DBS

Question 1

What is DBS?

Answer 1

procedure in which stimulating electrodes are placed stereotactically into certain deep brain structures

Question 2

What conditions will the NHS fund DBS for?

Answer 2

1. PD
2. Essential tremor (parts of body, usually head + forearms, shake uncontrollably)
3. Dystonia (sustained, repetitive muscle contraction)

Question 3

What other conditions can DBS be used for?

Answer 3

• *require individual funding request
  1. epilepsy
  2. chronic neuropathic pain

Current phase I/II clinical trials:

• tourette’s syndrome
• depression, OCD
• alzheimer’s
• obesity, anorexia
• addiction

Question 4

What is the criteria for DBS use in PD?

Answer 4

idiopathic PD with 4 classical symptoms:

1. rigidity
2. tremor
3. bradykinesia
4. postural instability

do not have sensory issues - numbness, tingling
do not get weakness or hyperreflexia
require an MRI scan
no mental disorder
treated with levodopa + still responsive to it
physically fit for surgery

**DBS can only treat the motor symptoms

Question 5

Describe the DBS procedure for PD.

Answer 5

Use MRI scan to work out the target site
connect a stereotactic frame on the patient’s head
drill a 4cm hole into the skull, then insert microelectrode tip to the target site
once the target site has been located, the microelectrode is removed + stimulating electrode is inserted
cap hole, close wound, MRI scan to check electrode at correct site, general anaesthesia for NT stimulus
return to clinic 1month later to programme DBS + adjust drug dosage

Question 6

What effects can DBS have on Parkinsonian symptoms?

Answer 6

Increase 'on' time
Reduce bradykinesia + rigidity 
reduce medication dose 
Improve dyskinesia
effectively treats tremor

Question 7

What brain regions might be targeted for PD?

Answer 7

1/ zona incerta –> target tremors
2/ subthalamic nucleus –> target tremors
3/ globus pallidus internal –> dystonia + tremor

Question 8

When would DBS be used on an epileptic patient? What area in the brain would be targeted?

Answer 8

When medication is inadequate

Target the anterior nucleus of the thalamus

Question 9

What sites would be targeted to treat chronic neuropathic pain with DBS?

Answer 9

Cingulate DBS
Thalamic DBS
Periventricular DBS
Spinal cord stimulation 
Intrathecal morphine pumps 
Peripheral nerve blocks

Question 10

What sites would be targeted to treat Tourette’s with DBS?

Answer 10

thalamic centromedian/ parafascicular complex

Question 11

What sites would be targeted to treat treatment-resistant depression with DBS?

Answer 11

Subcallosal cingulate

Question 12

What sites would be targeted to treat addiction with DBS?

Answer 12

nucleus accumbens

Question 13

What sites would be targeted to treat Alzheimer’s with DBS?

Answer 13

anterior of the fornix

Question 14

Describe the 4 main hypotheses of the mechanism of DBS.

Answer 14

1. Inhibition hypothesis: PD is due to overactive basal ganglia neurones int he subthalamic nucleus and/or GPi –> DBS can block this and remove spontaneous discharge from GPi neurones
2. Excitation hypothesis: DBS can excite afferent axons antidromically resulting in jamming the spontaneous activity
3. Disruption hypothesis: GPi receives input from direct (GABA), indirect (GABA) + hyperdirect (glutamate) pathways
   - -> DBS can inhibit cortical + spontaneous discharges, disrupting/blocking the information flow through the GPi
4. Neuronetwork modulation hypothesis: combination of the other 3 hypotheses as well as neuroprotection, release of astrocytic gliotransmitters, electrotaxis, cortical plasticity

Question 15

What sites would be targeted to treat anorexia with DBS?

Answer 15

hypothalamus