important target is sensorimotor thalamus, which in the age of radiofrequency lesioning, was considered as standard target [56, 57]. The mode of action of DBS in clinical improvement is quite intricate because of delayed and progressive effect exhibited over a period of months. The underlying mechanism for this was hypothesized as the alteration of maladaptive plasticity, progressive motor learning, and modification in pathological oscillatory activity in basal ganglia circuitry [58]. Dystonia can recur within minutes to hours after discontinuation of stimulation during the initial postoperative period; the advantages from stimulation that has been administered for several years can persist for days and weeks after

**37**

*Deep Brain Stimulation Approach in Neurological Diseases*

has contributed an EARLYSTIM study in dystonia [61].

target population choice are the challenges for DBS [62].

discontinuation [59, 60]. Therefore, DBS acts as a true treatment in case of dystonia where progressive treatments are absent or poorly successful. This rationale

AD is perhaps the most prevailing neurodegenerative disease but is characterized with years of gradual reduction in neurocognitive parameters. Many DBS strategies have been identified for AD, including areas anterior to the fornix, entorhinal cortex, and the nucleus basalis of Meynert (NBM). Several studies suggest that DBS can affect cognitive function in AD. Nonetheless, outcome influencing factors such as baseline neuroanatomical substrates, surgical technique, placement of lead, and

Psychiatric disorders are assorted conditions affecting multiple pathways with overlap. Such disorders have few (if any) biochemical markers that support treatment and outcomes, and there is a lack of data for its outcome assessment in patients. Thus, this affects the designing of clinical trial studies. In addition, the quality of surgical trials is also hindered due to significant selection barriers [63]. In an attempt to alleviate refractory psychiatric symptoms, numerous prospective studies have been done to evaluate if focal disruption at specific anatomic targets can impact circuitwide or network-wide changes. Though the strategy is enticing, there are still some

Due to the behavioral and cognitive issues in these patients, less than 300 patients

have endured DBS treatment across the world. Patients with chronic symptoms are improved less than those with mild symptoms as per a meta-analysis [64]. A randomized controlled trial in 2017 did not report any significant improvement of tics in Tourette syndrome patients treated with anteromedial GPi stimulation during the initial blinded phase of the study; however, tics improvement was documented during the study's transparent period [65]. There is need of more randomized control

Major depression is a serious disorder that can impact quality of life day-today working and, eventually, life expectancy significantly [66, 67]. As a result of advancement of imaging techniques, there is a suggestion that depression occurs due to alteration in mood-related circuits, which can be reversed with neuromodu-

Bipolar disorders are associated with acute and strong emotive condition, which are episodic and known as mood episodes; these disorders are less common than major depression but are linked with increased risk of suicide. Effective targets in bipolar disorders for DBS are thought to be SCC, the nucleus accumbens, and

trials for further development of DBS treatment in these patients.

lation along with other antidepressant therapies.

*DOI: http://dx.doi.org/10.5772/intechopen.91756*

**7.5 Alzheimer disease (AD)**

**8. DBS in psychiatric disorders**

challenges.

**8.1 Tourette syndrome**

**8.2 Major depression**

**8.3 Bipolar disorder**

slMFB, but studies are less [68].

discontinuation [59, 60]. Therefore, DBS acts as a true treatment in case of dystonia where progressive treatments are absent or poorly successful. This rationale has contributed an EARLYSTIM study in dystonia [61].
