Kelly Lynch

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Electrocorticography ECoG
Kelly Lynch March 26, 2009
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What is ECoG?

• Electrocorticography,or ECoG, is the practice of
  using electrodes placed directly on the exposed
  surface of the brain, after conducting a
  craniotomy. Its goal is to record electrical
  activity in the production of Epileptic Seizures
  in search of finding the zones of epileptic
  origin.
• Two Forms
• Intraoperative and Extraoperative

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What is ECoG?

• Types of ECoG electrodes
• 16 disposable stainless steal electrodes placed
  in a ball and socket joint attached to an
  overlying frame.
• Grid Electrodes ranging from 4 to 64 electrodes.
  These are transparent, flexible sheets numbered
  at each different electrode. (Preferred method
  due to the ability to slip under the dura matter.)

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What is an Epileptic Seizure?

• A seizure occurs when a brief, strong surge of an
  overabundance in electrical activity affects part
  or all of the brain lasting from a few seconds to
  a few minutes. It may bring about a change in
  sensation, awareness or behavior.
• They are classified as Epileptic if there is a
  reoccurrence typically more then twice with
  electrical brain activity.

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How Does It Work?
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Intraoperative ECoGPrimary Goal

• To localize the zone and origin point of seizure
  activity for mapping and resectioning of brain
  functions.

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From The Beginning

• 1930- Dr. Wilder Penfield developed the Montreal
  Procedure in Canada. First to detect auras in
  Epileptic patients.
• 1948- Rudolf M. Hess conducted first scalp EEG in
  a 31 year old patient in Switzerland.
• 1949- Hugo Krayenbuhl and Rudolf M. Hess- First
  attempt at ECoG surgery performed on May 18th at
  University Hospital in Switzerland. Hess and
  Krayenbuhl worked in union, Krayenbuhl preformed
  the surgery Hess monitored the electrical output
  of the brain.
• 1950- Dr. Wilder Penfield and Herbert Jasper
  began using the Krayenbuhl and Hess experiment
  and the Montreal Procedure in combination to
  create further developments, being the current
  ECoG methods.
• 2002- Kuruvilla, M.D and Flink, M.D. Uppsala
  University Hospital in Sweden. Began taking on
  the issue of Intraoperative ECoG and its
  reliability.

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Limitations and Problems

• Spontaneous brain activity consisting of unusual
  spikes and sharp waves for the patient.
• Due to the abnormal spikes and brain activity
  faulty information is being recorded as the
  origin of epileptic activity.
• Seizures are rarely recorded.
• Requires quick decisions

• Limited Sampling Time
• Both the background brain activity and epileptic
  activity maybe altered by the anesthetics.

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Schwartz, Bazil, Walczak, Chan, Pedley, and
Goodman

• Study consisted of 29 epileptic participants.
• All 29 underwent standard resectioning with
  Intraoperative ECoG.
• 11 patients (38) had residual epileptic spikes
  after resection.

• 18 (62) had new spikes post resection.
• Conclusion Spikes persisted in frequency with
  ill effect from resectioning with Intraoperative
  ECoG.

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Spenser, Tran, Javidan, Pacia, Marks

• Conducted at Yale University School of Medicine
  Department of Neurology and Neurosurgery.
• Study consisted of 36 patients with epilepsy and
  present brain tumors. Two groups of 18.
• Pre Intraoperative ECoG
• Group 1 85 of the participants had spikes
• (70 over tumor bed, 63 in surrounding tissue)
• Group 2 88 of the participants had spikes
• (55 over tumor bed, 89 in surrounding tissue)

• Post Intraoperative ECoG
• Group 1 60 of the participants had spikes
• (46 around of the resectioned area, 26
  elsewhere in the brain.)
• Group 2 67 of the participants had spikes
• (50 had spikes around the resectioned area, 67
  elsewhere in the brain.)
• Conclusion
• It was not found that Intraoperative ECoG
  accurately recorded active epileptic activity.
  The results were found to show post resection
  spikes and seizure recurrance.

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Is It Really What It Seems?

• Epilepsy- Intraoperative ECoG
• http//www.youtube.com/watch?vZpsMxejnxUE

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Heather Jensen-Siebens
But only by the strength of God and my family
have I been able to conquer the ups and downs
that this treatment comes with. -Heather

• Its trying. After surgery number two you begin
  to wonder if the doctors know what they are doing
  when you, nearly two weeks after surgery, end up
  having a Tonic-Clonic. You wonder if
  Electrocorticography is really going to work for
  you or anyone.
• -Heather