Role of radiology in central nervous system stimulation

Abstract

Central nervous system (CNS) stimulation is becoming increasingly prevalent. Deep brain stimulation (DBS) has been proven to be an invaluable treatment for movement disorders and is also useful in many other neurological conditions refractory to medical treatment, such as chronic pain and epilepsy. Neuroimaging plays an important role in operative planning, target localization and post-operative follow-up. The use of imaging in determining the underlying mechanisms of DBS is increasing, and the dependence on imaging is likely to expand as deep brain targeting becomes more refined. This article will address the expanding role of radiology and highlight issues, including MRI safety concerns, that radiologists may encounter when confronted with a patient with CNS stimulation equipment in situ.Central nervous system (CNS) stimulation is becoming increasingly prevalent. Deep brain stimulation (DBS) has been proven to be an invaluable treatment for movement disorders and is also useful in many other neurological conditions refractory to medical treatment, such as chronic pain and epilepsy. Neuroimaging plays an important role in operative planning, target localization and post-operative follow-up. ANATOMY OF THE DEEP BRAIN NUCLEIThe basal ganglia are a complex group of anatomically and neurochemically interconnected structures whose role is the control of complex and intentional movements and to inhibit unwanted movements.1 They comprise the corpus striatum (caudate nucleus, nucleus accumbens and putamen), globus pallidus [external segment (GPe) and internal segment (GPi)], substantia nigra [compact part and reticular part (SNr)] and the subthalamic nucleus (STN) (Figure 1). The pedunculopontine nucleus is highly interconnected with the basal ganglia and is now considered by many to be part of this group. Disorders of the basal ganglia therefore manifest by movement, posture and muscle tone abnormalities.There are wider connections to other parts of the brain such as the thalamus, limbic cortex and prefrontal cortex. These highlight their role in cognition and emotion and explain their implication in some psychiatric disorders and the cognitive symptoms associated with movement disorders.It is these structures and their interconnected neighbours that are the targets for treatment by DBS. The STN is the most common target for DBS treatment because it is capable of treating the entire gamut of advanced Parkinson's disease symptoms, including tremor, rigidity, bradykinesia and drug-induced dyskinesia.2 DBS reduces the need for dopaminergic medication. The benefits are a reduction of motor signs and improvement of functionality in the off-medication phase, a reduction of the required medication dose and its associated complications, and an increased quality of life.3 The benefits usually persist for at least 2 years and can last for many more.The STN plays a key role in the basal ganglia-thalamocortical motor circuit (Figure 2). The striatum receives input from the cerebral cortex and direct pathway information pa...