Which of the following is the most commonly used site for Transcranial Magnetic Stimulation to reduce frequency of Parkinsonism symptoms:
Answer is C (Subthalamic Nucleus): Primary Targets Subthalamic Nucleus (STN) Globus Pallidus Internus (GPI) Subthalamic Nucleus (STN) is the single most common preferred site for Deep Brain Stimulation in patients with Parkinsonism. Globus Pallidus Internus (GPi) is the second most common site for Deep Brain Stimulation in patients with Parkinsonism and provides comparable results to DBS of STN. Subthalamic nucleus and Globus Pallidus Internus both provide comparable efficacy (Believed to be equally effective) Other Targets Ventral Intermediate Nucleus of Thalamus (VMI) (Efficacious only in relieving Tremor from Parkinsonism. Other Parkinsonian motor symptoms may not respond and hence this target is not preferred) Pedunculopantine Nucleus (DBS of Pedunculopontine nucleus may be beneficial for patients with advanced parkinsonism and predominant axial symptoms, postural instability and gait disturbance. Results are however still limited to only a few patients) (Springer) 2007/180; Mardsen's Book of movement Disorders (Oxford) 2012/298 Subthalamic Nucleus is widely accepted as the preferred site for Deep Brain Stimulation (Transcranial Magnetic Stimulation) for patients with Parkinsonism. Deep Brain Stimulation for Parkinson's Disease (Taken from Operative Neuromodulation) Deep Brain Stimulation has become a standard therapy for patients with advanced Parkinson's Disease Although clinical efficacy of both GPi and STN stimulation is comparable it has become widely accepted to prefer STN over GPi The Rationale for STN targeting include: (i) The stimulation energy required to gain maximum clinical improvement seem to be lower for STN than for GPi (ii) STN stimulation seems to have more prominant and stable effects on L-DOPA responsive off-period symptoms in the long term. Subthalamic Nucleus Stimulation effectively improves all cardinal motor symptoms including gait, posture and balance and is the preferred target in Europe and Noh America' - Mardsen's Book of MOvement Disorders (Oxford) 2012/298 Note: STN stimulation bears a higher risk of cognitive and neuropsychiatric behavioural complications in comparison to GPi stimulation. GPI stimulation may be preferred over STN stimulation for patients with pre-existing conditions like depression. Deep Brain Stimulation for Parkison's Disease: Review What is Deep Brain Stimulation (DBS) DBS is a relatively new procedure that uses an implantable electrode into a specific target in the brain and is attached to a programmable pulse generator. The pulse generator is implanted in a pocket below the clavicle and connected to the DBS electrode in the Brain. (The pulse generation is just like a cardiac pacemaker but the wire goes to the specific site in the brain) What is the principle of DBS in Parkinson's Disease Parkinson's disease is characterized by loss of dopaminergic input to the striatium, which has been shown to be associated with hyperactivity of two key nuclei within the basal ganglia, namely the subthalamic nucleus and the Globus Pallidus Internus. Dopaminergic dennervation in PD leads to increased firing of neurons in the STN and GPi resulting in excessive inhibition of the thalamus, reduced activation of the coical motor systems and development of Parkinsonian Features. DBS is believed to reduce the neuronal overactivity of the STN and/or the GPi and thereby improve features of PD. What specific regions in the brain are targetted by DBS There are three brain targets that have been FDA approved for use in Parkinson's Disease for Deep Brain Stimulation Subthalamic nucleus (STN): Most preferred & commonly used target Globus pallidus Internus (GPi): Effective target (Results comparable with STN) Thalamus (Ventral Intermediate Nucleus): Only effective in relieving Tremor (not preferred anymore) What are the indications for DBS (Ideal candidate) The procedure is primarily indicated for patients who suffer disability from levodopa induced motor complications that cannot be satisfactorily controlled with drug manipulation. Symptoms that improve DBS are essentially the same individual symptoms that improve with levodopa (dopamine) with the exception of medication refractory tremor and dyskinesias. DBS provides effective relief from all cardinal dopaminergic motor symptoms including gait, posture and balance. Improves tremor, rigidity bradykinesia. It provides dramatic result with respect to "off' time and dyskinesias but does not improve features that fail to respond to levodopa. It does not prevent the development or progression of non-dopaminergic features such as freezing, falling and dementia. DBS does not improve cognitive (thinking ability). Decrease the dose of medications required (in many but not all cases)
Striatus
Globus Pallidus
Subthalamic Nucleus
Putamen