Clinical Neurophysiology Part IX - Basal Ganglia & Deep Brain Stimulation PDF

Clinical Neurophysiology Part IX Basal ganglia and deep brain stimulation Karsten Schwerdtfeger Klinik für Neurochirurgie, Universitätsklinikum des Saarlandes. Studiengang: Neural Engineering Master WS 2024/2025 Motor Pathways Extrapyramidal system...

Clinical Neurophysiology Part IX Basal ganglia and deep brain stimulation Karsten Schwerdtfeger Klinik für Neurochirurgie, Universitätsklinikum des Saarlandes. Studiengang: Neural Engineering Master WS 2024/2025 Motor Pathways Extrapyramidal system – Historical definition: all neuclei and tracts except the pyramidal system – Polysynaptic cortco- spinal projections – Cerebellum – Basal ganglia – Modulates spinal reflex arcs Usually inhibition Basal ganglia A group of subcortical nuclei at the base of the forebrain and the top of the midbrain They are associated with a variety of functions – Control of voluntary movements – Procedural learning – Habit learning – Conditional learning – Eye movements – Cognition – emotion  Basal ganglia A group of subcortical nuclei next to the thalamus Embedded in complex motor loops Tasks: – Initiation and termination of movements – Stabilization of movements – Stabilizing muscles at rest.  Basal ganglia Input from the cortex to basal ganglia: – Striatum Output to thalamus – Globus pallidus interna – Substantia nigra pars reticularis Direct pathway – Str -> SNret/GPi -> Thalamus – „- x - = +“ disinhibition = facilitation of thalamocortical projections Indirect pathway – Str -> GPe -> STN->Snret/Gpi Caution: this diagram depicts the functional -> Thalamus connections. Anatomical connections are different! – Results in an inhibition of thalamocortical projections  Basal ganglia Substantia nigra pars compacta: – Dopaminergic projections to the striatum as complex modulators – D1 receptors in the striatum yield to excitation – D2 receptors in the striatum yield to inhibition – By differences in the following pathways both projections result in a facilitation of thalamocortical impulse transmission  Basal ganglia Cortical stimulation cortical stimulation – Yields to a triphasic response in the basal ganglia output nuclei (SNret/GPi) recorded by means of an extracellular microelektrode – After a delay there is increased activity resulting in an inhibition of thalamocortical projections – This is followed by a decrease of activity resulting in a disinhibition and commonly thought to be associated with movement release – The third phase finally shows increased activity with inhibition of the thalamocortical projections stopping movement release.  Basal ganglia Cortical stimulation Motoric tasks – Initiation and termination of movements – Stabilization of movements – Stabilizing muscles at rest.  Basal ganglia diseases Parkinsons disease Parkinson's Disease, Animation – YouTube  Basal ganglia disease Cortical stimulation Parkinsons Disease – Loss of dopaminergic neurons in the substantia nigra pars compacta – Cortical activation yields to a hyperactivity of SNret and an inhibition of thalamocortical projections required for initation of movements. – Cardinal signs: Akinesia/Bradykinesia – Start/Stop – disturbance – Impaired facial expression – Micrography – Parkinsonian gait Tremor Rigidity postural instability – Other symptoms Neuropsychiatric vegetative  Basal ganglia diseases Parkinsons disease - Therapy – First line: drugs (L-Dopa, Dopaminagonists, ….) – In case of drug resistance – Deep brain stimulation (DBS) STN  Basal ganglia diseases PD_DBS.mpg  Basal ganglia diseases Parkinsons disease - DBS – Neurophysiological Biomarkers Recorded via extracellular microelectrodes (or the inserted DBS electrodes) Extracellular recording of a circumscibed neuron population - > raw data – High-pass filter –> neuronal firing action potentials of local neurons (Output?)  Basal ganglia diseases Parkinsons disease – Targeting the optimal DBS location by analysis of neuron firing – Microelectrodes record only from a limited number of neurons around the tip when compared to DBS electrodes  Basal ganglia diseases Parkinsons disease – DBS optimization with neuronal firing  Basal ganglia diseases Parkinsons disease - DBS – Neurophysiological Biomarkers Recorded via (extracellular microelectrodes or) the inserted DBS electrodes Extracellular recording of the surrounding neuron population -> raw data – Low-pass filter –> local field potential Pre- and postsynaptic potentials (Input?) Often transferred in the frequency domain and Labeled according the EEG frequency bands  Basal ganglia diseases Parkinsons disease – DBS optimization with local field potentials E0 is the common electrode showing a peak in the lower beta frequency band and is chosen for DBS In modern systems with more electrodes the channels not in use for stimulation may be used to record LFP which were evaluated for an adaptation of DBS (aDBS – closed loop stimulation)  Basal ganglia diseases Parkinsons disease – DBS effect upon local field potentials PAC – phase amplitude coupling  Basal ganglia diseases Parkinsons disease – DBS - Segmented stimulation  Basal ganglia diseases Parkinsons disease - DBS – Adverse effects Infections Hemorrhage Speech arrest Apathy Hallucinations Hypersexuality Cognitive dysfunction Depression Euphoria – Strategies to avoid adverse effects Single shot antibiotics Electrophysiologically optimized placement of the DBS-electrodes Closed loop stimulation Electrode optimization (directional stimulation)  Cerebellum Vestibulocerebellum – Maintenance of posture and equilibrium – Maintenance of muscle tone Spinocerebellum – Error correction, adjust posture – Smoothness and coordination of movements Cerebrocerebellum – Planning and programming – Coordination of complex movements – Sequence and precision of movements – Timing of movements Thank you for your attention