DBS: Its Role in the Management of Parkinson's Disease

Parkinson’s disease (PD) is clinically characterized by bradykinesia, rigidity, tremor and postural instability. PD is a neurodegenerative disease wherein deposition of Lewy bodies containing alpha synuclein is observed within neurons of various brain regions along with neuronal loss. 1 This results in abnormal function of multiple motor and non-motor neural circuits, particularly within the basal ganglia. PD patients initially show a good therapeutic response to levodopa, but with time, levodopa induced dyskinesia and motor fluctuations impair quality of life. Management of patients with dyskinesia and motor fluctuations using oral medications is quite challenging and with advancing disease, maintaining stable motor function may not be possible with oral medications alone. Before the advent of levodopa therapy, a few studies highlighting the potential role of surgical therapies in PD had been published. Dr R Meyers was the first to describe a partial caudate and pallidofugal fibre resection for the treatment of rigidity in a patient with PD. 2 This was followed by Dr Irving Cooper in 1952, while performing a mesencephalic pedunculotomy in a patient with PD; he accidentally cut the anterior choroidal artery and noted post-operative improvement in tremor and rigidity. 3 He attributed this serendipitous improvement to damage to the globus pallidus interna (GPi) and followed this case report with a surgical series. 4 The 1950’s heralded the introduction of stereotactic pallidotomy by Spiegel and Wycis. 5 Svennilson et al. demonstrated that posteroventral pallidotomy using radiofrequency ablation resulted in improvement of parkinsonian symptoms in a series of patients. 6 These findings were confirmed much later in several follow up studies 7–9 and it was observed that in addition to modest improvement in bradykinesia, rigidity and tremor, there was a marked improvement in drug induced dyskinesia following this procedure. Hassler and Riechert were the first to demonstrate thalamotomy as treatment for tremor. 10 Following exploration of various targets in the thalamus for tremor, the Ventral intermediate nucleus (Vim) of the thalamus was commonly used as a target for stereotactic lesions. 11 , 12 The subthalamic nucleus (STN) had also been used as a target for tremor control with stereotactic procedures. 13 The use of stereotactic lesions declined with the advent of effective medical therapy for PD with levodopa, only to reemerge as a treatment option with the recognition of motor complications associated with levodopa therapy. In general, stereotactic procedures are associated with significant disadvantages such as unpredictability of results, difficulties in precise identification of the target, permanence of the procedure with inability to modify outcomes and a gradual decline in efficacy. 14 Many of these drawbacks are overcome by deep brain stimulation, a technique in which one or more electrodes are inserted into the brain, targeting specific nuclei for electrical stimulation. ( Fig 1 ) Figure 1 The diagram illustrates brain anatomy and an activated motor circuit. It includes the thalamus, subthalamic nucleus, globus pallidus, cortex, and putamen, with a probe inserted into the brain. https://www.w3.org/1999/xlink" content-type="black-white" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003505488/098b2309-4468-4894-95ce-3123e2fe878e/content/fig20_1_B.tif "/>