L20: Epilepsy Surgery

Question 1

What is epilepsy?

Answer 1

Epileptic seizures, non-epileptic syncopal episodes (faints), psychogenic attacks (non-epileptic events)

Question 2

How common is epilepsy?

Answer 2

Very common, 5% chance of having an epileptic seizure in your life, and there is also a 75% chance of the seizure being controlled with medication

Question 3

How many seizures are “uncontrolled’? What does this mean for surgery?

Answer 3

25% uncontrolled seizures, and these are the potential candidates for epilepsy surgery

Question 4

What are the four types of investigations used before surgery?

Answer 4

History (semiology) and physical exam
Neuroimaging
EEG
Other stuff

Question 5

What is one type of surgery that is used for temporal epilepsy?

Answer 5

Standard Anterior Temporal Lobectomy
Only take the anterior part, decreased seizures a lot, most important to take out the hippocampal regions in the temporal lobe (CA1) and take out the mesial temporal sclerosis, want to be careful not to damage the AC (anterior carotid artery) and go in through the middle temporal gyrus into the temporal horn

Question 6

What was the first method used (70s and 80s) for brain imaging?

Answer 6

CT, still use them sometimes, but do not provide the level of detail necessary for surgery, only shows density of tissue

Question 7

How is MRI used in epilepsy surgery?

Answer 7

Can see the deep part of the temporal lobe, and used to identify the mesial temporal sclerosis which is usually the cause of temporal epilepsy and you want to remove that
Shows in depth detail, little greys areas deep in the temporal lobe show cortical dysplasia

Question 8

How is a high resolution MRI used?

Answer 8

You can digitally cut into the brain in a curvilinear fashion anyway you like, to see abnormalities deep within the brain.
Can bring the image into the stealth station which is a 3D way of reconstructing the brain
Can see tumors, vessels, etc
Can cut and segment different parts of the brain to look deeper and see how tumors interact with blood vessels

Question 9

What is an EEG and how is it used in epileptic surgery?

Answer 9

Electroencephalography, can be used to determine a RT or LT temporal seizure and record it, LT causes a loss of function, and can show spread of the seizure throughout time.
Shows where electrical signals come from.

Question 10

How is a PET scan used for epilepsy surgery?

Answer 10

Positron emission tomography, radio labelled nucleus to inject into patient, and shows the metabolism of the brain.
Areas that do not light up are the abnormalities because it is not taking up the radio-labelled ligands

Question 11

What is a SISCOM?

Answer 11

Subtracted Ictal SPECT (single photon emitted computer tomography)
Coregistered with MRI
See areas that are bright and not bright, areas that are brighter are the areas that the seizure comes from.
Areas that light up more than others, and only on one side, is likely the ictal onset for the seizure

Question 12

What does invasive monitoring refer to?

Answer 12

Electrodes in the brain, can be used two ways.
Grid electrodes lay on top of the brain, not as common because it requires a big craniotomy and exposure
Depth electrodes are placed into the brain, and are used more often because they can be poked through and brain does not have to be opened up.

Question 13

What is the other term used for depth electrodes? How are they inserted?

Answer 13

SEEG
Stereoelectroencephalography, pretty much a 3D EEG
Inserted via a robot or a robotic arm, and inserts them along coloured trajectories

Question 14

What are other epileptic surgery options?

Answer 14

Selective amygdalohippocampectomy
Extra temporal resection
Awake craniotomy
Vagal nerve stimulation
Laser Interstitial thermo therapy
Multiple subpial resection

Question 15

What is involved in a selective amygdalohippocampectomy?

Answer 15

More elegant way to remove the amygdala and hippocampus, white area on MRI is the area filled with fluid after it has been removed
Remove the parahippocampal gyrus as well as the hippocampus

Question 16

What was one of the very first selective amygdalohippocampectomy?

Answer 16

HM resection that has the temporal lobe removed on BOTH sides (not done anymore), has severe memory deficit and could not remember any new info

Question 17

When is an awake craniotomy used?

Answer 17

Intraoperative stimulation under local anesthesia, map out the areas of the brain that control motor/ sensory/ language functions come from
Use both bipolar stimulation as well as monopolar white matter stimulation
Stimulate precentral, postcentral and central sulci (thumb, lips, tongue)

Question 18

What is a multiple subpial transection?

Answer 18

Areas of the brain are cut with a special knife, allows you to cut interneurons that connect but do not affect the descending motor fibres so you can stop seizure spread

Question 19

How is vagal nerve stimulation used to treat seizures?

Answer 19

Put a wire around vagus nerve on LT side of brain and put in a pacemaker on LT side of chest to stimulate the LT side of vagal nerve, it can stop seizures in a small percentage of patients
Neuromodulatory/ palliative approach, 1/3 have decreased frequency of seizures, 1/3 have increased quality of life, and the last 1/3 have no difference

Question 20

At what point do you resort to surgery for epilepsy?

Answer 20

When it is focal, and the CT/MRI/EEG are all in agreement, or when there is focal/drug resistant/ disabling seizures

Question 21

What are the four new technology?

Answer 21

Intra-operative MRI
Diffusion weighted imaging (tomography)
Functional MRI
LiTT (laser interstitial thermo therapy)

Question 22

What is fMRI?

Answer 22

Functional MRI
Dependent on the Blood Oxygen Level Dependent (BOLD) signal, at the active level both O and DO flow across the vessel membrane, and we image the DO blood seen by differences in magnetic susceptibility (T2 change)

Question 23

What is involved in a hemodynamic response BOLD?

Answer 23

Baseline: T2 response
Move fast: BOLD response (T2 response) increases
Stop moving: T2 response falls back to baseline
Imaging the T2 response that happens when moving

Question 24

How is diffusion weighted imaging (tractography) used?

Answer 24

It capitalizes on asymmetric diffusion of H2O,
that preferentially moves down/ with the nerve fibres (diffusion anisotropy), therefore showing us tract localization

Question 25

What is LiTT?

Answer 25

Laser interstitial thermal therapy
Most new, started about 2 years ago
Laser to burn where the seizure comes from, and can do it without opening up the brain
Laser: light amplification caused by stimulation emission of radiation.
Need an energy source, medium and optical cavity.
Keep temperature below 43-45 degrees then tissues recover, but higher than that kills the cells and they cannot work or recover

Question 26

How does LiTT compare to selective amygdalohippocampectomy and standard anterior temporal lobectomy?

Answer 26

Both LiTT and SAHC do not remove the tissue and instead they kill the tissue, but the SATL removes it.

Question 27

How effective if LiTT?

Answer 27

Seizure free rate is comparable to the open surgery option as well, very effective and comparable to other methods