Deep brain stimulation Flashcards
What is stereotactic neurosurgery
Stereotactic neurosurgery is characterized by its use of three-dimensional coordinates to accurately target specific areas within the brain, emphasizes precise targeting and minimal invasiveness
Functional neurosurgery focuses on improving or restoring neurological functions affected by various conditions, such as movement disorders, epilepsy, chronic pain, and certain psychiatric disorders.
Stereotactic techniques enable the precise delivery of functional neurosurgical interventions. For instance, the accurate placement of electrodes for DBS requires stereotactic surgery to ensure the therapeutic benefits of modulating specific brain circuits.
The choice between stereotactic and functional neurosurgical approaches (or their combination) depends on the patient’s condition, the specific goals of treatment, and the potential benefits and risks of the procedure.
What is functional neurosurgery, and what disorders is this used for?
-surgery to alleviate symptoms of nervous system disorders by altering brain function
-movement disorder, chronic pain, psychiatric disorder, epilepsy
What is DBS?
DBS is a surgical procedure that implants a neurostimulator and electrodes that sends out electrical impulses to specific targets in brain responsible for movement control
what are the different parts of the basal ganglia?
striatum, globus pallidus, subthalamic nucleus, caudate putamen, substantia nigra
what is the main target for PD?
the subthalamic nucleus
what is the main target for dystonia?
Globus pallidus pars interna
what is the main target for essential tremor?
vim thalamus
what are the steps for DBS?
First do a MRI scan to localise the different brain regions, target these regions for the trajectory coordinates for the DBS surgery
why is it important to be very precise for DBS treatment and what part of the STN is targetted for PD?
-because there are many targets within the target
-The STN is a target for PD, during DBS, but you can see that within the STN there’s target within a target, it has different components to it- limbic system(medial part of STN), motor STN(dorsal lateral-which is the main target) and associative STN(lateral caudal part of STN). But the dorsal lateral part of STN is the main target for STN for DBS
how do you find the target within the brain region?
Finding the target
-atlas coordinates
-coordinates provided, Direct visualisation on MRI (STN
what machine is used for DBS
A head ring is attached to patients and the brain is imaged (MRI/CT). This helps determine the electrode placements, and coordination for precise localisation of the target of STN during DBS, secured by pins
what is the pulse of DBS used for PD?
This is the stimulation parameters. For PD we use a pulse width between 60-120 microseconds
Rate is number of pulses per second and traditionally its 130 hertz per second.
Intensity of stimulation is usually less than 3 volts
what is the difference between lesions and DBS?
Lesion involves ablation and DBS involves stimulation but both result in inhibition of output of target structure (inhibiting output in PD from STN) it reduces the abnormally increased firing/ abnormal firing patterns in STN/GPi. Low level of dopamine disrupts the nigrostriatal pathway and thus causes abnormal firing patterns which causes PD clinical features.
(The lesioning involves placing an electrode in targeted region, heating up that electrode and essentially burning that brain region, permanently altering it)
DBS is more expensive due to more sophisticated instruments
Bilateral STN therapy targets both STN
With unilateral therapy in lesioning, there’s a risk of developing hemiballismus (involuntary, vigorous movement one side of body-side effect)
Any implant of foreign object has risk of infection.
-both inhbit output of target strucure
-permenant vs malleable side effct
-chaeper vs more expensive
-unilateral vs bilateral therapy
-implant infection risk to both types of therapy
explain the purpose of DBS for PD and how this works?
So, you can see we have multiple contacts so depending where you position your lead you may stimulate contact 3 or 1,2,3 depends on condition of patient, and these can lead to different outcomes or targets of symptoms. So, if you misplace your lead, you can get side effects. So, by placing lead in STN, you expect to see reduction in bradykinesia, rigidity, tremors.
So it’s vital to stimulate specific contacts and have accuracy for lead placement to prevent side effects in regions other than target
what are some strategies for improving targetting accuracy?
-better imaging (MRI/CT scanner vs x-ray (select scanner that gives better detailing of brain)
-microelectrode recording (Shows you lead going through STN, and you would have a standard recording you expect to see In specific regions of brain, but if you are getting it, it suggests placemat of lead isn’t right due to different oscillations that what’s expected)
-awake monitoring (-keep patients awake and see after stimulation if their experience any side effects, alerting neurosurgeon placement of lead may not be accurate)
