SEIZURE ABATEMENT WITH SINGLE DC PULSES: IS PHASE RESETTING AT PLAY? IVAN OSORIO*, - PowerPoint PPT Presentation

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SEIZURE ABATEMENT WITH SINGLE DC PULSES: IS PHASE RESETTING AT PLAY? IVAN OSORIO*,

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SEIZURE ABATEMENT WITH SINGLE DC PULSES: IS PHASE RESETTING AT PLAY? IVAN OSORIO , and M. G. FREI The University of Kansas Medical Center – PowerPoint PPT presentation

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Title: SEIZURE ABATEMENT WITH SINGLE DC PULSES: IS PHASE RESETTING AT PLAY? IVAN OSORIO*,


1
SEIZURE ABATEMENT WITH SINGLE DC PULSESIS
PHASE RESETTING AT PLAY?IVAN OSORIO, and M.
G. FREIThe University of Kansas Medical
CenterandFlint Hills Scientific,
LLCInternational Journal of Neural Systems,
Vol. 19, No. 3 (2009) 18
  • Acknowledgement NIH grant R21NS056022

2
Background Information
  • 1.Oscillatorys systems phase may be reset
  • 2.Certain oscillatory systems have a null space
    or black hole
  • 3. Properly timed perturbations (delivered during
    the vulnerable period) leads to
  • Annihilation of oscillations
  • (Arthur Winfree)

3
Rhythmicity Phase Resetting
Null space/Black Hole
4
Methods
  • 8 male rats
  • Isoflurane followed by Ketamine, xylazine
    acepromazine, SC
  • 3-MPA (GABA synthesis blocker) 70 mg/Kg IV
    convulsions

5
Methods
  • Seven epidural screws (OD 1mm 1kohm) ECoG (3)
    DC pulses Ground Reference
  • X
  • X X
  • X X
  • X X
  • Synamps II (Neuroscan, El Paso, TX)
  • DC-2KHz
  • 10 KHz with 24 bits precision

6
Stimulation Protocol
  • Monophasic (DC) square pulses
  • 1.0- 8.0mA
  • 100-200us
  • Positive or negative polarity
  • Single or brief trains(0.1s _at_ 50 Hz)
  • Manual delivery

7
Annihilation Criterion
  • Seizure annihilation
  • Electrographic (and behavioral) activity must
    disappear within 200 ms of pulse delivery

8
Methods
  • Rhythmicity Index Degree of morphological
    stereotypia among seizure waves, estimated using
    the autocorrelation function, off-line.
  • 1s. windows (advanced by 0.1s)
  • RI gt 0.6 High rhythmicity
  • RI lt 0.3 Low rhytmicity

9
Angle Calculation
  • Morphological distance between 2 waves
  • Since, u . v u v cos (alpha),
    alpha is the angle between vectors u and v
  • alpha cos-1( u . v )/( u v ).
  • alpha 0 implies that one signal epoch is a
    scalar multiple of the other (i.e., have a
    correlation coefficient of /-1).

10
Results
  • 146 generalized seizures were stimulated
  • ( 50 with single DC pulses)
  • The RI varies during seizures
  • 30 seizures (20) were annilihated
  • In 29/30 annihilated seizures, the pulse was
    delivered when RI gt 0.6
  • Preliminary histology Non-specific changes

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14
Rhythmicity Phase Resetting
Null space/Black Hole
15
Conclusions
  • Seizure annihilation with single or very few DC
    pulses is feasible
  • Degree of neuronal synchronization as estimated
    with the RI may determine probability of success
    of stimulation (timing the stimulation) High
    RIs High probability of blockage
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