DBS

Question 1

function

Answer 1

• Deep brain stimulation (DBS) involves implanting electrodes within certain areas of the brain.
• These electrodes produce electrical pulses that modify electrical circuits that control neurological function.
• DBS-stimulation is delivered and controlled by a pacemaker-like device placed under the skin in the upper chest.
• A wire that travels under your skin connects this device to the electrodes in the brain.

Question 2

applications

Answer 2

• DBS is commonly used to treat a number of conditions, such as:
• Parkinson’s disease
• Essential tremor
• Dystonia
• Epilepsy
• Obsessive-compulsive disorder
• Conditions currently under investigation:
• Cognitive disorders such as Alzheimer’s Disease
• Psychiatric disorders such as clinical depression

Question 3

DBS surgery

Answer 3

1. A stereotactic head frame is employed to provide reference points for targeting and to keep the head still. At the beginning of the procedure, the frame is attached to the patient’s head using local anaesthetic to numb the scalp.
2. An indicator box is then attached to the head frame
3. MRI or CT scan is obtained to plan the trajectory of the electrodes
4. Then the leads and electrodes are placed in the brain
5. Programming of pulse charge and frequencies starts

Question 4

electrode placement

Answer 4

• Subthalamic nucleus: effective for tremor, slowness, rigidity, dystonia and dyskinesia. Most commonly used to treat Parkinson’s disease.
• Thalamus (VIM): effective for tremor. It is often used to treat essential tremor.
• Globus pallidus: effective for tremor, slowness, rigidity, dystonia and dyskinesia. It is used to treat dystonia and Parkinson’s disease.

Question 5

PD and BDS

Answer 5

• In this pathologically disrupted neural circuit, the electric and functional uncoupling of stimulated STN neurons inhibits the influence of afferent nerves (like SNc, GPe and M1)
• Uncoupling the STN from the SNc makes patients with STN‐DBS less dependent on dopamine and the SNc
• STN‐DBS appears to overwrite one form of pathologic activity with an artificially created “noisy” activity, which is less detrimental to the motor circuit.
• DBS does not recreate the physiological circuit but implements a less pathological one

Question 6

mechanism

Answer 6

• The DBS electrode is implanted in a selected target region. High‐frequency stimulation causes ortho‐ and antidromic (=opposite to physiological direction) axonal action potentials.
• Somatic action potentials are for the most part blocked from passing through the axon to the synapse.
• Afferent fibers projecting to the target region and passing fibers of other brain regions are entrained by the frequency of the stimulation.
• Non‐neural tissue (i.e., astrocytes, microglia, endothelial cells) located in the volume of tissue activated (VTA) is also affected by DBS.
  
  • glial modulation
  • BBB modulation