Deep brain stimulation in the treatment of Parkinson's disease: a review and update

Abstract

Deep brain stimulation (DBS) is a neurosurgical treatment of severe forms of Parkinson's disease, already applied to three targets, the thalamus, the internal pallidum (GPi) and the subthalamic nucleus (STN). Thalamic DBS mainly improves contralateral tremor and is therefore restricted to a small group of patients with tremor dominant disease. STN and GPi DBS improve off-motor periods and dyskinesias. The magnitude of the improvement seems more constant with STN DBS than with GPi, but there is very little comparative data between these procedures. The DBS procedure has the unique advantage of reversibility and adjustability over time. Most authors agree that bilateral DBS is reasonably safe, which is not the case of ablation. In any event, surgery is restricted to patients disabled by their condition but still responding well at times to levodopa, who are generally fit with no behavioural, mood or cognitive impairment. DBS can have side effects. Side effects more specific to the DBS procedure are infection, disconnection and hardware failure. DBS, like ablative surgery can induce an intracranial lesion like a hematoma or a stroke. There are side effects more specific to the target like postural instability, dysarthria or paresthesia in the thalamus and dyskinesias or eyelid opening apraxia in the STN. The mechanism by which high frequency DBS mimics the effect of ablation is not fully understood.