11: DBS Flashcards
functional neurosurgery
surgically altering NS in order to treat symptoms of neurologial + psychiatric illness
stereotactic neurosurgery
technique where any point in the brain can be defined according to a 3D cartesian coordinate system, allowing targets situated at specific coordinates to be reached by an intracranial probe
proposed mechnsm of action in lesioning
reduce overactivity in a particular area of the brain + the symptoms it causes, by partially destroying it with heat or caustic substance
the key to DBS?
make stimulation approach as minimally invasive as possible so as to avoid unnecessary damage to brain
major advance with DBS?
combining sterotaxis + small calibre electrodes
estimated # patients currently treat with DBS
world wide: 150 000 (90 000 for PD)
DBS definition
treatment of various pathological disease states by the chronic + reversible use of direct electrical current, applied focally to subcortical neural elements, aiming to alter function of these structures either in isolation or in relation to their role w/i larger networks/circuits
5 parts in DBS
electrodes, leads, extension, neurostimulator + patient programmer
steps to performing DBS
apply sterotactic frame (coordinate system). image pt’s brain and identify target, record + stimulate to define target electrophysiologically, affix electrodes implant pulse generator. DBS turned on after 4 weeks.
modifiable stimulation parameters: 4?
voltage/current. pulse width. frequency. electrode configuration (monopolar, bipolar)
DBS: what do you want the generated electrical field to maximize/minimize?
maximize stimulation to target, minimize excitation of surrounding structures
in contrast to traditional lesioning surgery, DBS is (3)?
reversible, adjustable and titratable
key considerations for safety
stimulation side effects (so location very important). hardware related failure. infection. intracerebral hemorrhage
why use DBS for PD when there are drugs?
motor symptoms respond well to L dopa, but many pts become refractory or develop side effects from prolonged use: end of dose deterioration, peak dose dyskinesias
2 sites for DBS for PD and overall result
globus pallidus internal segment + subthalamic nucleus = overall increased drive from thalamus to cortex= movement
DBS for PD: main mechanism of action?
disrupts pathologic oscillatory patterns and generates an information lesion
what letter oscillations and where? DA?
beta-band oscillations: normally present in cortex but dampened with activity. low dopamine = self correction breaks down so they aren’t dampened in PD: DBS will reduce these beta oscillations = movement
DBS and circuits?
modulates activity within dysfunctional brain circuits at specific nodes, either restoring functional activity or replacing dysfunctional activity with a therapeutic new normal
DBS for essential tremor: what is ET? target?
most common mvt disorder (4%) involuntary, rhythmic, oscillatory contraction of agonist/antagonist muscles. target the thalamus
fornix DBS: memory
may preserve memory function in AD
fornix DBS: result for metabolism
produces a reversal of hypometabolism in pariet-occiptal regions, known to be underactive in AD
DBS slowing down neurodegeneration?
see hippocampal neurogenesis (animal models). also increases blood vessel area and synaptic density
DBS and AD: brain structure?
saw that hippocampus enlarged in some patients: unprecedented! volume change correlated to clinical outcome
conclusion: DBS is a ___ therapy, for ___? works by?
an effective symptomatic therapy for several neurological + neurodegen. diseases. works by altering activity in a dysfunctional neural circuit.
